Compass-gait Biped Research Articles

Modeling, Analysis and Control of the Compass Gait Biped Robot and Extensions: A Review

Abstract This paper gives a review of recent results in the field of modeling and control of hybrid walking systems with a particular focus on the Compass Gait model. Since dynamic models of biped robots are hybrid in nature, the paper presents an overview of modeling the continuous and discrete dynamics of a hybrid system representing a walking robot. The paper briefly describes the design evolution in underactuated bipedal robots and presents several prominent prototypes, explains a number of related concepts and lists a variety of suitable control techniques.

Modeling and Control of Torso Compass Gait Biped Robot with AI Controller

Modeling and Control of Torso Compass Gait Biped Robot with AI Controller

Modeling and Control of Torso Compass Gait Biped Robot with AI Controller

This work presents the mathematical model for a torso compass gait biped robot with three degrees of freedom (DOF) which is comprised of two legs and torso. Euler Lagrange method's is used to drive the dynamic equation of robot with computed control is used as a controller. The relative angles are used to simplify the robot equation and get the symmetry of the matrix. Convention controller uses critical sampling to find the value of KP and Kv in computed controller, in this paper the Genetic optimization method is used to find the optimal value of KP and Kv with suitable objective function which employ the error and overshoot to make the biped motion smooth as possible. To investigate the work of robot a Matlab 2013b is used and the result show success of modeling.

Minimal feedback to a rhythm generator improves the robustness to slope variations of a compass biped

In recent years there has been a growing interest in the field of dynamic walking and bio-inspired robots. However, while walking and running on a flat surface have been studied extensively, walking dynamically over terrains with varying slope remains a challenge. Previously we developed an open loop controller based on a central pattern generator (CPG). The controller applied predefined torque patterns to a compass-gait biped, and achieved stable gaits over a limited range of slopes. In this work, this range is greatly extended by applying a once per cycle feedback to the CPG controller. The terrain’s slope is measured and used to modify both the CPG frequency and the torque amplitude once per step. A multi-objective optimization algorithm was used to tune the controller parameters for a simulated CB model. The resulting controller successfully traverses terrains with slopes ranging from +7° to −8°, comparable to most slopes found in human constructed environments. Gait stability was verified by computing the linearized Poincaré Map both numerically and analytically.

Switched Control for the Walking of a Compass Gait Biped Robot

This study presents a new approach for modeling and controlling of a compass gait biped robot based on the use of the switched systems. The linearization of the equations stemming from the formalism of Lagrange allows the construction of a set of local models used to describe the behavior of this non linear system. The selection of each model depends on its activation function depending on the system states. The synthesis of the stability of the walking robot is based on the use of second method of Lyapunov. The synthesis approach leads to a set of bilinear matrices inequalities non resolvable by actual numerical solvers. To come over these difficulties, some relaxations are brought to get useful and exploitable numerical solutions.

Control and Planning of 3-D Dynamic Walking With Asymptotically Stable Gait Primitives

In this paper, we present a hierarchical framework that enables motion planning for asymptotically stable 3-D bipedal walking in the same way that planning is already possible for zero moment point walking. This framework is based on the construction of asymptotically stable gait primitives for a class of hybrid dynamical systems with impacts. Each primitive corresponds to an asymptotically stable hybrid limit cycle that admits rules a priori for sequential composition with other primitives, reducing a high-dimensional feedback motion planning problem into a low-dimensional discrete tree search. As a constructive example, we develop this planning framework for the 3-D compass-gait biped, where each primitive corresponds to walking along an arc of constant curvature for a fixed number of steps. We apply a discrete search algorithm to plan a sequence of these primitives, taking the 3-D biped stably from start to goal in workspaces with obstacles. We finally show how this framework generalizes to more complex models by planning walking paths for an underactuated five-link biped.

On the Mechanics of Functional Asymmetry in Bipedal Walking

This paper uses two symmetrical models, the passive compass-gait biped and a five-link 3-D biped, to computationally investigate the cause and function of gait asymmetry. We show that for a range of slope angles during passive 2-D walking and mass distributions during controlled 3-D walking, these models have asymmetric walking patterns between the left and right legs due to the phenomenon of spontaneous symmetry-breaking. In both cases a stable asymmetric family of gaits emerges from a symmetric family of gaits as the total energy increases (e.g., fast speeds). The ground reaction forces of each leg reflect different roles, roughly corresponding to support, propulsion, and motion control as proposed by the hypothesis of functional asymmetry in able-bodied human walking. These results suggest that body mechanics, independent of neurophysiological mechanisms such as leg dominance, may contribute to able-bodied gait asymmetry.

Analysis of limit-cycle walking for a compass-like biped robot

We consider an impulsive mechanical system modeling dynamics of a planar two-link walker commonly known as a compass-gait biped. It is assumed that there is actuation in the hip but that the desired periodic trajectory describes an unstable passive walking gait. We recall and apply a recently developed technique for design of orbitally stabilizing feedback controllers. After that, we illustrate how to assess various properties of the closed-loop system. In particular, sensitivity to perturbations of the slope of the walking surface is analyzed and an estimate for possible deviations from the nominal trajectory is computed analytically.

PORT-BASED CONTROL OF A COMPASS-GAIT BIPEDAL ROBOT

We examine the control problem of curve-tracking for fully-actuated mechanical systems, applied to walking robots. First, we discuss earlier results on curve-tracking using a change of coordinates to split the kinetic energy in a desired and an undesired part. Then, we apply and extend these results to the case of a compass-gait biped, and show in a simulation how its robustness against surface height variations can be increased.

Passivity based control of the compass gait biped

In this paper we discuss the passivity based control of the two-link robot known as the Compass Gait Biped. Starting from a narrow region of initial conditions, the compass gait biped is capable of locomotion down shallow inclines without actuation or feedback control of any kind. We will discuss some feedback control strategies that can exploit these passive dynamics by shaping the energy of the system. Using potential energy shaping we can make the passive limit cycle slope invariant. We also discuss the use of switching control to address the sensitivity to initial conditions and robustness to disturbances.