Abstract: The positioning accuracy calibration method for a reconfigurable modular robot system is studied. The assembly incidence matrix is defined to describe the assembly relationships of adjacent models for any given configuration of the modular robot. According to the assembly information the kinematics is built in product of exponentials (POE) form automatically. According to the adjoint transformation relationship between the theoretical value and the actual value of joint twists in the POE formula, the kinematics is transformed to an equivalent form including the joint constrains. The linearized equation is got by differentiating the kinematics equation so as to describe the relationship between the positioning errors in the end of the manipulator and the errors in the joint twists and in the zero position. A kinematic parameters calibration model is presented based on the least-squares method and its generating method. The calibration model of a 5-DOF modular manipulator is given by program. Taking a laser tracker as the measuring equipment, the kinematic calibration experiment is taken out. The experimental results show that the calibration process can converge to stable value rapidly. The testing results show that the average positioning precision is increased about 4 times.

Key words: reconfigurable modular robot;product of exponential;parameter calibration