Geometric Error Correction for Portable Coordinate Measurement Arm

Portable coordinate measuring arm(PCMA) is used to measure large-scale workpieces and in reverse engineering,etc.It is one of the important measurement devices to guarantee the manufacturing accuracy in modern industry.Error analysis,measurement and correctness are important in developing measurement precision of PCMA.The error model was built by analyzing geometric error for one of six joints,including encoder eccentric error and non-orthogonal rotational axis error.Aiming at building error compensating model,30 standard spheres were measured,which were fixed regularly in a circle by both coordinate measuring machine(CMM) and PCMA to build geometric error data.Coordinates of 30 spheres were measured by PCMA again and compensated.The maximum measuring error reduced from 0.04 mm to 0.003 mm after error correction.The experimental results have demonstrated that the measuring accuracy can be calibrated accurately and effectively and improved by using this technique to calibrate PCMA.