Development of a 6-d.o.f. direct-drive wrist joint by pneumatic linear actuator drive

Consideration is given to a 6 d.o.f. direct-drive wrist joint consisting of six bellows-type pneumatic linear actuators and two plates which are connected like an octahedron. The static and dynamic performances of the prototype are described. The wrist joint is controlled by regulating the length of the actuators. To make control easier, the authors introduce an approximate model of the wrist joint by assuming that each actuator is free from mutual constraints, and design a position control system according to the PID control law. The experimental results show that this wrist joint can be accurately controlled with this system