The Design And Realization Of Pmsm Sliding Mode Observer Based On DSP

Most servosystem selectPermanent Magnet Synchronous Motor(PMSM)as itsdriver. PMSM rotor position and speed are needed in close-loop controlinservosystem. The engine body will occupy more space and cost high if rotorinformation is got through speedsensor, the servosystem’s stability also becomeweaker. In order to solve the problems caused by speedsensor, speed sensorlesscontrol in servosystem has become a research focus.FOC (Field Oriened Control) system is built with the reference of PMSMmathematical model and coordinate transformation.With the analysis of PMSMvoltage and current, rotor information can be derived from back electromotiveforce.From mathematical model of sliding mode,it has the characteristic ofnon-linearity and stability and it will produce chattering when run in the flat.Reachinglaw withexponent is adopted by control function to suppress chattering and improvereaching condition.Sliding mode control with exponent reaching law is introduced toPMSM servosystem, and PMSM sliding mode observerbased on current error flat isbuilt to extract rotor information.U/F control is introduced to combine with rotor observer in close control loop tosolve the problem of inaccurate rotor information got by sliding mode observer atstart.The time when rotor observer is imported to close loop control is judged by rotoracceleration cure calculated by sliding mode observer.PLL(Phase-locked Loop) isused in sliding mode observer to track the rotor position in order to cripple thechattering generated when calculating the rotor positon. Experimental evidence inMATLAB show that PLL has an effect in chattering weakness.Hardware platform is built with DSP processor as control kernal and IPM asdriver. PMSM control arithmeticwith twomodes is realized in this platform:speedsensor offering rotor information and PMSM sliding mode observer offering rotorinformation.Result obtained bytwo modes is analysed and compared. Experimentalevidence show that sliding mode observer has good character in position track, PLLcan cripple the chattering.Control system with rotor observer has good performance intracking and stability and can be generalized in engineering application.