What is the connection between the encoders on the servo motor?

The encoder is mounted on the tail of the servo motor and is not closely related to the current loop. The sampling is from the spatial position of the rotating rotor of the motor, not the motor current, and has no connection with the input, output and feedback of the current loop. The current loop is formed inside the driver. Even if there is no motor, a feedback loop can be formed by installing an analog load (such as a bulb) current loop on each phase.

Acceleration feedback is achieved by multiplying the motor speed feedback signal by the acceleration feedback gain to compensate the torque command to achieve speed loop vibration control. When the position command pulse and the feedback pulse are not equal, a speed pulse command is generated together. 

Encoder position loop: The position loop is the input position information pulse after the calculation smoothing filter processing and electronic gear calculation as the "position loop setting", and the pulse signal from the encoder feedback is calculated by the deviation counter. The value of the value of the feedforward signal after the PID adjustment of the position loop (proportional gain adjustment, no integral differential link) and the given feedforward position constitutes the given speed loop. The feedback of the position loop also comes from the encoder. The common phenomenon of position loop anomalies is the position error of multi-step loss. The same fault can occur with the encoder loose.

Common servo motor jitter is generally caused by improper parameter setting or related circuit hardware abnormalities. As far as the hardware is concerned, the speed loop hardware problem is mostly caused by the encoder feedback related circuit abnormality. The current loop is an abnormality in the current Hall detection related circuit. The position loop is mostly input pulse circuit interference (uncommon). Since the electronic devices that detect feedback are mostly normal and stable servo circuits, the parameters will not be matched due to aging of the components.