Rahim Mutlu

Emre Sariyildiz, Rahim Mutlu, Chuanlin Zhang

This paper proposes a new Active Disturbance Rejection based robust trajectory tracking controller design method in state space. It can compensate not only matched but also mismatched disturbances. Robust state and control input references are generated in terms of a fictitious design variable, namely differentially flat output, and the estimations of disturbances by using Differential Flatness and Disturbance Observer. Two different robust controller design techniques are proposed by using Brunovsky canonical form and polynomial matrix form approaches. The robust position control problem of a two mass-spring-damper system is studied to verify the proposed robust controllers.

Emre Sariyildiz, Rahim Mutlu, Haoyong Yu

This paper deals with the robust force and position control problems of Series Elastic Actuators. It is shown that a Series Elastic Actuator's force control problem can be described by a second-order dynamic model which suffers from only matched disturbances. However, the position control dynamics of a Series Elastic Actuator is of fourth-order and includes matched and mismatched disturbances. In other words, a Series Elastic Actuator's position control is more complicated than its force control, particularly when disturbances are considered. A novel robust motion controller is proposed for Series Elastic Actuators by using Disturbance Observer and Sliding Mode Control. When the proposed robust motion controller is implemented, a Series Elastic Actuator can precisely track desired trajectories and safely contact with an unknown and dynamic environment. The proposed motion controller does not require precise dynamic models of the actuator and environment. Therefore, it can be applied to many different advanced robotic systems such as compliant humanoids and exoskeletons. The validity of the motion controller is experimentally verified.