Design Of Hybrid Wheel-legged Mobile Robot For Forestry Applications

Introducing mobile robots into forestry applications can improve spatial resolution,real-time efficiency and accuracy when compared with labor-dominant method.Wheel-on-leg hybrid mobile platforms that are developed upon forestry specific purpose are applicable for unstructured terrains in forests by improving automation level and reducing labor intensity.They present ideal maneuverability and obstacle-traversing capability when carrying near-ground surveillance and cruising applications under unstructured terrains.This thesis proposed a novel wheel-legged hybrid mobile platform for forestry regard to address poor negotiating performance in current systems by analyzing features of current projects and specifying practical demands in forestry field.The proposed hybrid platform adopts cylinder motor configuration to drive the parallel structure,which improves the obstacle-crossing and stability concerns in traditional mobile platforms.Major works in this project are listed below.1.Firstly,forestry environment and classic terrain types are characterized to specify design demands,including leg and DOF numbers,leg configuration,hybrid method,driving mode,locomotion mode and detailed parts.To deal with fallen trees,slopes,rocks and miscellaneous obstacles,open-loop joint link driven by cylinder motor is selected as leg configuration to guarantee its obstacle traversing capability.The 3D model of structure parts and whole platform are built in Inventor software.2.Then the forward kinematics analysis of leg configuration is studied based on D-H parameter matrrix theory.The location and position of wheel under selected joint angle is calculated according to the forward equation then it was simulated in Matlab Robotics Toolbox.Valid volume space of leg configuration is simulated based on Monte Carlo method to validate the correctness of parameter settings and mechanical design.The velocity of wheel,torso,hip joint,ankle joint and cylinder are calculated.3.Furthermore the virtual prototype of hybrid mobile platform is built for simulation.Stress analysis of leg configuration 1s conducted through ABAQUS software and the drop impact condition is selected as extreme working condition for magnitude check.Four experiments are conducted to evaluate the dynamic performance of the designed structure under various modes and its stability is analyzed according to the generated curves.Lastly the control system is designed upon practical demand in wild forestry environment.The proposed hybrid wheel-legged robot combines characteristics of wheel and leg configurations and it is capable of presenting multiple locomotion modes including wheeled,legged and hybrid mobility.The novel mechanism can realize omnidirectional driving by changing its wheel distance,axis distance and platform height according to practical conditions.This mechanism presents competitive environment adaption and maneuverability under forestry unstructured terrains,and the research provides reference for forestry mobile platform development.