Rapport de Recherche INRIA N 791, F evrier 1988 1 1 PARALLEL MANIPULATOR 3 1 A lot of calculation... more Rapport de Recherche INRIA N 791, F evrier 1988 1 1 PARALLEL MANIPULATOR 3 1 A lot of calculation (in particular the results presented in the Appendices) has been obtained with the aid of MACSYMA [26], a large symbolic manipulation program developed at MIT or with REDUCE. 3,4,5,
We consider in this paper a Gough-type parallel robot whose leg lengths values are constrained to... more We consider in this paper a Gough-type parallel robot whose leg lengths values are constrained to lie within some fixed ranges and for which there may be mechanical limits for the motion of the passive joints.
We consider in this paper a Gough-type parallel robot and we present an efficient algorithm based... more We consider in this paper a Gough-type parallel robot and we present an efficient algorithm based on interval analysis that allows us to solve the forward kinematics, i.e., to determine all the possible poses of the platform for given joint coordinates. This algorithm is numerically robust as numerical round-off errors are taken into account; the provided solutions are either exact in the sense that it will be possible to refine them up to an arbitrary accuracy or they are flagged only as a "possible" solution as either the numerical accuracy of the computation does not allow us to guarantee them or the robot is in a singular configuration. It allows us to take into account physical and technological constraints on the robot (for example, limited motion of the passive joints). Another advantage is that, assuming realistic constraints on the velocity of the robot, it is competitive in term of computation time with a real-time algorithm such as the Newton scheme, while being safer.
Off-line verification of a trajectory of a parallel robot is very important in practical applicat... more Off-line verification of a trajectory of a parallel robot is very important in practical applications, for example when using such a machine for manufacturing operations. Indeed it is necessary to check if the trajectory is valid ie that it verifies a set of criteria, that will be called the validity criteria.
Abstract We are considering an dof parallel robot that has to move within a given workspace and w... more Abstract We are considering an dof parallel robot that has to move within a given workspace and whose geometry is defined by a set of parameters. The motion of active joints of the manipulator are measured with sensors with a known accuracy±Δρ. These errors together with bounded manufacturing errors on the parameters describing the geometry of the robot induces a positioning errors ΔX of the platform.
Abstract This paper addresses the problem of certifying the performance of a precision flexure-ba... more Abstract This paper addresses the problem of certifying the performance of a precision flexure-base mechanism design with respect to the given constraints. Due to the stringent requirements associated with the applications of flexure-based precision mechanisms, it is necessary to be able to evaluate and certify the performance at the design stage, taking into account the possible sources of errors: such as fabrication tolerance and modeling inaccuracies in flexure joints.
In optimal design problems we have to determine a set of design parameters such that a given mech... more In optimal design problems we have to determine a set of design parameters such that a given mechanism satisfies a list of requirements. In practice however these requirements may be classified as either compulsory or relaxable. For classical optimal design methodologies, it is very difficult to find the solutions that satisfy compulsory requirements simultaneously and make the best compromise between these two kinds of requirements.
Abstract This paper reports the first results of an ongoing work which aims at providing numerica... more Abstract This paper reports the first results of an ongoing work which aims at providing numerical tools useful to the design of a family of high speed parallel robots. The objective is to find sets of feasible values for the design parameters unlike more usual design procedures relying on optimization techniques. These tools are mainly based on interval analysis and take into account the dynamics of the parallel robots.
Abstract MIPS is a micro robot with a parallel mechanical architecture having three degrees of fr... more Abstract MIPS is a micro robot with a parallel mechanical architecture having three degrees of freedom (one translation and two orientations) that allow fine positioning of a surgical tool. The purpose of MIPS is to act as an active wrist at the tip of an endoscope and to provide to the surgeon an accurate tool that may furthermore offers a partial force-feedback. The current prototype has a diameter of 7 mm for a length of 2.5 cm and includes all the necessary hardware.
SUMMARY Miniaturized surgical devices are promising for the future development of minimally invas... more SUMMARY Miniaturized surgical devices are promising for the future development of minimally invasive and endoluminal surgery. However, the dexterity and therapeutic functions of these devices are limited. In this paper, a reconfigurable modular robotic system is proposed to perform screening and interventions in the gastrointestinal tract. In the proposed system, millimeter-sized robotic modules are ingested and tasked to assemble into an articulated mechanism in the stomach cavity.
Abstract We address the problem of finding all the solutions of the direct kinematics for every p... more Abstract We address the problem of finding all the solutions of the direct kinematics for every possible architectures of planar fully parallel manipulators. We show that for this problem all the possible kinematic chains can be reduced to a set of three basic chains and we explain how to calculate the solutions of the forward kinematics for all the combinations of these basic chains and consequently for all the possible architectures of planar parallel robots
Résumé: Synthesis of robots may be decomposed into two processes:{\ em structural synthesis}(dete... more Résumé: Synthesis of robots may be decomposed into two processes:{\ em structural synthesis}(determine the general arrangement of the mechanical structure such as the type and number of joints and the way they will be connected) and {\ em dimensional synthesis}(determine the length of the links, the axis and location of the joints, the necessary maximal joint forces/torques, $\ ldots $). The performances that may be obtained for a robot are drastically dependent on both synthesis.
An important step during the design of a parallel manipulators is the determination of its worksp... more An important step during the design of a parallel manipulators is the determination of its workspace. For a 6-dof parallel manipulator workspace limitations are due to the bounded range of their linear actuators, mechanical limits on their passive joints and links interference. The computation of the workspace of a parallel manipulator is far more complex than for a serial link manipulator as its translation ability is dependent upon the orientation of the end-effector.
Abstract: Determining if there is a singularity within a given workspace of a parallel robot is a... more Abstract: Determining if there is a singularity within a given workspace of a parallel robot is an important step during the design process of this type of robot. As this singular configuration must be avoided the designer may be interested only in a straight yes no answer.
Résumé: We consider parallel robots, that will be called cams-coupled parallel robots, whose mobi... more Résumé: We consider parallel robots, that will be called cams-coupled parallel robots, whose mobile platform has surfaces that are constrained to be in contact at a point with surfaces located on the base. Articulated passive xed length legs connect also the base to the platform while active legs allow to control the motion of the platform. We investigate the mobility of such robot and shows how the inverse and direct kinematics can be solved for arbitrary contact surfaces.
Summary: Parallel manipulators have a speci c mechanical architecture where all the links are con... more Summary: Parallel manipulators have a speci c mechanical architecture where all the links are connected both at the basis and at the gripper of the robot. This kind of manipulator has a better positionning ability than the classical robot. We have addressed in the rst part of this paper the direct kinematics problems. We have shown that it may be suspected that in some case for a given set of links lengths more than one solution may be given to this problem: we have thus a singular con guration for the manipulator.
