Design of Centrifugal Pendulum Vibration Absorber to Reduce the Axial Vibration of Rotating Shafts for Multiple Orders

Centrifugal Pendulum Vibration Absorbers (CPVA) are used to reduce the torsional fluctuation of rotating shafts at a certain vibration order. The concept can also be used to reduce the axial or longitudinal vibration of rotating shafts at the desired order. The axial vibration of driveshafts mainly at combustion order, i.e., 2× rpm for four-cylinder engines, is the reason for the generation of a high level of suspension forces and eventually increased levels of noise and vibration inside the passenger compartment of rear-wheel-drive vehicles. The axial vibration of a shaft at multiple orders (1× rpm and 2× rpm) also increases at higher levels of unavoidable parallel or angular misalignment. The vibration at multiple orders needs to be reduced in the vehicle driveline system in rear-wheel-drive vehicles to minimize the noise and vibration and provide enhanced comfort. A single pendulum vibration absorber can attenuate only one vibration order of the rotating shaft, and multiple absorbers are required to reduce the vibration at different orders. The design strategy to reduce the first- and second-order axial vibration, by using circular path pendulum absorbers, is explained in this work. The generated torsional vibration at the second order due to first-order oscillations of the pendulum is counteracted by the design of an additional CPVA. Torsional springs are used at the pivot joints of all pendulum absorbers to counteract the excessive oscillations due to braking and gravitational effects at low speeds. The additional advantage of introducing the springs and their influence on the natural frequencies is analyzed. The second-order equations of motion of the absorbers are solved analytically using the method of multiple timescales with a two-term approximation. The stability characteristics of the solutions are analyzed at the excitation frequencies and different dynamic axial force levels. Analytical results are compared with numerical simulation of a complete set of nonlinear equations. The performance of centrifugal pendulum-type axial vibration absorber (CPAVA) in reducing the predominant second-order longitudinal vibration at differential and passenger compartment is experimentally demonstrated by using CPAVA at the differential flange of a rear-wheel-drive vehicle. The proposed methodology helps in designing the CPAVAs for attenuating the axial vibration at multiple higher orders of rotating shafts.