1. Key Laboratory of 3D Printing Process and Equipment of Zhejiang Province, State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou 310027, China 2. Polytechnic Institute, Zhejiang University, Hangzhou 310027, China 3. Suzhou Xinzhi Mechatronics Technology Limited Company, Suzhou 215101, China 4. Suzhou Zijingang Intelligent Manufacturing Equipment Limited Company, Kunshan 215300, China
A robot assembly posture online correction algorithm based on machine vision was proposed in order to solve the problem that the relative position between the workpiece and fixture was uncertain in the process of clamping special-shaped parts with flexible fixture. A workpiece pose vector was established by image preprocessing and surface feature extracting. The correction of posture was decomposed into the original posture error, the posture error introduced by rotation and the residual posture error by system modeling, error analysis and function fitting. Linear combination of these three corrections was fed back to the robot as an error compensation for the posture error of the workpiece in order to guide the robot to complete the assembly task. Experiment was conducted by taking the assembly process for the rotating scroll of automotive aircon scroll compressor, and a robot hand-eye assembly system was established in order to verify the effectiveness of the method. The experimental results showed that the angular deviation and the displacement deviation in the x and y directions between the corrected posture and target posture were less than 0.6 degrees and 0.6 mm, respectively. The average assembly time was less than 20 seconds, and the assembly success rate in the experiment was 99.67%.
Da-zhao DONG,Guan-hua XU,Ji-liang GAO,Yue-tong XU,Jian-zhong FU. Online correction algorithm for posture by robot assembly based on machine vision. Journal of ZheJiang University (Engineering Science), 2021, 55(1): 145-152.
Fig.6Model of posture error introduced by rotation
$\Delta ^{{\rm{b}}}x$
$\Delta ^{ {\rm{b} } }{{y} }$
${k_1}$
${k_2}$
$\Delta ^{{\rm{b}}}x\geqslant 0$
$\Delta ^{ {\rm{b} } }{{y} }\geqslant 0$
0
1
$\Delta ^{{\rm{b}}}x\geqslant 0$
$\Delta ^{ {\rm{b} } }{{y} } < 0$
2
?1
$\Delta ^{{\rm{b}}}x < 0$
$\Delta ^{ {\rm{b} } }{{y} }\geqslant 0$
1
?1
$\Delta ^{{\rm{b}}}x < 0$
$\Delta ^{ {\rm{b} } }{{y} } < 0$
1
1
Tab.1Value table of ${k}_{1}\;{\text{and}}\;{k}_{2}$
Fig.8Flow chart of pose correction algorithm
Fig.7Error model of center of rotation
Fig.9Example diagram of eye-in-hand assembly system
Fig.10Measurement results of angular component of residual pose difference
Fig.11Measurement results of positional component of residual pose difference
Fig.12Fitting results of $\Delta {x_3}$ changed with correction angle
Fig.13Fitting results $\Delta {y_3}$ changed with correction angle
项目
${a_i}$
${b_i}$
${\omega _i}$
${c_i}$
拟合 $\Delta {x}_{3}(i=0)$
1.161
?0.3529
0.01923
0.2911
拟合 $\Delta { {{y} } }_{3}(i=1)$
1.246
0.2909
0.02011
?1.155
Tab.2Function parameter list
Fig.14Standardized residuals diagram of position error fitting
Fig.15Assembly system position error diagram
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