Design Of Low-power DC Servo Motor Speed Control System

DC servo motor has excellent speed control characteristics smooth and simple. It has strong starting torque and excellent starting and braking performance. It can control a large range of accuracy, speed and position. At the same time, it has a good overload capacity and can bear frequent impact loads. Therefore, the DC servo system is widely used in those high performance systems. Now, it has been widely used in rolling mills, paper machines, metal cutting machine tools and many other areas of high-performance controlled power drag.After 20th century 80s, with the development of science and technology, AC speed control system and brushless DC motor has been developed rapidly. And they have gradually replaced the brush DC motor speed trend. But thanks to DC brush servo's unique high performance, it can easily be variable speed and has good speed performance, so until now, it has not been replaced. It is still widely used in general industrial and civil occasions which is cost-sensitive.This article is to design a economic and reliable speed control system of DC servo motor. The system not only has reliable and low cost, but also has soft start, constant torque, wide speed, hard features and other functions, achieve smooth variable speed of DC motor and protection of the motor. The system of main circuit uses single-phase half-controlled rectifier bridge circuit, with voltage negative feedback and current positive feedback. The system uses thyristor power DC servo motor control circuit, that is by changing the thyristor conduction angle to adjust the output voltage, Therefore the motor can run smoothly at different speeds and different load conditions. According to modern control theory, the control circuit uses negative feedback manner with current compensation. So it can get a more satisfactory static and dynamic performance (improve the mechanical properties of hardness, increased speed range, speed up the system from the brake and so on). It also can eliminate the need for speed generator and reduce system cost. And provide a convenient installation and maintenance. Finally, the experimental results prove the feasibility of this control scheme.Firstly, this paper analyzes the development overview of DC servo motor and DC drive system, introduces the main structure and working principle of DC servo motor and this paper describes in-depth analysis of the basic principles of speed control system and the basic speed control method. Then introduced used of this system to the DC servo motor. Secondly this paper, the economy is good, high reliability and speed control system of thyristor rectifier for the rectification power supply, the main circuit and speed control circuit of the low power DC speed control system are designed, in which thyristors are used as controlled rectifier power. First, analysis the performance index of Speed control system. Emphasis analyzes the DC servo motor and positive current feedback and negative voltage feedback speed control mode static and dynamic characteristics. Then introduces the principle of work of the control system and protection circuit. At the same time, it is convenient for installation and maintenance before production practices to be considered, the system must be simulated in simulation software before application. This system is simulated by MATLAB Simulink Toolbox based on the transfer function of the control system, then related analysis and comparison are introduced. The results are analyzed and compared. Simulation results show the effectiveness of DC speed system, verify the rationality of other control algorithms and prove that DC speed control system can be applied in production practice. Lastly, according to previous theoretical groundwork, the hardware design experiment is operated based on the theoretical analysis. The original purpose is tested and realized. The experimental results show reliability of the system.Finally, this paper summarizes the work done, the knowledge gained through conclusion of this research and design and prospects for future work.