Résumé: Although they have many advantages in term of positioning accuracy, stiffness, load capac... more Résumé: Although they have many advantages in term of positioning accuracy, stiffness, load capacity parallel machines have also a main drawback: their performances are very sensitive to their dimensioning.
Abstract—Described in this paper is the design and verification of the parallel platform 'HexaSpi... more Abstract—Described in this paper is the design and verification of the parallel platform 'HexaSpine', targeted to physically reproduce the displacement-force behaviour of cervical vertebrae pairs. The parallel platform consists of six actuator legs of type RRPS, each comprising a hybrid unit of coaxial coil spring and fluidic muscle. The design of the platform targets at fulfilling the motion range between two vertebrae without singularities.
Abstract Global motion planners have been proposed for closed-loop robot based on the same paradi... more Abstract Global motion planners have been proposed for closed-loop robot based on the same paradigm than has been proposed for serial chains: a sparse representation of the configuration space of the robot is constructed as a set of nodes and a motion planning query consists simply in connecting the start and goal points through an appropriate set of nodes (usually minimizing the length of the trajectory).
Rapport de Recherche INRIA N 791, F evrier 1988 1 1 PARALLEL MANIPULATOR 3 1 A lot of calculation... more Rapport de Recherche INRIA N 791, F evrier 1988 1 1 PARALLEL MANIPULATOR 3 1 A lot of calculation (in particular the results presented in the Appendices) has been obtained with the aid of MACSYMA [26], a large symbolic manipulation program developed at MIT or with REDUCE. 3,4,5,
We consider in this paper a Gough-type parallel robot whose leg lengths values are constrained to... more We consider in this paper a Gough-type parallel robot whose leg lengths values are constrained to lie within some fixed ranges and for which there may be mechanical limits for the motion of the passive joints.
We consider in this paper a Gough-type parallel robot and we present an efficient algorithm based... more We consider in this paper a Gough-type parallel robot and we present an efficient algorithm based on interval analysis that allows us to solve the forward kinematics, i.e., to determine all the possible poses of the platform for given joint coordinates. This algorithm is numerically robust as numerical round-off errors are taken into account; the provided solutions are either exact in the sense that it will be possible to refine them up to an arbitrary accuracy or they are flagged only as a "possible" solution as either the numerical accuracy of the computation does not allow us to guarantee them or the robot is in a singular configuration. It allows us to take into account physical and technological constraints on the robot (for example, limited motion of the passive joints). Another advantage is that, assuming realistic constraints on the velocity of the robot, it is competitive in term of computation time with a real-time algorithm such as the Newton scheme, while being safer.
Off-line verification of a trajectory of a parallel robot is very important in practical applicat... more Off-line verification of a trajectory of a parallel robot is very important in practical applications, for example when using such a machine for manufacturing operations. Indeed it is necessary to check if the trajectory is valid ie that it verifies a set of criteria, that will be called the validity criteria.
Abstract We are considering an dof parallel robot that has to move within a given workspace and w... more Abstract We are considering an dof parallel robot that has to move within a given workspace and whose geometry is defined by a set of parameters. The motion of active joints of the manipulator are measured with sensors with a known accuracy±Δρ. These errors together with bounded manufacturing errors on the parameters describing the geometry of the robot induces a positioning errors ΔX of the platform.
Abstract This paper addresses the problem of certifying the performance of a precision flexure-ba... more Abstract This paper addresses the problem of certifying the performance of a precision flexure-base mechanism design with respect to the given constraints. Due to the stringent requirements associated with the applications of flexure-based precision mechanisms, it is necessary to be able to evaluate and certify the performance at the design stage, taking into account the possible sources of errors: such as fabrication tolerance and modeling inaccuracies in flexure joints.
In optimal design problems we have to determine a set of design parameters such that a given mech... more In optimal design problems we have to determine a set of design parameters such that a given mechanism satisfies a list of requirements. In practice however these requirements may be classified as either compulsory or relaxable. For classical optimal design methodologies, it is very difficult to find the solutions that satisfy compulsory requirements simultaneously and make the best compromise between these two kinds of requirements.
Abstract This paper reports the first results of an ongoing work which aims at providing numerica... more Abstract This paper reports the first results of an ongoing work which aims at providing numerical tools useful to the design of a family of high speed parallel robots. The objective is to find sets of feasible values for the design parameters unlike more usual design procedures relying on optimization techniques. These tools are mainly based on interval analysis and take into account the dynamics of the parallel robots.
Abstract MIPS is a micro robot with a parallel mechanical architecture having three degrees of fr... more Abstract MIPS is a micro robot with a parallel mechanical architecture having three degrees of freedom (one translation and two orientations) that allow fine positioning of a surgical tool. The purpose of MIPS is to act as an active wrist at the tip of an endoscope and to provide to the surgeon an accurate tool that may furthermore offers a partial force-feedback. The current prototype has a diameter of 7 mm for a length of 2.5 cm and includes all the necessary hardware.
SUMMARY Miniaturized surgical devices are promising for the future development of minimally invas... more SUMMARY Miniaturized surgical devices are promising for the future development of minimally invasive and endoluminal surgery. However, the dexterity and therapeutic functions of these devices are limited. In this paper, a reconfigurable modular robotic system is proposed to perform screening and interventions in the gastrointestinal tract. In the proposed system, millimeter-sized robotic modules are ingested and tasked to assemble into an articulated mechanism in the stomach cavity.
Abstract We address the problem of finding all the solutions of the direct kinematics for every p... more Abstract We address the problem of finding all the solutions of the direct kinematics for every possible architectures of planar fully parallel manipulators. We show that for this problem all the possible kinematic chains can be reduced to a set of three basic chains and we explain how to calculate the solutions of the forward kinematics for all the combinations of these basic chains and consequently for all the possible architectures of planar parallel robots
Résumé: Synthesis of robots may be decomposed into two processes:{\ em structural synthesis}(dete... more Résumé: Synthesis of robots may be decomposed into two processes:{\ em structural synthesis}(determine the general arrangement of the mechanical structure such as the type and number of joints and the way they will be connected) and {\ em dimensional synthesis}(determine the length of the links, the axis and location of the joints, the necessary maximal joint forces/torques, $\ ldots $). The performances that may be obtained for a robot are drastically dependent on both synthesis.
An important step during the design of a parallel manipulators is the determination of its worksp... more An important step during the design of a parallel manipulators is the determination of its workspace. For a 6-dof parallel manipulator workspace limitations are due to the bounded range of their linear actuators, mechanical limits on their passive joints and links interference. The computation of the workspace of a parallel manipulator is far more complex than for a serial link manipulator as its translation ability is dependent upon the orientation of the end-effector.
