The inverse power transformation logit and dogit mode choice models

This paper explores the properties of inverse Box-Cox and Box-Tukey transformations applied to the exponential functions of logit and dogit mode choice models. It is suggested that inverse power transformations allow for the introduction of modeler ignorance in the models and solve the “thin equal tails” problem of the logit model; it is also shown that they allow for asymmetry of response functions in both logit and dogit models by introducing alternative-specific parameters which make cross elasticities of demand among alternatives generally asymmetric. In the dogit model, modeler ignorance and consumer captivity remain conceptually distinct. Standard logit and dogit models appear as very special “perfect knowledge” cases in broad spectra of models which also include, among others, the reciprocal extreme value or log-Weibull variants. These improvements over the simple symmetric-thin-equal-tail-perfect-knowledge logit and the symmetric-pure-captivity dogit are achieved at the cost of introducing at the most two new parameters per alternative considered in the original logit and dogit mode choice models.     

The dogit model

This paper presents the dogit model. That model is flexible enough to permit the choice among specific pairs of alternatives to be consistent with the independence from irrelevant alternatives axiom, as in a logit model, but it simultaneously allows the choice among other pairs not to be. Dogit parameters add an “income effect” to the “substitution effect” already built into the logit model; alternatively, they allow for the joint presence of compulsive and discretionary elements in consumer behavior, or for the identification of captive markets. Eventual estimation of the values of the parameters of the dogit model appears simpler than for the probit model.     

Development and performance analysis of an automotive power seat for disabled persons

As the number of disabled people grows, independence and mobility become a priority for those individuals. To achieve this goal, a ‘Turny-type power seat’ was developed in this study to assist a disabled person rise from a vehicle without trouble. The design and modeling of the power seat were performed using AutoCAD and CATIA software. The major motions of the power seat system are swiveling, sliding, and extending, which are accomplished primarily by DC motors, chains, and gears. Most of the power seat parts were made from mild steel. Welding technology was used throughout the frame fabrication. To ensure the safety and stability of the power seat, various tests were performed, and the results analyzed. The static analysis of the power seat was carried out by ANSYS 11.0. The results showed that the power seat conformed to the Americans with Disabilities Act (ADA) standards. The durability test was performed by repeatedly rotating and sliding the power seat under loading conditions. Dynamic crash simulation was carried out using the LS-DYNA software. The durability test ensured a longer life of the power seat, while the crash analysis showed a small rotational distortion that was not harmful to passengers. However, the front seat had a slightly larger forward displacement, which was not comfortable for passengers. Therefore, further modifications of the power seat should be done to improve the performance, with attention given to the reduction of the forward displacement in the event of a crash.     

黄土地区公路边坡冲蚀及防排水措施

结合现场调查和资料分析,研究黄土地区公路路基边坡的降雨冲蚀破坏原因和破坏特点,并提出了相应的防排水措施,可供同行参考。     

Simple design approach for improving characteristics of interior permanent magnet synchronous motors for electric air-conditioner systems in HEV

In this paper, a simple design method for improving the performance of an interior permanent magnet synchronous motor (IPMSM), for driving the air-conditioning compressor used in hybrid electric vehicles, is presented. There are many design methods that optimize the IPMSM. Each method deals with a variety of design factors, such as slot opening, pole arc, and rotor shape. However, as the number of design variables increases, a lot of modeling and analysis time is needed in order to improve the characteristics of an IPMSM. This paper demonstrates that the optimization of a double-layer IPMSM, satisfying the given design conditions, is possible with only a flux barrier shape design. Then, response surface methodology is applied as the optimization method, and the validity of the design approach is verified by comparison with test results.     

New design of a road profiler

Macro and micro road profiles are of significant importance for vehicular motion studies, reliable calculations of vehicle system properties, and ensuring vehicular safety. As such, road profiles should be considered carefully. Macro profiles consider the spatial geometry of the road (curves, longitudinal and lateral slopes) while micro profiles consider roughness in longitudinal and lateral directions. These profiles have random characteristics that can be quantified under onroad and off-road conditions using a road profiler. This paper presents an analysis of a new concept for a universal profiler without gyroscopic stabilizers.     

Rollover mitigation for a heavy commercial vehicle

A heavy commercial vehicle has a high probability of rollover because it is usually loaded heavily and thus has a high center of gravity. An anti-roll bar is efficient for rollover mitigation, but it can cause poor ride comfort when the roll stiffness is excessively high. Therefore, active roll control (ARC) systems have been developed to optimally control the roll state of a vehicle while maintaining ride comfort. Previously developed ARC systems have some disadvantages, such as cost, complexity, power consumption, and weight. In this study, an ARC-based rear air suspension for a heavy commercial vehicle, which does not require additional power for control, was designed and manufactured. The rollover index-based vehicle rollover mitigation control scheme was used for the ARC system. Multi-body dynamic models of the suspension subsystem and the full vehicle were used to design the rear air suspension and the ARC system. The reference rollover index was tuned through lab tests. Field tests, such as steady state cornering tests and step steer tests, demonstrated that the roll response characteristics in the steady state and transient state were improved.     

Numerical Optimization of the Linear Dynamic Behaviour of Commercial Vehicles

The demands upon the dynamic behaviour of a vehicle can be stated as an optimization problem. The optimum solution is calculated using an iterative optimization algorithm. Scaling the problem by non-linear transformations reduces the number of iterations. Lagrange multipliers provide useful information about the sensitivity of the optimum with respect to changes of the constraints. The analysis of the dynamic behaviour is performed in the frequency domain. New structural variants are calculated using system synthesis. As an example, the engine, cab and wheel suspension systems of a tractor/semi-trailer have been optimized all together.