Wheel Ground Clearance Control for Lunar Rover’s Active Suspension: A Dual-Objective Cooperative Static Output-Feedback H∞ Controller Under Interest Bandwidth

Under conditions of low gravity and a rough lunar surface, the wheels of the lunar rover may lose contact with the lunar surface, compromising vehicle control and safety. This article proposes a dual-objective cooperative static output-feedback H∞ controller under interest bandwidth to minimize wheel ground clearance (WGC) for lunar rover active suspensions. By analyzing the suspension spring preload at the initial position and the movement behavior of the lunar rover after it leaves the lunar surface, we identify critical factors contributing to the rover’s increased susceptibility to liftoff compared to ground vehicles. Building upon this analysis, we innovatively adopt a dual-objective control framework that coordinates both wheel and body vertical velocities, replacing the traditional single-objective control theory for ground vehicles that focuses solely on wheel dynamic deflection (WDD). Furthermore, suspension dynamic deflection (SDD), a readily measurable variable, is selected as the measurement variable. A static output-feedback H∞ controller, equipped with a band-pass filter, is designed to concentrate the control effect within the bandwidth of interest. A two-degree-of-freedom (2-DOF) quarter-vehicle multibody dynamics model is developed. First, the robustness of the controller is demonstrated by incorporating nonlinear factors into the dynamic model. Second, it is shown that, compared to the single-objective control strategy, the dual-objective control strategy provides significant advantages in controlling the WGC. This improvement is attributed to its consideration of both wheel and body motion characteristics in relation to WGC. Further comparative analysis demonstrates that the dual-objective control strategy is more effective under lunar surface conditions characterized by high ruggedness. Additionally, the filtered control exhibits superior performance compared to the unfiltered control in terms of SDD and WGC. We further compare the grounding boundaries of active and passive suspensions under continuous harmonic excitation. Finally, a quarter-vehicle test is conducted experimentally under simulated lunar gravity and rugged terrain conditions. The results confirm that the performance of the dual-objective control strategy is significantly superior to that of the control strategy targeting only WDD regulation. Furthermore, the static output-feedback H∞ controller has been proven effective in reducing WGC within the bandwidth of interest.