Speed Control for Lifting Devices with Conical Cable Drum through Indirect Position Determination

Lifting devices are often provided with a spring to compensate their constant weights. But because the force of a spring is depending on its stretch, the compensation ratio during a lifting process is fluctuating. By changing the characteristic of the load with the help of a variable radius drum it is possible to mitigate this drawback. In this paper a torsion spring and a conical cable drum are used for compensation. Because the wound cable length per revolution is changing, the lifting speed also varies. For the introduced speed controller the position of the drum is measured with an absolute, magnetic sensor. The actual lifting speed is then indirectly determined by calculation utilizing the cable drum parameters.