Abstract
Although previous research has improved the energy efficiency of humanoid robots to increase mobility, no study has considered the offset between hip joints to this end. Here, we optimized the offsets of hip joints in humanoid robots via the Taguchi method to maximize energy efficiency. During optimization, the offsets between hip joints were selected as control factors, and the sum of the root-mean-square power consumption from three actuated hip joints was set as the objective function. We analyzed the power consumption of a humanoid robot model implemented in physics simulation software. As the Taguchi method was originally devised for robust optimization, we selected turning, forward, backward, and sideways walking motions as noise factors. Through two optimization stages, we obtained near-optimal results for the humanoid hip joint offsets. We validated the results by comparing the root-mean-square (RMS) power consumption of the original and optimized humanoid models, finding that the RMS power consumption was reduced by more than 25% in the target motions. We explored the reason for the reduction of power consumption through bio-inspired analysis from human gait mechanics. As the distance between the left and right hip joints in the frontal plane became narrower, the amplitude of the sway motion of the upper body was reduced. We found that the reduced sway motion of the upper body of the optimized joint configuration was effective in improving energy efficiency, similar to the influence of the pathway of the body’s center of gravity (COG) on human walking efficiency.
Highlights
As quality of life improves, the demand for humanoid robots to help or replace humans in various activities is increasing
Tsagarakis et al [4] studied an asymmetric compliant antagonistic joint design to improve performance mobility, which is closely related to energy efficiency
Previous research has improved the energy efficiency of humanoid robots, no study has considered the offset between hip joints to this end
Summary
As quality of life improves, the demand for humanoid robots to help or replace humans in various activities is increasing. Several studies have aimed to improve energy efficiency by reducing power consumption in the actuators of humanoid robots. Previous research has improved the energy efficiency of humanoid robots, no study has considered the offset between hip joints to this end. We optimized the hip joint offset in a humanoid robot to improve energy efficiency by reducing consumption at the actuating joints. We analyzed the mechanical power consumption of the actuated hip joints using a humanoid model, implemented in physics simulation software (MuJoCo, Roboti, Seattle, DC, USA) for energy optimization. It is more appropriate to use numerical optimization for this study It becomes impractical, given the time-consuming generation of many complex simulation models of humanoid robot legs with different joint offset configurations. For the Taguchi method, we set the joint offsets as control factors and the four abovementioned types of motions as noise factors
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