Talking about the working principle of servo drive

How does the servo drive work:

At present, mainstream servo drives use digital signal processors (DSP) as the control core, which can realize relatively complex control algorithms and realize digitization, networking and intelligence. Power devices generally adopt the drive circuit designed with the intelligent power module (IPM) as the core. Start the circuit to reduce the impact on the driver during the start-up process.

The power drive unit first rectifies the input three-phase power or mains power through a three-phase full-bridge rectifier circuit to obtain corresponding DC power. After the rectified three-phase electricity or mains electricity, the three-phase permanent magnet synchronous AC servo motor is driven by the frequency conversion of the three-phase sinusoidal PWM voltage type inverter. The whole process of the power drive unit can be simply said to be the process of AC-DC-AC. The main topological circuit of the rectification unit (AC-DC) is a three-phase full-bridge uncontrolled rectification circuit.

With the large-scale application of servo systems, the use of servo drives, servo drive debugging, and servo drive maintenance are all important technical issues for servo drives today. More and more industrial control technology service providers have conducted in-depth technical research on servo drives.

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. Especially the servo drive used to control the AC permanent magnet synchronous motor has become a research hotspot at home and abroad. Current, speed, and position 3 closed-loop control algorithms based on vector control are generally 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.

Servo drive system requirements:

1. Wide speed range

2. High positioning accuracy

3. Sufficient transmission rigidity and high speed stability.

4. In order to ensure productivity and processing quality, in addition to requiring high positioning accuracy, good fast response characteristics are also required, that is, the response to tracking command signals is required to be fast, because the CNC system requires addition and subtraction when starting and braking. The acceleration is large enough to shorten the transition process time of the feed system and reduce the contour transition error.

5. Low speed and high torque, strong overload capacity

Generally speaking, the servo driver has an overload capacity of more than 1.5 times within a few minutes or even half an hour, and can be overloaded by 4 to 6 times in a short period of time without damage.

6. High reliability

It is required that the feed drive system of CNC machine tools has high reliability, good working stability, strong environmental adaptability to temperature, humidity, vibration, and strong anti-interference ability.

The requirements of the servo drive for the motor:

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 high torque. Generally, DC servo motors are required to be overloaded 4 to 6 times within a few minutes without damage.

3. In order to meet the requirements of quick response, the motor should have a small moment of inertia and a large stall torque, and have as small a time constant and starting voltage as possible.

4. The motor should be able to withstand frequent starting, braking and reverse rotation.

Post time: Jul-07-2023