Determining stiffness

The configuration of some application types (e.g. tower sway and belly sway) requires the definition of the parameters "Spring stiffness between tower and traveling trolley" and "Damping ratio between tower and vehicle". If you do not already know these values, for example, from mechanical simulations, or the suggested tower sway values are not satisfactory, they can be determined from the signal course of the oscillating system.

  1. Activate the "Support for parameter determination" ("From measurement") function in the "Basic settings" section 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 sway 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 trolley at measurement time" 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 sway can occur even at lower lifting heights or with less load. Update the parameters accordingly. With the belly sway application type, the "Distance between lifting and traveling trolley at measurement time" is specified as half the tower height since the measurement must take place at this lifting height.
  3. Deactivate the anti-sway control to measure the sway by selecting the "Anti-sway control off" setting 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 using 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 sway. 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 "Sway period" can also be determined across multiple periods (e.g. measured time / number of sway 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" configuration menu.
    • 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. Perform a plausibility check using the value "Deflection at lifting height" in the "General information for assessing the design" section in the "Anti-sway control" configuration menu.