| The linear servo system based on permanent magnet linear synchronous motor(PMLSM) is a hot research in recent years. As it has the advantages in direct driving(the linear servo system can drive linear motion load directly without reducer and ballscrew), high speed, high precision, high thrust, high acceleration, fast response andhigh reliability, so it is widely applied in the high-end numerical control equipmentsand the linear motion control occasions that require high speed and high precision,such as large-scale integrated circuit packaging equipment,3D printing,3D carvingand precision laser cutting equipment, high-end web guiding system and so on.Therefore, the linear servo system based on LM-series PMLSM is studied deeply inthis paper by combining theoretical analysis, computer simulation and experimentalverification.Firstly, the mathematical model of PMLSM and the theory of space vector pulsewidth modulation (SVPWM) are introduced, then the parameters identificationmethods based on the PMLSM mechanism model, and the regulators type selectionand their parameters self-tuning methods based on the i*d0vector control systemare analyzed. Among them, the normal PI control is utilized as the current loopregulator, the variable structure P/PI control is utilized as the velocity loop regulator,and the variable parameter P control is utilized as the position loop regulator. Besides,a nonlinear s-shaped instruction form based on cosine function is employed toimprove the rapid, stably tracking ability of instruction. The results of Matlabsimulation show that the measure-control algorithm has a good parameteridentification precision and a better control effect, and the dynamic stability of servosystem is improved significantly, while the dynamic quickness of servo system stillremains unchanged after adopting the nonlinear s-shaped instruction form.Secondly, the load resistance observer and the velocity observer are designed.The load resistance observer is a sliding mode observer based on the equivalentcontrol principle. It takes the PMLSM motion equations as the observation model andadopts proportional control rule, and it can estimate the load resistance with no staticerror. The velocity observer is an extended sliding mode observer based on theback-EMF. It takes the PMLSM current and back-EMF state equations as the observation model, and also adopts proportional control rule. Its observational resultof back-EMF is a continuous sinusoidal variable and can be directly used to estimatevelocity. The results of Matlab simulation show that the servo system has a highanti-interference ability after adopting the load resistance observer, and can estimatethe actual velocity effectively in the area of high-velocity after adopting the velocityobserver, and the velocity observer is not sensitive to the PMLSM parameters yet.Furthermore, the design of the hardware and software of the servo system iscompleted independently. In terms of hardware, the hardware is divided into driveboard, grating-signal amplification board, grating-signal subdivision board, controlboard and human-machine interface board for different functions. Among them, agrating-signal detection method based on the phase-shift between square waves isproposed while designing the grating-signal amplification and subdivision boards.According to this method，the grating displacement is extracted from the relativephase-shift between the two square waves, and the strict sinusoidal similarity ofgrating-signal is not required. In terms of software, the main program, thegrating-signal detection program, the SVPWM program, the PMLSM linear servosystem control algorithm program, the PMLSM observer program and thehuman-machine interface program are analyzed, and their flow charts are given.Finally, the productive prototype of PMLSM linear servo driver is self-developedunder the above hardware and software schemes, and the experimental platform is setup. The experimental results show that the parameter identification precision based onthe PMLSM mechanism model can satisfy the parameters self-tuning requirement ofregulators. The servo system has a good dynamic and static performance afteradopting the s-shaped instruction form. The subdivision precision of grating is0.09m and the positional precision of servo system is±0.9m after adopting thesquare-wave phase-shift subdivision method for grating-signal. The servo system isunaffected by the load disturbance after adopting the load resistance observer. Theservo system can operate well without the grating sensor in the area that above themaximum velocity of10%. |
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