Development of Force Compliant in Series Elastic Actuator Systems

This article proposed to develop a prototype and to design the position control with force compliant strategy of reaction force series elastic actuator. The prototype attached an elastic material for absorbing the suddenly exerted force. This work aimed to use as an actuator in human-machine collaborated system which can prevent both indirect/direct damages to the working environment. Two coil springs were installed behind the power transmission of actuator to absorb the reaction force. In this work, the PID and PID-feedforward based position control has been implemented. To evaluate the performance under the load, two test signals: step and ramp signal were used for the reference position of end-effector. The result shows that PID controller providing the RMSE value are 2.12 cm and 3.76 cm, respectively. For PID-feedforward controller, the result shows that the RMSE value of step and ramp input are 10.91 cm and 0.46 cm, respectively. In summary, the PID-feedforward control has the better performance for ramp input under the load. When the end-effectors collides with the obstacle, the impact force is detected by the spring deflection and utilized as the adapted reference position. By applying the force compliant strategy, the result shows that the interaction force can be reduced for 10 times.