Abstract
When a permanent magnet synchronous motor runs at low speed, the inverter will output discontinuous current and generate torque ripple; when the motor is runs at high speed, a large amount of stator harmonic current generates, which affects its speed following ability and torque stability. To ensure the fast and smooth switching of a permanent magnet synchronous motor in the full speed domain, this paper proposes the nonsingular terminal sliding mode control of PMSM speed control based on the improved exponential reaching law. Firstly, the improved exponential reaching law is composed of the state variables and power terms of the sliding mode surface functions. The reaching law function is designed in sections to balance the fast dynamic response of the system and chattering control. Secondly, an improved exponential reaching law based on the sliding mode control strategy of the PMSM speed loop is proposed. By designing the initial value of the integral term in the nonsingular terminal sliding mode surface function, the initial state of the system is located on the sliding mode surface. The integral sliding mode surface is used to reduce the system steady-state error, while the proposed sliding mode reaching law is used to increase the arrival speed and suppress system chattering, ultimately affecting modeling error problems, complex working conditions, and uncertainty factors. This paper proposes a sliding mode observer based on an improved exponential reaching law to compensate for the disturbances. Lyapunov stability theory can prove that this system can make the speed tracking error converge to zero in finite time. Hardware-in-the-loop experiments were used to validate the effectiveness of the proposed method.
Highlights
The traditional motor drive mode is that of a motor plus a reducer
PMSMs have the advantages of small torque ripple, high efficiency, simple structure, small size, etc., so they are widely used in direct drive systems [1,2,3,4]
Because a direct drive system does not have a transmission mechanism, disturbance on the load side will affect the stability of the PMSM speed control system
Summary
The traditional motor drive mode is that of a motor plus a reducer. The existence of the reducer increases the overall energy consumption of the transmission system, and reduces the stability and reliability of the transmission system. Different approaches had been developed to suppress chattering, such as the higher-order sliding mode [19,20], adaptive algorithms [21,22], the researchers prposed disturbance observers [23,24,25] and reaching law methods [26,27,28,29]. In [23], the researchers proposed a control method that effectively improved the incompatibility between rapidity and stability, and solved the problem that the constant rate reaching law cannot satisfy both rapidity and low chattering in the sliding mode observer.
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