Research On Sensorless Control Algorithm For Surface-mounted Permanent Magnet Synchronous Motor Across Full Speed Range

Permanent magnet synchronous motors(PMSMs)are widely used in various fields such as robotics,electric vehicles,and aerospace due to their advantages such as high efficiency,high power density,and high torque-to-inertia ratio.However,accurate rotor position is crucial for achieving high efficiency and performance in motor control.In many industrial applications,low-precision encoders are widely used for reading rotor position information due to cost considerations.Nevertheless,these encoders have problems such as delay,increased motor size,and reduced system robustness.In recent decades,research has shown that sensorless control algorithms have advantages over low-precision sensor control algorithms.However,some issues still make it difficult to use sensorless technology in the entire speed range for surface-mounted PMSMs(SPMSMs).Therefore,based on extensive literature review and previous work,this paper focuses on in-depth research of fieldoriented vector control technology with an observer over the entire speed range and proposes corresponding improvements and solutions.To achieve stable speed control of a PMSM,this paper studies a motor control scheme based on field-oriented control and explains its underlying principle.Additionally,a mathematical model of the SPMSM is established,and the mathematical model in the synchronous rotating coordinate system is obtained for tuning the loop parameters of the closed-loop system.To achieve rotor position observation at standstill and low speed,this paper studies two aspects:rotor magnetic saliency and linearity of observation angle.First,the saliency of SPMSM is analyzed to ensure the feasibility of the high-frequency injection(HFI)method for rotor position detection.Second,a simplified mathematical model is established for high-frequency signal injection at low speeds.Based on the high frequency square wave voltage injection(HFSWVI)method,this paper proposes a compensator to correct the nonlinearity of the observation angle.At the same time,this paper analyzes the convergence problem of HFSWVI at standstill and identifies the initial position through high-frequency pulse voltage injection(HFPVI).To achieve rotor position observation in the medium-to-high speed range,this paper studied an angle observer based on a sliding mode observer(SMO).First,the mathematical model of the SPMSM in the two-phase stationary coordinate system was established.Second,a high-order SMO(HSMO)was constructed based on the established mathematical model,combined with a normalized PLL(NPLL)as the basic observer model.On this basis,this paper analyzed and proposed a method to compensate for the issue of external direction signals required by the observer model.This is achieved through orthogonal decoding to provide direction signal compensation using only the backEMF.Furthermore,this paper combined HFI with SMO,and introduced a hysteresis loop in the medium-speed section of the speed observation to achieve smooth switching between the two observers.