SAE International Optimization of Front Wheel Drive Engine Mounting System for Third Order Shudder Improvement 2017-01-9175

Nowadays, the vehicle design is highly ruled by the increasing customer demands and expectations. In addition to ride comfort and vehicle handling, the Noise, Vibration and Harshness (NVH) behavior of the powertrain is also a critical factor that has a big impact on the customer experience. To evaluate the powertrain NVH characteristics, the NVH error states should be studied. A typical NVH event could be decoupled into 3 parts: source, path, and receiver. Take-off shudder, which evaluates the NVH severity level during vehicle take-off, is one of the most important NVH error states. The main sources of Front Wheel Drive (FWD) take-off shudder are the plunging Constant Velocity Joints (CVJ) on the left and right half shafts. This is because a plunging CVJ generates a third order plunging force with half shaft Revolution Per Minute (RPM), which is along the slip of the plunging CVJ. The primary path of take-off shudder is the Engine Mounting System (EMS), which isolates the vibration inputs from the vehicle body. A typical receiver of shudder is the passenger seat, so seat track acceleration and velocity are usually chosen to be the design objective for vehicle NVH optimization. This paper presents the optimization of FWD engine mounts for third order shudder improvement. Pointer automatic optimizer is used to perform the optimization with respect to a large number of design variables.