Fifth International Conference on Advanced Robotics 'Robots in Unstructured Environments, 1991
Presents experimental results which are obtained by using a nonlinear control law on a two link f... more Presents experimental results which are obtained by using a nonlinear control law on a two link flexible robot. Using finite element description of the arms, the authors get a nonlinear model of the robot. The nonlinear decoupling control law uses the inverse dynamic model. This control law, which is very efficient for a rigid robot, has been adapted for flexible structures. The elastic vibrations must be damped by adding to the computed torque a complementary feedback term. This term permits one to obtain a satisfactory behaviour of the structure, but reduces the theoretical interest of the decoupling method. It is computed by linearizing the set of equations on a given point of the desired trajectory and by using a classical LOR method. The experimental results demonstrate the interest of the method and shows its sensitivity versus the position of the linearization point
Proceedings of the Fourth International Workshop on Robot Motion and Control (IEEE Cat. No.04EX891), 2004
The problems under interest are the stabilization in single support of the vertical posture and t... more The problems under interest are the stabilization in single support of the vertical posture and the walking control of a three-link biped, via controllers and nonlinear observers. The control laws are designed, for the stabilization by using a linear model and the associated Jordan form, and for the walking a decoupling input-output linearization control. The observers are necessary to reconstruct
Proceedings of the 16th IFAC World Congress, 2005, 2005
An observer-based controller is proposed for the walking of a biped without feet, i.e. an underac... more An observer-based controller is proposed for the walking of a biped without feet, i.e. an underactuated system in single support phase. The originality is both: first, the observer is based on second-order sliding mode approach and is original in biped robot context. Secondly, an existing "simplified" Poincaré's sections-based analysis of the stability of the walking is adapted to nonlinear system with not fully available state variables.
2010 10th IEEE-RAS International Conference on Humanoid Robots, 2010
Usually the bipedal robots use knee joints with only one degree of freedom. Several biomechanical... more Usually the bipedal robots use knee joints with only one degree of freedom. Several biomechanical researches have proved that the human knee joint is a complex joint with more than one degree of freedom. In the sagittal plane the human knee joint allows a rolling and a sliding of the thigh on the shin. In the case of a bipedal
This paper deals with the online decomposition of intramuscular electromyographic (iEMG) signals.... more This paper deals with the online decomposition of intramuscular electromyographic (iEMG) signals. A Markov model is proposed, which takes into account a varying number of firing motor neurons. A Bayes filter detects online the firing motor units by using a dictionary of approximated motor unit action potentials waveforms, and estimates precisely the action potential shapes and the respective firing rates. The method was tested on both simulated and experimental signals.
2008 International Workshop on Variable Structure Systems, 2008
The objective in neuromusculoskeletal simulation consists in finding a set of muscles excitations... more The objective in neuromusculoskeletal simulation consists in finding a set of muscles excitations in order to produce the desired motion and is an exciting challenge for medical operators. In this paper, muscle excitations are computed by using a second order sliding mode controller which is optimal with respect of a functional cost based on the tracking error and the torque square. The proposed strategy was tested using a two-dimensional human anthropomorphic arm composed of two joints and six muscles.
2009 9th IEEE-RAS International Conference on Humanoid Robots, 2009
Computation of contact forces is essential for the simulation of mechanical systems with unilater... more Computation of contact forces is essential for the simulation of mechanical systems with unilateral constraints, like bipedal robots. Most methods are based on the rigid body assumption. They can be categorized into constraint-based and penalty-based approaches. In the former, contact forces are computed by solving an optimization problem based on linear or nonlinear complementarity conditions. Unfortunately, these methods cannot be directly applied to articulated systems described in generalized coordinates. In the second approach, spring-damper models are used to minimize interpenetration between the surfaces in contact. The main criticism to penalty approaches are parameter tunning, static friction handling, and the difficulties to treat multiple simultaneous unilateral contacts. In this work we present a new compliant approach based on input-output feedback linearization. The main advantages of the proposed approach are, the spring-damper parameters are independent of the parameters of the system (i.e masses, inertias), no a priori-defined velocity thresholds are required to distinguish between dynamic and static friction, multiple simultaneous unilateral contacts are naturally handled. The proposition has been succesfully applied to the simulation of a 3D bipedal walking robot.
In this paper a new neuromusculoskeletal simulation strategy is proposed. It is based on a cascad... more In this paper a new neuromusculoskeletal simulation strategy is proposed. It is based on a cascade control approach with an inner muscular-force control loop and an outer joint-position control loop. The originality of the work is located in the optimization criterion used to distribute forces between synergistic and antagonistic muscles. The cost function and the inequality constraints depend on an estimation of the muscle fiber length and its time derivative. The advantages of a such criterion are exposed by theoretical analysis and numerical tests. The simulation model used in the numerical tests consists in an anthropomorphic arm model composed by two joints and six muscles. Each muscle is modeled as a second order dynamical system including activation and contraction dynamics. Contraction dynamics is represented using a classical Hill's model.
Abstract This index covers all technical items-papers, correspondence, reviews, etc.-that appeare... more Abstract This index covers all technical items-papers, correspondence, reviews, etc.-that appeared in this periodical during the year, and items from previous years that were commented upon or corrected in this year. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author's name. The primary entry includes the coauthors' names, the title of the paper or other item, and its location, specified by the ...
The motion planning and the synthesis of a tracking controller of a exible robot arm is studied i... more The motion planning and the synthesis of a tracking controller of a exible robot arm is studied in an algebraic framework using Mikusi nski's operational calculus. Experimental results are reported.
