Harshness Improvement in Mid-Size Trucks

Ride comfort is a critical factor to customer perception of vehicle quality as it is related to vehicle experience when driving. It adds value to the product and, consequently, to vehicle brand. It has become a demand not only for passenger unibody vehicles but also to larger segments including mid-size trucks. Ride quality is usually quantified as harshness which is a measure of how the vehicle transmits the road irregularities to the customer at the tactile points such as the steering wheel and seats. Improving harshness requires tuning of different parts including tires, chassis frame/subframe and suspension mounts and bushings. This paper describes the methodology to enhance the harshness performance for a mid-size truck using a full vehicle CAE model. The influence of stiffnesses of body mounts and control arms bushings to harshness response is investigated through sensitivity analysis and the optimal configuration is found. A DOE (Design of Experiments) of bushings stiffnesses is generated to assess their influence on harshness response. The Kriging method is used to create response surface of the CAE model that predicts harshness at seat track and steering wheel. The optimal mounting configuration is found by minimizing the average of the root-mean square of harshness response using the Monte Carlo Method. A design proposal that minimizes the design restrictions of the optimal solution is presented and its performance improvement is confirmed by a single number metric.