Inclination-angle-constraint-based kinematic calibration method for Stewart parallel robot

Abstract

The invention discloses an inclination-angle-constraint-based kinematic calibration method for a Stewart parallel robot. The method comprises the following steps of: firstly, theoretically establishing a novel kinematic constraint, which is an inclination angle constant constraint, namely keeping two inclination angles of a motion platform of the Stewart parallel robot relative to a horizontal plane constant group by group; secondly, using a servo regulating way to physically realize the established kinematic constraint in a high-precision way; thirdly, establishing a calibration model on the basis of a principle of least square according to the kinematic constraint; and finally, identifying a model parameter by solving a nonlinear least square optimizing problem and compensating for the model parameter in a robot control software. By making full use of a characteristic that a repeating precision of a measuring instrument is superior to a position measuring precision of the measuring instrument, the method has the advantages of good calibration effect, simple measurement, high automatism in the calibrating process and the like.

Description

Technical field: [0001] The invention belongs to the field of automation, and relates to a Stewart parallel robot kinematics calibration method, in particular to a calibration method based on inclination constraints. Background technique: [0002] Stewart parallel robots have the advantages of high structural rigidity, strong bearing capacity, good dynamic performance, and small cumulative error, and have been widely used in industrial production, scientific research, and life services. Motion accuracy is an important index to measure the working performance of parallel robots. It is affected by many factors such as manufacturing and installation errors of robot parts, control errors, joint and hinge clearances, thermal deformation, and vibration. Among them, the manufacturing and installation errors of parts are the most important factors affecting the accuracy of the pose (position and attitude) of the end of the parallel robot movement, which can be identified and compens...

AI Technical Summary

Problems solved by technology

However, it is not easy to install redundant sensors on the passive joint hinges of parallel robots to obtain internal motion information. It needs to be considered in advance in the design stage of the robot, and it cannot be applied to already constructed robotic equipment, and the installation of redundant sensors still needs to be considered Effects on mechanical strength of passive joints

Using a mechanical locking device to impose motion constraints will reduce the freedom of movement at the end of the parallel robot, requiring the drive joints of the robot to have the ability to operate passively and provide motion measurement, so it cannot be applied to many parallel robots driven by "motor + ball screw"

At the same time, the use of a mechanical locking device will greatly reduce the original narrow working space of the parallel robot, which limits the selection space of the calibration measurement configuration, which is not conducive to fully stimulating the structural characteristics of the robot.

In addition, during the calibration process, relying on mechanical locking devices to achieve motion constraints, it is easy to generate a leverage effect between the components and cause deformation, which affects the accuracy of the calibration results in the lightest cases, and may damage the relatively "fragile" passive joint hinges in severe cases

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