A comparison of methods for the control of redundantly-actuated robotic systems

Abstract

Abstract. Mechanical hands, legged vehicles and cooperating manipulators are robotic systems containing closed kinematic chains which are typically driven by more actuators than required. As a result, the force distribution existing in these systems cannot be determined simply from the governing rigid-body statics or dynamics equations since these equations are underdetermined. Techniques have been proposed to overcome this obstacle -the most common being to formulate an optimization problem whose solution will be a force distribution which is optimal in a prescribed sense. A second approach which has been suggested is one in which the elasticity of the constituent bodies is considered in order to render the force-distribution problem determinate, in a manner analogous to the techniques typically used in structural mechanics to analyze hyperstatic structures. A third approach would be to deactivate certain actuators in order to reduce the number of unknowns so that the problem becomes determinate. In the present paper, these methods are compared and the first is shown to yield the best results.

Numerical synthesis of three-dimensional gait cycles by dynamics optimization

“…During the DSP, the biped locomotion system is equivalent to an overactuated 27 closed-loop mechanism (closed kinematic chain driven by more actuators than required). The loopclosure constraints and the overactuation exhibit more complicated dynamics than for kinematic trees.…”

Kinematic manipulability of general constrained rigid multibody systems

“…This problem has been noted in the walking robot literature [15], [16]. In [17], several different approaches to resolve this issue have been compared.…”

“…The force relationship is given by (17) which states that the stacked contact force is zero in the direction where the contact is unconstrained (i.e., where relative motion is allowed) and the contact forces sum at the task frame to . Solving in terms of , we have:…”

Kinematic control and posture optimization of a redundantly actuated quadruped robot

“…As shown by Nahon [49], there are several potential strategies for creating an effective objective function. The particular optimization technique used allows both linear and non-linear constraints, both through equality and inequality equations.…”

“…Only in the exact neutral position was MHT's mobility calculated to be eight, while in any other configuration, it was seven. Furthermore, MHT can be classified as redundantly actuated, where Equation (3.4) can be applied to calculate its actuation redundancy, r, as described by Nahon [49].…”