Lecture Notes in Control and Information Sciences, 2001
The subject of this chapter is the motion control problem of wheeled mobile robots (WMRs). With r... more The subject of this chapter is the motion control problem of wheeled mobile robots (WMRs). With reference to the unicycle kinematics, we review and compare several control strategies for trajectory tracking and posture stabilization in an environment free of obstacles. Experiments are reported for SuperMARIO, a two-wheel differentially-driven mobile robot. From the comparison of the obtained results, guidelines are provided
2013 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2013
ABSTRACT The video illustrates on-going activities at DIAG Sapienza on physical Human-Robot Colla... more ABSTRACT The video illustrates on-going activities at DIAG Sapienza on physical Human-Robot Collaboration (pHRC), based on a control framework imposing robot behaviors that are consistent with safety and coexistence requirements.
2013 IEEE International Conference on Robotics and Automation, 2013
ABSTRACT For robots that are redundant with respect to a given task, we present an optimal differ... more ABSTRACT For robots that are redundant with respect to a given task, we present an optimal differential kinematic inversion method in the presence of hard bounds on joint range, joint velocity, and joint acceleration. These hard bounds specify the robot motion capabilities that cannot be exceeded at any time. On the other hand, scaling of the desired task trajectory is allowed whenever the robot capabilities are insufficient to execute the original task. For a problem formulated in this way, we have recently presented the Saturation in the Null Space (SNS) algorithm that produces an efficient solution, based on Jacobian pseudoinversion and recovery in the null space of the saturation effects of a reduced number of joint velocity commands. To investigate the optimality properties of the SNS algorithm, we recast the problem as a constrained quadratic programming (QP) problem, in which the joint velocity norm as well as the task scaling are to be minimized. Its solution leads to a variant of the original algorithm, the Optimal Saturation in the Null Space (Opt-SNS). The Opt-SNS guarantees an optimal solution also when the basic SNS fails to do so and improves the numerical performance over the state-of-the-art QP solver. The possible existence of discontinuous solutions for the formulated problem is avoided by the introduction of a task scaling margin. The extension to the multi-task case is also presented. Simulation results for the 7R lightweight KUKA LWR IV robot illustrate the properties and computational efficiency of the new algorithm.
2011 IEEE International Conference on Robotics and Automation, 2011
ABSTRACT We propose a novel approach for estimating the nonlinear stiffness of robot joints with ... more ABSTRACT We propose a novel approach for estimating the nonlinear stiffness of robot joints with flexible transmissions. Based on the definition of dynamic residual signals, we derive stiffness estimation methods that use only position and velocity measurements on the motor side and needs only the knowledge of the dynamic parameters of the motors. In particular, no extra force/torque sensing is needed. Two different strategies are considered, a model-based stiffness estimator and a black-box stiffness estimator. Both strategies consist of two stages. The first stage of the model-based estimator generates a residual signal that is a first-order filtered version of the flexibility torque of the transmission, while in the second stage a least squares fitting method is used to estimate the model parameters of the stiffness. The black-box estimator uses in the first stage a second-order residual that is directly a filtered version of the stiffness multi plied by the deformation rate of the transmission. In the second stage, a simple regressor provides the transmission stiffness in a singularity-robust way. Numerical results reported for the cases of constant, nonlinear, or variable stiffness transmissions demonstrate the effectiveness of the approach and the relative merits of the two estimation strategies.
2010 IEEE International Conference on Robotics and Automation, 2010
Depth and presence sensors are used to prevent collisions in environments where human/robot coexi... more Depth and presence sensors are used to prevent collisions in environments where human/robot coexistence is relevant. To address the problem of occluded areas, we extend in this paper a recently introduced efficient approach for preventing collisions using a single depth sensor to multiple depth and/or presence sensors. Their integration is systematically handled by resorting to the concept of image planes, where computations can be suitable carried out on 2D data without reconstructing obstacles in 3D. To maximize the on-line collision detection performance by multiple sensor integration, an off-line optimal sensor placement problem is formulated in a probabilistic framework, using a cell decomposition and characterizing the probability of cells being in the shadow of obstacles or unobserved. This approach allows to fit the optimal numerical solution to the most probable operating conditions of a human and a robot sharing the same working area. Three examples of optimal sensor placement are presented.
49th IEEE Conference on Decision and Control (CDC), 2010
We consider the problem of perfect cancellation of gravity effects in the dynamics of robot manip... more We consider the problem of perfect cancellation of gravity effects in the dynamics of robot manipulators having flexible transmissions at the joints. Based on the feedback equivalence principle, we aim at designing feedback control laws that let the system outputs behave as those of a desired model where gravity is absent. The cases of constant stiffness (elastic joints), nonlinear flexible,
... London Wendell Fleming, Brown University, Providence, Rhode Island Michel Fliess, CNRS-ESE, G... more ... London Wendell Fleming, Brown University, Providence, Rhode Island Michel Fliess, CNRS-ESE, Gif-sur-Yvette, France Keith Glover, University of Cambridge, England DiederichHinrichsen, University of ... Zero Dynamics in Robotic Systems ALESSANDRO DE LUCA Abstract. ...
