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Some of the main investigations on calibration methods of parallel mechanisms are briefly discussed in this work. Initially, the identification of errors in these structures applied to machine tools is presented, later the kinematics and the concept of parallel mechanisms calibration is introduced. Additionally, the main characteristics of the existing methods of calibration are discussed, such as the parametrical approaches, the calibration methods with internal/external measuring devices, innovative calibration methods and works that provide assistance to this aim.Keywords: Parallel mechanisms, calibration, machine tools, inverse kinematics, forward kinematics. Resumen

This research ponders the origin of errors due to manufacturing and assembling processes that affect pose accuracy of any given robot. The estimation of these errors allows designers to define the influence of individual elements in the overall compliance. Two methods for assessing pose accuracy in parallel robots are presented in this paper: the simplified and the comprehensive methods. The former, based on the assumption that each actuator has a constant error, produces a preliminary rough estimation of pose accuracy; the latter, based on error propagation, requires the measurement of the displacement error of each actuator. Both methods were applied to estimate the accuracy of a high-precision Stewart platform and to verify it experimentally. These methods were validated through an actual platform, and results showed good agreement between them.

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