Spring-damper model and articulation control of pneumatic artificial muscle actuators

Abstract

Recently, research and development in robotics have focused on robots performing tasks traditionally done by people. Therefore, it is necessary for robots to have the same flexibility as people. Additionally, such robots need to incorporate high-level safety features so as not to incur injury on others. We present artificial muscle-type pneumatic actuators as the driving source of a robot hand that is both safe and flexible. Development of robot hands using pneumatic actuators has already taken place. However, when a pneumatic actuator is used, a large compressor is needed. Therefore, the driving system also needs to be large. This is a major problem. Therefore, we developed low-pressure, low-volume pneumatic actuators for driving a robot hand that works flexibly and safely among people and a five-fingered robot hand with these pneumatic actuators installed. To accurately control the five-fingered robot hand, an accurate model with a pneumatic actuator is needed. We constructed such a model by using a spring element, which expresses the generative force of pneumatic pressure, and a damper element, which expresses the hysteresis characteristics. We then made a 1-link arm that has one degree of freedom using the pneumatic actuators and constructed a 1-link armmodel. We also constructed a spring-damper element model of the pneumatic actuators and a proportional-integral-derivative (PID) controller system. The gains of the system were determined with a simulation that uses our 1-link arm model. The step response of the joint angle was examined with these determined gains.