Torque-limited path following by online trajectory time scaling

Dahl, Ola; Nielsen, Lars

doi:10.1109/70.62044

Cited by 182 publications

(54 citation statements)

References 6 publications

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“…While the naïve approach directly aims to reproduce the planned configuration space trajectory, several classical methods relax this by allowing for an adaptive timing [20], [21], [22]. A further step to make execution more robust is to only reproduce the plan in a select task space, which facilitates exploiting online feedback to influence the null space (e.g.…”

Section: Robust Execution Of Pre-planned Pathsmentioning

confidence: 99%

Dual execution of optimized contact interaction trajectories

Toussaint

Ratliff

Bohg

et al. 2014

2014 IEEE/RSJ International Conference on Intelligent Robots and Systems

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Abstract-Efficient manipulation requires contact to reduce uncertainty. The manipulation literature refers to this as funneling: a methodology for increasing reliability and robustness by leveraging haptic feedback and control of environmental interaction. However, there is a fundamental gap between traditional approaches to trajectory optimization and this concept of robustness by funneling: traditional trajectory optimizers do not discover force feedback strategies. From a POMDP perspective, these behaviors could be regarded as explicit observation actions planned to sufficiently reduce uncertainty thereby enabling a task. While we are sympathetic to the full POMDP view, solving full continuous-space POMDPs in high-dimensions is hard. In this paper, we propose an alternative approach in which trajectory optimization objectives are augmented with new terms that reward uncertainty reduction through contacts, explicitly promoting funneling. This augmentation shifts the responsibility of robustness toward the actual execution of the optimized trajectories. Directly tracing trajectories through configuration space would lose all robustness-dual execution achieves robustness by devising force controllers to reproduce the temporal interaction profile encoded in the dual solution of the optimization problem. This work introduces dual execution in depth and analyze its performance through robustness experiments in both simulation and on a real-world robotic platform.

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Section: Robust Execution Of Pre-planned Pathsmentioning

confidence: 99%

Dual execution of optimized contact interaction trajectories

Toussaint

Ratliff

Bohg

et al. 2014

2014 IEEE/RSJ International Conference on Intelligent Robots and Systems

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“…The walking gait consists of single support phases where the stance foot is flat on the ground separated by impacts, that is, instantaneous double support phases where leg exchange takes place. The vector q = [q 1 , q 2 , q 3 , q 4 , q 5 , q 6 ] T of configuration variables (see Fig. 1) describes the shape of the biped during single support.…”

Section: A the Bipedmentioning

confidence: 99%

“…Only tracking of the desired path is sought, and a timescaling control law as in [6] is used. A reference joint and ZMP paths q d (s) and l d (s) are assumed to be known as a function of a scalar path parameter s, which plays the role of a normalized virtual time.…”

Section: The Impact Modelmentioning

confidence: 99%

A Path-Following Approach to Stable Bipedal Walking and Zero Moment Point Regulation

Djoudi

Chevallereau

Grizzle

2007

Proceedings 2007 IEEE International Conference on Robotics and Automation

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Abstract-Consider a biped evolving in the sagittal plane. The unexpected rotation of the supporting foot can be avoided by controlling the zero moment point or ZMP. The objective of this study is to propose and analyze a control strategy for simultaneously regulating the position of the ZMP and the joints of the robot. If the tracking requirements were posed in the time domain, the problem would be underactuated in the sense that the number of inputs would be less than the number of outputs. To get around this issue, the proposed controller is based on a path-following control strategy previously developed for dealing with the underactuation present in planar robots with unactuated ankles. In particular, the control law is defined in such a way that only the kinematic evolution of the robot's state is regulated, but not its temporal evolution. The asymptotic temporal evolution of the robot is completely defined through a one degree of freedom subsystem of the closed-loop model. Simple analytical conditions, which guarantee the existence of a periodic motion and the convergence towards this motion, are deduced.

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“…On the zero dynamics manifold, the evolution ofṡ during one step can be determined by integration of the dynamic equation corresponding to the global equilibrium in rotation (8).…”

Section: Stability Studymentioning

confidence: 99%

“…Only tracking of the desired path is sought and a timescaling control law as in [8] is used. Reference paths for the joints and ZMP, q d (s) and l d (s), respectively, are assumed to be known as a function of a scalar path parameter s, which plays the role of a normalized virtual time.…”

Section: The Control Strategymentioning

confidence: 99%

Stable Bipedal Walking With Foot Rotation Through Direct Regulation of the Zero Moment Point

2008

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Abstract-Consider a biped evolving in the sagittal plane. The unexpected rotation of the supporting foot can be avoided by controlling the zero moment point or ZMP. The objective of this study is to propose and analyze a control strategy for simultaneously regulating the position of the ZMP and the joints of the robot. If the tracking requirements were posed in the time domain, the problem would be underactuated in the sense that the number of inputs would be less than the number of outputs. To get around this issue, the proposed controller is based on a pathfollowing control strategy previously developed for dealing with the underactuation present in planar robots without actuated ankles. In particular, the control law is defined in such a way that only the kinematic evolution of the robot's state is regulated, but not its temporal evolution. The asymptotic temporal evolution of the robot is completely defined through a one degree of freedom subsystem of the closed-loop model. Since the ZMP is controlled, bipedal walking that includes a prescribed rotation of the foot about the toe can also be considered. Simple analytical conditions are deduced which guarantee the existence of a periodic motion and the convergence towards this motion.

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Torque-limited path following by online trajectory time scaling

Cited by 182 publications

References 6 publications

Dual execution of optimized contact interaction trajectories

Dual execution of optimized contact interaction trajectories

A Path-Following Approach to Stable Bipedal Walking and Zero Moment Point Regulation

Stable Bipedal Walking With Foot Rotation Through Direct Regulation of the Zero Moment Point

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