Fast Terminal Sliding-Mode Control with High-Gain Observer for Series Elastic Actuator Robot

Series Elastic Actuator (SEA) robots play an important role in applications that require precise force control, interaction with humans, adaptability, and reliable performance. However, because SEA incorporates a compliant element, such as a spring or an elastic material, precise position control is difficult to obtain. To solve this problem, in this paper, fast terminal sliding mode control is applied to design position control for the SEA robot. In addition, a High Gain Observer (HGO) is also developed to observe the system state variables instead of measuring them. The efficiency of the proposed control algorithm is demonstrated through simulation. A comparison of the fast terminal sliding mode to conventional sliding mode control has been done. The results show that the fast terminal sliding mode control shows a better performance in terms of control input and position accuracy with the SEA robot system.