Abstract
The aim of this work is the control design and analysis of a semiactive axle suspension system for vibration reduction in a wheel loader. Unlike a traditional semiactive suspension system with continuously adjustable shock absorber, in this work, a novel axle suspension with multiple damping modes is proposed for the wheel loader. The multimode switching damping characteristics are achieved by just changing the discrete statuses of two high-speed switch electromagnetic valves, which makes the damping adjustment simpler and more reliable. However, because of the existence of discrete events, i.e., the on-off statuses of switch electromagnetic valves, the axle suspension proposed for the wheel loader poses a challenging hybrid control problem. To solve this problem, the mixed logical dynamical (MLD) modeling approach for hybrid systems is applied to model the dynamic characteristics of the system damping control procedure. Using this model, a hybrid model predictive control (HMPC) strategy is further designed, which can determine the optimal switching sequences of the discrete damping modes according to the axle suspension performance indices. Finally, to verify the effectiveness of the proposed semiactive axle suspension with multiple damping modes and its control approach, simulation analyses are conducted.
Highlights
Because of the high working efficiency, good flexibility, and convenient operation, wheel loaders are often used in the construction and mining fields [1, 2]
Compared with the traditional semiactive suspension system with continuously adjustable shock absorber, the aim of this work is to design a new semiactive axle suspension with multiple damping modes for the wheel loader. e multimode switching damping characteristics are achieved by just changing the discrete statuses of two high-speed switch electromagnetic valves, which make the oil flow paths change during the piston moving up and down. is means that the controller designed for the new semiactive axle suspension must obtain the optimal switching sequences of the discrete damping modes by considering the suspension performance requirements
The rate of reduction is even larger, which demonstrates the potential advantages of the proposed wheel loader semiactive axle suspension, which contains the target shock absorber with multiple damping modes, controlled by using the hybrid MPC methodology. e same simulation results for the suspension deflection under bump input can be obtained from Figure 6, which verifies that the system control objectives reflected in the objective function are achieved effectively by the designed control strategy
Summary
Because of the high working efficiency, good flexibility, and convenient operation, wheel loaders are often used in the construction and mining fields [1, 2]. Note that since the statuses of the high-speed switch electromagnetic valves are typical discrete events, the damping control process of the new semiactive axle suspension proposed for the wheel loader can be regarded as a class of hybrid systems. Erefore, to design an effective damping multimode switching control strategy for the semiactive axle suspension proposed for the wheel loader, whose damping control process exhibits typical hybrid characteristics, the MLD modeling approach is chosen in this work. E main contributions of this paper are to apply a new semiactive axle suspension with multiple damping modes for vibration reduction in a wheel loader and to show how the hybrid systems theory can be effectively used to solve both the missions of modeling and optimal control of the proposed semiactive axle suspension.
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