Servo drives are an important part of modern motion control and are widely used in automation equipment such as industrial robots and CNC machining centers. In particular, servo drives used to control AC permanent magnet synchronous motors have become a research hotspot at home and abroad. Currently, the three closed-loop control algorithms of current, speed and position based on vector control are commonly used in the design of AC servo drives. Whether the speed closed loop design in this algorithm is reasonable or not plays a key role in the performance of the entire servo control system, especially the speed control performance.
Basic requirements for servo drives:
1. Wide speed range
2. High positioning accuracy
3. Sufficient transmission rigidity and high speed stability
4. Quick response, no overshoot
In order to ensure productivity and processing quality, in addition to requiring higher positioning accuracy.
It also requires good fast response characteristics, that is, the response to the tracking command signal must be fast, because when the CNC system starts and brakes, the acceleration and deceleration are required to be large enough to shorten the transition process time of the feed system and reduce the contour transition. error.
5. Low speed and large torque, strong overload capability
Generally speaking, servo drives have an overload capacity of more than 1.5 times within a few minutes or even half an hour, and can be overloaded 4 to 6 times in a short period of time without damage.
6. High reliability
The feed drive system of CNC machine tools is required to have high reliability, good working stability, strong adaptability to temperature, humidity, vibration and other environments, and strong anti-interference ability.
Requirements for motors
1. The motor can run smoothly from the lowest speed to the highest speed, and the torque fluctuation should be small. Especially at low speeds such as 0.1r/min or lower, there is still a stable speed without crawling.
2. The motor should have a large overload capacity for a long time to meet the requirements of low speed and large torque. Generally, DC servo motors are required to be overloaded 4 to 6 times within a few minutes without being damaged.
3. In order to meet the requirements of fast response, the motor should have a small moment of inertia and a large locked-rotor torque, and have the smallest possible time constant and starting voltage.
4. The motor should be able to withstand frequent starting, braking and reversal.
