Closed Loop Control

Closed Loop control uses feedback from the system being controlled. First, the RMC generates a target (position, velocity, pressure, or force) which specifies where the axis should be at each moment in order to move to the requested position. Then, the RMC compares the feedback to the target and calculates how much Control Output should be given to make the feedback match the target. The RMC repeats this for every control loop time. All closed-loop commands specify the target to be generated. The tuning parameters specify how to calculate the Control Output, which makes the axis follow the target.

Closed Loop Control Algorithms

The RMC offers several different algorithms for closed-loop control, depending on the feedback type:

Feedback Type	Closed-Loop Control Algorithms
Position	Position PID Advanced: Position I-PD Velocity PID Velocity I-PD
Velocity	Velocity PID Advanced: Velocity I-PD
Pressure	Pressure/Force Control and Pressure/Force Limit
Force	Pressure/Force Control and Pressure/Force Limit

Dual-Loop Control

The RMC supports dual-loop control, for example position-pressure or position-force. This allows controlling two quantities with a single actuator. For example, consider an injection molding application. The system first moves in position control to inject the material, then needs to maintain a certain force. Using dual-loop control, this can be done with a single actuator (typically a hydraulic valve).

On the RMC, dual-loop control requires one Control Output, one position (or velocity) feedback, and a pressure or force input (this is called the secondary feedback).

Dual-Loop Control Requirements

To define a dual-loop control axis, the RMC requires:

RMC75: Dual-loop control requires that the secondary feedback is from an AP2 module.

RMC150: Dual-loop control requires a pressure-control enabled RMC150, designated as an RMC151.

RMC200: Each dual-loop control axis requires two control loops on the Feature Key.

See the Position-Pressure and Position-Force Control topic for more details.

Closed Loop Commands

See the List of Commands topic for a list of closed-loop commands.