Control system for electromechanical arrangements having open-loop instability

Abstract

Control system for electromechanical arrangements having open-loop instability. The system is built around a control unit that processes sensing signals and provides control signals to maintain a movable member, such as a rotor or shaft, in the desired position. The control unit according to the invention includes a specially designed compensation filter, which isolates the open-loop instability so that the shaft is treated as a pure mass. In magnetic bearings, the open-loop instability is manifested as negative stiffness. The invention isolates the negative stiffness thus providing for better positive stiffness and improved bandwidth. Various filters, summers, and other operators required to carry out the invention are preferably implemented on a programmed processing platform such as a digital signal processor (DSP) or an arrangement of multiple digital signal processors. Algorithms involved can be implemented using background processing to obtain a compensation filter, which is then read into memory on the DSP and used to process the error signals at the DSP sampling rate. Alternatively, algorithms involved can be automated as part of a machine power up sequence and background monitoring can detect and adjust for changes in the magnetic bearing dynamics. The later option involves an on-line system id capability as well as highly sophisticated fitting algorithms that replace the decision-making capability of the operator.