Research On Sensorless Vector Control Of Pmsm

Along with the fast development of power electronics, micro-electronics, automation, micro-computers, sensor, rare earth permanent materials and motor control theory, permanent magnet synchronous motor(PMSM) has been widely applied in motion control system of medium or low capacity, especially in the servo drive field. PMSM has the advantages of superior power density, high efficiency and dispenses with excitation current, PMSM has become the developing direction of servo drive, and gradually takes the place of DC motor and step motor in servo drive field.In traditional servo control system, optical encoder or tachometer generator is widely used to measure the rotor position and speed to realize field orientation. However the installation of position sensor, increases the maintenance requirements, cost of system, the moment of inertia in rotor shaft, the motor size and the interface circuit between the motor and the control system, makes the system easily disturbed by environment and decreases the system reliability, thus limits the application range of PMSM. The fast development of sensorless control technique provides a good approach to solve these problems, it uses measured voltage, current and the motor mathematical model to estimate the rotor position and speed, has the advantages of not change motor structure, not use expensive position sensor, decreases maintenance expense, fearless of dust and dampness.This paper first introduces coordinate conversion theory, sets up mathematical models in different coordinate system of PMSM, expatiates the space vector pulse width modulation theory, sector judge method and three phase SVPWM modulation. Then discusses the flux-weaking theory of PMSM, uses max torque/current ratio control strategy when the motor speed below rated speed, and use flux-weaking control strategy when the motor speed above rated speed, thus enlarges the speed modulation range of PMSM. Last expatiates the principle of PMSM speed modulation and sensorless algorithm, a kind of linear state observer is introduced for sensorless control, it uses stator voltage and current in two-phase still coordinate as state variable to estimate the rotor position and speed by linear state observer, thus realize the vector control of PMSM.The MCU of STM32F103 is adopted as the core of the system, and shinano PMSM is adopted as the control object, the designed hardware mainly includes power module, drive module, current measure module, HALL/ENCODER module, over temperature protect module, RS232 interface module. This paper emphasizes on introducing the software of PMSM vector control, mainly includes system structure diagram, SVPWM interrupt service routine, PMSM state machine diagram, startup disposal, fixed point algorithm, triangle function, coordinate conversion, PID adjustor, current sampling and filtering algorithm and RS232 communication.At last, by debugging, modifying and optimizing of sensorless algorithm of PMSM, analyzes the experiment waves of PWM drive, stator current, speed, torque and SVPWM stator voltage and shows that the sensorless algorithm designed for PMSM has the advantages of simply algorithm, good regulation performance, stable running in medium or high speed, and realizes the flux-weaking speedup that enlarges the speed modulation range of PMSM,thus measure up the system design requirements.