Sensorless control method for permanent magnet synchronous motor based on improved sliding mode control

Abstract

The application discloses a kind of permanent magnet synchronous motor position sensorless control methods based on improved sliding mode control, belong to motor control technical field.The application includes: constructing integral terminal sliding mode surface and the speed loop sliding mode controller of compound approach law of variable gain, improves dynamic response and restrains chattering;Adaptive superhelix sliding mode observer is constructed, and adaptive estimation of back electromotive force is realized;Improved second-order generalized integrator with negative feedback compensation is constructed, and the rotor position and speed are extracted with high-precision filtering to back electromotive force.The application does not need mechanical position sensor, has the advantages such as fast response, high steady accuracy, strong anti-disturbance ability, small estimation error in medium and high speed range, and is suitable for new energy vehicles, industrial robots and other high-performance drive systems.

Description

Technical Field

[0001] This invention belongs to the field of motor control technology, specifically relating to a sensorless control method for a permanent magnet synchronous motor (PMSM), which is particularly suitable for applications with high requirements for dynamic response and anti-disturbance performance, such as new energy vehicles, industrial robots, and servo drives. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) offer advantages such as high efficiency, high power density, and fast dynamic response, making them widely used in high-end manufacturing and electric transportation. Traditional PMSM vector control systems typically rely on mechanical position sensors to obtain rotor position and speed information. However, mechanical sensors are costly and easily damaged in harsh environments, reducing system reliability.

[0003] Therefore, sensorless control technology has become a research hotspot. Existing sensorless control methods for medium and high speeds mainly include extended Kalman filtering, model reference adaptive systems, and sliding mode observers. Among them, sliding mode observers have attracted attention due to their strong robustness to system parameter perturbations and external disturbances. However, traditional sliding mode control suffers from severe chattering, low back EMF extraction accuracy, and phase delay. In speed loop control, although terminal sliding mode can improve dynamic response, it easily exacerbates steady-state chattering, making it difficult to balance speed and stability. Furthermore, fixed-gain super-spiral sliding mode observers are difficult to adapt to changes in motor parameters and complex operating conditions. Summary of the Invention

[0004] This invention aims to overcome the problems in existing sensorless control systems for permanent magnet synchronous motors, such as difficulty in balancing dynamic response and steady-state accuracy of the speed loop, severe chattering of the sliding mode observer, and phase delay and DC bias in back EMF extraction. It provides a sensorless control method for permanent magnet synchronous motors based on improved sliding mode control.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: First, an integral terminal sliding surface is constructed in the speed loop, the linear term of the speed error, the integral term of the error, and the nonlinear power term of the terminal are coupled together, and a variable gain composite reaching law is designed. At the same time, a piecewise continuous switching function is used to replace the traditional sign function, thereby improving the dynamic response speed of the system while effectively suppressing steady-state chattering and achieving fast and stable speed control.

[0006] Secondly, in the medium-to-high speed sensorless estimation stage, an adaptive super-helical sliding mode observer is constructed. The continuous control characteristics of the second-order sliding mode are used to reduce chattering, and an adaptive gain adjustment strategy is introduced so that the observer gain can be dynamically adjusted according to the current estimation error to adapt to changes in motor parameters and load disturbances. At the same time, for the back EMF filtering stage, an improved second-order generalized integrator with an integral negative feedback compensation branch is designed to effectively filter out harmonics and suppress DC bias in the sampled signal while maintaining a small phase delay, thereby improving the estimation accuracy of rotor position and speed.

[0007] Finally, the reference current output by the improved sliding mode speed controller and the rotor position and speed signals output by the improved second-order generalized integrator are fed back to the vector control system to form a sensorless closed-loop control. This invention eliminates the need for mechanical position sensors and offers advantages such as fast response, high steady-state accuracy, strong anti-disturbance capability, and small estimation error in the medium-to-high speed range, making it suitable for high-performance applications such as new energy vehicles, industrial robots, and servo drives. Addressing the challenges of balancing dynamic response and steady-state accuracy in sensorless control systems, including severe chattering in the sliding mode observer and phase delay and DC bias in back EMF extraction, this invention provides a sensorless control method for permanent magnet synchronous motors based on improved sliding mode control. Attached Figure Description

[0008] Figure 1 : Schematic diagram of a variable gain composite reaching law sliding mode speed controller

[0009] Figure 2 Block diagram of the improved second-order generalized integrator.

Claims

1. A sensorless control method for a permanent magnet synchronous motor based on improved sliding mode control, characterized in that, Includes the following steps: Step Step 1: Construct an improved sliding mode controller with a speed loop, employing an integral terminal sliding surface and a variable gain composite reaching law, and using a piecewise continuous switching function to reduce chattering; Step 2: Construct an adaptive superspiral sliding mode observer, employing an adaptive gain adjustment strategy and a piecewise exponential switching function to estimate the back EMF; Step 3: Construct an improved second-order generalized integrator with an integral negative feedback compensation branch to filter the back EMF, extract in-phase and quadrature components, and calculate the rotor position and velocity; Step 4: Feed back the estimated rotor position and velocity to the vector control system to achieve sensorless closed-loop control.

2. The method according to claim 1, characterized in that, The integral terminal sliding surface is composed of a linear term for rotational speed error, an integral term for error, and a power term for terminal nonlinearity.

3. The method according to claim 1, characterized in that, The variable gain composite reaching law is dominated by a power-law reaching law when the system state is far from the sliding surface, and dominated by a variable-speed reaching law when it is close to the sliding surface, thus achieving segmented adjustment.

4. The method according to claim 1, characterized in that, The gain of the adaptive superspiral sliding mode observer is dynamically adjusted according to the current estimation error. The larger the error, the larger the gain, in order to adapt to changes in motor parameters and load disturbances.

5. The method according to claim 1, characterized in that, The improved second-order generalized integrator adds an integral negative feedback compensation branch to the standard second-order generalized integrator to suppress DC bias in the sampled signal.

6. The method according to claim 1, characterized in that, The piecewise continuous switching function or piecewise exponential switching function changes continuously within the boundary layer and exhibits saturation characteristics outside the boundary layer to suppress system chattering.

7. The method according to claim 1, characterized in that, The method is applicable to medium and high speed operating ranges and can achieve closed-loop control of rotor position and speed without the need for mechanical position sensors.

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