Abstract: Determining if there is a singularity within a given workspace of a parallel robot is a... more Abstract: Determining if there is a singularity within a given workspace of a parallel robot is an important step during the design process of this type of robot. As this singular configuration must be avoided the designer may be interested only in a straight yes no answer.
Résumé: We consider parallel robots, that will be called cams-coupled parallel robots, whose mobi... more Résumé: We consider parallel robots, that will be called cams-coupled parallel robots, whose mobile platform has surfaces that are constrained to be in contact at a point with surfaces located on the base. Articulated passive xed length legs connect also the base to the platform while active legs allow to control the motion of the platform. We investigate the mobility of such robot and shows how the inverse and direct kinematics can be solved for arbitrary contact surfaces.
Summary: Parallel manipulators have a speci c mechanical architecture where all the links are con... more Summary: Parallel manipulators have a speci c mechanical architecture where all the links are connected both at the basis and at the gripper of the robot. This kind of manipulator has a better positionning ability than the classical robot. We have addressed in the rst part of this paper the direct kinematics problems. We have shown that it may be suspected that in some case for a given set of links lengths more than one solution may be given to this problem: we have thus a singular con guration for the manipulator.
Résumé: Although they have many advantages in term of positioning accuracy, stiffness, load capac... more Résumé: Although they have many advantages in term of positioning accuracy, stiffness, load capacity parallel machines have also a main drawback: their performances are very sensitive to their dimensioning.
Abstract—Described in this paper is the design and verification of the parallel platform 'HexaSpi... more Abstract—Described in this paper is the design and verification of the parallel platform 'HexaSpine', targeted to physically reproduce the displacement-force behaviour of cervical vertebrae pairs. The parallel platform consists of six actuator legs of type RRPS, each comprising a hybrid unit of coaxial coil spring and fluidic muscle. The design of the platform targets at fulfilling the motion range between two vertebrae without singularities.
Abstract Global motion planners have been proposed for closed-loop robot based on the same paradi... more Abstract Global motion planners have been proposed for closed-loop robot based on the same paradigm than has been proposed for serial chains: a sparse representation of the configuration space of the robot is constructed as a set of nodes and a motion planning query consists simply in connecting the start and goal points through an appropriate set of nodes (usually minimizing the length of the trajectory).
Gait analysis and human joint motion mea-
surement has been studied extensively in the recent pa... more Gait analysis and human joint motion mea-
surement has been studied extensively in the recent past.
Common approaches that have been used include using in-
ertial sensors, multi-camera optical and IR tracking sys-
tems, X-ray and fluoroscopy based imaging, force sensors,
magnetic sensors and bone-fixed pins for measurement.
Soft tissue artifacts (STA) are a common source of error
in most type of measurements and the standard procedure
in gait analysis has been to use a combination of measure-
ment methods for efficient estimation of joint angles and the
link poses. However, there are few studies where a multiple
number of methods have been compared and the correla-
tion between results from various approaches studied. In
this paper, we propose an outline for measurement for hu-
man joint motion using a number of sensors that can give
complete information relating to the joints.
Our proposed experiment assumes a human joint to be a
6 DOF joint between 2 links. We will mount collars on the
limbs close to anatomical landmarks, treating the actual
pose of the system with respect to the bones as unknowns.
These collars will hold markers and sensors that will be
used in the experiments. We will be using a 10 camera op-
tical (IR) tracking system, accelerometers and gyroscopes,
7 wire passive measurement system, 7 wire active measure-
ment system, in-shoe pressure pads, variable length resis-
tive wires, collar-mounted force sensors, and IR distance
sensor to measure the pose of the trunk. Our experiment
will focus on the knee joint and it’s motion during activi-
ties such as walking. This paper describes the experimental
setup and the sensor and collar calibration that has been
performed.
Sur la base de cette phase exploratoire, nous avons élaboré une stratégie reposant sur quelques p... more Sur la base de cette phase exploratoire, nous avons élaboré une stratégie reposant sur quelques principes essentiels. Les systèmes doivent s' adapter dynamiquement aux capacités physiques et cognitives des utilisateurs et à leur environnement, et non pas le contraire. ils doivent emporter leur adhésion au regard de l'intérêt de l'aide fournie. ils ne doivent pas heurter leur sensibilité en étant trop sophistiqués ou bien en bouleversant leur environnement de manière trop importante.
ANG is a family of low cost modular walking
aids based on commercially available Rollator. We pr... more ANG is a family of low cost modular walking
aids based on commercially available Rollator. We present
two models of this family: the simplest ANG-light which is
intended to be used as a diagnosis tool for walking and as a fall
detection tool and ANG-II, a motorized walker with over 20 on-
board sensors. Trajectography obtained through ANG-light
with 24 healthy subjects has been used to obtain gold standards
of walking pattern and the walker is currently being used at
Nice hospital with 30 elderly end-users in order to determine
if trajectory records obtained during the daily use of a walker
may allow doctors to objectively characterize abnormal walking
patterns, to follow the progress of a rehabilitation process
and to detect emerging pathologies. The more sophisticated
ANG-II is intended to be used as a test platform for original
functionalities, some of which will be presented.
A rollator has been instrumented with encoders
in the rear wheel and 3D accelerometer/gyrometer.... more A rollator has been instrumented with encoders
in the rear wheel and 3D accelerometer/gyrometer. This low-
cost instrumentation allows one to determine the trajectory of
the rollator with the purpose of determining if it enables to
characterize the walking pattern of elderly people. For that
purpose an experiment has involved 30 elderly people and 24
young adults that were requested to perform two different
trajectories that are classically used for analyzing walking
abilities. It appears that the analysis of the trajectory provides
very discriminating indexes that characterize walking patterns.
A major advantage of this instrumentation is that it can be
used at all time for monitoring the state of health of elderly
people, especially at home, and may possibly detect very early
the beginning of a pathology by detecting rare events.
We present the overall design of ANG, a new walking aid for the elderly. The objectives
of this ... more We present the overall design of ANG, a new walking aid for the elderly. The objectives
of this walking aid is to provide a low-cost and low-intrusivity aid for the elderly. ANG is based
on a classical 4-wheel Rollator, the two rear wheels being fixed while the two front are caster
wheels. The rear wheels have been motorized, a bistable clutching mechanism allowing to clutch
and unclutch the motors at will. ANG will provide fall prevention, navigation assistance, walking
aid and may also be used as a rehabilitation tool. We present in this paper the mechanical design
of ANG and some of the modes in which it may be used.
