Zhang Qiang, Sun Dingyang, Qian Wei, Xiao Xiaohui, Guo Zhao
School of Power and Mechanical Engineering, Wuhan University, Wuhan, China.
UNC/NCSU Joint Department of Biomedical Engineering, NC State University, Raleigh, NC, United States.
Front Neurorobot. 2020 Feb 25;14:13. doi: 10.3389/fnbot.2020.00013. eCollection 2020.
This paper focuses on the design, modeling, and control of a novel remote actuation, including a compact rotary series elastic actuator (SEA) and Bowden cable. This kind of remote actuation is used for an upper limb rehabilitation robot (ULRR) with four powered degrees of freedom (DOFs). The SEA mainly consists of a DC motor with planetary gearheads, inner/outer sleeves, and eight linearly translational springs. The key innovations include (1) an encoder for direct spring displacement measurement, which can be used to calculate the output torque of SEA equivalently, (2) the embedded springs can absorb the negative impact of backlash on SEA control performance, (3) and the Bowden cable enables long-distance actuation and reduces the bulky structure on the robotic joint. In modeling of this actuation, the SEA's stiffness coefficient, the dynamics of the SEA, and the force transmission of the Bowden cable are considered for computing the inputs on each powered joint of the robot. Then, both torque and impedance controllers consisting of proportional-derivative (PD) feedback, disturbance observer (DOB), and feedforward compensation terms are developed. Simulation and experimental results verify the performance of these controllers. The preliminary results show that this new kind of actuation can not only implement stable and friendly actuation over a long distance but also be customized to meet the requirements of other robotic system design.
本文重点关注一种新型远程驱动装置的设计、建模与控制,该装置包括一个紧凑型旋转串联弹性驱动器(SEA)和鲍登电缆。这种远程驱动装置用于具有四个动力自由度(DOF)的上肢康复机器人(ULRR)。SEA主要由一个带行星齿轮箱的直流电机、内/外套筒以及八个线性平移弹簧组成。关键创新点包括:(1)用于直接测量弹簧位移的编码器,可等效用于计算SEA的输出扭矩;(2)嵌入式弹簧可吸收齿隙对SEA控制性能的负面影响;(3)鲍登电缆实现了长距离驱动,并减少了机器人关节上的庞大结构。在对这种驱动装置进行建模时,考虑了SEA的刚度系数、SEA的动力学以及鲍登电缆的力传递,以计算机器人每个动力关节的输入。然后,开发了由比例 - 微分(PD)反馈、干扰观测器(DOB)和前馈补偿项组成的扭矩和阻抗控制器。仿真和实验结果验证了这些控制器的性能。初步结果表明,这种新型驱动装置不仅能够在长距离上实现稳定且友好的驱动,还能够进行定制以满足其他机器人系统设计的要求。