Research On Key Technologies Of Permanent Magnet Synchronous Motor Servo Drive Systems

Permanent Magnet Synchronous Motor (PMSM) servo drive systems are adopted as final executive components in many automation equipments, and become the key aspects to decide the performance of the entire equipments. Meanwhile PMSM servo drive systems are required to be high speed, high precision and high efficiency with the rapid development of equipment manufacturing industry.The PMSM servo drive system is a complex Opto-Electro-Mechanical system, and its performance improvement involves various factors as shown in the following examples:Due to the limited feedback information provided by the output pulse of incremental photoelectric encoders, the method of taking full advantage of the limited information to obtain a high precision speed and position information, is an important research content for the improvements of servo drive systems performance; The elasticity of transmission components will lead to the undesirable mechanical resonance, and as a result, the existence of the resonance limits the system bandwidth, potentially causes the system instability, and has turned to be one of the urgent problems in high performance drive systems; The analog voltage or pulses command interface has some limitations such as poor anti-interference ability and less data capacity, while the further development of high speed standard field bus has been blocked by its technology monopoly and expensive price. To meet the communication requirements of high real-time and mass data capacity in servo drive systems, a kind of cost-effective and hard real-time bus interface solution is necessary to be developed; Overheating is the main reason of motor insulation damage, but excessive heat protection will restrict the load capacity of motors and reduce the efficiency. To bring into full play the motor load capacity so as to improve the operation efficiency of drive systems, an appropriate and reliable thermal protection method has great practical significance.This paper aims at improving the performance of PMSM servo drive systems, especially focuses on the key technologies of the speed and position measuring method, mechanical resonance suppression, bus interface technology and Real-time Thermal Model (RTTM) for motor thermal protection, and has carried out some theoretical research and engineering practice in these key technologies. The main contents are as follows:A Relay-style Digital Speed Measurement (RDSM) method, a Dynamic Position Subdivision (DPS) algorithm and a linear estimation method of instantaneous speed are proposed to make full use of the feedback information of the incremental encoder pulses. The relay-style detection approach making the actual sample point always prior to the periodic sampling point is achieved by synchronizing the encoder pulse rising edge with the sampling clock, and the hardware and software implementation method of R.DSM is also studied, meanwhile the characteristics and performance of the RDSM method are carefully analyzed. The method of subdividing a single encoder pulse in time is presented to improve the dynamic position resolution, and the linear estimation method of instantaneous velocity utilizing two adjacent speed measurements is performed to obtain the accurate speed information with less delay.A Filtered-x Least Mean Square (FxLMS) control structure is built for resonance suppression, and one type of particle damping fall algorithm is put forward to accelerate the LMS convergence. To speed up the convergence of the adaptive algorithm, the particle damping fall in a gravity field is presented to analogize the optimization behavior of the filter coefficients, based on which the algorithm of particle damping fall is achieved and the determination of its control parameters scope is elaborated. The theory analysis and practice prove that the proposed control structure has good following performance and robustness, and can effectively suppress the resonance.A set of Real-time Ethernet (RTE) including master and slave controllers is studied, and especially the methods enhancing bus real-time performance are presented to break the bottleneck of communication encountered in high performance servo drive systems. The cut-through mechanism is introduced to decrease the process time of slave controllers, thereby shortening the communication cycle period. A scheduled synchronization scheme and a kind of Phase Locked Loop (PLL) based on a Proportional-Integral (PI) regulator are performed to improve the synchronization precision between the master and slave clock, so as to satisfy the requirement of high synchronization performance such as the application of numerical control systems.A real-time thermal model of motor is established on the basis of the heat transfer mechanism and the physical structure of PMSM, and online temperature prediction algorithm is achieved. The calculation of motor core losses is accomplished by the association of the losses to the motor speed and current, and the approach using a variable thermal resistance to simulation the variation tendency of motor cooling capacity with the different speeds is developed. The determination method of the model parameters and the software process of the motor thermal protection are described in detail, and the accuracy of the temperature prediction and the effectiveness of the thermal protection are verified by the experiments.The hardware and software platform of the drive system is set up, and the system integration plan of the above key technologies is researched with emphasis. Two axis movements of the circular interpolation in an actual lathe are applied to verify the control performance of the whole integrated servo drive system.