Direct Kinematic Analysis of Delta Robot Based on Exponential Product

For kinematics analysis of parallel mechanism, there exist two kinds of methods: D-H parameters method and vector method. The former has the shortcoming that each link's local coordinate system should be established and kinematic equation be obtained according to the transformation between link coordinates, which makes the process to be relatively complicated. The latter can solve the problem of multiple solutions in the positive kinematics, but it cannot represent the end attitude of the actuator, which is lack of generality. This paper presents an exponential product (POE) method based on screw theory. The method makes kinematics model simple by establishing inertial coordination system S and tool coordination system T. It has a clear physical and geometric meaning. Then the positive kinematics and working space of typical Delta parallel robot could be solved based on POE method.