The Pendulum Motion Measured Digital Photogrammetry for a Centrifugal Pendulum Vibration Absorber

Centrifugal Pendulum Vibration Absorber (CPVA for short) is used to absorb torsional vibrations caused by the shifting motion of the engine. It is increasingly used in modern powertrains. In the research of the dynamic characteristics of the CPVA, it is necessary to obtain the real motion of the pendulum to compensate the fitting performance of mathematical model. The usual method is to install an angle sensor to measure the movement of the pendulum. On the one hand, the installation of the sensor will affect its movement to a certain extent, so that the measurement results do not match the actual motion. On the other hand, the motion of the pendulum is not only the rotational motion around the rotational axis of the CPVA rotor, but also has translation relative to it. As a result, it is difficult to obtain accurate motion only by the angle sensor. We proposed a non-contact centrifugal pendulum motion measurement method. A high-speed camera is used to photograph the motion of the CPVA. For two adjacent images recording its motion, we use the ORB descriptor with rotation invariance to obtain the key points of the images. The Brute-Force Matcher(BF Mathcer) is used to match these points. Then, we calculate the rotational motion of the absorber rotor and the translation of the centrifugal pendulum relative to the rotor after peeling off the rotational motion around it. The method can obtain the motion of the centrifugal pendulum without affecting the motion of the CPVA. It is a feasible method without installation limitation of sensors to study the dynamic characteristics of the CPVA.