Friction is responsible for several servomechanism problems, and their elimination is always a challenge for control engineers. In this paper, feedback model-based compensation of friction is used for servomechanism set point and tracking... more
Friction is responsible for several servomechanism problems, and their elimination is always a challenge for control engineers. In this paper, feedback model-based compensation of friction is used for servomechanism set point and tracking tasks. Basic friction models are tested and their influence on system response is examined using describing function analysis. Analytical predictions are compared to simulations and experimental results. Various control laws using friction compensation are compared ...
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This paper studies the attitude dynamics and the control of quadruped robots using tail-like appendages during the flight phases of high speed locomotion. Inspiration and data are first obtained from cheetah’s fast galloping techniques. A... more
This paper studies the attitude dynamics and the control of quadruped robots using tail-like appendages during the flight phases of high speed locomotion. Inspiration and data are first obtained from cheetah’s fast galloping techniques. A two-body template is then used to simply describe the dynamics of a large body whose attitude is controlled by a rotating appendage. The equations of motion for a tail and a reaction wheel are given, while by employing cyclic coordinates, all possible reductions are performed to finally lead to the design of model-based controllers. A main contribution lies on the thorough discussion on the holonomy of the system, which only depends on the system’s geometry and the initial angular momentum. A comparison between a reaction wheel and a tail is also carried out, while basic steps and formulas are proposed for selecting the key parameters concerning the design of such systems. Finally, simulation results are presented in order to validate the methods proposed herein.
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In this work we study the attitude dynamics and the control of legged robots using tail-like appendages during the aerial phases of high speed locomotion. A free floating two-body system is used to describe the dynamics of a large body... more
In this work we study the attitude dynamics and the control of legged robots using tail-like appendages during the aerial phases of high speed locomotion. A free floating two-body system is used to describe the dynamics of a large body controlling its attitude using a rotating appendage. The equations of motion for a tail and a reaction wheel are given, and the meaning of the generalized coordinates being ignorable or palpable is discussed in detail. A thorough discussion on the holonomy of the system is also included. Analytical expressions are given for a further reduced dynamical model and model-based controllers are then proposed. Finally, we present a series of simulation results, and we derive conclusions that can serve as guidelines when designing such systems.
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UK PubMed Central (UKPMC) is an archive of life sciences journal literature.
ABSTRACT Higher-order layerwise piezoelectric laminate mechanics are presented for predicting the low-velocity impact response of pristine composite and sandwich composite plates with piezoelectric transducers. The present formulation... more
ABSTRACT Higher-order layerwise piezoelectric laminate mechanics are presented for predicting the low-velocity impact response of pristine composite and sandwich composite plates with piezoelectric transducers. The present formulation enables prediction of the global (temporal variation of impact force, deflection, strain and sensory potential) and local through-thickness (distribution of displacement, stress and strain) impact response of plates with piezoelectric layers or patches. Its enhanced capabilities include efficiency in terms of computational cost, since the system matrices are reduced by means of a Guyan scheme or by using the eigenvectors, thus leading to a plate-impactor system containing a single or two deflection amplitudes per vibration mode, depending on consideration of transverse compressibility. The transfer of the plate-impactor system to state-space enables investigation of the feasibility of real-time active control towards impact force reduction by using output feedback control laws.
The Multiple Impedance Control (MIC) is anew algorithm which enforces a designated impedance onboth a manipulated object, and all cooperating manipulators. In this paper, the MIC is applied to a space roboticsystem in which robotic arms,... more
The Multiple Impedance Control (MIC) is anew algorithm which enforces a designated impedance onboth a manipulated object, and all cooperating manipulators. In this paper, the MIC is applied to a space roboticsystem in which robotic arms, mounted on a free-flyingbase, manipulate an object. The general formulation of theMIC is extended to include the dynamic coupling betweenthe arms and the base. It is shown that under the MIC law, all participating manipulators, the free-flyer base, and themanipulated object exhibit the same ...
