Kinematic calibration of parallel robots using orientation constraint

Kinematic calibration is an effective and economical way to improve the accuracy of the parallel robot. A new calibration method using an orientation constraint is presented in this paper. The main idea is to keep two attitude angles of the end-effector constant at different measurement configurations with the help of a commercial biaxial inclinometer. Repeatability and resolution of the inclinometer contribute to constructing the orientation constraint instead of the accurate values of the attitude angles. The corresponding calibration algorithm is derived according to that constraint. The required measurement data only are the variables of the active joints at each measurement configuration. Simulations have been performed to show validity and effectiveness of the proposed method.