用于四足机器人的并联弹性腿足关节设计与优化

Design and Optimization of a Parallel Elastic Actuator Leg for Quadruped Robots

为了提升四足机器人腿足的运动性能,设计一种具有并联弹性驱动器(Parallel Elastic Actuator,PEA)的腿足关节,通过模仿四足动物的肌腱作用原理,将拉簧并联在小腿连杆和大腿连杆之间,在膝关节处实现了并联弹性驱动,具有尺寸小、质量和惯量低的特点。建立了PEA膝关节的动力学模型,并借助该模型,在预设跟踪任务轨迹下,综合考虑峰值力矩、峰值功率和能量利用率,对拉簧的刚度系数进行多目标优化,得到全局最优的拉簧刚度为5510 N/m。为了对比本PEA关节与电机直驱关节的性能,从仿真和实验两个方面进行验证。利用Gazebo机器人仿真环境,使用带有刚度的滑动副来实现PEA拉簧的效果,通过物理引擎模拟获取关节电机的输出力矩、输出功率、机械能耗;搭建PEA膝关节实验平台开展样机实验,获取膝关节电机的电源输入参数,如输入电流、输入功率、电源能耗。实验结果表明:PEA对比电机直驱关节,在0.5~2.0 s的轨迹周期下,电机输出方面可以减少峰值力矩40%~79%、峰值功率52%~89%和机械能损耗40%~89%,电机输入方面可以减少峰值电流46%~77%、峰值电功率43%~76%和电能损耗62%~73%。

A parallel elastic actuator(PEA)leg is proposed to improve the motion performance of quadruped robots.By imitating the tendon-driven mechanism of quadruped animals,a tension spring is connected in parallel between the calf link and the thigh link to achieve parallel elastic effect at the knee joint.The PEA leg exhibits small size,low mass,and low inertia characteristics.A dynamics model of PEA knee joint is established.The proposed model is used for a multi-objective optimization of spring stiffness in considering peak torque,peak power,and energy efficiency in a predefined trajectory tracking task.The most optimal spring stiffness is determined to be 5510 N/m.The performances of PEA joint and rigid actuator(RA)joint are compared through simulation and prototype experiments.A prismatic joint with stiffness is employed to simulate the effect of PEA tension spring in the Gazebo robot simulation environment.The output torque,power,and mechanical energy consumption of knee motor are obtained through physics engine simulation.A PEA knee joint experimental platform is constructed,and the prototype experiments are conducted to obtain the electrical parameters of the knee joint motor,such as input current,input power,and electrical energy consumption.The experimental results demonstrate that,compared to RA joint,the PEA joint achieves significant improvements.Specifically,within the trajectory period from 0.5 s to 2.0 s,the PEA joint reduces peak torque by 40%to 79%,peak power by 52%to 89%,and mechanical energy consumption by 40%to 89%in terms of motor output.Regarding motor input,the PEA joint reduces peak current by 46%to 77%,peak power by 43%to 76%,and electrical energy consumption by 62%to 73%.