Determining stiffness

The configuring of some application types (e.g. tower sway and belly sway) requires the defining of the parameters "Spring stiffness between tower and traveling trolley" and "Damping ratio between tower and traveling trolley". If you do not already know these values, e.g. from the mechanics simulation, they can be determined from the signal course of the oscillating system.

  1. Activate the "Support for parameter determination" function in the "Basic settings" area in the "Anti-sway control" configuration menu.
  2. Load your application with the required payload and move the lifting axis to the position where the greatest vibration of the tower occurs. With the "Tower sway" application type, for example, this is most often the highest point on the tower, and with the "Belly sway" application type in the middle of the tower. For the stiffness determination period, update the value for the "Distance between lifting and traveling vehicle" parameter to the lifting height at which the measurement is performed. If the application does not permit movement to the suggested lift position without the anti-sway control, the oscillation can occur even at lower lifting heights or with less load. Update the parameters accordingly.
  3. Deactivate the anti-sway control to measure the vibration by selecting the setting "Anti-sway control off" as the "Application type" or switch the anti-sway control off and on via the fieldbus interface in the optional process data under anti-sway control via the control word.
  4. Run the application and record the amplitudes of the oscillating system, e.g. by means of a video recording at the point of greatest oscillation. If there is enough torque back to the motor from the oscillating mass, a scope recording of the torque can also be used.
  5. Determine the 3 parameters shown below on the basis of the recordings. The peaks of the oscillation amplitudes can be specified proportionally to one another even independently of their amplitude (e.g. 1 : 0.8). The "Oscillation period" can also be determined across multiple periods (e.g. measured time / number of oscillation periods)

[20]

Oscillation amplitude (1st peak)

[21]

Oscillation amplitude (2nd peak)

[22]

Oscillation period (time between 1st and 2nd oscillation amplitude)

  1. Reactivate the anti-sway control by selecting your application type. Check the "Name of the axis for lifting position" setting if you are using the "Tower sway" application type.
  2. Enter the determined measured values (see diagram) into the corresponding setting fields in the "Anti-sway control".
    • The values "Damping ratio between tower and horizontal drive" and "Spring stiffness between tower and horizontal drive" are calculated and used directly for the anti-sway control.
    • The natural frequency, resonant frequency and "Deflection at lifting height" are determined for plausibility checks against reality and design calculations.
  3. Run a plausibility check with the aid of the "Deflection at lifting height" value in the "General information for assessing the design" area in the "Anti-sway control" configuration menu.
  4. Deactivate the "Support for parameter determination" if the "Distance between lifting and traveling vehicle" parameter is used as the "Source of distance between lifting and traveling vehicle" or the "Payload mass" parameter for the operation of the application.