Design of a variable-gain adjacent cross-coupled controller for coordinated motion of multiple permanent magnet linear synchronous motors

Coordination position control of multi-motors systems is widely applied in agricultural and industrial fields that require high precision and synchronization among motors. Current adjacent cross-coupled control is unable to change the control gains as motor states are time-variant. The invariant gain compensation will inevitably weaken the coordinated control performance, especially in the presence of load disturbances. To solve this issue, this paper proposes a variable-gain adjacent cross-coupled controller. A sliding mode controller is adopted to cope with the disturbances and uncertainties for each single permanent magnet linear synchronous motor (PMLSM). The motor state of each PMLSM can be detected through system identification in real time. According to the motor states of the PMLSMs based on the system identification technique, a fuzzy position control algorithm is implemented for regulating the gain compensation. A consistent steady-state performance is subsequently maintained even with the existence of system uncertainties and load disturbances. It is proved from the experimental results that, compared with fixed-gain adjacent cross-coupled control scheme, the proposed controller has a better synchronization, a higher tracking accuracy and synergistic accuracy, under both no load and time-varying load conditions. For the variable-gain adjacent cross-coupled control, a position tracking error and a synergistic error within 7 μm and 8 μm can be achieved, respectively.