Design Of Rigid-flexible Coupling Walking Mechanism And System For Mobile Robots Used As Transmission Goods In The Local Area

Service robot is a kind of intelligent system that is used in mechanics,electronics,communications and so on,which is mainly used in the field of life.Compared with wheel type,foot type and so on,the composite walking mechanism,such as wheel-leg,wheel-foot,foot-pedrail,has the advantages of synthesizing multiple single walking mechanisms,which can effectively improve the adaptability of walking mechanism to the environment.However,there are deficiencies in the complexity of structure,difficulty in control,low practical value,and problems of popularization.In this paper,a robot walking mechanism with the characteristic of "rigid and flexible coupling" is proposed and its system design is carried out.According to the different environment,the robot transforms the corresponding walking mode to realize the purpose of running in different landforms,and applies the walking mechanism to the local delivery to solve the problem of "the last kilometer"of goods transfer and to improve the delivery of short distance items that still depends on manpower.The main contents of the paper are as follows:(1)A "rigid-flexible" deformable walking mechanism is proposed and its kinematics is analyzed.Based on the analysis of typical working environment,the principle design of rigid-flexible coupling wheel is proposed and the motion process simulation is carried out.Secondly,the concrete design and the number of spokes are analyzed for the rigid-flexible coupling wheel.Besides,the mathematical model of two-wheel angular velocity and poses are established by kinematics analysis.The kinematic conditions of zero-radius steering and straight-traveling of the walking mechanism are obtained.This provides a theoretical basis for the control of the walking mechanism.(2)The performance of obstacle surmounting,climbing performance and climbing stair stability of the "rigid-flexible coupling" deformable traveling mechanism can be studied.The influence factors of structural parameters such as friction coefficient,centroid offset distance,wheel radius,mass ratio and size ratio on the obstacle height are studied in the analysis of obstacle surmounting performance.In the analysis of climbing performance,the influence factors of structural parameters such as friction coefficient,mass ratio and size ratio on the climbing angle are studied.The degree of robot centroid fluctuation is used as the basis for judging the stability of the stairs.The Adams simulation analysis is carried out on the three models.The results show that in the "cross-over obstacle" and "rolling out climbing" modes,the ultimate height and angle of the rigid and flexible coupling wheel are 504mm and 45.8°respectively.During the stair climbing process,the variance of the centroid fluctuation curve is 0.993.The above lays a theoretical foundation for improving the overall performance of the robot and the robot motion strategy and system design in different environments.(3)Based on the theoretical analysis of the rigid-flexible coupling wheel,the robot structure and the simulation analysis are completed.Based on the analysis of obstacle performance and climbing performance,the model of the robot is established.The random vibration analysis is performed based on modal analysis,and the shock absorber foot and gear strength check are performed.The results show that the natural frequency is 33.709 Hz,which is much higher than the resonance frequency of 2.7 Hz,so the robot does not resonate due to the national standard road excitation.Besides,according to the above analysis,the model meets the strength requirements.(4)The system design and prototype of local delivery mobile robot were designed,and the experiments of obstacle surmounting,steering,straight running,slope and lawn were carried out.The experimental results show that the climbing stair tests were carried out by measuring the linear distance of the stair inclination of the stairway as the basis for measuring the stability of the stairway of the robot.When the robot is going upstairs at a speed of 0.2m/s,the inclination of the centroid of the robot is less than 10.9mm.The distance between the midpoints of the steps is less than 7mm;The speed steering and direct running experiments of the robot with 0.03m/s shows that the steering and direct errors are lower than those of 8.023mm and 13.4 mm respectively.The above experimental results verify the rationality of the structural design and the effectiveness of the theoretical analysis.