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This paper focuses on the modeling, parameter estimation, andmodel validation in open and closed-loop of an experimentalforestry machine manipulator. Symbolic Newton-Euler and lineargraph methodologies are used in deriving mathematical... more
This paper focuses on the modeling, parameter estimation, andmodel validation in open and closed-loop of an experimentalforestry machine manipulator. Symbolic Newton-Euler and lineargraph methodologies are used in deriving mathematical models ofthe swing, boom and stick subsystems. Actuation dynamics areintegrated with manipulator dynamics to result in a completemanipulator and actuation model. Identification proceduresemployed in estimating physical parameters are discussed. Modelvalidation studies show good ...
Mobile manipulator systems, comprised of a mobile platformwith one or more manipulators, are of great interest in a numberof applications. This paper presents a planning and controlmethodology for such systems allowing them to... more
Mobile manipulator systems, comprised of a mobile platformwith one or more manipulators, are of great interest in a numberof applications. This paper presents a planning and controlmethodology for such systems allowing them to followsimultaneously desired end-effector and platform trajectorieswithout violating the nonholonomic constraints. Based on areduction of system dynamics, a model-based controller i sdesigned to eliminate tracking errors without requiring largegains. The sensitivity to parameter errors is examined ...
The Multiple Impedance Control (MIC) is anew algorithm which enforces a designated impedance onboth a manipulated object, and all cooperating manipulators. In this paper, the MIC is applied to a space roboticsystem in which robotic arms,... more
The Multiple Impedance Control (MIC) is anew algorithm which enforces a designated impedance onboth a manipulated object, and all cooperating manipulators. In this paper, the MIC is applied to a space roboticsystem in which robotic arms, mounted on a free-flyingbase, manipulate an object. The general formulation of theMIC is extended to include the dynamic coupling betweenthe arms and the base. It is shown that under the MIC law, all participating manipulators, the free-flyer base, and themanipulated object exhibit the same ...
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UK PubMed Central (UKPMC) is an archive of life sciences journal literature.
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Mobile manipulators operating in field environmentsare susceptible to dangerous and costly rollover ortipover instabilities, particularly when operating overuneven terrain or when exerting large forces or moments. By monitoring the static... more
Mobile manipulators operating in field environmentsare susceptible to dangerous and costly rollover ortipover instabilities, particularly when operating overuneven terrain or when exerting large forces or moments. By monitoring the static and dynamic tipoverstability margins of a mobile manipulator it is possibleto predict such tipovers and take appropriate actionsto prevent the tipover from occurring. This paperdescribes a scheme for automatic tipover prediction, and prevention, which uses the static and dynamicForce--Angle ...
ABSTRACT
Coupled higher-order layerwise piezoelectric laminate mechanics are presented, applicable to shallow cylindrical composite and sandwich shells subjected to static mechanical loads and/or electric voltages. The current formulation enables... more
Coupled higher-order layerwise piezoelectric laminate mechanics are presented, applicable to shallow cylindrical composite and sandwich shells subjected to static mechanical loads and/or electric voltages. The current formulation enables efficient prediction of (i) global electromechanical response, (ii) local through-thickness distribution of electromechanical variables and (iii) interlaminar shear stress at the interface between adjacent material layers. Using the developed mechanics, the effects of curvature, thickness and ply angle on the global and local through-thickness response of sandwich composite shells are studied.
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ABSTRACT An efficient model reduction based methodology is presented for predicting the global (impact force, plate deflection and electric potential) and through-thickness local (interfacial strains and stresses) dynamic response of... more
ABSTRACT An efficient model reduction based methodology is presented for predicting the global (impact force, plate deflection and electric potential) and through-thickness local (interfacial strains and stresses) dynamic response of pristine simply-supported cross-ply composite and sandwich composite plates with piezoelectric sensory layers subjected to low-energy impact. The through-thickness response of the laminate is modelled using coupled higher-order layerwise displacement-based piezoelectric laminate theories. Linearized contact laws are implemented for simulating the impactor–target interaction during impact. The stiffness, mass, piezoelectric and permittivity matrices of the plate are formulated from ply to structural level and reduced by applying a Guyan reduction technique to yield the structural system in state space. This reduction technique enables the formulation of a plate–impactor structural system of minimum size (1 term per vibration mode for composite plates – 2 terms for sandwich plates) and reduces computational cost, thus facilitating applicability for real-time impact and vibration control.
