General Stepping Motor Controller Programmed In The Field

Stepping motor is widely used in many fields according to its advantages, which include non-accumulated error,high positioning accuracy simple control and high performance-price ratio. With the continuous development of technology, intelligent and miniaturization is the main developing direction of stepping motor controller. Also, application program could be modified in the field and multi-axis interpolation with high precision is needed.One stepping motor controller, which is based on microcontroller and Field Programmable Logic Array(FPGA), is selected as the research object. The overall scheme, the hardware interface and the pulse generating module were studied in detail. Beginning with the introduction of advantages and disadvantages of current control scheme for stepping motors, system architecture scheme combining microcontroller with FPGA was proposed to realize operating convenience and programming in the field. Hardware interfaces were realized by use of resources on chip of microcontroller, and the function of pulse generating module, linear interpolation and circular interpolation was realized by FPGA. So programming flexibility of the microcontroller and parallel processing characteristics of FPGA are well integrated. Some hardware interfaces, which included LCD interface, touch screen interface, nonvolatile memory module and human-computer interaction module, and related software programming were descripted in detail. Also, the principle of three point correction method for touch screen was introduced. Theory and implementation of the pulse generating module and interpolation module were deeply discussed.Considering the problem of system output error caused by the wrong number of transmit pulse or the parameter value for the acceleration and deceleration, system would stop the acceleration process and start to slow down when the system had not reached the maximum operating speed while half of specified number of pulses had been transmitted. In this way, stepping motor could stop with low speed. Duo to the fact that calculation formula of the deviation was different for circular interpolation in different quadrant, interpolation quadrant was switched only when the interpolation point reached the axis for the first time. So the error was avoided. At the same time, the quadrant of starting point on the axis was processed respectively for clockwise circular interpolation and counterclockwise arc interpolation.System hardware design, processing and system experiment verification were conducted. At last, the circuit diagram of the system was given. The whole design could satisfy the system requirements. Considering more complex and diverse stepping motor controlling system in the future, system could be upgraded from several aspects, which include programming flexibility, instruction richness, display diversity and interpolation accuracy, etc.