Abstract
As the basis of dynamic analysis and driving force calculation, dynamic models and dynamic parameters are important issues in mechanical design and control. In this paper, a dynamics verification experiment, which covers both dynamic models and dynamic parameters as a whole, is carried out on the typical Stewart parallel manipulator. First, the complete dynamic model of the Stewart manipulator is derived, considering the force sensors. The Newton-Euler method with clear physical meaning is adopted to facilitate understanding and parameter definitions. The dynamic parameters are deduced based on the established three-dimensional virtual prototype and adjusted with actual measurements. The recorded trajectory, instead of the theory trajectory, is adopted to calculate the theoretical limb forces. The practical limb forces are measured using pull pressure sensors. Finally, the dynamic model and identified parameters are verified by comparing the limb forces obtained using the above two approaches. Experiment results show that theoretical and practical limb forces coincide well, with a small maximum RMS (root mean square) error of 1.516N and forces ranging from 10N to 40N. Additionally, the established dynamics verification algorithm, which involves dynamic modelling, a parameter identification approach and a data analysis method, are generic and practical, and can be flexibly applied to the dynamic analysis of other parallel manipulators.
Highlights
A parallel manipulator is a closed-loop mechanism that consists of a base and an end effector connected through several identical limbs [1]
In this paper, a dynamics verification experiment is carried out using the Stewart platform, which includes dynamic modelling, parameter identification and data analysis
The theory trajectory of the end effector is easier to achieve, recorded practical limb lengths are instead adopted in the experiment, which reflect the actual impacts of the interpolation algorithm, as well as the dynamic performance of the drive module
Summary
A parallel manipulator is a closed-loop mechanism that consists of a base and an end effector connected through several identical limbs [1]. It has been acknowledged that parallel manipulators possess advantages in terms of accuracy, rigidity, large load-to-weight ratio and high acceleration, compared to traditional serial manipulators [2, 3] This statement can be verified by their wide applica‐ tion as machine tools [4, 5], positioning devices [6, 7], motion simulators [8, 9] and high-speed pick-and-place robots [10, 11]. In this paper, a dynamics verification experiment is carried out using the Stewart platform, which includes dynamic modelling, parameter identification and data analysis. The study of this paper concerns the Stewart platform, a 6-DOF (6-degree-of-freedom) parallel mechanism [19] with a base and end effector connected via six identical extensible limbs. Êë -sq cq sy cqcy úû where s is the sine operation and c is the cosine operation
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