— We consider in this paper cable driven parallel robot (CDPR) with m catenary cables that presen... more — We consider in this paper cable driven parallel robot (CDPR) with m catenary cables that present a significant deformation due to their elasticity and own mass and we address the inverse kinematics (IK) of such a robot i.e. determining the lengths at rest of the cables for a given pose of the platform. We show that the IK requires to solve a square system of equations if the robot has up to 6 cables and an underconstrained system if the number of cables is larger than 6. In this paper we address the problem of finding all solutions of the IK when the number of cables is lower or equal to 6. We propose an algorithm that allows one to determine all possible solutions. for any number of cables. We illustrate the use of the IK solver on a CDPR with 6 cables and shows that the IK may have no solution even if the pose lie within the envelope of the base points or may have several solutions, in which case some cables may have a length at rest that is much larger than the distance between the anchor points of the cable.
—Cable-driven parallel robot (CDPR) are parallel robots that use coilable cables as legs. We are ... more —Cable-driven parallel robot (CDPR) are parallel robots that use coilable cables as legs. We are interested here in suspended CDPR for which there is no cable that exert a downward force on the platform. If we assume that the cables are mass-less and not elastic it has been shown that at a given pose whatever is the number m > 6 of cables there will always be at most 6 cables under tension simultaneously. A cable configuration (CC) at a given pose is the set of cables number that are under tension and usually there are several possible CC for the same pose. These CC are not equivalent in terms of cable tensions, sensitivity to measurement errors and therefore it make sense from a control viewpoint to enforce the " best " CC to obtain the optimal robot configuration, which can be done by controlling the length of the cables that are not members of the CC so that we are sure that they are slack. Hence we are interested in ranking the different CC in term of ro-bustness. We propose several ranking indices for a CC and algorithms to calculate these indices at a pose, on a tra-jectory or when the robot moves on a surface and we show examples for a CDPR with 8 cables.
— This paper addresses the problem of the forward kinematics of cable-driven parallel robots (CDP... more — This paper addresses the problem of the forward kinematics of cable-driven parallel robots (CDPR) having elastic or non elastic cables under the assumption that the cables are submitted to small changes in their lengths compared to an initial situation at which the pose is known, a situation that is typical of a real-time forward kinematics used for control purposes. We show that at the initial point it is necessary to have not only the pose but also the cable configuration, i.e. having the knowledge of which cables are under tension and that the result of the forward kinematics should be both the pose and the cable configuration after the change in cable lengths. We exhibit a first algorithm that allows one to determine all possible final poses and cable configurations. Then a second algorithm is proposed to determine all possible cable configurations also during the coiling process which is an important point as the CDPR state, including the cable tensions, may drastically change at this point. The last algorithm assumes a model of the coiling process and is able to determine the unique final pose and cable configuration. These algorithms provide safer real-time forward kinematics which will improve the CDPR control
— We consider in this paper cable driven parallel robot (CDPR) with m catenary cables that presen... more — We consider in this paper cable driven parallel robot (CDPR) with m catenary cables that present a significant deformation due to their elasticity and own mass and we address the kinematics of such a robot uder the assumption of static state. We show that the inverse kinematics (IK) requires to solve a square system of equations if the robot has up to 6 cables and an underconstrained system if m > 6. We first show that usual methods for solving the IK of CDPR with other cable model cannot be used and we propose an algorithm that allows one to determine all possible solutions. We then address the forward kinematics (FK) that is known to be usually a difficult task for parallel robots. We show that solving the FK always amounts to solve a square system of equations and that the problem is even more complex than solving the FK of parallel robots with rigid legs as the system is non algebraic and has a larger number of equations. We then propose a generic algorithm for solving the FK for any number of cables. We illustrate the use of the IK and FK solver on a CDPR with 8 cables.
The main advantage of CDPRs is large workspaces. However, multiple legs and large workspace are b... more The main advantage of CDPRs is large workspaces. However, multiple legs and large workspace are both factors for interference. We consider a CDPR platform within a 6D workspace, and as sources of interference the collisions with the robot's environment and self interference. We present two algorithms and their interval analysis-based applications to handle the different types of interference. Finally, the efficiencies of the algorithms are presented.
Marionet-Assist is a CDPR designed for transfer operations. Our crane robot has a configuration t... more Marionet-Assist is a CDPR designed for transfer operations. Our crane robot has a configuration that provides three translational d.o.f.. Four wires are used to control the position of the end-effector, but as they have no elasticity, only three of them at most will be under tension. For a given position, different triplet of cables under tension are possible, and for a given trajectory, transition between two cable configurations may occur, which can lead to a loss of controllability. Therefore we propose a scheme that rank all the possible sequences for a given trajectory, using interval analysis to guaranty our computing. When a triplet of wires under tension is selected, the fourth one will be forced to be slack by adding purposely extra length. It allows to control changes of cable configurations and thus to have safer trajectories.
Solving the forward kinematics (FK) of parallel
robots is known to be a difficult task. With rig... more Solving the forward kinematics (FK) of parallel
robots is known to be a difficult task. With rigid legs 20 years
have been required to understand the geometry of the problem,
determine the maximal number of solutions and exhibit an
example with 40 solutions. The problem is even more complex
for cable driven parallel robot (CDPR): the system of equations
that has to be solved is larger than with rigid legs as the static
equations have to be taken into account. The problem is even
more complex if we take into account the deformation of the
cables because of their elasticity and their mass. We present
for the first time a generic algorithm that allows to calculate
all the FK solutions for any CDPR and illustrate its use for a
CDPR with 8 cables.
obots are controlled with a discrete-time controller that includes a high-
level loop for motion... more obots are controlled with a discrete-time controller that includes a high-
level loop for motion control and a faster internal loop that controls the actuators. We
intend to simulate the behavior of the whole chain for a cable-driven parallel robot
(CDPR) with linear elastic cables and we will show that such a simulation cannot
be performed using classical simulation tools. We exhibit a simulation algorithm
which computes exactly the pose and cable tensions on a given trajectory. As an
example we consider a redundantly actuated robot with 8 cables. We show that the
discrete-time control has a moderate influence on the accuracy of the positioning
but a very large influence on the cable tensions.
Cette proposition COLOR porte sur la définition d'une approche de conception optimale et d'étalon... more Cette proposition COLOR porte sur la définition d'une approche de conception optimale et d'étalonnage de robots parallelesa câbles, ce type de robots offrant des potentialités d'applications tres larges. Cette étude comportera des développements théoriques et une étape de validation expérimentale sur des prototypes réels. Sa durée prévue est de un an.
