Active damping of vibrations in elevator cars

Abstract

AbstractThe goal of this dissertation was to develop an active vibration damping system for high‐speed elevator cars to achieve a ride comfort not reached before by passive means. The system developed comprises eight actuators, six accelerometers, eight position sensors, a signal conditioning unit, and power electronics. It is controlled by a real‐time computer utilizing a digital signal processor. A laboratory test rig was designed and constructed to allow testing the active damping system fitted to a full‐scale high‐speed elevato car. The unevennes of the two guide rails, which is the main source of vibrations, is emulated using eight hydraulic cylinders. A multivariable system identification procedure in the frequency domain was developed to obtain a linear time‐invariant system model. A first controller loop utilizes the acceleration outputs to suppress the vibrations. Due to asymmetric load distributions in the cabin, the orientation of the car with respect to the guide rails may change to the extent that for one or more actuators there may not be enough actuation distance. To correct the car orientation, a second controller loop utilizing position outputs is used. However, since the position measurements are taken between the car and the guide rails, nulling the position error signals means forcing the car to follow an average line of the two rail profiles which is the main source of vibrations. To avoid a conflict between the two loops, a frequency domain separation of the bandwidths of the two controllers is achieved. The two multivariable controllers are designed using the H∞ robust design method and employing the plant non‐inverting GS/T weighting scheme. The effectiveness of the active system was tested using rail profiles previously measured in a real building and emulated by the hydraulic excitation system. The vibration reduction factor achieved is around 5 as to a passive damping system. Meanwhile, the controller is capable of correcting the car orientation caused by asymmetric loads.