Adaptive feedforward control of an industrial H-drive positioning with permanent magnet linear motors

Adaptive feedforward method for an industrial permanent magnet linear motor H-drive application is presented. Industrial H-drives consist of two parallel linear motors in the X-direction connected mechanically together through an intermediate beam with a third linear motor in the Y-direction. H-drives can have a remarkable backlash, and the assembly may have different mechanical parameters such as different air gaps making the motors behave differently. Because of these non-idealities the control of the H-drive with a traditional fully linear controller becomes difficult and inaccurate. Feedforward controllers are commonly used to increase the performance of the linear motor drives, but precise parameters are essential for achieving high tracking performance and positioning accuracy of the system with feedforward terms. However, the parameters, like the friction of the mover, can change during operation and reduce the effectiveness of the feedforward control. For this purpose a new, easily applicable adaptive feedforward for the H-drive application is developed and suggested. The experimental results given verify the increased position accuracy during highly dynamic movements with the proposed adaptive feedforward method compared to regular feedforward with constant parameters.