Fault Tolerant Property And Motion Planning Of A Hexapod Robot

Since six-legged robots have superior performance,such as stability,load capacity and adaptability to the ground.They are more frequently used to operating in hazardous environments where are dangerous for human beings.However,the possibility of failure of the robot itself may greatly increase in these hazardous environments.Besides,the robot cannot be repaired immediately since it is beyond the scope of the operators.Under these circumstances,the fault-tolerant control and fault-tolerant walking is very crucial.Good fault-tolerant control can ensure stability and reduce the risk of falling,and fault-tolerant walking can enable the robot to walk out of harsh places to return the controllable range.The dissertation’s main work can be concluded as:(1)According to the input-output incidence relation and set theory,the parallel leg and robot remaining mobility after failure has been studied.And we proposed a new evaluation of the remaining mobility: the extent of fault tolerance,which use a number between 0 and 1 to describe the capabilities and features of end-effector intuitively.(2)Using the equivalent axial method,we described the rotational capability and the orientation workspace of the robot body about a fixed point.Equivalent axial method can effectively avoid the singularities problem which the Euler angles dose not hold.On this basis,the after failure workspace is calculated and proposed,providing an intuitive description of the scope of robot translational and rotational mobility.(3)We choose crab as bionic object and summed up crab fault-tolerant policies when one or more limbs are missing through a series of walking experiment.Combining the carb policies of hexapod robot,we proposed a 3-2 bionic based fault-tolerant gait.With all the basic gait parameters set,we re-arranged the footholds of ever leg to get a proper static gait.On the contrary,we keep the foothold unchanged and planning the ZMP trajectory to get the dynamic gait.Subsequently,some simulations and stability analysis have proven the effectiveness of these two fault-tolerant gaits.(4)A motion planning method via the fault-tolerant Jacobian matrix was proposed.This method can enable the robot to accomplish desired movement using broken legs along with other certain concomitant motions as compensation.The robot could walk continuously just like injured animal or human staggering.The robot also maintained its best remaining mobility and enhanced moving capability to a certain extent.This method greatly improves the hexapod robot’s adaptability to harsh environments.Finally,experiments and simulations of multiple faults demonstrate the real effect on the Octopus robot.