| Abstract: | When precise motion is required, robot accuracy must be improved. The purpose of this research is to improve robot positioning accuracy through kinematic parameter identification. Several researchers have selected models, developed identification algorithms, and estimated parameters using measurements or simulated data. However, much more work remains to be done. In this research, four related works are discussed. First, several identification models from the recent literature were found to be incomplete. Therefore, the theory of kinematic parameter identification for industrial robots is discussed. The necessary conditions for a complete and viable identification algorithm are revealed. Two concepts of completeness and equivalence are introduced to enable the selection and verification of a model for calibration purposes. It has been shown that a complete model must contain a minimum set of independent parameters. Next, the identification model is derived from the differential equations of the kinematic equations. Second is the realization of the difficulty in measuring the position and orientation of the end effector of a robot in free space. To be an inexpensive fix, a simple measuring device was constructed and is capable of sensing a fixed position accurately in free space. Third is to facilitate hardware implementation. Various measurement schemes are studied, from which a convenient procedure for data collection can be formulated. As an example, a three post scheme is illustrated for a complete measurement scheme. Fourth, a method for determining the required precision of measuring devices and the selection of locations for data collection is realized. Toward this end, the sensitivity of robot accuracy to measurement errors of the position and orientation of the end effector is developed by the upper bound of measurement errors and parameter errors. An experiment of robot calibration was performed on an IBM 7565. This demonstrates the feasibility of the work by improving the robot accuracy from 0.12 inches to 0.04 inches. |
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