Design of Position Control System for Magnetic Lead Screw-Based Radial-Gap Rotary-Linear Two-Degree-of-Freedom Actuator

T In this paper, a linear-rotary Two-Degree-of-Freedom (2-DOF) position control system was proposed for the Magnetic Lead Screw (MLS) based 2-DOF actuator. An MLS converts torque into linear force through the helical constructed magnetic field providing by permanent magnets. As the mechanical transmissions are eliminated and there is no physical contact between the rotary and linear parts, the friction of MLS-based actuators is low and the backdrivability is high. Conventional MLS-based actuators can only realize linear drive. To meet the requirement in applications where both rotary and linear drive are needed, the 2-DOF MLS-based actuator was designed. In this research, principle of the 2-DOF actuator was analyzed and a 3-mass system model was built. Based on the model, angle transmission and load disturbance observer was designed. Additionally, position control system which controls the linear and rotary position independently while compensating the load disturbances was proposed. Finally, feasibility of the control method and system robustness against load-side disturbance torque/force were evaluated with simulation.