Research On Motion Control System Based On FPGA+DSP

With the rapid development of advanced manufacturing technology, flexible manufacture and fabricating automation techniques, open-frame motion control turns into one of main progressing trends in CNC field. In this research, byutilizing the logic reconfigurable capability of field programmable gate array (FPGA) device and the high computing power of digital signal processor (DSP), a new approach of open-frame motion control scheme based on FPGA+DSP composite structure is proposed and investigated in detail.Accordingly, considering the control requirements of general electromechanical equipment,it elaborates on core controller, servo motor drive, man-machine interface, etc. Meanwhile, it raises a plan of logic design and software function for the pulse sele ction module, the quadrature encoded pulse (QEP) decoding unit, the acceleration and deceleration unit, and the interpolation unit. Hence the design of electrics circuit is carried out containing the power supply section, the FPGA sub-module, the DSP sub-module, and the interfaces for 4-axis servo motor drivers.In particularly, taking into accounting the complexity of traditional S-curve method, a new discrete sampling iteration formula for seven-segment S-curve process is derived and the application algorithm for determining each of the speed shift points is synthesized. Then high speed discrete sampling control of S-curve process is transferred into FPGA hardware logic. And by using the VHDL language, a speed control module implementing S-curve method is designed and built, which mainly consists of counting unit, speed regulation unit, position comparingunit, and the driving pulse generation module. With the built speed control module, experiment platform for acceleration and deceleration operation is set up. The experimental data obtained from servo motor encoder indicates that motor speed variation is continuous, smooth. In addition, the dynamic time is short and the mechanical impact is slight.Besides, regarding the demand of multi-axis linkage motion control, the characteristics of point by point comparison and minimum deviation methodologies are compared and studied for linear interpolation and arc interpolation operation. Thereby, interpolation schemes employing reconfigurable electronic gear/cam boxes are developed and the corresponding application algorithms are carried out. Similarly, by using the VHDL language, interpolation modules for linear interpolation and circular interpolation are designed and realized. Hence experiment platform for multi-axis linage control is set up. The experimental data shows that within a tragedy of 5000 pulses, the maximum deviation of linear interpolation is below 5 pulses for the executed result of physical mechanism, which is approximately 0.084% of the full track. As for the circular interpolation with a radius of 15000 pulses, the maximum deviation is below 14 pulses, which is about 0.088% of the radius.This research indicates that the proposed open-frame motion control system and the implemented FPGA+DSP scheme is distinguished with outstanding logical processing capability, as well as the significant simplified software motion instructions. Moreover, since there is still large amount of redundant resources of logical units and computation power left, even though the 4-axis servo motors have been pulled in, thus more servo motors and more complicate machining track can be fulfilled with the presented FPGA+DSP platform in the future.