Judgment And Adjustment Of Instability For Hexapod Robot On Rough Terrain

For a hexapod robot walking on uneven terrains, the ability of real-time response andadjustment to instability is essential to avoid damage to its body and loads. With furtherresearch and analysis of the stability problem of fast-moving hexapod robot on rough terrain,this thesis proposes the corresponding stability judgment criterion and relative instabilityadjustment strategies.The rough terrains are inducted and classified into four typical terrains according to theanalysis from aspects of their geometric features and physical properties. Based on thesetypical terrains, different situations of hexapod robot’s instability are analyzed, consideringthe mechanical and movement features of the hexapod robot. And adjustment strategies areestablished for different types of tipping instability with the analysis of the robot’s mechanicalequilibrium.The relation between drive space, joint space and motion space is analyzed according tothe structure of the hexapod robot. Direct and inverse kinematic models of the hexapod robotare established and the calculation method of its motion parameters is derived. The equivalentinertia force and moment of robot’s real-time center of gravity are obtained by the principle ofequivalence. And a criterion combining ZMP and FASM is proposed to judge the stability ofwalking hexapod robot.According to the case of sideline tipping instability, a method is proposed to solveanalytically the adjusting-leg’s reachable workspace, and select a foothold by the principle ofmaximizing force arm. Five order curve interpolation based on the adjusting time is adaptedto softening the adjusting process of robot’s stability restoration, and the posture of thehexapod robot is recovered to the initial state through the mechanism of reflection motioncontrol.Taking the unstable condition of hexapod robot’s sideline tipping on a45°slope terrainas an example, Adams-Simulink co-simulation results verify the effectiveness of the proposedmethod of judgment and adjustment for hexapod robot’s instability.