Servo control system working system

For the closed-loop control of elevator car lifting, an encoder is installed on the elevator host to provide incremental A, B sine  cosine signals, 2048 pulse cycles per week,  single cycle C, D sine  cosine signals, single cycle C, D sine  cosine signal signals are divided by coarse position, which can provide motor UVW commutation information;  there are 2048 cycles of sine  cosine signals per week, which can be further subdivided to obtain high-resolution position changes. This high-resolution position change information is mainly used for acceleration calculation in a short time. Since accurate acceleration feedback is required when the time variable is small, a higher resolution is required. More position change information requires the encoder to have a high resolution  precise position accuracy, so as to ensure precise acceleration feedback to control the input current of the motor.

However, due to the mechanical error in the elevator mechanical system, when stopping at each floor, an external leveling sensor is still required to feed back the elevator to obtain precise positioning, such as using leveling photoelectric switches,  directly using leveling absolute value multi-turn encoders. Closed loop servo system with precise position.

In fact, the servo system may require two encoders ( only one). One is to perform motor commutation  acceleration feedback at the high-speed end of the motor. This feedback enters the motor driver  determines the commutation of the motor control current. Like the size (torque loop), the other is used to accurately determine the end position of the low speed end. The motor-side encoder needs high resolution, usually a high-resolution incremental encoder is used to obtain subtle changes in acceleration; while the encoder at the motion end needs to be accurate  reliable in position, commonly used absolute multi-turn encoders (linear gratings can also be used) . If only one encoder is used (for example, only the motor-side encoder is used), it is necessary to rely on the high precision of the mechanical transmission part,  the current high-precision mechanical transmission is almost in the hands of Japanese  German manufacturers. monopoly. Installing sensors (encoders) in the terminal is a way to avoid this monopoly.

In the inverter control system, since the motor commutation signal is  required, the encoder can be directly installed on the motion terminal, that is, the low-speed end.

We have two concepts, one is a servo system  the other is a servo motor. These two concepts are different. Servo motor is a special actuator. Its motor drive design is a closed-loop control of position, speed,  torque  the beginning, but as a part of the actuator, the motor does  represent the entire servo system.

Can closed-loop control be called a servo system? No, but to achieve rapid control  accuracy assurance in space (position) accuracy  time response. However, the "tightness" of tracking is related to the accuracy of positioning,  there will always be a certain deviation. This is also one of the characteristics of the servo system. The real servo is to eliminate the influence of this deviation on the control result.