Lecture Notes in Control and Information Sciences, 2001
The subject of this chapter is the motion control problem of wheeled mobile robots (WMRs). With r... more The subject of this chapter is the motion control problem of wheeled mobile robots (WMRs). With reference to the unicycle kinematics, we review and compare several control strategies for trajectory tracking and posture stabilization in an environment free of obstacles. Experiments are reported for SuperMARIO, a two-wheel differentially-driven mobile robot. From the comparison of the obtained results, guidelines are provided
2013 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2013
ABSTRACT The video illustrates on-going activities at DIAG Sapienza on physical Human-Robot Colla... more ABSTRACT The video illustrates on-going activities at DIAG Sapienza on physical Human-Robot Collaboration (pHRC), based on a control framework imposing robot behaviors that are consistent with safety and coexistence requirements.
2013 IEEE International Conference on Robotics and Automation, 2013
ABSTRACT For robots that are redundant with respect to a given task, we present an optimal differ... more ABSTRACT For robots that are redundant with respect to a given task, we present an optimal differential kinematic inversion method in the presence of hard bounds on joint range, joint velocity, and joint acceleration. These hard bounds specify the robot motion capabilities that cannot be exceeded at any time. On the other hand, scaling of the desired task trajectory is allowed whenever the robot capabilities are insufficient to execute the original task. For a problem formulated in this way, we have recently presented the Saturation in the Null Space (SNS) algorithm that produces an efficient solution, based on Jacobian pseudoinversion and recovery in the null space of the saturation effects of a reduced number of joint velocity commands. To investigate the optimality properties of the SNS algorithm, we recast the problem as a constrained quadratic programming (QP) problem, in which the joint velocity norm as well as the task scaling are to be minimized. Its solution leads to a variant of the original algorithm, the Optimal Saturation in the Null Space (Opt-SNS). The Opt-SNS guarantees an optimal solution also when the basic SNS fails to do so and improves the numerical performance over the state-of-the-art QP solver. The possible existence of discontinuous solutions for the formulated problem is avoided by the introduction of a task scaling margin. The extension to the multi-task case is also presented. Simulation results for the 7R lightweight KUKA LWR IV robot illustrate the properties and computational efficiency of the new algorithm.
2011 IEEE International Conference on Robotics and Automation, 2011
ABSTRACT We propose a novel approach for estimating the nonlinear stiffness of robot joints with ... more ABSTRACT We propose a novel approach for estimating the nonlinear stiffness of robot joints with flexible transmissions. Based on the definition of dynamic residual signals, we derive stiffness estimation methods that use only position and velocity measurements on the motor side and needs only the knowledge of the dynamic parameters of the motors. In particular, no extra force/torque sensing is needed. Two different strategies are considered, a model-based stiffness estimator and a black-box stiffness estimator. Both strategies consist of two stages. The first stage of the model-based estimator generates a residual signal that is a first-order filtered version of the flexibility torque of the transmission, while in the second stage a least squares fitting method is used to estimate the model parameters of the stiffness. The black-box estimator uses in the first stage a second-order residual that is directly a filtered version of the stiffness multi plied by the deformation rate of the transmission. In the second stage, a simple regressor provides the transmission stiffness in a singularity-robust way. Numerical results reported for the cases of constant, nonlinear, or variable stiffness transmissions demonstrate the effectiveness of the approach and the relative merits of the two estimation strategies.
2010 IEEE International Conference on Robotics and Automation, 2010
Depth and presence sensors are used to prevent collisions in environments where human/robot coexi... more Depth and presence sensors are used to prevent collisions in environments where human/robot coexistence is relevant. To address the problem of occluded areas, we extend in this paper a recently introduced efficient approach for preventing collisions using a single depth sensor to multiple depth and/or presence sensors. Their integration is systematically handled by resorting to the concept of image planes, where computations can be suitable carried out on 2D data without reconstructing obstacles in 3D. To maximize the on-line collision detection performance by multiple sensor integration, an off-line optimal sensor placement problem is formulated in a probabilistic framework, using a cell decomposition and characterizing the probability of cells being in the shadow of obstacles or unobserved. This approach allows to fit the optimal numerical solution to the most probable operating conditions of a human and a robot sharing the same working area. Three examples of optimal sensor placement are presented.
49th IEEE Conference on Decision and Control (CDC), 2010
We consider the problem of perfect cancellation of gravity effects in the dynamics of robot manip... more We consider the problem of perfect cancellation of gravity effects in the dynamics of robot manipulators having flexible transmissions at the joints. Based on the feedback equivalence principle, we aim at designing feedback control laws that let the system outputs behave as those of a desired model where gravity is absent. The cases of constant stiffness (elastic joints), nonlinear flexible,
... London Wendell Fleming, Brown University, Providence, Rhode Island Michel Fliess, CNRS-ESE, G... more ... London Wendell Fleming, Brown University, Providence, Rhode Island Michel Fliess, CNRS-ESE, Gif-sur-Yvette, France Keith Glover, University of Cambridge, England DiederichHinrichsen, University of ... Zero Dynamics in Robotic Systems ALESSANDRO DE LUCA Abstract. ...
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