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ABSTRACT A global-local methodology is presented for predicting the response of sandwich composite plates with piezoelectric transducers to low-velocity impact. Model reduction techniques have been employed in order to build a... more
ABSTRACT A global-local methodology is presented for predicting the response of sandwich composite plates with piezoelectric transducers to low-velocity impact. Model reduction techniques have been employed in order to build a computationally efficient plate-impactor structural system, solution of which yields the global plate’s response. Higher-order layerwise kinematic assumptions enable estimation of the stress distribution locally through the thickness of the laminate and prediction of stress at the interface between different materials. Using the developed method, impact identification studies have been conducted in order to estimate impact location and impactor mass and velocity, and to reconstruct the impact event, including impact force history, posteriori. In order to validate the developed methodology, a low-cost portable experimental configuration for impact testing has been designed and impact measurements were compared to the predictions.
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UK PubMed Central (UKPMC) is an archive of life sciences journal literature.
ABSTRACT An autonomous dynamic positioning scheme for a novel triangular floating marine platform is developed, that stabilizes its linear and angular velocities as well as its position and orientation. For this platform, the required... more
ABSTRACT An autonomous dynamic positioning scheme for a novel triangular floating marine platform is developed, that stabilizes its linear and angular velocities as well as its position and orientation. For this platform, the required closed-loop forces and moments are provided by three rotating pump-jets, located at the bottom of three partly submerged cylinders, located at the corners of the platform. With this control configuration, the platform is over-actuated, i.e., it has more control inputs than degrees of freedom (DOF). Design guidelines leading to balanced actuator loading are identified. A control allocation scheme is developed that allows for station keeping under realistic constraints, disturbances and hardware limitations, without violating thruster dynamics. Furthermore, a model-based controller is proposed that aims at the reduction of fuel consumption. Simulation results, in the presence of realistic environmental disturbances, are presented that demonstrate the performance of the controller and of the allocation scheme developed. Preliminary Hardware-In-the-Loop (HIL) real time experiments are conducted and presented, showing effective platform station keeping.
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ABSTRACT In this paper we consider the dynamic modeling and the speed control of vibration micro-motors, under power and sensor hardware constraints due to the centimeter-scale dimensions of the motors. The micro-motors are attached on a... more
ABSTRACT In this paper we consider the dynamic modeling and the speed control of vibration micro-motors, under power and sensor hardware constraints due to the centimeter-scale dimensions of the motors. The micro-motors are attached on a centrifugal-force micro-robotic mobile platform. The dynamic model of the low cost motor is presented, and discussed. The experimental procedure for the motors' parameter identification is presented, and the design of a model-based controller aiming at the control of the speed of the motors is analyzed. In addition, the practical implementation of the designed controller is discussed and experimentally evaluated. In order to measure the rotational speed of each centimeter-scale vibration motor, a rotary encoder with one count per revolution is designed and constructed. Despite this sensor hardware limitation, the experimental results indicate that the micro-motors were successfully modeled, and that the proposed controller results in the minimization of the steady-state error and in an increase of the motors' bandwidth by a factor of three. Additional experiments showed that the application of the model-based speed controller results in a motion of the micro-robotic platform of higher precision.
Abstract Canada is one of the world's leading forestry nations, and luckily there are still some Canadian world class forestry equipment manufacturers. This is all the more important since new technology in the... more
Abstract Canada is one of the world's leading forestry nations, and luckily there are still some Canadian world class forestry equipment manufacturers. This is all the more important since new technology in the resource industries is most easily introduced by equipment manufacturers, not end-users. The four-year, 2.2 M $ ATREF project is one large-scale attempt in Canada to address this issue, by bringing together key players within the province of Quebec: Denharco, one of Canada's leading forestry equipment manufacturers, Autolog ...
