A design Approach to Optimize Suspension Clanking Noise in Electric Cars

Designing an electric car suspension system is a key challenge for all OEMs because balancing buzz, squeak, and rattle (BSR) acoustic performance at low-speed driving and improving ride quality at high-speed driving conditions is difficult. Suspension noise deteriorates in-cab acoustic quietness and overall vehicle performance. For this reason, optimizing these noises is becoming increasingly prioritized as a key design issue throughout the development process of suspension system. This paper studies the various components of suspension system and their noises in an electric car. Based on customer voice index and drive pattern, suspension anomalous clanking noise was identified in Electric Car. This noise phenomenon was cascaded from the vehicle level to BSR rig and eventually to the suspension rig for root cause analysis. At the vehicle level evaluation, clanking noise problematic frequency identification was done for both near suspension source and incab with the help of a sound diagnosis analysis tool and time-domain wavelet transformation. Furthermore, this noise was cascaded at BSR rig level for subsystem frequency analysis and intensity quantification. Eventually, this noise was cascaded at the suspension rig level and the major component, and its critical frequency (200Hz -2 KHz) were identified by time-domain wavelet analysis tool. After this investigation, design modification was done on the suspected stopper cap and significant noise improvement was found in overall noise level subjectively and objectively in the defined frequency range. This modified stopper cap with suspension system performance was assessed at BSR rig and vehicle level for clanking noise improvement validation purposes. The output of this work was a reduction in overall 4dBA clanking noise in vehicle incab as well as a significant increase in overall acoustic performance of the car without affecting ride and handling quality. With additional to that, this cascading methodology could be used to address various suspension noises.