Human-inspired multi-contact locomotion with AMBER2

Zhao, Huihua; Ma, Wen-Loong; Zeagler, Michael B.; Ames, Aaron D.

doi:10.1109/iccps.2014.6843723

Cited by 37 publications

(65 citation statements)

References 10 publications

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“…To achieve the simulation results presented, we utilizes two control methods as a point of comparison: existing hybrid zero dynamics based controllers for fully actuated robots that have proven successful on hardware [34,30,15,38], termed the "constant v" controller, and the abstraction-based controllers presented in this paper. Importantly, the simulation results are performed to both show the improved performance of the abstraction-based controller in terms of realizing the specifications enumerated in the first part of this paper.…”

Section: Simulation and Experimental Resultsmentioning

confidence: 99%

“…We begin by introducing hybrid (control) systems (also referred to as systems with impulse effects [13,14]). We consider hybrid systems with one domain because the specific biped models considered in this paper applies to flat-footed walking; for more complex foot behavior, more elaborate hybrid systems must be considered [6,12,14,15,20,38].…”

Section: Bipedal Robot Models Walking Gaits and Physical Constraintsmentioning

confidence: 99%

“…Initial results indicate that the controller based on formal methods enforces constraints better than a controller based only on regulating system outputs. The platform we consider in this paper, AMBER 3, is a successor to AMBER 2 [21,38], the platform modeled in [5]. AMBER 3 is approximately 40 % larger than AMBER 2 and its size more closely approximates an adult human.…”

Section: Introductionmentioning

confidence: 99%

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First steps toward formal controller synthesis for bipedal robots with experimental implementation

Ames

Tabuada

Jones

et al. 2017

Nonlinear Analysis: Hybrid Systems

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Bipedal robots are prime examples of complex cyber-physical systems (CPS). They exhibit many of the features that make the design and verification of CPS so difficult: hybrid dynamics, large continuous dynamics in each mode (e.g., 10 or more state variables), and nontrivial specifications involving nonlinear constraints on the state variables. In this paper, we propose a two-step approach to formally synthesize controllers for bipedal robots so as to enforce specifications by design and thereby generate physically realizable stable walking. In the first step, we design outputs and classical controllers driving these outputs to zero. The resulting controlled system evolves on a lower dimensional manifold and is described by the hybrid zero dynamics governing the remaining degrees of freedom. In the second step, we construct an abstraction of the hybrid zero dynamics that is used to synthesize a controller enforcing the desired specifications to be satisfied on the full order model. Our two step approach is a systematic way to mitigate the curse of dimensionality that hampers the applicability of formal synthesis techniques to complex CPS. Our results are illustrated with simulations showing how the synthesized controller enforces all the desired specifications and offers improved performance with respect to a classical controller. The practical relevance of the results is illustrated experimentally on the bipedal robot AMBER 3. High-level motion primitives were used on MABEL to allow walking over rough ground without tripping. While tools for automatic low-level control algorithm synthesis are well developed, at the state machine level, all tuning was done by hand for lack of appropriate tools. "Probable correctness" was established through extensive simulation and experiments.

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Section: Simulation and Experimental Resultsmentioning

confidence: 99%

Section: Bipedal Robot Models Walking Gaits and Physical Constraintsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

First steps toward formal controller synthesis for bipedal robots with experimental implementation

Ames

Tabuada

Jones

et al. 2017

Nonlinear Analysis: Hybrid Systems

Self Cite

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“…In this chapter, we therefore review the preliminaries in modeling that will set the stage for the introduction of control barrier functions in the context of robotic walking. We introduce a mathematical model of a 7-link bipedal robot AMBER2 [26,41], which is a fully actuated system because there are 6 actuators, shown in Figure 3.1. In addition, We consider the AMBER2 as a hybrid system, which contains continuous dynamics and discrete dynamics.…”

Section: Bipedal Robot Modelmentioning

confidence: 99%

Control barrier function based quadratic programs with application to bipedal robotic walking

Hsu

Ames

2015

2015 American Control Conference (ACC)

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166

121

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This thesis presents a methodology for the development of control barrier functions (CBFs) through a backstepping inspired approach. Given a set defined as the superlevel set of a function, h, the main result is a constructive means for generating control barrier functions that guarantee forward invariance of this set. In particular, if the function defining the set has relative degree n, an iterative methodology utilizing higher order derivatives of h provably results in a control barrier function that can be explicitly derived. To demonstrate these formal results, they are applied in the context of bipedal robotic walking. Physical constraints, e.g., joint limits, are represented by control barrier functions and unified with control objectives expressed through control Lyapunov functions (CLFs) via quadratic program (QP) based controllers. The end result is the generation of stable walking satisfying physical realizability constraints for a model of the bipedal robot AMBER2.

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“…Dynamic legged locomotion has been a center of attention for the past few decades [2,3,4,5,6,7]. The work in [8] pioneered robust hopping locomotion of point-foot monoped and bipedal robots using simple dynamical models but with limited applicability to semi-periodic hopping motions.…”

Section: Introductionmentioning

confidence: 99%

Robust Phase-Space Planning for Agile Legged Locomotion over Various Terrain Topologies

Zhao

Fernandez

Sentis

Robotics: Science and Systems XII

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Abstract-In this study, we present a framework for phasespace planning and control of agile bipedal locomotion while robustly tracking a set of non-periodic keyframes. By using a reduced-order model, we formulate a hybrid planning framework where the center-of-mass motion is constrained to a general surface manifold. This framework also proposes phase-space bundles to characterize robustness and a robust hybrid automaton to effectively design planning algorithms. A newly defined phasespace locomotion manifold is used as a Riemannian metric to measure the distance between the disturbed state and the planned manifold. Based on this metric, a dynamic programming based hybrid controller is introduced to produce robust locomotions. The robustness of the proposed framework is validated by using simulations of rough terrain locomotion recovery from external disturbances. Additionally, the agility of this framework is demonstrated by using simulations of the dynamic locomotion over random rough terrains.

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Human-inspired multi-contact locomotion with AMBER2

Cited by 37 publications

References 10 publications

First steps toward formal controller synthesis for bipedal robots with experimental implementation

First steps toward formal controller synthesis for bipedal robots with experimental implementation

Control barrier function based quadratic programs with application to bipedal robotic walking

Robust Phase-Space Planning for Agile Legged Locomotion over Various Terrain Topologies

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