Controller Structure

Overview

The controller structure corresponds to the classical cascaded closed loop with current controller, velocity controller and position controller. In addition, the reference value of the velocity controller can be smoothed via a filter.

The controllers are tuned one after the other from the "inside" to the "outside" in the following sequence: current control, velocity control, position control.

 

1   Position controller

2   Velocity controller

3   Current controller

4   Encoder evaluation

See chapter Overview of the Controller Structure for a detailed description of the controller structure.

Current Controller

The current controller determines the torque of the motor. The current controller is automatically optimally tuned with the stored motor data.

Velocity Controller

The velocity controller controls the motor velocity by varying the motor current depending on the load situation. The velocity controller has a decisive influence on the dynamic response of the drive. The dynamics of the velocity controller depend on:

oMoment of inertia of the drive and the controlled system

oPower of the motor

oStiffness and elasticity of the elements in the flow of forces

oBacklash of the drive elements

oFriction

Position Controller

The position controller reduces the difference between the reference position and the actual position of the motor (position deviation) to a minimum. When the motor is at a standstill, the position deviation is close to zero in the case of a well-tuned position controller.

An optimized velocity control loop is a prerequisite for good amplification of the position controller.

Control Loop Parameters

This device allows you to use two control loop parameter sets. It is possible to switch form one set of control loop parameter sets to the other during operation. The active control loop parameter set is selected with the parameter CTRL_SelParSet.

The corresponding parameters are CTRL1_xx for the first control loop parameter set and CTRL2_xx for the second control loop parameter set. The following descriptions use the notation CTRL1_xx (CTRL2_xx) if there are no functional differences between the two control loop parameter sets.