Accumulated tolerance analysis of suspension by geometric tolerances based on multibody elasto-kinematic analysis

Tolerance design of vehicle suspension is an important factor that affects the ride and handling quality and cost of the vehicle. Also, applying geometric tolerance to an analysis model is found to be a difficult process. This paper presents a method for tolerance analysis of wheel alignment of vehicle suspension. Monte-Carlo simulation method is applied to multibody elasto-kinematic model to analyze the accumulated geometric tolerances. As an example, Macpherson Strut Type front half car model is used, and wheel alignment dispersion and contribution ratio to the dispersion by accumulated geometric tolerances is computed. This paper also presents an efficient modeling and analysis method for elasto-kinematic model of vehicle suspensions by computing the stiffness matrix analytically. The simulation results of a Macpherson Strut Type demonstrates the validity and accuracy of the proposed method.     

Al2O3陶瓷／Cu界面晶体位向关系对断裂性能的影响

以单晶α－Ａｌ２Ｏ３陶瓷和单晶Ｃｕ为母材，采用真空扩散焊接获得具有两种不同的界面晶体位向关系的Ｃｕ／Ａｌ２Ｏ３扩散焊接头以及带Ｎｂ膜中间层的Ｃｕ／Ｎｂ／Ａｌ２Ｏ３扩散焊接头，研究了面晶体位向关系对接头断裂能量的影响。     

New energy recovery H∞ robust controller for electric bicycles

The electric controller is one of the most crucial components in an electric bicycle. The overall performance of the whole system heavily depends on the properties of the controller. The authors use the robust control theory to design a new H_∞ robust controller for the closed speed-current dual-loop driving and braking system. The designed controller also incorporates the driving and energy recovery braking circuit. Therefore, it has energy recovery ability, which coverts the kinetic energy wasted in braking into electric energy to recharge the battery. This prolongs the driving distance per battery charge. The simulations and experiments show that the new H_∞ robust controller out-performs the traditional PID controller in many respects including stability, error, responding speed and driving distance per battery charge.     

Future applications of Ni-Ti alloys in automotive safety systems

The shape memory alloys present unusual thermo-mechanical properties. The most important of them are pseudo-elasticity and memory effect. The paper investigates this behaviour for the Ni-Ti wires under static (v < 50 mm/s) and dynamic conditions (v > 50 mm/s) at different temperatures. Ni-Ti actuator and pseudoelastic wires with diameter between 0.1 mm to 0.5 mm are being tested. For dynamic investigation a new testing plant able to satisfy the testing conditions is created. This new testing plant is still under development and the reported results originate from the first tests on this new machine. The new device is designed to reach speeds higher than 50 mm/s. These speeds can be achieved using a drop weight which will hit a bottom plate and by this the kinetic energy is transferred to the sample. Because the weight is dropped, the stroke for the sample is measured in two points. The force of this impact will be in-line measured and, if the sample will be electrically activated during this test, it is also possible to log the electrical voltage. To widen the application range of the shape memory alloys it is necessary to study their behaviour in the dynamic region. With the new testing facility, it is expected to test the damping properties of SMA wires. In that case, these results can generate the basis for finding new applications for shape memory alloys especially in the automotive safety industry.     

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.     

Vibrational characteristics of automotive transmission

A mathematical model of an automotive transmission is developed, that considers the flexibility of the shafts, bearings, and gear teeth, and gyroscopic effects of geared rotors. The transverse, torsional, and axial motions are strongly coupled due to helical gearing. The excitation forces acting on the automotive transmission are classified into first, second, and third grades, based on the magnitudes of the forces that are determined by the perturbation method. The excitation forces are caused by the mass imbalances among gears, misalignment of shafts, clearance and non-linear deformation of bearings, transmission errors, and the periodic variation of the gear mesh stiffness. A bench test on loading conditions is carried out for the third speed of the automotive transmission. The experimental results of vibration characteristics are compared with those from theoretical analysis. The results show good agreement, i.e., within a tolerance of 3.3%.     

Evaluation of low-temperature diesel combustion regimes with n-Heptane fuel in a constant-volume chamber

The concept of Low Temperature Combustion (LTC) has been advancing rapidly because it may reduce emissions of NOx and soot simultaneously. Various LTC regimes that yield specific emissions have been investigated by a great number of experiments. To accelerate the evaluation of the spray combustion characteristics of LTC, to identify the soot formation threshold in LTC, and to implement the LTC concept in real diesel engines, LTC is modeled and simulated. However, since the physics of LTC is rather complex, it has been a challenge to precisely compute LTC regimes by applying the available diesel combustion models and considering all spatial and temporal characteristics as well as local properties of LTC. In this paper, LTC regimes in a constant-volume chamber with n-Heptane fuel were simulated using the ECFM3Z model implemented in a commercial STAR-CD code. The simulations were performed for different ambient gas O₂ concentrations, ambient gas temperatures and injection pressures. The simulation results showed very good agreement with available experimental data, including similar trends in autoignition and flame evolution. In the selected range of ambient temperatures and O₂ concentrations, soot and NOx emissions were simultaneously reduced.