Multi-harmonic adaptive vibration control of misaligned driveshaft systems - An experimental study

Active Magnetic Bearings (AMBs) have been proposed by many researchers as an alternative to traditional contact bearings in rotor and driveline systems. Such active, non-contact bearings do not have frictional wear and have been used as actuators to suppress vibration in many rotordynamic applications. However, one important issue not previously addressed in AMB driveline control studies is the effect of non-constant velocity (NCV) flexible couplings, such as U-Joint or disk couplings. When driveshaft misalignment is present, NCV effects introduce periodic parametric and forcing actions that are functions of shaft speed, misalignment and load-torque. Previous research found that NCV couplings greatly impact stability and cause significant excitation at shaft speed harmonics. Thus, to ensure closed-loop stability and acceptable performance of any AMB-driveline with NCV couplings, these effects must be accounted for in the control design. In this paper, a hybrid control law consisting of a PID feedback augmented with multiple harmonic adaptive vibration control (MHAVC) is developed for a U-joint-driveline supported by AMBs. Here, the PID control ensures stability while the MHAVC suppresses steady-state vibration. This paper focuses on experimental demonstration of the active control where it is shown that the MHAVC effectively suppresses multi-harmonic imbalance, misalignment and load-torque vibrations without explicit knowledge of the driveline operating conditions.