Fifth International Conference on Advanced Robotics 'Robots in Unstructured Environments, 1991
Presents experimental results which are obtained by using a nonlinear control law on a two link f... more Presents experimental results which are obtained by using a nonlinear control law on a two link flexible robot. Using finite element description of the arms, the authors get a nonlinear model of the robot. The nonlinear decoupling control law uses the inverse dynamic model. This control law, which is very efficient for a rigid robot, has been adapted for flexible structures. The elastic vibrations must be damped by adding to the computed torque a complementary feedback term. This term permits one to obtain a satisfactory behaviour of the structure, but reduces the theoretical interest of the decoupling method. It is computed by linearizing the set of equations on a given point of the desired trajectory and by using a classical LOR method. The experimental results demonstrate the interest of the method and shows its sensitivity versus the position of the linearization point
Proceedings of the Fourth International Workshop on Robot Motion and Control (IEEE Cat. No.04EX891), 2004
The problems under interest are the stabilization in single support of the vertical posture and t... more The problems under interest are the stabilization in single support of the vertical posture and the walking control of a three-link biped, via controllers and nonlinear observers. The control laws are designed, for the stabilization by using a linear model and the associated Jordan form, and for the walking a decoupling input-output linearization control. The observers are necessary to reconstruct
Proceedings of the 16th IFAC World Congress, 2005, 2005
An observer-based controller is proposed for the walking of a biped without feet, i.e. an underac... more An observer-based controller is proposed for the walking of a biped without feet, i.e. an underactuated system in single support phase. The originality is both: first, the observer is based on second-order sliding mode approach and is original in biped robot context. Secondly, an existing "simplified" Poincaré's sections-based analysis of the stability of the walking is adapted to nonlinear system with not fully available state variables.
2010 10th IEEE-RAS International Conference on Humanoid Robots, 2010
Usually the bipedal robots use knee joints with only one degree of freedom. Several biomechanical... more Usually the bipedal robots use knee joints with only one degree of freedom. Several biomechanical researches have proved that the human knee joint is a complex joint with more than one degree of freedom. In the sagittal plane the human knee joint allows a rolling and a sliding of the thigh on the shin. In the case of a bipedal
This paper deals with the online decomposition of intramuscular electromyographic (iEMG) signals.... more This paper deals with the online decomposition of intramuscular electromyographic (iEMG) signals. A Markov model is proposed, which takes into account a varying number of firing motor neurons. A Bayes filter detects online the firing motor units by using a dictionary of approximated motor unit action potentials waveforms, and estimates precisely the action potential shapes and the respective firing rates. The method was tested on both simulated and experimental signals.
2008 International Workshop on Variable Structure Systems, 2008
The objective in neuromusculoskeletal simulation consists in finding a set of muscles excitations... more The objective in neuromusculoskeletal simulation consists in finding a set of muscles excitations in order to produce the desired motion and is an exciting challenge for medical operators. In this paper, muscle excitations are computed by using a second order sliding mode controller which is optimal with respect of a functional cost based on the tracking error and the torque square. The proposed strategy was tested using a two-dimensional human anthropomorphic arm composed of two joints and six muscles.
2009 9th IEEE-RAS International Conference on Humanoid Robots, 2009
Computation of contact forces is essential for the simulation of mechanical systems with unilater... more Computation of contact forces is essential for the simulation of mechanical systems with unilateral constraints, like bipedal robots. Most methods are based on the rigid body assumption. They can be categorized into constraint-based and penalty-based approaches. In the former, contact forces are computed by solving an optimization problem based on linear or nonlinear complementarity conditions. Unfortunately, these methods cannot be directly applied to articulated systems described in generalized coordinates. In the second approach, spring-damper models are used to minimize interpenetration between the surfaces in contact. The main criticism to penalty approaches are parameter tunning, static friction handling, and the difficulties to treat multiple simultaneous unilateral contacts. In this work we present a new compliant approach based on input-output feedback linearization. The main advantages of the proposed approach are, the spring-damper parameters are independent of the parameters of the system (i.e masses, inertias), no a priori-defined velocity thresholds are required to distinguish between dynamic and static friction, multiple simultaneous unilateral contacts are naturally handled. The proposition has been succesfully applied to the simulation of a 3D bipedal walking robot.
In this paper a new neuromusculoskeletal simulation strategy is proposed. It is based on a cascad... more In this paper a new neuromusculoskeletal simulation strategy is proposed. It is based on a cascade control approach with an inner muscular-force control loop and an outer joint-position control loop. The originality of the work is located in the optimization criterion used to distribute forces between synergistic and antagonistic muscles. The cost function and the inequality constraints depend on an estimation of the muscle fiber length and its time derivative. The advantages of a such criterion are exposed by theoretical analysis and numerical tests. The simulation model used in the numerical tests consists in an anthropomorphic arm model composed by two joints and six muscles. Each muscle is modeled as a second order dynamical system including activation and contraction dynamics. Contraction dynamics is represented using a classical Hill's model.
Abstract This index covers all technical items-papers, correspondence, reviews, etc.-that appeare... more Abstract This index covers all technical items-papers, correspondence, reviews, etc.-that appeared in this periodical during the year, and items from previous years that were commented upon or corrected in this year. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author's name. The primary entry includes the coauthors' names, the title of the paper or other item, and its location, specified by the ...
The motion planning and the synthesis of a tracking controller of a exible robot arm is studied i... more The motion planning and the synthesis of a tracking controller of a exible robot arm is studied in an algebraic framework using Mikusi nski's operational calculus. Experimental results are reported.
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