Torque Feed-forward
The torque
Torque is the tendency of a force to rotate an object about an axis. Just as a force is a push or a pull, a torque can be thought of as a twist feed-forwardThis describes an element or pathway within a control system which passes a controlling signal from a source in the control system's external environment, often a command signal from an external operator, to a load elsewhere in its external environment tells the controller what forces is required to move the axis in an arbitrary trajectory.
Here are the major features of torque feed-forward:
- TorqueTorque is the tendency of a force to rotate an object about an axis. Just as a force is a push or a pull, a torque can be thought of as a twist feed-forward results in virtually instantaneous response of the system.
- Feedback control loops (using PID"Proportional-Integral-Derivative"
A PID controller is a generic control-loop feedback mechanism widely used in industrial control systems.
An "error" occurs when an event or a disturbance triggers off a change in the process variable.
A PID controller attempts to correct the error between a measured process variable and a desired setpoint by calculating and then outputting a corrective action that can adjust the process accordingly loop or similar) take a finite amount of time before reacting.
- Torque feed-forward relies on an imperfect model of the system. This means that the feed-forwards need help from the feedback control loop in order to get accurate motion.
- Torque feed-forward can make the bulk of the move very quickly, while the feedback control loops correct the small errors that remain. As a result, a faster settling time can be achieved than if torque feed-forward was not used.
- There is a common misconception that torque feed-forward is similar to control loops and result in instability. Torque feed-forward is open loop, so it cannot suffer from closed loop instability.
- Torque feed-forward is typically less sensitive to being misadjusted than closed loop parameters.
- Feedback control systems can be excited into instability by grossly misadjusted torque feed-forward. However, the amount of misadjustment in the torque feed-forward necessary to cause such instability is very rare.
