Online parameter-estimation of feedforward gains in cascaded control structures for servo drives

High running comfort and precise positioning in elevators needs well adjusted feedforward gains in the cascaded control structure for servo drives. For avoidance of the start jerk, the machine has to be energized before the mechanical brake opens. The energizing current has to be in accordance with the load difference between the cabin's and the counterweight's side, which depends on the payload and the position. In addition, the torque needed for acceleration of the elevator inertia is also being feed-forwarded to ensure a dynamic response and precise positioning. The manual adjustment of the feedforward gains is time consuming, expensive and not done satisfyingly all the time and thus an automatic adjustment is proposed in this paper. Also, as existing procedures need additional test weights for the calibration, this paper proposes an estimation procedure which runs during the travel and does not need additional excitation which would annoy the passengers. An online estimation method is presented which allows an automated starting up without manual adjustments or the need additional weights for calibration. Simulations, as well as measurements at a test elevator, show good and robust performance of the algorithm. Already after the first run no start jerk occurs and the parameters are optimized further as soon as the first time passengers travel with the elevator. Also, as the algorithm runs during the travel, an additional parametrization of the inertia caused by the passengers is possible.