Trajectory design of harmonic loading machine input by central pattern generator

A new method was provided to control linear time-varying systems in which the reference signal is a harmonic function with variable amplitude, mean or frequency, such as block loading. The results of practical tests on the voice coil actuator fatigue test machine indicate that this method is robust to noise and disturbance. Also proposed control method compensates unknown time-varying time-delay which leads to bandwidth increase in harmonic loading. On the other hand in this paper the central pattern generator (CPG) was used to design the trajectory of input signal to the main plant. Because of soft applying of changes by CPG, it prevents excitation of high frequency dynamics. To implement the proposed method main plant, which can be estimated with a fourth-order single-input single-output (SISO) model was considered as a two-input two-output (TITO) decoupled system that each relevant input-output is first-order. The level of control loop pairs to each other is investigated by calculation of dynamic relative gain array (DRGA) matrix. The test results also show that loading control was properly carried out in the presence of various uncertainties such as nonlinearities, unmodeled dynamics and time-varying parameters.