Research On Deformable Walking Mechanism For Unstructured Pavement Unmanned Ground Vehicle

In recent years,with the rapid development of robot technology,unmanned ground platforms have been widely used in civil and military fields such as rescue and disaster relief,detection and disposal of explosives,logistics and supply,which has greatly reduced the casualty rate in dangerous and extreme operating environment.The unmanned ground vehicle often travels on unstructured pavement,which has so many obstacles that greatly limits the passing ability of conventional unmanned ground vehicle.Based on the requirements of the unstructured road environment for the trafficability of unmanned ground vehicle,it is of great significance to develop a walking mechanism that can not only maintain the efficient flexibility of movement,but also of great obstacle crossing ability.Based on wheeled walking mechanism and the characteristics of the foot walking mechanism,in this paper,a wheel-foot composite deformable walking mechanism for unmanned ground vehicle on unstructured pavement is designed.The main research work of this paper is as follows:Firstly,the trafficability mechanism of wheeled unmanned ground vehicle is studied.The influence of wheel layout on driving resistance is explored,and the variation of axle number and wheelbase’s influence on obstacle crossing ability and axle load distribution is analyzed.Then,different configurations of walking mechanisms are investigated,the influence of special-shaped wheels and deformable wheels on the trafficability of unmanned ground vehicle is analyzed,through the investigation of the walking mechanism,the reasons why special-shaped wheels and planetary wheels can improve the trafficability of unmanned ground vehicle are expounded,and the mathematical model between the height of obstacles that wheeled unmanned ground vehicle can cross and geometric parameters of the wheel is constructed.To move forward,the scheme selection and structure design of the deformable walking mechanism are carried out.Proposed a scheme that composes of drive,transmission and walking system,further more according to the requirements of extreme working conditions,the motor parameters are calculated.Then combined with the principle and characteristics of the planetary alignment mechanism,the planetary gear shifting transmission and the planetary wheel deformation scheme are proposed,and then the structural design and three-dimensional model of the planetary wheel are carried out.After that,the finite element analysis of the walking mechanism is carried out,combined with the static analysis of the stress distribution and topology optimization results,the structure design is optimized,finally a feasible structure design scheme with better bearing capacity and more lightweight is put forward.Then,the influence of unstructured pavement on the trafficability of unmanned ground vehicle is studied.The force of wheel and foot walking mechanism crossing independent step is analyzed,then constructed the mathematical model of front and rear wheels crossing steps,and obtained the expression of the ratio of obstacle height to wheel diameter as well as the relationship between obstacle crossing gully and step.The physical and mechanical characteristics of soft pavement are analyzed,and it is shown that the change of geometric parameters of wheel can improve the force condition and passing performance of unmanned ground vehicle.The influencing factors of road adhesion coefficient are analyzed,the relationship curve between adhesion coefficient and sliding rate is obtained,and the mathematical model of the friction coefficient between vehicle speed and road surface is obtained.Finally,the control strategy is developed and the obstacle crossing simulation is carried out.After explored the identification method of characteristic parameters of unstructured pavement,we obtained the geometric parameters of vertical obstacle and wheel subsidence by Lidar and the vision sensor respectively.The road adhesion coefficient is estimated through vehicle dynamics parameters and verified by simulation.The control strategy of the walking mechanism is formulated,and the choice of transmission gear and walking mode of the walking mechanism under different conditions are described.At last,the obstacle-crossing ability of the walking mechanism is simulated,which verified the rationality and effectiveness of the design of the deformable walking mechanism.In this paper,a wheel-foot compound deformable walking mechanism is proposed.Through theoretical analysis and simulation verification,it is shown that the foot walking mechanism has more superior obstacle crossing ability and adaptability to different types of road,which verified the rationality and effectiveness of the research in this paper,and provided reference significance for the research and development of improving the trafficability of unmanned ground vehicle under the unstructured pavement.