Nonlinear Stabilization Control of Multiple-RTAC Systems Subject to Amplitude-Restricted Actuating Torques Using Only Angular Position Feedback

Multiple rotational translational actuator (RTAC) systems are nonlinear complicated mechatronic systems introduced to investigate the self-synchronized phenomenon in mechanical engineering, which consist of a series of single-RTAC subsystems connected one by one through elastic springs. This paper studies the globally stabilizing control problem for multiple-RTAC systems by considering that the actuators are constrained in torque amplitudes and velocity signals are unavailable for feedback. More precisely, by carefully analyzing the system energy storage function and respecting the maximum allowable control torques, a novel amplitude-restricted control law is developed without requiring velocity feedback, which can stabilize multiple-RTAC systems from any initial condition theoretically. It is beneficial that the proposed control law does not involve any plant parameters, which consequently makes it insensitive to parameter uncertainties. The stability and convergence characteristics of the designed control system are rigorously supported with Lyapunov techniques. To the best of our knowledge, the proposed controller is the first one that can stabilize a multiple-RTAC system while simultaneously ensuring the practical control amplitude-restricted constraints, by using only output feedback. Both numerical simulation and hardware experiments are included to verify the effectiveness of the proposed control approach.