Dans notre travail, on présente les concepts relatifs à une nouvelle machine de rééducation des m... more Dans notre travail, on présente les concepts relatifs à une nouvelle machine de rééducation des membres inférieurs à base d'un robot parallèle à câbles. Une partie du papier sera consacrée à la cinématique de la machine ainsi que son architecture mécanique en répondant à un ensemble des contraintes. La deuxième partie introduit la notion de la modélisation géométrique de l'espace de travail et de la singularité.
Abstract The wrench-closure workspace of parallel cable-driven mechanisms is the set of poses of ... more Abstract The wrench-closure workspace of parallel cable-driven mechanisms is the set of poses of their mobile platform for which the cables can balance any external wrench. The determination of this workspace is an important issue since the cables can only pull and not push on the mobile platform. This paper deals with the wrench-closure workspace of six-degrees-of-freedom (DOF) parallel mechanisms driven by m cables, m≥ 7.
Abstract Wire-driven parallel robot (WDPR) is a special class of parallel robot in which the rigi... more Abstract Wire-driven parallel robot (WDPR) is a special class of parallel robot in which the rigid legs are replaced by wires, with potential advantages in terms of intrusivity and workspace. Although the study of WDPR seems to be a well-addressed subject, we will show that there are still numerous challenging open issues in this field.
This paper studies the kinematics and statics of cable-driven parallel robots with less than six ... more This paper studies the kinematics and statics of cable-driven parallel robots with less than six cables, in crane configuration. A geometrico-static model is provided, together with a general procedure aimed at effectively solving, in analytical form, the inverse and direct position problems. The stability of equilibrium is assessed within the framework of a constrained optimization problem, for which a purely algebraic formulation is provided. A spatial robot with three cables is studied as an application example.
Abstract—Wire-driven parallel robots offers potential advan-tages for various applications such a... more Abstract—Wire-driven parallel robots offers potential advan-tages for various applications such as medical rehabilitation, entertainment, virtual reality. However as any parallel robot their performances is greatly varying with their geometry and no fixed geometry allows to fulfill all requirements for all possible applications. Hence it is interesting to consider a modular parallel robot, whose geometry may be adapted to the task at hand.
Abstract This paper deals with the wrench-feasible workspace (WFW) of n-degree-of-freedom paralle... more Abstract This paper deals with the wrench-feasible workspace (WFW) of n-degree-of-freedom parallel robots driven by n or more than n cables. The WFW is the set of mobile platform poses for which the cables can balance any wrench of a given set of wrenches, such that the tension in each cable remains within a prescribed range. Requirements of nonnegative cable tensions, as well as maximum admissible tensions, are thus satisfied.
Abstract AN− 1 wire-driven parallel robot is a robot for which all the N≥ 3 wires are connected a... more Abstract AN− 1 wire-driven parallel robot is a robot for which all the N≥ 3 wires are connected at the same point of the platform, allowing to control the location of this point. We are interested in the positioning accuracy of such a robot. If the wires are not elastic we show that the influence on the accuracy of the co-location errors of the wire anchor points on the platform is moderate, although a full analysis is a very difficult task.
We are interested in wire-driven parallel robot with four wires and at least two distinct attachm... more We are interested in wire-driven parallel robot with four wires and at least two distinct attachment points on the end-effector. Such type of robot is non redundant, it exhibits 4 dof and can be used as a crane. This paper addresses the inverse and forward kinematics problem, taking into account the mechanical equilibrium equations. We show that surprisingly the forward kinematics can be solved, either for determining all solutions or in a real-time context, but that the inverse kinematics is still an open issue.
We present several prototypes of wire-driven parallel robots that we have recently designed and w... more We present several prototypes of wire-driven parallel robots that we have recently designed and which use two different actuation schemes. Two of them have been completed and submitted to extensive tests. These tests have allowed to determine interesting open problems related to kinematics that are presented.
Abstract Wire-driven parallel robots are special types of Gough-Stewart platform in which the rig... more Abstract Wire-driven parallel robots are special types of Gough-Stewart platform in which the rigid extensible legs are substituted by extensible wires. Usually wire length change is obtained by coiling the wire on a drum actuated by a rotary motor. We present here a robot using linear actuator and a pulley system allowing a higher modularity of the actuation system. The kinematics of this redundant system (the system has 7 wires), taking into account the elasticity of the wires, is presented.
Abstract The wrench-feasible workspace (WFW) of a parallel cable-driven mechanism is the set of p... more Abstract The wrench-feasible workspace (WFW) of a parallel cable-driven mechanism is the set of poses of its mobile platform for which the cables can balance any wrench in a specified set of wrenches, such that the tension in each cable remains within a prescribed range. The WFW is fundamental since it takes into account both the requirement of non-negative cable tension and the requirement of a maximum admissible cable tension.
ABSTRACT In this paper, the geometric design problem of serial4link robot manipulators with three... more ABSTRACT In this paper, the geometric design problem of serial4link robot manipulators with three revolute (R) joints is solved for the first time using an interval analysis method. In this problem, five spatial positions and orientations are defined and the dimensions of the geometric parameters of the 34R manipulator are computed so that the manipulator will be able to place its end4effector at these pre4specified locations.
Abstract In this paper the problem of interference avoidance for robots subject to dynamic constr... more Abstract In this paper the problem of interference avoidance for robots subject to dynamic constraints is investigated. First computed-torque method is used to obtain a linearized closed-loop system. For this linearized system the desired state that the robot is going to take at the next sampling period is checked by phase plane analysis to ensure the robot can be stopped without interferences, dynamic constraints are taken into account by calculating the bounds of the drive torques with interval evaluation.
Numerical constraint systems are often handled by branch and prune algorithms that combine splitt... more Numerical constraint systems are often handled by branch and prune algorithms that combine splitting techniques, local consistencies, and interval methods. This paper first recalls the principles of\ tt Quad, a global constraint that works on a tight and safe linear relaxation of quadratic subsystems of constraints. Then, it introduces a generalization of\ tt Quad to polynomial constraint systems.
• Tolerance problems: a property must be checked for all points in some higher-dimensional space,... more • Tolerance problems: a property must be checked for all points in some higher-dimensional space,• Constraint satisfaction problems: one (existence) or all (covering) points must be found that satisfy a given set of constraints• global optimization problems: point (s) must be found satisfying given constraints and attaining the absolute extreme values (global minimum or global maximum or both) of some variable or objective function.
Interval analysis is a relatively new mathematical tool that allows one to deal with problems tha... more Interval analysis is a relatively new mathematical tool that allows one to deal with problems that may have to be solved numerically with a computer. Examples of such problems are system solving and global optimization, but numerous other problems may be addressed as well.
