Aiming at the problem of force measurement in microassembly

a new visual force measurement method based on geometric moment invariants analysis is proposed. The method uses shape descriptor of geometric moment invariants to describe the microgripper shape before and after deformation. Mapping relationship between applied forces and feature vectors of geometric moment invariants is deduced. On this basis

set up force measurement model and its solution. Then

a training set is established

where the input represents the feature vector corresponding to shape of microgripper

and the output represents the corresponding known applied force

respectively. Similarly

a testing set is established

where the input represents the feature vector corresponding to shape of microgripper and the output represents the corresponding unknown applied force

respectively. Finally

a support vector machine（ SVM） compares each feature vector in the testing set with those ones in the training set

implements multi-class classification

so as to measure unknown applied force. Experimental results show that the proposed method is accurate and stable.