Study On The Motion Characteristics Of The Six Limb-leg Crawler-foot Vehicle Spanning The Fissure

The Antarctic inland ice sheet is densely covered with fissures and other extreme terrains,which are prone to safety accidents such as vehicle and personnel sinking.Existing wheeled and single-track scientific research vehicles have their wheels and tracked vehicles stuck and trapped in the ice when they cross the fissures.It is difficult to provide effective support for the car body and other issues.Therefore,a new type of six limb-leg crawler-foot vehicle using multi-legged and multi-tracked vehicle cooperative driving technology is studied,which has the function of crossing cracks and meets the driving requirements under cracked terrain conditions.The new type of six limb-leg crawler-foot vehicle has complicated movements when it crosses cracks.It is necessary to carry out researches on the construction of a theoretical model of kinematics,planning of gait and trajectory across fissures,and analysis of motion characteristics.The specific contents are as follows:(1)Research on the kinematics of six limb-leg crawler-foot vehicle.Construct a modified D-H model for the limb-leg crawler-foot mechanism of the scientific research vehicle,derive the forward kinematics equation,and solve and analyze its working space,which accurately reflects the maximum space range that can be reached at the end of the limb-leg crawler-foot.Proposed a simplified analytic method of inverse kinematics to derive corresponding equations.At the same time,a mapping model of the drive space and joint space of the scientific research vehicle is constructed to accurately reflect the maximum space range that can be reached at the end of the limb-leg crawler-foot.(2)Research on gait planning of six limb-leg crawler-foot vehicle spanning the fissure.An initial gait across cracks is planned,and an optimized gait across cracks is proposed on this basis.And according to the COG static stability criterion,it is verified that the scientific research vehicle can run stably without overturning in the optimized gait across the fissure.(3)Research on the trajectory planning of the foot end of six limb-leg crawler-foot vehicle.Using the multi-segment LFPB trajectory planning method,select the typical steps of the trajectory foot of the right-hind leg in the joint space to verify the trajectory planning example of the right-hind leg in the joint space to optimize the gait.Establish the trajectory equation of each joint and draw the corresponding trajectory curve;the planned trajectory passes through the corresponding path points,and is smooth and has no sharp points,which ensures the continuity of speed.(4)Simulation and verification of six limb-leg crawler-foot vehicle.The kinematics simulation was carried out on the typical motions of the leg raising conditions when crossing the fissure,the trajectory of the foot,the initial gait,and the process of optimizing the gait.Among them,the correlation coefficient between the numerical solution and the simulation solution of the articulated point coordinate of the limb-leg crawler-foot mechanism in the typical action of the leg-lifting condition is more than 0.99,and the average relative error is less than 2.2%,which verifies the correctness of the kinematics equation.Comparing the trajectory,joint angular velocity,and angular acceleration between the simulation results of the foot end trajectory of the scientific research vehicle and the example verification result verifies the correctness and rationality of the planned foot end trajectory across the fissure.Compared with the initial gait,the optimized gait is simplified from 23 steps to 15 steps,the time to cross the crack is shortened by 89 s,the driving distance is shortened by 9979 mm;the crossing distance is increased by 180 mm,and the lateral offset is reduced At 576 mm,optimizing gait requires real-time monitoring of the position of the center of gravity of the scientific research vehicle to ensure stable operation and avoid overturning.