| China is the country with the largest cultivation area of navel oranges.However,the growing conditions of navel oranges are very poor,90% of which are grown in mountainous areas.Affected by the terrain,the degree of agricultural mechanization in mountain orchards is very low.Although a small number of mountain orchards have mobile operating machinery,their mobile operating capacity is very limited.The task of mobile transportation between mountain orchards is mainly done manually,lacking a comprehensive agronomic mobile operating platform.In response to this problem,this paper conducts an in-depth study on the structure and kinematics performance of a composable hexapod robot adapted to mountain orchards.According to the requirements of comprehensive agronomic mobile operations in mountain orchards,a composable hexapod robot mechanism is proposed as a comprehensive agronomic work platform in mountain orchards.Based on the Position and Orientation Characteristics Theory,27 types of serial mechanical leg mechanisms and 93 types of parallel mechanical leg mechanisms are synthesized,among which 70 are new mechanisms.A kind of single loop connector mechanism is designed,which can connect and separate several composable hexapod robots conveniently and reliably.The layout of the robot legs and connectors on the body of the combined hexapod robot is studied,so that the hexapod robot can achieve better kinematics performance.Five typical combination modes of 2 ～ 3 hexapod robots are proposed,which can better meet the requirements of mountain orchards mobile operation.The forward and inverse kinematics model,velocity model and acceleration model of the combined hexapod robot are established.The working space of mechanical leg mechanism and the composable hexapod robot are drawn by Monte Carlo method,and the influence of the position of the landing point of the mechanical leg on the workspace of the composable hexapod robot is analyzed.The climbing models of single body mode and five typical combination modes on transverse slope and longitudinal slope are established.The relationship between the maximumclimbing angle and the parameters of the combined hexapod robot is obtained.The climbing ability of the composable hexapod robot is analyzed.The models of bump obstacle,step obstacle and gully obstacle of the composable hexapod robot are established,and the obstacle surmounting ability of the composable hexapod robot under various obstacles is analyzed.A stable cone determination model for a composable hexapod robot is established.Based on the method of minimum stability Angle,the static stability of the individual mode and the five typical combination modes of the composable hexapod robot is analyzed respectively.And based on the method of tilting performance index,the dynamic stability of the individual mode and the five typical combination modes of the composable hexapod robot is analyzed respectively.The effects of slope and attitude angle on the stability of the composable hexapod robot are studied.The virtual simulation experiments of climbing slope(including transverse slope and longitudinal slope),surmounting obstacle(including boss obstacle and gully)and stability on slope(including transverse slope and longitudinal slope)of the composable hexapod robot’s individual mode and five typical modes are established.Compared with the theoretical model,the correctness of the theoretical model is verified.Finally,some experiments are carried out to verify the correctness of the theoretical model and the simulation model. |
