Study On No-sensor Control System Of Permanent Magnet Synchronous Motor

Generally speaking, in the PMSM (Permanent-magnet synchronous motors) control system, mechanical sensor on the rotor shaft is required to detect the position and speed of the rotor. This sensor is often encoder or speed generator. The machine sensor gives the rotor signal that the motor needed, but bring some questions to the control system, too. (1) The machine sensor increases the rotary inertia of the rotor shaft, and it increases the volume of the motor; (2) The machine sensor is easy affected by temperature, humidity and librations, this limits its using range; (3) The machine sensor and its ancillary circuit increases the cost of the speed regulating system. In order to resolve these questions above, no-sensor speed regulating system is a new solution and very promising. No-sensor speed regulating system means using the correlating electrical signal in motor winding of electromotor to calculate the position and speed of the rotor by using information distinguishable technology, which can replace mechanical sensor to achieve the electromotor control. In this paper, permanent-magnet synchronous motor was given as the study objective, on the basis of phase-locked loop (PLL) theory, a novel no-sense controller was deduced. This paper includes undermentioned content: First, based on the method and theory analysis of various no-speed sensor controllers at present and the characteristics of the math model of PMSM, we design a math model to detect the position information of the electromotor, which bases on phase-locked loop math model. This method is based on the case that the voltage and current of the electromotor has a correlative relation to the rotor real time position. By sampling the voltage and current of the PMSM, we can draw out the position and speed of the rotor by using PLL math model. Secondly, on the basis of theory analysis, the designed math model can be simulated by Simulink block function in MATLAB. The simulation procession uses double closed loop control system. The exterior loop is speed loop, which using PI controller. The inside loop is current loop, which using lag loop controller. We can examine the correctness of the math model by closing the speed loop which using the position signal calculation with PLL math model. The result of the simulation indicates that this method to inspect the rotor real time position is feasible and gives out some idiographic parameters reference range. Theoretical analysis and simulation results both show that the novel no-sensor controller in PMSM with PLL model is practical. In the end of this paper, we give the glorious further of our work and summarize all process of design and simulation.