Development Of Multi-axis Digital Servo Controller

With the development of large scale integrated circuits and high-performance microprocessors, the modern servo control technology has been gradually moving towards all-digital. Aiming at the specific plant—hydraulic system and combining the advanced digital technology, this dissertation has completed the design and development of a multi-axis digital servo controller.Firstly, according to the exisiting hardware and software resources now available and the comparision of the methods, which are popularly used to design digital servo controller nowadays. This dissertation made a design plan based on ARM and FPGA. As the master controller, the responsibility of ARM is to send commands and complete control algorithrm. However, to FPGA, as the slave controller, its duty is to receive and translate the commands coming from ARM and perform specific functions. This dissertation chose an FPGA to achieve the interaction between external modules and ARM, not only simplifying the system design but also improving the flexibility of the system. Besides, with FPGA, the logic of reading and writing in peripheral devices is all fulfilled by hardware, which greatly improved the ability of real-time performance in this system.Secondly, by analyzing system requirements deeply, this dissertation has accomplished the schematic design, PCB design and FPGA internal logic design of the servo control board based on FPGA. Then using the development tool QuartusⅡ, the simulation and board-level verification has been carried out to the FPGA board. The functions of the controller are described as follows: it has 8-channel analog inputs, 8-channel analog outputs, 8-channel digital inputs, 8-channel digital outputs, 8-channel incremental encoder inputs interfaces. And especially, according to the feature of the hydraulic system detector, through full duplex RS485/422 transceivers and FPGA internal logic design, the controller can capture 8-channel SSI absolute encoder inputs with high speed.Finally, in order to complete the joint contol of ARM and FPGA, this dissertation has established the cross-compliling enviriment based on embedded Linux, realized the SPI device driver, which allows ARM and FPGA communicate normally. And then, based on thses resources, this dissertation designed a PID closed loop control which verifies the feasibility and correctness of the controller.