Meng Xiang, Yu Zhangguo, Chen Xuechao, Huang Zelin, Dong Chencheng, Meng Fei
School of Mechatronical Engineering, Beijing Institute of Technology, Beijing 100081, China.
Key Laboratory of Biomimetic Robots and Systems, Ministry of Education, Beijing 100081, China.
Biomimetics (Basel). 2023 Mar 10;8(1):114. doi: 10.3390/biomimetics8010114.
Smooth state switching and accurate speed tracking are important for the stability and reactivity of bipedal robots when running. However, previous studies have rarely been able to synthesize these two capabilities online. In this paper, we present an online running-gait generator for bipedal robots that allows for smooth state switching and accurate speed tracking. Considering a fluctuating height nature and computational expediency, the robot is represented by a simplified variable-height inverted-pendulum (VHIP) model. In order to achieve smooth state switching at the beginning and end of running, a segmented zero moment point (ZMP) trajectory optimization is proposed to automatically provide a feasible and smooth center-of-mass (CoM) trajectory that enables the robot to stably start or stop running at the given speed. To accurately track online the desired speed during running, we propose an iterative algorithm to compute target footholds, which allows for the robot to follow the interactive desired speed after the next two steps. Lastly, a numerical experiment and the simulation of online variable speed running were performed with position-controlled bipedal robot BHR7P, and the results verified the effectiveness of the proposed methods.
对于双足机器人跑步时的稳定性和反应能力而言，平稳的状态切换和精确的速度跟踪非常重要。然而，以往的研究很少能够在线综合这两种能力。在本文中，我们提出了一种用于双足机器人的在线跑步步态生成器，它能够实现平稳的状态切换和精确的速度跟踪。考虑到高度波动特性和计算简便性，机器人由简化的可变高度倒立摆（VHIP）模型表示。为了在跑步开始和结束时实现平稳的状态切换，提出了一种分段零力矩点（ZMP）轨迹优化方法，以自动提供可行且平稳的质心（CoM）轨迹，使机器人能够以给定速度稳定地开始或停止跑步。为了在跑步过程中精确地在线跟踪期望速度，我们提出了一种迭代算法来计算目标立足点，这使得机器人能够在接下来的两步之后跟踪交互式期望速度。最后，使用位置控制的双足机器人BHR7P进行了数值实验和在线变速跑步模拟，结果验证了所提方法的有效性。