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ABSTRACT Coupled higher-order layerwise piezoelectric laminate mechanics are presented, applicable to composite and sandwich composite plates subjected to static mechanical loads and/or electric voltages. In the development of these... more
ABSTRACT Coupled higher-order layerwise piezoelectric laminate mechanics are presented, applicable to composite and sandwich composite plates subjected to static mechanical loads and/or electric voltages. In the development of these formulations through-thickness compressibility is either considered (3-D) or neglected (2-D). Their advantage compared to linear layerwise theories lies in the efficient prediction of the local through-thickness response by using a gross through-thickness discretization, while retaining simplicity in through-thickness kinematic assumptions. Moreover, they enable prediction of interlaminar shear and transverse normal stress at the interface between discrete layers, which is crucial information for prediction of delamination initiation. Using the developed mechanics, the effects of transverse compressibility and ply angle on the local through-thickness response of composite and sandwich plates are studied.
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Στην εργασία αυτή μελετάται η σχεδιαστική αναβάθμιση Διαστημικών Ρομποτικών Οχημάτων (ΔΡΟ – rover) για εξερεύνηση πλανητών, μέσω της εισαγωγής επίγειων Μίκρο - Νάνο Τεχνολογιών (Μicro-Nano Technologies ή MNT) στα υποσυστήματά τους. Στόχος... more
Στην εργασία αυτή μελετάται η σχεδιαστική αναβάθμιση Διαστημικών Ρομποτικών Οχημάτων (ΔΡΟ – rover) για εξερεύνηση πλανητών, μέσω της εισαγωγής επίγειων Μίκρο - Νάνο Τεχνολογιών (Μicro-Nano Technologies ή MNT) στα υποσυστήματά τους. Στόχος είναι η μείωση του όγκου, της μάζας και των απαιτήσεων ισχύος τους, με παράλληλη βελτίωση των λειτουργιών τους. Η εισαγωγή ΜΝΤ στο σχεδιασμό ΔΡΟ γίνεται με βάση ανάλυση η οποία υποδεικνύει τις προβληματικές περιοχές ανά υποσύστημα. Οι προτεινόμενες αντικαταστάσεις ανά υποσύστημα και οι κύριες αλλαγές στο σχεδιασμό, οδηγούν σε κατευθυντήριες γραμμές για το σχεδιασμό μελλοντικών ΔΡΟ.
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Research Interests:
ABSTRACT This work addresses the optimal selection of propulsion components for a multi-rotor aerial vehicle (MRAV), for a given payload, payload capacity, number of rotors and flight duration. A steady state model is developed for... more
ABSTRACT This work addresses the optimal selection of propulsion components for a multi-rotor aerial vehicle (MRAV), for a given payload, payload capacity, number of rotors and flight duration. A steady state model is developed for motors, propellers, electronic speed controllers (ESC), and batteries, using a simplified analysis. Based on technical specifications of batteries, motors and ESCs, component functional parameters are expressed as a function of an equivalent length. Propeller models are developed using experimental data. An optimization program is developed, which calculates the optimal design vector, employing as objective function the energy consumption or the vehicle diameter. Using this program, the influence of the payload and of the number of rotors on the design vector and the MRAV size is studied. The results obtained by the program were compared successfully to existing commercial MRAVs.
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Résumé/Abstract In a number of industrial, space, or mobile applications, reaction forces and moments transmitted by a manipulator to its base are undesirable. In this paper, we analyze the problem offorce and torque transmission in... more
Résumé/Abstract In a number of industrial, space, or mobile applications, reaction forces and moments transmitted by a manipulator to its base are undesirable. In this paper, we analyze the problem offorce and torque transmission in robotic systems, and propose design and planning methods that can eliminate it, or reduce it. Based on force and moment transmission analysis, a three DOF redundant manipulator design is selected. Dynamic reaction forces are eliminated by force balancing. Reaction moments are eliminated by ...