A robot is typical of systems that are inherently submitted to uncertainties although they should... more A robot is typical of systems that are inherently submitted to uncertainties although they should be highly reliable (ie for a robot used in surgical applications). The sources of uncertainties are the manufacturing tolerances of the mechanical parts constituting the robot which make the real robot always different from its theoretical model and control errors.
Finding the zeros of polynomials is a problem that arises in many field of applied mathematics. F... more Finding the zeros of polynomials is a problem that arises in many field of applied mathematics. For example stability system analysis, molecular configuration and so on. In general the coefficients of the polynomials to be studied are based upon physical values that are approximated with finite accuracy through measures or estimations, and only approximations of the “real” polynomials are available. Very often probabilistic representation is used for modelling problems with uncertainty.
alias is a C++ library implementing interval analysis and constraint programming methods for stud... more alias is a C++ library implementing interval analysis and constraint programming methods for studying and solving set of equation over the reals. In this paper, we describes a distributed implementation of the library.
Résumé La Commission d'Évaluation (CE) de l'INRIA a souhaité mener une réexion sur les indicateur... more Résumé La Commission d'Évaluation (CE) de l'INRIA a souhaité mener une réexion sur les indicateurs bibliométriques de façon à mieux comprendre ce qu'ils mesurent, leur pertinence et leur abilité, en particulier dans le contexte de la recherche menée à l'INRIA. Le présent document est le résultat du travail d'un groupe de réexion animé par Jean-Pierre Merlet et composé également de AM. Kermarrec, E. Faou, P. Robert et L. Segoufin.
The INRIA Evaluation Committee (EC) decided to examine bibliometric indicators to better
underst... more The INRIA Evaluation Committee (EC) decided to examine bibliometric indicators to better
understand what they measure, their relevance and their reliability, particularly in the context
of research at INRIA. This document was produced by a study group led by Jean-Pierre
Merlet and composed of A-M. Kermarrec, E. Faou, P. Robert and L. Segoufin. The document
was discussed during the Evaluation Committee meetings held in January and September
2007 and integrates the remarks of the committee members.
We show that all possible 388 4-dim Kochen–Specker (KS)(vector) sets (of yes–no questions) with 1... more We show that all possible 388 4-dim Kochen–Specker (KS)(vector) sets (of yes–no questions) with 18 through 23 vectors and 844 sets with 24 vectors all with component values from {− 1, 0, 1} can be obtained by stripping vectors off a single system provided by Peres 20 years ago. In addition to them, we have found a number of other KS sets with 22 through 24 vectors. We present the algorithms we used and features we found, such as, for instance, that Peres' 24-24 KS set has altogether six critical KS subsets.
Abstract We give a constructive and exhaustive definition of Kochen–Specker (KS) vectors in a Hil... more Abstract We give a constructive and exhaustive definition of Kochen–Specker (KS) vectors in a Hilbert space of any dimension as well as of all the remaining vectors of the space. KS vectors are elements of any set of orthonormal states, ie, vectors in an n-dimensional Hilbert space, Hn, n⩾ 3, to which it is impossible to assign 1s and 0s in such a way that no two mutually orthogonal vectors from the set are both assigned 1 and that not all mutually orthogonal vectors are assigned 0.
Projet Coprin Rapport de recherche n 5388—Novembre 2004—39 pages Abstract: The Kochen-Specker the... more Projet Coprin Rapport de recherche n 5388—Novembre 2004—39 pages Abstract: The Kochen-Specker theorem is one of the fundamental theorems in quantum mechanics. It proves that the non-contextuality hypothesis that assumes that the values of observables are independent of the context, ie, of the way that measurements are performed on the system and therefore predetermined, does not hold for quantum systems.
Abstract We show that all possible 388 4-dim Kochen-Specker (KS) setups with 18 through 23 vector... more Abstract We show that all possible 388 4-dim Kochen-Specker (KS) setups with 18 through 23 vectors and 844 setups with 24 vectors all with component values from {-1, 0, 1} can be obtained by stripping vectors off a single system provided—in effect—by Asher Peres 20 years ago. In addition to them, we have found a number of other KS setups with 22 through 24 vectors. Key words: Kochen-Specker sets, MMP diagrams, lattice theory
Recent robotics is the result of a large historical tradition dating back from Antiquity and base... more Recent robotics is the result of a large historical tradition dating back from Antiquity and based on still older religious beliefs. We will here give some important landmarks in this tradition, starting from Antiquity, going through the Middle Age and up to the 60's.
Trigonometric functions appear very frequently in mechanism kinematic equations (for example as s... more Trigonometric functions appear very frequently in mechanism kinematic equations (for example as soon a revolute joint is involved in the mechanism). Dealing with these functions is difficult and trigonometric substitutions are used to transform them into algebraic terms that can be handled more easily. We present briefly the origin of the trigonometric functions and of these substitutions.
Abstract—We are considering1 an dof parallel robot that has to move within a given workspace and ... more Abstract—We are considering1 an dof parallel robot that has to move within a given workspace and whose geometry is defined by a set of parameters. The motion of active joints of the manipulator are measured with sensors with a known accuracy±∆ ρ. These errors together with bounded manufacturing errors on the parameters describing the geometry of the robot induces a positioning errors∆ X of the platform. Keywords: optimal design, accuracy, parallel robot
Résumé: Les mécanismes utilisés pour les suspensions automobiles sont en général des mécanismes e... more Résumé: Les mécanismes utilisés pour les suspensions automobiles sont en général des mécanismes en chaînes fermées à un degré de liberté. La modélisation géométrique consiste à déterminer la posture du corps terminal du mécanisme en fonction de la valeur d'un des paramètres du système, appelé le paramètre fixe.
R? esum? e: Les m? ecanismes utilis? es pour les suspensions automobiles sont en g? en? eral des ... more R? esum? e: Les m? ecanismes utilis? es pour les suspensions automobiles sont en g? en? eral des m? ecanismes en cha^? nes ferm? ees? a un degr? e de libert? e. La mod? elisation g? eom? etrique consiste? ad? eterminer la posture du corps terminal du m? ecanisme en fonction de la valeur d'un des param? etres du syst? eme, appel? e le param? etre fixe. De part la nature des m? ecanismes employ? es ce probl? eme n'a pas une solution unique alors qu'usuellement on utilise pour le r? esoudre une proc?
Abstract This article addresses the problem of computing stable grasps of three-dimensional polyh... more Abstract This article addresses the problem of computing stable grasps of three-dimensional polyhedral objects. We consider the case of a hand equipped with four hard fingers and assume point contact with friction. We prove new necessary and sufficient conditions for equilibrium and force closure, and present a geometric characterization of all possible types of four-finger equilibrium grasps. We then focus on concurrent grasps, for which the lines of action of the four contact forces all intersect in a point.
