To reduce the convergence time and improve the anti-disturbance capability of the permanent magnet synchronous motor (PMSM) drivers, a fast sliding mode speed controller based on a new compound reaching law (NCRL) and disturbance observer compensation technique is proposed. Firstly, to solve the conflict between fast convergence rate and chattering reduction in the existing solutions, the NCRL is proposed by introducing the exponential function and the power term piecewise function. The convergence of NCRL is proved and the reaching time is certified to be independent of the system’s initial state. The proposed NCRL can effectively reduce the reaching time, and smooth the output signal while maintaining the high tracking performance of the controller under different conditions. However, external load disturbances may degrade the performance of the proposed NCRL-based speed controller. The proposed controller is then combined with an improved sliding mode observer (ISMO), named the NCRL+ISMO method, to improve the estimation accuracy of the lumped disturbance and the robustness of the system. The stability of the proposed method is analyzed by the Lyapunov function. Experimental results show that the proposed method can reduce speed fluctuation and convergence time, and enhance anti-disturbance capability.

In the back electromotive force (EMF)-based sensorless control of interior permanent magnet synchronous motor (IPMSM), the inverter nonlinearity and flux linkage spatial harmonics will possibly give rise to (6k±1)th harmonics in the estimated back-EMF, especially the 5th and 7th harmonics. Those harmonics will consequently introduce (6k)th harmonic ripples to the estimated rotor position, especially the 6th harmonic component. In order to solve this problem, a bilinear recursive least squares (BRLS) adaptive filter is proposed and integrated into a sliding mode position observer to suppress the dominant harmonic components in the estimated back-EMF and as a result, the accuracy of the estimated rotor position can be greatly improved. A unique feature of the BRLS adaptive filter is its ability to track and suppress the specified harmonic components in different steady state and dynamic operational conditions. The proposed method can compensate harmonic ripples caused by the inverter nonlinearity and machine spatial harmonics at the same time; this method is also robust to machine parameter variation and the BRLS algorithm itself is machine parameter independent. The implementation of the proposed BRLS filter in the sensorless control of IPMSM is explained in details in this paper. The enhanced drive performances using the BRLS filter have been thoroughly validated in different steady state and dynamic operational conditions on a 1.5kW IPMSM sensorless drive.

High-speed and high-precision position servo system of permanent magnet synchronous motor (PMSM) is the key part of the research and development of the manipulator's joint. The active disturbance rejection control (ADRC) is one of the commonly used methods in the position servo system, which has the advantages of fast speed and easy physical realization. However, the existing ADRC mostly adopts the three-loop structure of position-speed-current, which has some problems such as slow positioning response, poor positioning accuracy, and poor load adaptability caused by difficult parameter tuning. Therefore, a new load adaptive two-loop drive system based on an improved position-speed integrated ADRC with a parameter fuzzy self-tuning method is proposed. In order to verify the effectiveness of the scheme, a test platform for a Selective Compliance Assembly Robot Arm (SCARA) is established. The results show that the drive system designed by the proposed method has high positioning accuracy, fast positioning response, and adaptability to load changes.

The effective identification of the load torque is one of the key methods to improve the positioning accuracy of the position servo system, and the sliding mode observer (SMO) is a common identification method in the speed control system because of its advantages of insensitive parameters and easy physical realisation. However, the existing SMO can not achieve high precision and high response identification of load torque in the full speed range when the motor is running at variable-speed or variable-load, which limits its application in the position servo system. Based on the analysis of the stability and the adaptive law of feedback gain coefficient, an improved SMO for adaptive identification based on adaptive control and improvement of cut-off frequency is proposed. To verify the proposed method, the dedicated simulation model and test platform are built. The results show that the proposed observer can realise the adaptive identification of the load torque under the condition of variable-speed or variable-load, and the estimation accuracy is high. The position servo system designed by the proposed observer can improve the response against load change, which is an effective method for high-precision positioning control of the position servo system with a variable-speed or variable-load.

Effective identification of the load torque is one of the key aspects in improving the performance of servo drive systems against load disturbances. Sliding mode variable structure control has become a popular method in the development of a load torque identification (LTID) algorithm due to its parameter insensitivity and easy realization features. However, existing LTID sliding mode observers with conventional structure have the disadvantages of high frequency chattering and poor estimation accuracy, which limit its application in high performance servo systems. In this paper, the mathematical model of the conventional LTID sliding mode observer is deduced and analyzed. A new LTID sliding mode observer is proposed by replacing the sign function with a saturation function and an additional feedback loop in the load torque observer. The effectiveness of the proposed observer is verified by various experiments. The results show that compared to conventional load torque observer, the proposed observer can identify the load torque with higher accuracy and faster response in different operation conditions.

Improving the positioning response is one of the key goals for permanent magnet synchronous motor position servo systems. The sliding mode variable structure controller (SMVSC) is an effective method due to the advantages of strong robustness, fast response, and easy practical implementation. However, the existing SMVSCs have difficulties in optimizing the position tracking response speed and chattering performance at the same time. This article proposes an improved position speed integrated SMVSC (ISMVSC) with a new variable exponential reaching law based on position error and a saturation function, and a speed-limiting method using speed error and trajectory planning. The general design principle is given and various tests are carried out to verify the effectiveness of the proposed method. The experimental results show that compared with traditional methods, the ISMVSC can improve the positioning response speed and reduce chattering problems at the same time; it also exhibits a stronger transient speed-limiting ability. All these advantages make the proposed controller a superior method to achieve high-response positioning control of the servo system that performs point-to-point motion.