This paper proposes an ontology-based fault diagnosis method which overcomes the difficulty of understanding complex fault diagnosis knowledge of loaders and offers a universal approach for fault diagnosis of all loaders. This method contains the following components: (1) An ontology-based fault diagnosis model is proposed to achieve the integrating, sharing and reusing of fault diagnosis knowledge for loaders; (2) combined with ontology, CBR (case-based reasoning) is introduced to realize effective and accurate fault diagnoses following four steps (feature selection, case-retrieval, case-matching and case-updating); and (3) in order to cover the shortages of the CBR method due to the lack of concerned cases, ontology based RBR (rule-based reasoning) is put forward through building SWRL (Semantic Web Rule Language) rules. An application program is also developed to implement the above methods to assist in finding the fault causes, fault locations and maintenance measures of loaders. In addition, the program is validated through analyzing a case study.

In order to improve the dynamic quality of traditional sliding mode control for an active suspension system, an optimal sliding mode control (OSMC) based on a genetic algorithm (GA) is proposed. First, the overall structure and control principle of the active suspension system are introduced. Second, the mathematical model of the quarter car active suspension system is established. Third, a sliding mode control (SMC) controller is designed to manipulate the active force to control the active suspension system. Fourth, GA is applied to optimize the weight coefficients of an SMC switching function and the parameters of the control law. Finally, the simulation model is built based on MATLAB/Simulink (version 2014a), and the simulations are performed and analyzed with the proposed control strategy to identify its performance. The simulation results show that the OSMC controller tuned using a GA has better control performance than the traditional SMC controller.

Considering the demand for vehicle stability control and the existence of uncertainties in the four-wheel steering (4WS) system, the mixed H2/H∞ robust control methodology of the 4WS system is proposed. Firstly, the linear 2DOF vehicle model, the nonlinear 8DOF vehicle model, the driver model, and the rear wheel electrohydraulic system model were constructed. Secondly, based on the yaw rate tracking strategy, the mixed H2/H∞ controller was designed with the optimized weighting functions to guarantee system performance, robustness, and the robust stability of the 4WS vehicle stability control system. The H∞ method was applied to minimize the effects of modeling uncertainties, sensor noise, and external disturbances on the system outputs, and the H2 method was used to ensure system performance. Finally, numerical simulations based on Matlab/Simulink and hardware-in-the-loop experiments were performed with the proposed control strategy to identify its performance. The simulation and experimental results indicate that the handling stability of the 4WS vehicle is improved by the H2/H∞ controller and that the 4WS system with the H2/H∞ controller has better handling stability and robustness than those of the H∞ controller and the proportional controller.

For the sake of realizing dynamic switch among three steering modes for the four wheel independent steering (4WIS) rescue vehicle in the non-stop state, the switch control strategy and the optimized wheel switch trajectory are studied in this paper. Aiming at ensuring the constant turning radius of the 4WIS rescue vehicle in the switch process of steering modes, the steering angle relationships between the driving wheel and driven wheels are derived, and the desired driving wheel angle of the target steering mode is calculated. The B-spline curve is proposed to design the switch trajectory of the driving wheel. Two objectives including minimizing the sudden change of vehicle dynamic parameters and minimizing the energy consumption in the switch process are discussed. A multi-objective genetic algorithm (MOGA) based on non-dominated sorting genetic algorithm II (NSGA-II) is proposed to deal with the optimization problem of the wheel switch trajectory. The numerical simu-lations based on Matlab/Simulink indicate that the presented algorithm can generate the Pareto optimal solutions and is suitable for the optimization of the wheel switch trajectory. In addition, the proposed switch control strategy of steering modes for the 4WIS rescue vehicle in the non-stop state is validated to be reasonable and effective.

The research of reliability design for impact vibration of hydraulic pressure pipeline systems is still in the primary stage, and the research of quantitative reliability of hydraulic components and system is still incomplete. On the condition of having obtained the numerical characteristics of basic random parameters, several techniques and methods including the probability statistical theory, hydraulic technique and stochastic perturbation method are employed to carry out the reliability design for impact vibration of the hydraulic pressure system. Considering the instantaneous pressure pulse of hydraulic impact in pipeline, the reliability analysis model of hydraulic pipeline system is established, and the reliability-based optimization design method is presented. The proposed method can reflect the inherent reliability of hydraulic pipe system exactly, and the desired result is obtained. The reliability design of hydraulic pipeline system is achieved by computer programs and the reliability design information of hydraulic pipeline system is obtained. This research proposes a reliability design method, which can solve the problem of the reliability-based optimization design for the hydraulic pressure system with impact vibration practically and effectively, and enhance the quantitative research on the reliability design of hydraulic pipeline system. The proposed method has generality for the reliability optimization design of hydraulic pipeline system.

Wheel loader shovel loading operation tests showed that when the tire slips, it not only causes waste of the engine power, but also increases the tire wear. In this paper, the regression prediction model is combined with the electro-hydraulic proportional control technology. For the first time, the method of adjusting the posture of the working device is proposed to realize the skid-proof shovel control strategy of the wheel loader. In this control strategy: (1) The electro-hydraulic proportional control technology applied to this wheel loader is introduced. (2) The load spectrum of the wheel loader is analyzed during the shovel loading operation. Moreover, combined with the drive shaft torque, pilot pressure and boom cylinder displacement, the particle swarm optimization-support vector machine (PSO-SVM) algorithm is used to complete the construction of the regression prediction model of the boom cylinder displacement. (3) A controller is designed based on the fractional-order PID control algorithm. The skid-proof control strategy is simulated and verified by constructing the joint simulation model. The corresponding program is prepared in the hydraulic system controller and the effectiveness of the control strategy and algorithm are verified by the wheel loader shovel loading operation.