Research On Hexapod-quadruped Mobile Robot System

In modern society,mobile robots have been used widely to take the place of human beings in dangerous and complex environments,such as search and rescue,investigation and detection of nuclear radiation.Compared with the mobile robot in other motion forms,multi-legged robot has better environmental adaptability and obstacle climbing ability.As the typical representatives,hexapod robots and quadruped robots have received more attention.However,most of the existing hexapod robots did not make full use of their own redundant structure and the legs which have multiple degrees of freedom.As a result,they basically have no operational capacity,or complete the task through the additional manipulator.In order to solve this problem,a mobile robot system with hexapodquadruped double movement modes and certain operational capacity is designed and some experiments are carried out in this paper.The functional and performance requirements of the robot system are determined according to the task requirements in a complex environment.The structure of a hexapodquadruped mobile robot system is designed,including the segmented torso,the transformation mechanism,the modular legs and a four degrees of freedom tail.The kinematics model of each mechanism is established,and kinematics analysis is carried out.Then two kinds of typical gaits and obstacle avoidance planning are carried out corresponding to double movement modes of the robot.In order to analyze the stability of robot and provide a theoretical basis for stabilizing motion planning,the mass distribution of robot is simplified and the system centroid expression is deduced.In this paper,the stability criterion based on the pressure center is defined,and the equation of stability margin is derived.Furthermore,a stable gait planning method based on tail selfadjusting is proposed,that is to keep the balance during the movement and operation by adjusting the pose of the tail.The embedded control system is developed based on STM32 series chip.The robot control program and the PC program are written,and the wireless communication between the PC and the robot is realized.Finally,the prototype of hexapod-quadruped mobile robot system is developed and a series of experiments are performed,including basic movement experiment,stair climbing experiment and object carrying experiment.Experimental results show that the designed robot has good mobility and operational capability.