How does a servo driver board achieve high-precision synchronization of position/speed/torque through closed-loop control algorithms?

The servo driver board achieves high-precision synchronization of position, speed, and torque through a closed-loop control algorithm. The core of this approach lies in a dynamic "feedback-comparison-correction" adjustment mechanism, combining a multi-loop control architecture with intelligent algorithm optimization. The following is a simplified explanation of its working principle:

1. The Core Logic of Closed-Loop Control: Feedback and Correction
The closed-loop control of a servo system is similar to "autonomous driving":

Target Setting: The user inputs a position command (e.g., "move to 100mm"), a speed command (e.g., "500rpm"), or a torque command (e.g., "10N·m").
Real-Time Feedback: The encoder (or Hall effect sensor) continuously monitors the actual motor position, speed, and torque and transmits this data to the driver board.
Error Comparison: The driver board calculates the difference between the target value and the feedback value (e.g., "Current position 95mm, error 5mm").
Dynamic Correction: The output voltage/current is adjusted to compensate for the error, bringing the actual value closer to the target value.

2. Three-Loop Control Architecture: Collaborative Layered Control
Servo driver boards typically employ a three-layered control system: position loop, velocity loop, and current loop (torque loop). Each loop is responsible for different dimensions of accuracy:

Current Loop (Torque Control):
Function: Directly controls motor current, achieving fast torque response.
Principle: By adjusting the PWM signal duty cycle, the motor's magnetic field strength is precisely controlled to ensure that the output torque matches the command.
Analogym: Like "muscle control," it directly determines the amount of force applied.
Speed ​​Loop:
Function: Building on the current loop, it stabilizes motor speed.
Principle: Based on encoder feedback, it adjusts the current loop command to eliminate speed fluctuations (such as deceleration during sudden load changes).
Analogym: Like "throttle control," it maintains a steady driving speed.
Position Loop:
Function: Ultimately achieves precise positioning.
Principle: Based on the target position and actual position, it generates a velocity command (e.g., "Current position 95mm, accelerate to 500rpm"), which is then executed by the velocity and current loops.
Analogym: Like a "navigation system," it plans routes and directs driving. Synergy Mechanism:

The output of the outer loop (position loop) serves as the input to the inner loop (speed loop), which in turn serves as the input to the current loop, forming a "layered" correction chain.
For example, when position error is large, the position loop will increase the speed command, while the speed loop will increase the speed by increasing the current, rapidly reducing the error.