It is based on unit quaternion to represent orientation parameters and deduce the singularity expression of Stewart manipulator in the Euler parameter space at a certain position.

Method Studies on Error Modeling and Calibration of the Stewart Platform;

The orientation-singularity expression of the Stewart platform is deduced by using unit quaternion which can avoid singularity when using Euler angles to represent the orientation of rigid body, and then the algorithm of orientation-workspace of the manipulator at a certain position is proposed.

Unit quaternion is used to represent the orientation of rigid body,orientation-singularity expression of the Stewart platform at a given position is deduced,and the singularities caused by Euler angles are avoided.

The actual parameters of Stewart mechanism can be calibrated by means of the measurements of the length of all legs and the relation of the first-order static influence coefficient matrix and Jacobian matrix.

A new measurement method based on the Stewart mechanism was used to measure the positioning of the feed fine-tuning test platform of the five-hundred-meter aperture spherical telescope (FAST).

Based on the new singularity kinematics principles,a cubic polynomial expression that represented the singularity loci of 3/6-SPS Stewart manipulator was obtained and a singularity-equivalent-mechanism was proposed as well.

Using this particular orientation representation and the inverse kinematics solution of the Stewart manipulator, a discretization method was proposed for the computation of orientation- workspace and practical orientation-workspace of the manipulator taking i.

Nonlinear coupling in Stewart platform makes the design and testing of this kind of machine tools very complicated and must be implemented with the computer.