基于步态切换的欠驱动双足机器人控制方法

由于高维、非线性、欠驱动等特点, 3-D双足机器人的稳定性控制依然是一个研究难点. 一些传统的控制方法, 如基于事件的反馈控制方法和PD控制方法, 抗扰动能力较弱, 鲁棒性较差. 通过观察, 人类受到外部扰动影响时, 会通过调整步态重新获得稳定性,相较之下仅依靠一个步态获得的稳定性是有限的. 受此启发, 本文针对上述问题提出一种基于步态切换的欠驱动3-D双足机器人控制方法. 首先, 以能耗最少为优化目标, 通过非线性优化方法预先设计多组不同步长、步速的步态作为参考步态, 以构建一个步态库; 然后, 通过综合考虑步态切换过程中的稳定性与能效, 建立了多目标步态切换函数; 最后, 将该步态切换函数作为优化目标, 并求解该最小化问题获得下一步的参考步态, 从而实现步态切换, 达到使用步态库?多轨迹方法来提高鲁棒性的目的. 在仿真实验中运用该步态切换控制方法, 欠驱动3-D双足机器人可实现相对高度在-20, 20] mm内随机变化的不平整地面上行走, 而仅采用单步态控制策略则无法克服这样的外部扰动, 从而说明了基于步态切换的欠驱动双足机器人控制方法的有效性. 

CONTROL METHOD OF AN UNDERACTUATED BIPED ROBOT BASED ON GAIT TRANSITION

The stability control of underactuated 3-D biped robot is still a hard nut to crack, as a result of locomotion characteristics which mix high dimension, strong nonlinearity and underactuation. Some traditional control methods, such as event-based feedback control and PD control, are poor in robustness and weak in resistance to external disturbances. Through observation, it is certain that humans adjust gaits tactically to regain stability when they are affected by external disturbances, by contrast with trying to keep the stability sustained by only one gait which is quite limited. Inspired by this, a control method based on gait transition is proposed for the underactuated 3-D biped robot. First of all, taking the minimum energy consumption as the optimization goal, a multi group of gait and step gait is designed as the reference gait to build a gait library by nonlinear optimization method. Secondly, to obtain an optimal performance in terms of the balance between the stability and input torques, a multi-objective gait transition function is established. Finally, a reference gait that minimizes the gait transition function is obtained by solving a quadratic optimization problem, and it is then used as the walking gait for the next step with the purpose of using gait library (multiple trajectories) method to reach the goal of improving robustness. In the simulation experiment, using the proposed gait transition control method, the underactuated 3-D biped robot can walk through the rough ground with the relative height varying within the range -20,20] mm without falling down, in contrast to the failure of previous one-gait control method. The results show the effectiveness of the method.