Research On The Key Technologies Of Industrial Ethernet Based Bus-type Servo System

AC permanent magnet synchronous motor (PMSM) servo system plays an irreplaceable role in the field of motion control such as the modern numerical control machining and robotics. However, because of the late beginning, insufficient experience and low technological level for the domestic servo industry, most of high-end servo drive systems are monopolized by foreign countries. In order to promote Chinese manufacturing industry upgrading and raise the level of national manufacturing, the key technologies of bus-type servo system were further researched in this dissertation. Industrial Ethernet technology was applied to the AC servo system to realize a networked control servo drive system by means of research on bus interface technology for the servo system. On-line self-tuning for servo system control parameters and high-performance speed control in ultra-low speed range were realized by means of analyzing and studying the related theories which include model reference adaptive system (MRAS) and Kalman filter (KF).First of all, the study was focused on the application of real-time industrial Ethernet in the servo drive system. The EtherMAC (Ethernet for Manufacturing Automation), which was developed by our research group, was improved and perfected. According to the special requirements of bus control interface for servo drivers, the physical layer, data link layer and application layer of EtherMAC based servo driver slave station were designed. And the communication protocol, which includes communication commands, servo commands and data feedback in Ethernet data frames, was planned for bus-type servo drive system. The experimental results show that, without the hard real-time operating system and special equipments, the designed bus-type servo drive slave station can meet the requirements of real-time and synchronism for servo system.Secondly, in order to provide a good theoretical basis for controlled object parameters identification, system control parameters self-tuning and ultra-low speed stable control, the transfer functions of each link were analyzed and the mathematical models of current loop, speed loop and position loop were built correspondingly. Besides, in order to improve the efficiency and speed adjusting performance of interior permanent magnet synchronous motors (IPMSM), an engineering approximate algorithm for maximum torque per ampere (MTPA) control was given to facilitate engineering application.Thirdly, the self-tuning strategy for servo system control parameters was studied. The MRAS based on-line controlled object parameters identification was presented by means of analyzing the controlled object of servo system. The adjustable parameter models of permanent magnet synchronous motor (PMSM) winding resistance, equivalent inductance, permanent magnet flux linkage and system total inertia were built. Then the corresponding adaptive laws were designed according to Popov hyperstability theory. Based on the deep research on each control loop mathematical model, self-tuning rules for current loop, speed loop and position loop were derived according to two-rank optimum system and three-rank optimum system theories. And the identified parameters were used to realize the self-tuning of control parameters. The simulation and experimental results show a good adaptability of the proposed on-line identification method. The varying parameters can be identified with enough response time and identification precision. The dynamic performance and robustness of servo system are improved with the self-tuning control parameters.Then, the ultra-low speed control strategies for PMSM servo system were studied. According to the difficulty of low and ultra-low speed control for servo drive system, an optimal state estimator based on the extended Kalman filter (EKF) was used to provide exact estimation for instantaneous speed, position and equivalent disturbance load torque in a random noisy environment. The MRAS was incorporated to identify the variations of inertia moment real-timely, and the identified inertia was used to adapt the EKF for better dynamic performance. The estimated equivalent load torque was used for feedforward control which can decrease the torque ripple of the motor effectively. Meanwhile, the conventional M/T speed detection method was improved so as to eliminate the error from non-complete pulse period. With analyzing the servo system operation characteristics in different speed ranges. a variable structure optimization for servo drive system was designed. This optimization method adjusts the sampling periods of current loop and speed loop dynamically and configures the optimized speed feedback method according to the current speed. The experimental results show that the optimization method can improve the dynamic response of medium and high speed region, and confirm stable in low and ultra-low speed range. The presented strategy provides a precise speed control over a wide range of speeds and the proposed system is robust to modeling error and system noise.Finally, a real-time industrial Ethernet based bus-type AC servo system was developed, which includes the bus-type servo driver hardware platform, the field oriented control library, application layer software based on STM32F4ARM processor and graphical user application for servo control and debugging. The experimental results show that the designed bus-type servo drive system has good dynamic and static performance of current, speed and position loop.The successful implementation of this research provides an effective way to apply industrial Ethernet in servo drive system. It also gives a solution to solve the key problems of control parameters self-tuning and ultra-low speed stable control.