Research On Efficient Mobile Strategy Of Hexapod Wheel-legged Lunar Robot

Exploration robots serviced on the Moon and Mars successfully are composed of wheeled mobile system.Wheeled robot shows good mobility on flat terrain,but it is difficult to adapt to rugged and complex terrain.Wheel-legged robot,which combines leg robot and wheeled robot,has both advantages of fast moving speed of wheeled robot and flexible bionic characteristics of legged robot,has gradually become an important direction of the development of the exploration robot.Wheel-legged robot has superior adaptability in complex environment,but more drive unit is needed,which increases the complexity of structure and difficulty of motion planning.How to achieve the efficient movement of wheel legged robot in complex terrain and reduce redundant actions in motion become the key and difficult point in its development technology,and the key to achieve efficient mobile is to develop efficient mobile strategy.In this paper,a new type of hexapod wheel-legged lunar robot is selected as the main research object.Aiming at the problem of how to achieve efficient movement in complex terrain,the main contents of this paper are as follows:(1)According to the configuration characteristics of the Hexapod wheel-legged lunar robot,the forward and inverse kinematics models of the robot are established,the workspace of leg is obtained.The problem of solving the foot force of multi legged robot is studied,pseudoinverse method is used to established the model of tip-point force.Based on the Lagrange method,the dynamic equation of the robot leg is derived,and the dynamic model of the leg including the wheel-ground contact force is established.(2)Research on motion planning of the hexapod wheel-legged lunar robot is pursued.The trajectory planning methods of robot leg and body are studied respectively in the legged motion planning.The differences of gait are analyzed by studying the basic gait of robot,the walking scheme of the hexapod wheel-legged lunar robot is determined.Wheeled linear motion and turning motion are studied respectively in wheeled motion planning.The wheeled motion characteristics of the hexapod wheel-legged lunar robot are analyzed(3)The representation method of the wheel-legged hybrid mobile strategy of the wheel-legged robot is studied.The state quantity of joint space is introduced to describe the position and posture of the legs relative to the body,and the position and posture conversion quantity is introduced to describe the motion process between the state quantities of adjacent temporal state.A wheel-legged hybrid mobile strategy planning method is proposed,which transforms the movement process of wheel-legged robot into multiple wheeled motion and legged motion,the planning method reduces the complexity of movement strategy planning.The mobile strategy model including time and energy consumption index is established.Taking the state quantity of joint space and the position and posture conversion quantity as optimization variable.Taking the shortest obstacle crossing time and the lowest energy consumption as optimization goals,and the wheellegged efficient mobile strategy is formed through optimization iteration,based on the above research,an efficient mobile simulation software for the hexapod wheel-legged lunar robot is developed.(4)The virtual prototype of the hexapod wheel-legged lunar robot is established.The locomotion of the robot in the legged motion mode and the steering movement in the wheeled motion mode are simulated.The complex terrain including step,gullie and slope is established.Trafficability simulation of the hexapod wheel-legged lunar robot in the complex terrain is delivered by using the conventional moving strategy and the optimization strategy.Legs movement,mobile time and energy consumption of the robot under two mobile strategies are studied,the effectiveness of the efficient mobile strategy is verified.In summary,an optimization method of efficient wheel-legged hybrid mobile strategy is proposed,and its effectiveness is verified by simulation,which provides theoretical basis for improving the mobile efficiency of wheel-legged robot in complex terrain.