An Inverse Optimal Control Approach for the Transfer of Human Walking Motions in Constrained Environment to Humanoid Robots

Abstract

Abstract-In this paper we present an inverse optimal control based transfer of motions from human experiments to humanoid robots and apply it to walking in constrained environments. To this end we introduce a 3D template model, which describes motion on the basis of center of mass trajectory, foot trajectories, upper body orientation and phase duration. Despite of its abstract architecture with prismatic joints combined with damped series elastic actuators instead of knees, the model (including dynamics and constraints) is suitable to describe both, human and humanoid locomotion with appropriate parameters. We present and apply an inverse optimal control approach to identify optimality criteria based on human motion capture experiments. The identified optimal strategy is then transferred to the humanoid robot for gait generation by solving an optimal control problem, which takes into account the properties of the robot and differences in the environment. The results of this approach are the center of mass trajectory, the foot trajectories, the torso orientation, and the single and double support phase durations for a sequence of multiple steps allowing the humanoid robot to walk within a new environment. We present one computational cycle (from motion capture data to an optimized robot motion) for the example of walking over irregular step stones with the aim to transfer the motion to two very different humanoid robots (iCub Heidelberg01 and HRP-2 14). The transfer of these optimized robot motions to the real robots by means of inverse kinematics is work in progress and not part of this paper.

A novel approach for the generation of complex humanoid walking sequences based on a combination of optimal control and learning of movement primitives

“…Optimal control based studies on human and humanoid walking using a 3D template model are presented in [26,27]. Earlier works on whole body human and humanoid gait generation based on optimal control have been conducted by e.g.…”

Static and Dynamic Path Planning of Humanoids using an Advanced Regression Controller

“…Tingbin and Qisong [37] performed robot path planning using a stable and mature arti cial potential eld approach. Clever and Mombaur [38] introduced an inverse optimal control to transfer motion from humans to humanoids. They prepared a 3D template model to extract motion constraints from a human walking and used the extracted parameters in humanoid walking.…”

Bio-Inspired Optimal Control Framework to Generate Walking Motions for the Humanoid Robot iCub Using Whole Body Models

“…Optimal control has previously been used to generate challenging motions using whole-body models for robots such as HRP-2 [12][13][14][15][16][17][18]. In an approach that is situated between whole-body optimization and motion generation by reduced models, optimization of template models has been used for generating walking motion of humanoid robots in challenging scenarios [19]. Collocation has been a popular method to compute walking motions for humanoid robots using whole-body models and contact constraints, such as in [20,21], where motions could be obtained in a time in the range of minutes to hours.…”

“…These criteria can then be applied to humanoid models in optimal control problem formulations as the one presented in this paper. We have demonstrated a similar approach based on simpler template models of human and humanoid walking in [19], also for the HeiCub, but it would be new to apply this concept of transferring bio-inspired optimization criteria to whole-body models of the HeiCub robot.…”