Résumé La commande par retour d'effort consiste à prendre en compte les actions de contact entre ... more Résumé La commande par retour d'effort consiste à prendre en compte les actions de contact entre un robot et son environnement afin de réaliser un objectif donné. Cette commande sera utilisée lorsque les autres moyens de perception (vision, proximétrie..) donneront une information trop riche, trop imprécise ou ne satisferont pas à des critères de sécurité.
Abstract—The Abstract must be a self-contained, com-prehensive, concise summary of the paper, lim... more Abstract—The Abstract must be a self-contained, com-prehensive, concise summary of the paper, limited to 150 words and to one single paragraph. The paper should be interesting to the audience targeted by the conference organization, as spelled out in the conference scope; moreover, the paper should be comprehensive and concise, written in good English. Authors are free to choose either American or British English, but should not use a mixture of both.
Abstract—The Abstract must be a self-contained, comprehensive, concise summary of the paper, limi... more Abstract—The Abstract must be a self-contained, comprehensive, concise summary of the paper, limited to 150 words and to one single paragraph. The paper should be interesting to the audience targeted by the conference organization, as spelled out in the conference scope; moreover, the paper should be comprehensive and concise, written in good English. Authors are free to choose either American or British English, but should not use a mixture of both.
Résumé Nous décrivons l'utilisation d'un éditeur de dessin fonctionnant sur SUN dans l'environnem... more Résumé Nous décrivons l'utilisation d'un éditeur de dessin fonctionnant sur SUN dans l'environnement suntools. Cet éditeur génère des fichiers pour l'éditeur de texte MTjjKsous la forme d'un environnement "picture" ou des images au format inrimage. Il permet la manipulation aisée de primitives géométriques variées (lignes, textes, rectangles, polygones, ellipses, ovales, courbes quelconques) de manière similaire au logiciel Macdraw sur Macintosh en possédant toutefois des fonctionnantes supplémentaires par rapport à celui-ci.
Résumé: Nous decrivons l'utilisation d'un editeur de dessin fonctionnant sur SUN dans l'environne... more Résumé: Nous decrivons l'utilisation d'un editeur de dessin fonctionnant sur SUN dans l'environnement suntools ou sur n'importe quelle station de travail dans l'environnement X. Cet editeur genere des fichiers au format Latex pour les textes et au format Postcript pour les dessins qui peuvent etre inclus dans un source Latex car ils sont englobes dans un environnement picture.
Although the concepts of jacobian matrix, manipulability and condition number have been floating ... more Although the concepts of jacobian matrix, manipulability and condition number have been floating around since the early beginning of robotics their real significance is not always well understood, although these conditioning indices play an important role e.g. for optimal robot design. In this paper we re-visit these concepts for parallel robots and exhibit some surprising results (at least for the author!) that show that these concepts have to be manipulated with care for a proper understanding of the kinematics behavior of a robot.
Interval analysis is a relatively new mathematical tools that allows one to deal with problems th... more Interval analysis is a relatively new mathematical tools that allows one to deal with problems that may have to be solved numerically with a computer. Examples of such problems are system solving and global optimization but numerous other problems may be addressed as well. This approach has the following general advantages: • it allows to find solutions of a problem only within some finite domain • numerical computer round-off errors are taken into account so that the solutions are guaranteed A further inherent property that is of interest for robotics problems is that this approach allows one to deal with the uncertainties that are unavoidable in robotics. Although the basic principles of interval analysis are easy to understand and to implement, this approach will be efficient only if additional methods are used and if the problem at hand is formulated appropriately. In this paper we will emphasize various robotics problems that have been solved with interval analysis, many of which are currently beyond the reach of other mathematical approaches.
Recent robotics is the result of a large historical tradition dating back from Antiquity and base... more Recent robotics is the result of a large historical tradition dating back from Antiquity and based on still older religious beliefs. We will here give some important landmarks in this tradition, starting from Antiquity, going through the Middle Age and up to the 60’s.
Although the concepts of jacobian matrix, manipulability and condition number have been floating ... more Although the concepts of jacobian matrix, manipulability and condition number have been floating around since the early beginning of robotics their real significance is not always well understood, although these conditioning indices play an important role e.g. for optimal robot design. In this paper we re-visit these concepts for parallel robots and exhibit some surprising results (at least for the author!) that show that these concepts have to be manipulated with care for a proper understanding of the kinematics behavior of a robot.
HAL (Le Centre pour la Communication Scientifique Directe), Apr 1, 2004
This paper addresses the workspace analysis of two 3-DOF translational parallel mechanisms design... more This paper addresses the workspace analysis of two 3-DOF translational parallel mechanisms designed for machining applications. The two machines features three fixed linear joints. The joint axes of the first machine are orthogonal whereas these of the second are parallel. In both cases, the mobile platform moves in the Cartesian x − y − z space with fixed orientation. The workspace analysis is conducted on the basis of prescribed kinetostatic performances. Interval analysis based methods are used to compute the dextrous workspace and the largest cube enclosed in this workspace.
This paper focuses on the problem of the initial-pose estimation by means of proprioceptive senso... more This paper focuses on the problem of the initial-pose estimation by means of proprioceptive sensors (self-calibration) of suspended under-actuated Cable-Driven Parallel Robots (CDPRs). For this class of manipulators, the initialpose estimation cannot be carried out by means of forward kinematics only, but mechanical equilibrium conditions must be considered as well. In addition, forward kinematics solution is based on cable-length measurements, but if the robot is equipped with incremental sensors cables' initial values are unknown. In this paper, the self-calibration problem is formulated as a non-linear least square optimization problem (NLLS), based on the direct geometricostatic problem, where only incremental measurements on cable lengths and on swivel pulley angles are required. In addition, a data acquisition algorithm and an initial value selection procedure for the NLLS are proposed, aiming at automatizing the self-calibration procedure. Simulations and experimental results on a 3-cable 6-degree-of-freedom robot are provided so as to prove the effectiveness of the proposed methodology.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 1, 2004
This paper addresses an interval analysis based study that is applied to the design and the compa... more This paper addresses an interval analysis based study that is applied to the design and the comparison of 3-DOF parallel kinematic machines. Two design criteria are used, (i) a regular workspace shape and, (ii) a kinetostatic performance index that needs to be as homogeneous as possible throughout the workspace. The interval analysis based method takes these two criteria into account: on the basis of prescribed kinetostatic performances, the workspace is analysed to find out the largest regular dextrous workspace enclosed in the Cartesian workspace. An algorithm describing this method is introduced. Two 3-DOF translational parallel mechanisms designed for machining applications are compared using this method. The first machine features three fixed linear joints which are mounted orthogonally and the second one features three linear joints which are mounted in parallel. In both cases, the mobile platform moves in the Cartesian x − y − z space with fixed orientation.
