A practical approach for cross-functional vehicle body weight optimization

The goal of optimization in vehicle design is often blurred by the myriads of requirements belonging to attributes that may not be quite related. If solutions are sought by optimizing attribute performance-related objectives separately starting with a common baseline design configuration as in a traditional design environment, it becomes an arduous task to integrate the potentially conflicting solutions into one satisfactory design. It may be thus more desirable to carry out a combined multi-disciplinary design optimization (MDO) with vehicle weight as an objective function and cross-functional attribute performance targets as constraints. For the particular case of vehicle body structure design, the initial design is likely to be arrived at taking into account styling, packaging and market-driven requirements. The problem with performing a combined cross-functional optimization is the time associated with running such CAE algorithms that can provide a single optimal solution for heterogeneous areas such as NVH and crash safety. In the present paper, a practical MDO methodology is suggested that can be applied to weight optimization of automotive body structures by specifying constraints on frequency and crash performance. Because of the reduced number of cases to be analyzed for crash safety in comparison with other MDO approaches, the present methodology can generate a single size-optimized solution without having to take recourse to empirical techniques such as response surface-based prediction of crash performance and associated successive response surface updating for convergence. An example of weight optimization of spaceframe-based BIW of an aluminum-intensive vehicle is given to illustrate the steps involved in the current optimization process.

Cost and leadtime estimates for improved pillar padding, automatic slack adjusters, visual brake adjustment indicators and tractor/trailer ABS connections. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Accident information related to driver visibility and mirrors. Final report.

National Highway Traffic Safety Administration, Office of Vehicle Safety Standards, Washington, D.C.

Visibility tests of 1978 model cars. [Part 2]. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Evaluation of passive belts for different size occupants. Final report, phase I.

National Highway Traffic Safety Administration, Washington, D.C.

Visibility tests of 1978 model cars. [Part 1]. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Tri-level study: modification. Task 1: final report on potential benefits of various improvements in vehicle systems in preventing accidents or reducing their severity. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Oldsmobile Omega X-body baseline weight data. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Development of a motor vehicle materials historical, high volume industrial processing rates cost data bank (light truck). Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Body/repair shop visits to determine distribution of replacement parts sources. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Steel optimization and substitution for 1980 Oldsmobile Omega X-body car. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington, D.C.

Implementation cost to consumers of Part 581 - Bumper Standard, Phase II; weight and cost study of three "X" body bumper systems; and consumer replacement cost for complete bumper systems studied. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Vehicle weight reduction study. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington, D.C.

Stiffness-damping matching method of an ECAS system based on LQG control

A novel method of matching stiffness and continuous variable damping of an ECAS (electronically controlled air suspension) based on LQG (linear quadratic Gaussian) control was proposed to simultaneously improve the road-friendliness and ride comfort of a two-axle school bus. Taking account of the suspension nonlinearities and target-height-dependent variation in suspension characteristics, a stiffness model of the ECAS mounted on the drive axle of the bus was developed based on thermodynamics and the key parameters were obtained through field tests. By determining the proper range of the target height for the ECAS of the fully-loaded bus based on the design requirements of vehicle body bounce frequency, the control algorithm of the target suspension height (i.e., stiffness) was derived according to driving speed and road roughness. Taking account of the nonlinearities of a continuous variable semi-active damper, the damping force was obtained through the subtraction of the air spring force from the optimum integrated suspension force, which was calculated based on LQG control. Finally, a GA (genetic algorithm)-based matching method between stepped variable damping and stiffness was employed as a benchmark to evaluate the effectiveness of the LQG-based matching method. Simulation results indicate that compared with the GA-based matching method, both dynamic tire force and vehicle body vertical acceleration responses are markedly reduced around the vehicle body bounce frequency employing the LQG-based matching method, with peak values of the dynamic tire force PSD (power spectral density) decreased by 73.6%, 60.8% and 71.9% in the three cases, and corresponding reduction are 71.3%, 59.4% and 68.2% for the vehicle body vertical acceleration. A strong robustness to variation of driving speed and road roughness is also observed for the LQG-based matching method.