Permanent magnet linear synchronous motors with section power supply are affected by disturbances like load force, detent force, and friction force. In the field of electromagnetic drive, the stator track is long. Linear motors usually adopt a segmented structure to save inverter capacity. However, it is difficult to ensure that the air gap of each segmented stator is equal during installation. Therefore, the mover is affected by the normal force. In addition, the load is usually accelerated to the target speed in a short time, so electromagnetic drive devices are usually operated under high current and high acceleration conditions, where the motor parameters are prone to change. Due to the lack of intermediate transmission devices in PMLSMs, these disturbances will directly affect the motor drive system and are included in the output of the controller. An SMSC with a novel convergence law is designed to ensure the fast convergence of speed and suppress the chattering. The designed TSMDO observes the disturbance output to ensure the disturbance suppression performance. Then, the acceleration fluctuations are reduced, and the thrust fluctuations are suppressed in the motor output.

Firstly, a mechanical motion model of PMLSM is established based on Newton's second law. It takes the disturbances as the lumped disturbance d(t) caused by load force, detent force, friction force, normal force, and parameter variation. Secondly, the shortcomings of conventional sliding mode control are analyzed, and a new adaptive sliding mode approaching law is proposed. The designed sliding mode approaching law ensures that variables can approach the sliding mode surface at a fast speed. As the state variables of the system gradually approach the sliding mode surface, the designed sliding mode approaching law can reduce the speed to weaken chattering. Then, due to the presence of d(t) in the output of the sliding mode speed controller, the TSMDO is designed to compensate for it. This observer is equivalent to a first-order low-pass filter. Finally, the proposed SMSC strategy is compared with PI control and conventional SMSC.

The experiments show that the PI controller can improve the dynamic tracking performance of speed by increasing h. However, this increases the acceleration fluctuation. At the same time, there is a noticeable overshoot when the rotor enters the constant speed range. The conventional SMSC has better dynamic tracking performance than PI control, resulting in small acceleration fluctuations. However, due to the fixed sliding mode gain, the increasing sliding mode gain increases the overshoot. The proposed SMSC has a faster tracking speed and better dynamic response than the conventional approaching law because of the new sliding mode approaching law. The proposed SMSC can adaptively change its gain when the speed state changes, ensuring good speed-tracking performance and reducing overshoot. The designed TSMDO effectively reduces the impact of thrust disturbances, acceleration fluctuations, and thrust fluctuations.

The main conclusions are as follows. (1) The proposed new sliding mode approaching law has a fast convergence speed due to the adaptive gain function f(x₁, s) for adaptively adjusting the sliding mode gain. It can weaken chattering, ensuring speed dynamic tracking performance and convergence speed. (2) The designed TSMDO has a small chattering phenomenon. The introduction of TSMDO effectively suppresses the total disturbance d(t) in the SMSC output, reduces acceleration fluctuations, and ensures stable thrust output of the motor.