Study On A Novel Soft-Terrain Vehicle With Hexapod Air-Cushion Boots

It has been a difficult but hot subject to improve the vehicle trafficability in some complex soft-terrain environments in the research area for off-road vehicle dynamics and control. Based on previous study on a semi-tracked air-cushion vehicle, a novel soft-terrain concept vehicle with an air-cushion boots walking mechanism is proposed in order to futher improve vehicle crossing-terrain and adaptive ability on uneven terrain conditions, and intend to extend its application areas.In this dissertation, a novel structure with hexapod air-cushion boots is creatively designed as the waliking mechanism of soft-terrain vehicle in order to reduce the ground contact pressure. By inflation/deflation of the air boots, the inner pressure and height of boots can be adjusted, thus walking operation and required vehicle attitude can be realized.Firstly, the designing idea and the working principle are described. And the control scheme is designed. The key structural parameters of vehicle are optimized and the feasibility of the scheme is tested in principle in order to provide the basis for the prototype manufacturing and feasibility testing of the control algorithm, kinematics direct and inverse problems.Secondly, the kinematics direct problems of the new soft-terrain vehicle are studied and the general solutions to different boots moving with different speeds are obtained by using principle of minimum stream power. By geometric analysis, kinematic equations and their simplified expression function under a most commonly-used gait for the vehicle, i.e. tripod gait, are obtained, in order to provide reference for off-line cycle gait design and navigation algorithms feasibility testing, and also to provide useful informations for vehicle dynamics simulations, e.g. the body position, body posture and foothold coordinates.Thirdly, a new navigation algorithm, i.e., artificial potential field-curvature method, is designed based on artificial potential field method and then improved by fuzzy control theory. The method can provide the preliminary control signal of cycle gait and offer new approach of navigation algorithm for the vehicle.Fourthly, by theoretical analysis, finite element simulations of orthogonal design and experimental verification, the force- deformation theory model and parametric linear regression model of air-cushion-boots are obtained. The results are crucially important for vehicle dynamics modeling, and also provide a reference for air cushion boots structure optimization.Finally, for this hexapod air-cushion boots vehicle, its dynamics model is established and the gait correction algorithm is preliminary designed. The rationality and feasibility of the designed control scheme are verified. The vehicle dynamics model can predict vehicle state variables properly, including centroid height, pitch angle and roll angle of vehicle body, the height and pressure of boots, the displacement between boots and body, load distribution, the total mass comsumption of high pressure air, etc. Thus the useful references for gait planning, attitude control, soil parameter identification, energy consumption optimization control algorithm design can be provided.The study results show the feasibility of the proposed new soft-terrain vehicle and establish a rational framework of future systematic study.