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The concentration of wear debris in used lubricating oil is generally observed from spectral oil analysis. The element concentration data are one of the commonly used oil field data for degradation evaluation of power-shift steering transmission. However, in practical applications, the underlying degradation degree of the power-shift steering transmission is difficult to evaluate due to the complexity of element concentration data. To solve this problem, we propose a health index extraction methodology using a weighted average method to better characterize the underlying degradation, which leads to an accurate estimation of the residual life before the power-shift steering transmission needs to be maintained. The extracted health index not only maximizes the monotonic trend of underlying degradation but also minimizes the failure threshold variance between different power-shift steering transmissions. The method includes element concentration data modification, data selection, and data fusion steps that result in a reasonable power-shift steering transmission degradation model. Finally, a case study is provided to illustrate the proposed method. The results show that the extracted health index outperforms each selected element concentration data.

Remaining useful life prediction is a critical issue to fault diagnosis and health management of power-shift steering transmission. Power-shift steering transmission wear, which leads to the increase of wear particles and severe wear afterwards, is a slow degradation process, which can be monitored by oil spectral analysis, but the actual degree of the power-shift steering transmission degradation is often difficult to evaluate. The main purpose of this article is to provide a more accurate remaining useful life prediction methodology for power-shift steering transmission compared to relying solely on an individual spectral oil data. Our methodology includes multiple degradation data fusion, degradation index construction, degradation modelling and remaining useful life estimation procedures. First, the robust kernel principal component analysis is used to reduce the data dimension, and the state space model is utilized to construct the wear degradation index. Then, the Wiener process–based degradation model is established based on the constructed degradation index, and the explicit formulas for several important quantities for remaining useful life estimation such as the probability density function and cumulative distribution function are derived. Finally, a case study is presented to demonstrate the applicability of the proposed methodology. The results show that the proposed remaining useful life prediction methodology can objectively describe the power-shift steering transmission degradation law, and the predicted remaining useful life has been extended as 65 Mh (38.2%) compared with specified maintenance interval. This will reduce the maintenance times of power-shift steering transmission life cycle and finally save the maintenance costs.

The purpose of this article is to propose an upshift control strategy for off-highway vehicles equipped with a new kind of drivetrain architecture, which is called multi-clutch transmission, by means of analysis, modeling, and experiments. First, the structure and working principle of the multi-clutch transmission is investigated in detail. Then, to achieve a smooth 3–4 upshift process with two on-coming clutches and two off-going clutches working together, the method of power flow investigation is introduced. From the analysis results, the optimal relationship between clutches is presented to avoid engine flare and clutch tie-up. Additionally, the engagement sequence of on-coming clutches is also optimized to reduce the shift time and friction work. Then, with the proposed control strategy, a dynamic model for the integrated off-highway vehicle is developed using MATLAB/Simulink. From the variations in torque and speed output obtained from the simulation results, the vehicle equipped with multi-clutch transmission possesses good longitudinal dynamic performance, with acceptable friction work generated from two slipping clutches during the entire upshift process. Finally, to assess the shift quality, the test bench has been conducted. The obtained experimental data show a good agreement with the simulation results and the effectiveness of the control strategy is validated.

Static steering torque at parking is an important factor for steering portability of vehicle. At present, the most commonly used estimation method is empirical formula calculation, which, however, cannot explain the phenomenon that the steering torque increases rapidly when steering angle becomes very large (over 300°). This article proposes an estimation method of static steering torque on the basis of a mathematic model of tire-patch sliding torque, taking into account the changeable torque transmission ratio from steered wheel to steering wheel. Three components of static steering torque are modeled and analyzed, including the tire-patch sliding torque, gravity aligning torque, and internal friction torque of the steering system. In order to investigate the static steering torque at steering wheel, the transmission ratio of steering torque is obtained on the basis of rack-suspension mathematical analysis. An example of static steering torque estimation is conducted with the proposed method and is compared with experimental results. The comparison shows that the estimation results given by the proposed method are in better accordance with experimental results than other approaches.

The thermal problem of plate slides against symmetrically located contacting pads is investigated. The aim is to find out the influences of plate thickness, moving speed, and convection on the temperature field of the plate. Proper models and computing methods for specific situations can be determined based on these analyses. Finite element method of moving heat input is used to calculate the temperature field which is validated by comparing with some existing analytical solutions. The results show that the characteristic time for the steady state of temperature can be approximated exponentially as a function of moving speed. If the plate is thinner than the critical thickness, the surface temperature is increased significantly, which means that the temperature field is very sensitive to the plate thickness in this situation. The increasing moving speed increases the peak surface temperature almost linearly, and the convection outside of the contact area can decrease the peak surface temperature significantly if the heat sources move slowly, while it hardly affects the peak surface temperature if the heat sources move fast. Based on these results, the criterion of choosing a model and computing methods for studying the temperature fields in the similar structures is established.

In this article, a degradation assessment model has been proposed for electro-hydraulic shift valve in power-shift steering transmission. Our work is motivated by the failure mechanism of abrasive wear with a mathematic model. Abrasive wear will consecutively enlarge the clearance between the friction pairs. It is an overwhelming wear mechanism in the degradation of shift valve within serious contaminated fluid. Herein, a mathematic model is proposed by considering particle morphology and abrasion theory. Such model has been verified for its applicability and accuracy through comparison between the theoretical and experimental results.