机器人串联弹性关节驱动器的刚度控制方法

机器人关节的柔顺性在人机协作过程中具有重要作用,然而固定的关节柔性无法满足动态变化的人机协作需求,因此对机器人的关节驱动器提出了具有刚度调节能力的要求.本文采用阿基米德螺旋线平面涡卷弹簧作为机器人关节的柔性元件,并提出一种可用于具有固定刚度的串联弹性驱动器的刚度控制方法.根据关节刚度的定义,将测量得到的弹簧输出端角度用于计算弹簧的输入端转角,使得机器人关节驱动器的等效刚度可以被调整到所期望的大小.该方法以电机位置控制为内环,关节刚度控制为外环,简化了控制器设计,并实现了解耦控制.对所设计的刚度控制器进行了分析.最后在自主设计的单自由度薄型串联弹性驱动器实验平台上进行了刚度调节实验,包括刚度的双向阶跃、零刚度和正弦变化的刚度,实验结果表明关节等效刚度能准确跟踪期望值,验证了该方法的有效性.

Robot Joint Stiffness Control Based on Series Elastic Actuator

The flexibility of robot joints plays an important role in the human-robot collaboration process. However, the fixed flexible joint cannot meet the demands for the dynamic variation of human-robot collaboration. Thus, it is necessary for the robot joint actuator to be capable of stiffness tuning. A stiffness control method that can be applied to a series elastic actuator with fixed stiffness and in which Archimedes spiral spring is adopted as the flexible element of robot joint is proposed. According to the definition of joint stiffness, the measured output angle of spring can be used to calculate the input angle of spring, so that the equivalent stiffness of robot joint actuator can be adjusted into the expected value. This method regards the motor position controller as the inner loop and the joint stiffness controller as the outer loop, which simplifies the design of controllers and enables the decoupling control. The designed stiffness controller is theoretically analyzed. Finally, a stiffness adjustment experiment was carried out on the experiment platform with the self-designed single DOF thin-type series elastic actuator for cases of two-way step of stiffness, zero stiffness, and stiffness with sinusoidal variation. The experiment results show that the equivalent stiffness of joint can accurately trace the expected value, which verifies the validity of the proposed method.