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Research Interests:
Space debris removal and mitigation using space robots are complex missions, which require extensive analysis prior to launch. An important aspect during such a mission is the capturing task; any unsuccessful attempt may create more... more
Space debris removal and mitigation using space robots are complex missions, which require extensive analysis prior to launch. An important aspect during such a mission is the capturing task; any unsuccessful attempt may create more problems than solve. In this paper, the modelling of the impact docking between two multibody systems is studied. The effects of mass ratios on the resulting changes of relative velocities are analysed and discussed. An extension of the rigid body impact theory to multibody systems is developed, where the effect of system mass ratios to the change of the relative velocities is quantified, and its significance is discussed. Velocity requirements leading to a successful latching at first impact will be identified. Simulation results are presented that validate the proposed analytical approach. Future work is discussed.
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Recent successes of missions such as the MSL and the Rosetta have increased the interest in the robotic exploration of other planets and asteroids. Although most of these missions envisage the use of rovers, legged robots have shown the... more
Recent successes of missions such as the MSL and the Rosetta have increased the interest in the robotic exploration of other planets and asteroids. Although most of these missions envisage the use of rovers, legged robots have shown the potential to outperform wheeled vehicles on rough terrains in terms of speed and energy efficiency. In this paper, the x-MP controller presented in recent work, is used to evaluate the performance of a monopod robot under the effect of different gravitational fields and terrain types. The performance of the x-MP controller during regulating the robot motion on rough terrains and for the exploration of different types of planetary environments will be examined using simulations. Additionally using the Cost of Transport index, useful conclusions regarding the performance of legged robots for planetary exploration will be extracted.
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To validate on-orbit servicing strategies, extensive sim- ulations and terrestrial emulation of robotic systems are necessary. The NTUA has developed a Space Robot Emulator to emulate the operation of free-flying robotic servicers, as... more
To validate on-orbit servicing strategies, extensive sim- ulations and terrestrial emulation of robotic systems are necessary. The NTUA has developed a Space Robot Emulator to emulate the operation of free-flying robotic servicers, as already presented in previous works. Until recently, the emulator consisted of one robot with two manipulators, capable of hovering over a flat granite ta- ble using air bearings, and of planar motion employing CO2 thrusters and a reaction wheel. To extend the capa- bilities of the Emulator, a second robot was developed with similar operational and design principles. In this paper, the mechatronic design of the robotic systems is presented. The limitations of the first robot and the de- velopments to overcome them in the second as well as some preliminary validation tests are presented.
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On-Orbit Servicing plays a key role in the exploitation of space. To study related issues, the NTUA has devel- oped a Space Robot Emulator for free-flying robotic servicers. In this emulator, the fusion of data from an overhead camera and... more
On-Orbit Servicing plays a key role in the exploitation of space. To study related issues, the NTUA has devel- oped a Space Robot Emulator for free-flying robotic servicers. In this emulator, the fusion of data from an overhead camera and on-board optical sensors is partic- ularly challenging. This becomes more complex due to the large time delay induced by the camera and image processing. To cope with these challenges, a Discrete Extended Kalman Filter (DEKF) is developed and ana- lyzed. Methods for reducing camera distortion errors and for calibration are discussed and simulation results are presented. Experiments validating the developed methodology are included.
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In this paper, the development of an Orbital Robotics educational prototype platform is presented, consisting of a hardware-developed physical system and an accompanying set of curriculum-based lessons (IB Physics curriculum) that target... more
In this paper, the development of an Orbital Robotics educational prototype platform is presented, consisting of a hardware-developed physical system and an accompanying set of curriculum-based lessons (IB Physics curriculum) that target upper secondary students (16-18 years old target group). The students interactively use the hardware , consisting of a bespoke space-emulating table and small satellite mockups. During the lessons, this platform allows students to acquire knowledge of the dynamics of space systems, as well as the environmental conditions and physical constraints that characterize on-orbit operations. Students will be able to manipulate the space robot (satellite) mockups performing basic tasks such as docking, and landing or grasping space debris. Additionally, a smartphone application has been implemented to allow the interaction with the platform, via a dedicated User Interface (UI). The lessons are inquiry-based and are structured so that the students are actively engaged in the learning process, according to a learner-centric approach.
