Design Of Two-phase Micro-step Driver Based On FPGA

Stepping motors have been widely applied in various automation control systems. The running performance of the stepping motor is not only related with its characteristics, but also depends largely on the drive technology which the stepping motor adopted. Development of highperformance stepping motor driver can improve the accuracy of stepping motor and the operation stability, reliability and flexibility, thus promoting the use of stepping motor more widely. Based on the analysis of stepping motor characteristics and working principle, this paper emphatically studies the stepping motor driver control technology. According to the driving principle and control characteristics of the two-phase hybrid stepping motor, this article comprehensively adopts subdivided driving technology and constant frequency chopping constant-current technology, so that the internal synthesis of magnetic field of the stepping motor is uniform and also round rotating, thus driving a two-phase hybrid stepping motor smoothly. The stepping motor's torque is determined by the amplitude of Synthetic magnetic vector and the stepping angle is determined by the angle between adjoining two Synthetic magnetic vectors. Based on this principle, a micro step driver for two-phase hybrid stepping motors with small or medium-sized power used in instruments is designed.This article compares and analyzes the characteristics of several common controllers of different types, compares advantages and disadvantages between separated and integrated power drive circuits, also presents two measures for constant-current realization. For one measure, it's based on DAC and voltage comparator. For the oher one, it's based ADC and PI adjustment. Finally the design scheme this paper applies is established. The stepping motor driver, with FPGA as control core, communicates with PC via RS232 serial port. PC is adopted to be as the superior machine for convenient. On the PC side, the control software programmed in LABVIEW can be used to set working mode, Subdivided level, direction, run or stop, steps for accelerate, constant rate, deceleration , etc. Using the LabVIEW web publishing tools, the user can view and operate the control interface through the client browser. So the stepping motor can be controlled remotely. The driver will drive stepping motor correspondingly according to the received commands sent by PC. Also, the driver can send the operating condition to PC. Drivers have nine subdivided level, the maximum of subdivision can reach 256. Two kinds of working mode are optional. For one mode, it needs the accurate number of steps; for another mode, the stepping motor will stop automatically if it runs to the desired position. The output current of driver can be adjusted, so it can drive many kinds of stepping motors with different rated current which under 2.8 ampere. The driver can protect itself for it owns over-current protection, overheating protection.At last, the two-phase hybrid stepping motor driver's performances are tested. Test results show that the driver matches each index set before the system design. The driver is safe, reliable and flexible and steady. The whole system circuit, with excellent performance and versatility, is applicable to drive several types of two-phase hybrid stepping motor with small or medium-sized power such as 57 series, 42 series and 28 series, etc.