We present velocity-based stability margins for fast bipedal walking that are sufficient conditions for stability, allow comparison between different walking algorithms, are measurable and computable, and are meaningf...
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ISBN:
(纸本)3540361189
We present velocity-based stability margins for fast bipedal walking that are sufficient conditions for stability, allow comparison between different walking algorithms, are measurable and computable, and are meaningful. While not completely necessary conditions, they axe tighter necessary conditions than several previously proposed stability margins. The stability margins we present take into consideration a biped's Center of Mass position and velocity, the reachable region of its swing leg, the time required to swing its swing leg, and the amount of internal angular momentum available for capturing balance. They predict the opportunity for the biped to place its swing leg in such a way that it can continue walking without falling down. We present methods for estimating these stability margins by using simple models of walking such as an inverted pendulum model and the Linear Inverted Pendulum model. We show that by considering the Center of Mass location with respect to the Center of Pressure on the foot, these estimates are easily computable. Finally, we show through simulation experiments on a 12 degree-of-freedom distributed-mass lower-body biped that these estimates are useful for analyzing and controlling bipedal walking.
Walking, running or jumping are special cases of articulated motions which rely heavily on contact forces for their accomplishment. This central role of the contact forces is widely recognized now, but it is rarely co...
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ISBN:
(纸本)3540361189
Walking, running or jumping are special cases of articulated motions which rely heavily on contact forces for their accomplishment. This central role of the contact forces is widely recognized now, but it is rarely connected to the structure of the dynamics of articulated motion. Indeed, this dynamics is generally considered as a complex nonlinear black-box without any specific structure, or its structure is only partly uncovered. We propose here to precise this structure and show in details how it shapes the movements that an articulated system might realize. Some propositions are made then to improve the design of control laws for walking, running, jumping or free-floating motions.
For fast motions in biomechanics and robotics, stability and robustness against perturbations are critical issues. The faster a motion the more important it is to exploit the system's natural stability properties ...
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ISBN:
(纸本)3540361189
For fast motions in biomechanics and robotics, stability and robustness against perturbations are critical issues. The faster a motion the more important it is to exploit the system's natural stability properties for control. The stability of a periodic motion can be measured in terms of the spectral radius of the monodromy matrix. We optimize this stability criterion for a given robot topology, using special purpose optimization methods and leaving the model parameters, actuator inputs, trajectory start values and cycle time free to be determined by the optimization. This approach allows us to create simulations of robots that can move stably without any feedback. In order to analyze the robustness of a resulting periodic motion, we propose two methods, the first of which relies on forward simulations using perturbed start data and parameters while the second is based on the pseudospectra of the matrix. As a new example for a fast open-loop stable motion that has been produced by stability optimization, we present a biped gymnastics robot performing repetitive flip-flops (i.e. back handsprings). A similar model has previously been shown capable of performing open-loop stable running motions and repetitive somersaults.
Dynamic walking with two-legged robots is still an unsolved problem of todays robotics research. Beside finding mathematical models for the walking process, suitable mechanical designs and control methods must be foun...
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ISBN:
(纸本)3540361189
Dynamic walking with two-legged robots is still an unsolved problem of todays robotics research. Beside finding mathematical models for the walking process, suitable mechanical designs and control methods must be found. This paper presents concepts for the latter two points. As biological walking makes use of the elastic properties of e.g. tendons and muscles, a joint design using a pneumatic rotational spring with adjustable stiffness is proposed. Equations to model the spring's dynamics as well as the supporting sensor systems and electronics are presented. For controlling the robot a behaviour-based approach is suggested.
The problem of model based signal estimation is fundamental to control theory and signal processing, and several approaches have been developed in last decades, for instance, the Kalman filter (H2 optimal filtering) [...
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作者：
Alamir, M.Boyer, F.CNRS
Lab Automat Grenoble INPG UJF F-38400 St Martin Dheres France IRCCYN
F-44321 Nantes 3 France
In this paper, a constrained nonlinear predictive control scheme is proposed for a class of under-actuated nonholonomic systems. The scheme is based on fast generation of steering trajectories that inherently fulfill ...
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ISBN:
(纸本)3540361189
In this paper, a constrained nonlinear predictive control scheme is proposed for a class of under-actuated nonholonomic systems. The scheme is based on fast generation of steering trajectories that inherently fulfill the contraints while showing a "translatability" property which is generally needed to derive stability results in receding-horizon schemes. The corresponding open-loop optimization problem can be solved very efficiently making possible a real-time implementation on fast systems (The resulting optimization problem is roughly scalar). The whole framework is shown to hold for the well known challenging problem of a snakeboard constrained stabilization. Illustrative simulations are proposed to assess the efficiency of the proposed solution under saturation constraints and model uncertainties.
This paper presents a survey of some recent results which are primarily concerned with the action of relatively simple controllers working in complex networks. Feedback system design is all about getting the right amo...
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The objective of this study is to analyze the stability of two control strategies for a planar biped robot. The unexpected rotation of the supporting foot is avoided via the control of the center of pressure or CoP. F...
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ISBN:
(纸本)3540361189
The objective of this study is to analyze the stability of two control strategies for a planar biped robot. The unexpected rotation of the supporting foot is avoided via the control of the center of pressure or CoP. For the simultaneous control of the joints and of the CoP, the system is under-actuated in the sense that the number of inputs is less than the number of outputs. Thus a control strategy developed for planar robot without actuated ankles can be used in this context. The control law is defined in such a way that only the geometric evolution of the biped configuration is controlled, but not the temporal evolution. The temporal evolution during the geometric tracking is completely defined and can be analyzed through the study of a model with one degree of freedom. Simple conditions, which guarantee the existence of a cyclic motion and the convergence toward this motion, are deduced. These results are illustrated with some simulation results. In the first control strategy, the position of the CoP is tracked precisely, in the second one, only the limits on the CoP position are used to speed-up the convergence to the cyclic motion.
Mechanical properties of complex biological systems are non-linear, e.g. the force-velocity-length relation of muscles, activation dynamics, and the geometric arrangement of antagonistic pair of muscles. The control o...
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ISBN:
(纸本)3540361189
Mechanical properties of complex biological systems are non-linear, e.g. the force-velocity-length relation of muscles, activation dynamics, and the geometric arrangement of antagonistic pair of muscles. The control of such systems is a highly demanding task. Therefore, the question arises whether these mechanical properties of a muscle-skeletal system itself are able to support or guarantee for the stability of a desired movement, indicating self-stability. Self-stability of single joint biological systems were studied based on eigenvalues of the equation of motions and the basins of attraction were analysed using Lyapunov functions. In general, we found self-stability in single muscle contractions (e.g. frog, rat, cui), in human arm and leg movements, the human spine and even in the co-ordination of complex movements such as tennis or basketball. It seems that self-stability may be a general design criterion not only for the mechanical properties of biological systems but also for motor control.
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