Control

Distance control can be used optionally with P, PI, PD or PID controllers. This helps to combine the different advantages of the individual controllers. If distance control with a P-only controller does not work fast enough or problems occur with oscillation, we advise you to execute control as a PD controller. The I component should only be considered for permanent control deviations.

Characteristics of individual controllers for distance control:

P controller

Weights the output value and affects distance control dynamics. Can be set using P-AXIS-00759.

I controller

Permanent control deviations are completely compensated after a certain time. If there is no permanent control deviation, we advise you to disable the I component using P-AXIS-00764 = 0 to avoid a negative effect on distance control dynamics.

D controller

The faster the distance values change, the stronger the reaction of the D controller. This helps to reduce oscillations. Can be set using P-AXIS-00765.

Step-by-step and iterative parameterisation of the controller:

  1. Setting the proportional component using P-AXIS-00759:
    First set the controller as a P-only controller. This means disabling the I and D controllers by using P-AXIS-00764=0 and P-AXIS-00765=0, respectively. To avoid controller instability, start with a low Kp factor. Normally, a good start value is Kp=0.2. Then observe the response of the control loop at a defined input step, i.e. a change in distance. You can increase the Kp factor step by step until there is a recognisable but rapid drop in oscillation.
  2. Setting the integral component using P-AXIS-00764:
    The integral component ensures that permanent control deviations are completely compensated after a certain time. If there are no permanent control deviations, you should disable the integral component.
  3. The controller then operates as a PI controller. To avoid instability, start with a high integral action time value Tn. Normally, a good start value is Tn=5. In analogy to section 1, observe the response of the control loop at a defined change in distance and gradually reduce Tn. A good value for Tn is reached when the control deviation is compensated within the required time without causing any undesirable oscillations.
  4. Setting the derivative component using P-AXIS-00765:
    The controller is then used as a PID or a PD controller. Again, start with a passive value for the derivative action time Tv. Normally, a good start value is Tv=0.01. As before, increase the derivative component step by step and observe the step response. The aim is to damp oscillations as much as possible without negatively affecting control loop dynamics.
  5. Readjusting:
    To obtain the best controller response, you can even readjust the parameters again. For example, you can correct the P component upwards by using the D component.