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Highlights Consideration of the effects of permanent ground deformation and compaction. Development of a controller immune to terrain compliance. No knowledge requirement of ground parameters. Successful tackle of foot slip effects and... more
Highlights Consideration of the effects of permanent ground deformation and compaction. Development of a controller immune to terrain compliance. No knowledge requirement of ground parameters. Successful tackle of foot slip effects and hard impacts during touchdown. The methodology can be extended to other legged robots such as quadrupeds. Abstract One of the most intriguing research challenges in legged locomotion is robot performance on compliant terrains. The foot-terrain interaction is usually tackled by disregarding some of the effects of ground deformation, like permanent deformation and compaction; however this approach restricts their application to stiff environments. In this work, the foot-terrain interaction is studied, and used in developing a controller immune to terrain compliance. An impact dynamics model is developed, employing a viscoplastic extension a b b
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Development and prototyping of robotic systems requires the involvement of many people and many hours of design, development and cooperation; significant time and effort overhead is required for evaluating conceptual ideas in design,... more
Development and prototyping of robotic systems requires the involvement of many people and many hours of design, development and cooperation; significant time and effort overhead is required for evaluating conceptual ideas in design, control and technology, and for bringing them fast into reality for testing. Based on the important advances of the last decade in hardware and software, a simple and low cost framework and its underlying ideas are presented, with steps that aim at accelerating robotics research work in academia and industry. The framework’s functionality is validated and illustrated by two application examples concerning the control systems of a single- legged hopping robot and an instrumented treadmill. The software required to conduct the same experiments is provided, with the intention to help the reader reuse it in similar applications.
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In this paper, the development of an Orbital Robotics educational prototype platform is presented, consisting of a hardware-developed physical system and an accompanying set of curriculum-based lessons (IB Physics curriculum) that target... more
In this paper, the development of an Orbital Robotics educational prototype platform is presented, consisting of a hardware-developed physical system and an accompanying set of curriculum-based lessons (IB Physics curriculum) that target upper secondary students (16–18 years old target group). The platform was the outcome of a joint project between the European Space Agency and the National Technical University of Athens. The students use the hardware interactively, consisting of a bespoke space-emulating table and small satellite mockups. The lessons are inquiry-based and are structured so that the students are actively engaged in the learning process, according to a learner-centric approach. During the lessons, this platform allows students to acquire knowledge of the dynamics of space systems, as well as of the environmental conditions and physical constraints that characterize on-orbit operations. Students are able to manipulate the space robot (satellite) mockups performing basic tasks such as docking and landing, or grasping space debris. Additionally, a smartphone application has been implemented to allow the interaction with the platform, via a dedicated User Interface (UI).
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Space is an exciting but fundamentally unfriendly environment for mankind. Space robotic systems (robots in orbit, planetary rovers or even satellites) are of great importance to space exploration and perform hazardous or impossible for... more
Space is an exciting but fundamentally unfriendly environment for mankind. Space robotic systems (robots in orbit, planetary rovers or even satellites) are of great importance to space exploration and perform hazardous or impossible for humans tasks. Using micro/nano technologies in space robotic systems results ei- ther in miniaturized systems in terms of volume and mass, while retaining or in- creasing their capabilities, or in space robots with increased capabilities while re- taining their size due to the nature of their tasks. Examples of miniaturization possibilities for space robots and satellites are given, focusing on the challenges and the enabling technologies. The miniaturization process and the use of ad- vanced micro/technologies in space will have a large beneficial impact in the years to come.