There’s one mechanical element that most people use every day and have been doing so for over 10,... more There’s one mechanical element that most people use every day and have been doing so for over 10,000 years. It’s cheap, easy to handle and, thanks to ongoing research, it has become even stronger and more lightweight over the millennia. This element is the cable, present versions of which have superb properties. For nearly twenty years, a community of engineering researchers has been using simple cables for sophisticated purposes, to develop and build extremely large and fast robots that open up new branches of automation.
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
This paper focuses on cable-suspended parallel robots (CSPRs), a subclass of cable-driven paralle... more This paper focuses on cable-suspended parallel robots (CSPRs), a subclass of cable-driven parallel robots, and particularly on the analysis of their workspace. CSPRs present, among other interesting characteristics, large workspaces and high reconfigurability, which make them attractive for a large variety of applications, especially for pick and place operations over wide spaces. This paper is based on the assumption that the safest (and cheapest) control scheme for a redundant CSPR consists, at the current state of development, in actuating only 6 cables at a time. This paper shows how, under this assumption, it is still possible to take advantage of redundancy to enhance the workspace and eventually reduce the maximal tension among cables. A simple interval-analysis routine is presented as a tool for the workspace and trajectory analysis of a redundant CSPR, and the results of a case study on an existing prototype are discussed.
Kinematic and Dynamic Issues in Sensor Based Control, 1990
Classical manipulators are not very convenient to perform tasks involving a high positioning accu... more Classical manipulators are not very convenient to perform tasks involving a high positioning accuracy. This is partly due to the joints and links flexibility but also to the sequential disposition of their links.
Computer Methods in Biomechanics and Biomedical Engineering, 2013
The accuracy of the Content should not be relied upon and should be independently verified with p... more The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden.
Uploads
Parallel robots papers by Jean-Pierre Merlet
surement has been studied extensively in the recent past.
Common approaches that have been used include using in-
ertial sensors, multi-camera optical and IR tracking sys-
tems, X-ray and fluoroscopy based imaging, force sensors,
magnetic sensors and bone-fixed pins for measurement.
Soft tissue artifacts (STA) are a common source of error
in most type of measurements and the standard procedure
in gait analysis has been to use a combination of measure-
ment methods for efficient estimation of joint angles and the
link poses. However, there are few studies where a multiple
number of methods have been compared and the correla-
tion between results from various approaches studied. In
this paper, we propose an outline for measurement for hu-
man joint motion using a number of sensors that can give
complete information relating to the joints.
Our proposed experiment assumes a human joint to be a
6 DOF joint between 2 links. We will mount collars on the
limbs close to anatomical landmarks, treating the actual
pose of the system with respect to the bones as unknowns.
These collars will hold markers and sensors that will be
used in the experiments. We will be using a 10 camera op-
tical (IR) tracking system, accelerometers and gyroscopes,
7 wire passive measurement system, 7 wire active measure-
ment system, in-shoe pressure pads, variable length resis-
tive wires, collar-mounted force sensors, and IR distance
sensor to measure the pose of the trunk. Our experiment
will focus on the knee joint and it’s motion during activi-
ties such as walking. This paper describes the experimental
setup and the sensor and collar calibration that has been
performed.
aids based on commercially available Rollator. We present
two models of this family: the simplest ANG-light which is
intended to be used as a diagnosis tool for walking and as a fall
detection tool and ANG-II, a motorized walker with over 20 on-
board sensors. Trajectography obtained through ANG-light
with 24 healthy subjects has been used to obtain gold standards
of walking pattern and the walker is currently being used at
Nice hospital with 30 elderly end-users in order to determine
if trajectory records obtained during the daily use of a walker
may allow doctors to objectively characterize abnormal walking
patterns, to follow the progress of a rehabilitation process
and to detect emerging pathologies. The more sophisticated
ANG-II is intended to be used as a test platform for original
functionalities, some of which will be presented.
in the rear wheel and 3D accelerometer/gyrometer. This low-
cost instrumentation allows one to determine the trajectory of
the rollator with the purpose of determining if it enables to
characterize the walking pattern of elderly people. For that
purpose an experiment has involved 30 elderly people and 24
young adults that were requested to perform two different
trajectories that are classically used for analyzing walking
abilities. It appears that the analysis of the trajectory provides
very discriminating indexes that characterize walking patterns.
A major advantage of this instrumentation is that it can be
used at all time for monitoring the state of health of elderly
people, especially at home, and may possibly detect very early
the beginning of a pathology by detecting rare events.
of this walking aid is to provide a low-cost and low-intrusivity aid for the elderly. ANG is based
on a classical 4-wheel Rollator, the two rear wheels being fixed while the two front are caster
wheels. The rear wheels have been motorized, a bistable clutching mechanism allowing to clutch
and unclutch the motors at will. ANG will provide fall prevention, navigation assistance, walking
aid and may also be used as a rehabilitation tool. We present in this paper the mechanical design
of ANG and some of the modes in which it may be used.
robots is known to be a difficult task. With rigid legs 20 years
have been required to understand the geometry of the problem,
determine the maximal number of solutions and exhibit an
example with 40 solutions. The problem is even more complex
for cable driven parallel robot (CDPR): the system of equations
that has to be solved is larger than with rigid legs as the static
equations have to be taken into account. The problem is even
more complex if we take into account the deformation of the
cables because of their elasticity and their mass. We present
for the first time a generic algorithm that allows to calculate
all the FK solutions for any CDPR and illustrate its use for a
CDPR with 8 cables.
level loop for motion control and a faster internal loop that controls the actuators. We
intend to simulate the behavior of the whole chain for a cable-driven parallel robot
(CDPR) with linear elastic cables and we will show that such a simulation cannot
be performed using classical simulation tools. We exhibit a simulation algorithm
which computes exactly the pose and cable tensions on a given trajectory. As an
example we consider a redundantly actuated robot with 8 cables. We show that the
discrete-time control has a moderate influence on the accuracy of the positioning
but a very large influence on the cable tensions.
understand what they measure, their relevance and their reliability, particularly in the context
of research at INRIA. This document was produced by a study group led by Jean-Pierre
Merlet and composed of A-M. Kermarrec, E. Faou, P. Robert and L. Segoufin. The document
was discussed during the Evaluation Committee meetings held in January and September
2007 and integrates the remarks of the committee members.