Abstract
Gait pattern generation has an important influence on the walking quality of biped robots. In most gait pattern generation methods, it is usually assumed that the torso keeps vertical during walking. It is very intuitive and simple. However, it may not be the most efficient. In this paper, we propose a gait pattern with torso pitch motion (TPM) during walking. We also present a gait pattern with torso keeping vertical (TKV) to study the effects of TPM on energy efficiency of biped robots. We define the cyclic gait of a five-link biped robot with several gait parameters. The gait parameters are determined by optimization. The optimization criterion is chosen to minimize the energy consumption per unit distance of the biped robot. Under this criterion, the optimal gait performances of TPM and TKV are compared over different step lengths and different gait periods. It is observed that (1) TPM saves more than 12% energy on average compared with TKV, and the main factor of energy-saving in TPM is the reduction of energy consumption of the swing knee in the double support phase and (2) the overall trend of torso motion is leaning forward in double support phase and leaning backward in single support phase, and the amplitude of the torso pitch motion increases as gait period or step length increases.
Highlights
Propose a gait pattern generation method for biped robots with the torso pitch motion, define the cyclic gait of a biped robot with multiple gait parameters, choose the minimum total energy consumed by the joint actuators per unit distance as the optimization objective, and determine the gait parameters by optimization; Generate the optimal gait of TPM and torso keeping vertical (TKV) for different step lengths and different gait periods and compare the energy consumption of the two gait patterns; the optimization results show that TPM is over 12% more energy-efficient than TKV; Carry out parameter study
The optimization results show that the same results are obtained by the sequential quadratic program (SQP) algorithm with different initial values obtained by the genetic algorithm
The joint angular acceleration is discontinuous when the single support phase (SSP) is switched to the double support phase (DSP) because the acceleration of the swing ankle is discontinuous at that moment
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Mu et al [15], Song et al [16], and Ghiasi et al [17] designed the gait pattern of a five-link biped robot, and Farzadpour et al [9] and Fattah et al [18] designed the gait pattern of a seven-link biped robot In their methods, the trajectories of hip and feet were defined in different ways first, joint angles were obtained by inverse kinematics. Propose a gait pattern generation method for biped robots with the torso pitch motion, define the cyclic gait of a biped robot with multiple gait parameters, choose the minimum total energy consumed by the joint actuators per unit distance as the optimization objective, and determine the gait parameters by optimization; Generate the optimal gait of TPM and TKV for different step lengths and different gait periods and compare the energy consumption of the two gait patterns; the optimization results show that TPM is over 12% more energy-efficient than TKV; Carry out parameter study.
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