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One of the most demanding tasks for a robotic servicer is capturing a target. During this task, the mechanical systems can be subject to large forces for short duration (impacts). In space servicers, these impacts may render the capturing... more
One of the most demanding tasks for a robotic servicer is capturing a target. During this task, the mechanical systems can be subject to large forces for short duration (impacts). In space servicers, these impacts may render the capturing of a target impossible without the use of undesirable fuel-consuming maneuvers. This paper presents an approach for minimizing impact reactions, using the Center of Percussion (CoP), a characteristic of rigid bodies rotating around an axis. This work generalizes and delineates the exact requirements for its use. Application of CoP in multibody systems is demonstrated using the Newton-Euler Algorithm. Implementation guidelines are discussed. Simulations of a planar space robot system, and a three-dimensional PUMA-like manipulator on a satellite base confirm the benefit of using the CoP during tasks that include impacts.
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As part of its Education Programme, the European Space Agency (ESA) is taking several steps towards the devel- opment of Educational activities and platforms that use Space Robotics as a mean to support and reinforce STEM (Science,... more
As part of its Education Programme, the European Space Agency (ESA) is taking several steps towards the devel- opment of Educational activities and platforms that use Space Robotics as a mean to support and reinforce STEM (Science, Technology, Engineering and Mathematics) school education in Europe. In this paper the on-going development of an Orbital Robotics educational prototype platform is presented, consisting of a hardware-developed physical platform and an accompanying set of curriculum-based lessons (IB Physics curriculum) that target upper secondary students (16-18 y/o target group). The hardware, a friction-less air-hockey table (physical platform) engineered for this purpose, will be used by students to interac- tively acquire the necessary experience of the dynamics of space systems, as the environmental conditions and physical constraints that are characteristic of on-orbit systems are emulated. The stu- dents will be able to manipulate space robot (satellite) mockups performing basic tasks such as docking, landing and grasping space debris. Additionally, a smartphone application has been implemented to allow the interaction with the platform, via a dedicated User Interface (UI). The lessons are inquiry-based and are structured so that the students are actively engaged in the learning process according to a learner centered approach. The project is jointly undertaken by the ESA Education Office and the ESA Automation and Robotics Section, with the support of the Control Systems Laboratory of the National Technical University of Athens. The development is taking place at the facilities of the Automation and Robotics Laboratory (ARL) of ESTEC, ESA’s European Space Research and Technology Centre in the Netherlands.
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Terrain compliance is a critical parameter for the performance of legged locomotion. In this work, a single actuator monopod robot hopping on a rough compliant terrain is considered. Based on our controller for flat compliant terrains,... more
Terrain compliance is a critical parameter for the performance of legged locomotion. In this work, a single actuator monopod robot hopping on a rough compliant terrain is considered. Based on our controller for flat compliant terrains, this paper introduces the necessary modifications, which allow the robot to tackle the disturbance of small inclinations. Using the developed method, the robot is examined on its performance to traverse rough terrains, while maintaining the goals of reaching a desired height and forward velocity. As the increased compliance and inclination alter the energy requirements from the controller actuator, the Cost of Transport index for a number of scenarios is studied. The correlation between terrain parameters and the CoT is presented, and useful conclusions, which can aid the understanding of the behavior of legged robots in realistic terrains are extracted.
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Legged locomotion is a rapidly advancing area in robotics, yet still a large number of open questions exist. This work focuses on the foot-terrain interaction and its effect on the motion of a one-legged system. This interaction is... more
Legged locomotion is a rapidly advancing area in robotics, yet still a large number of open questions exist. This work focuses on the foot-terrain interaction and its effect on the motion of a one-legged system. This interaction is usually tackled by disregarding some of the effects of ground deformation like permanent deformation and compaction. Inspired by other areas of engineering, an impact dynamics model is developed, allowing a more thorough study of the behavior during fast dynamic walking. This approach can be regarded as a viscoplastic one. The monopod controller presented in previous work is extended to cope with deformable terrains, based on energy dissipation considerations, without requiring the knowledge of the ground parameters. Simulation results prove the validity of the theory presented.