Automatic Cutting Control Of Deformable Objects With Vision/Force Feedback

Automatic operation of deformable objects is important in a variety of applications,such as industrial parts operations,food processing,medical surgery robots and service robots.And the cutting of deformable objects is the basic operation and key step.The complex physical properties of deformable objects such as non-linearity and stiffness make it difficult to calculate the high-dimensional deformation and time-varying topology caused by the interaction of objects and tools in the cutting process.The operation is limited by real-time sensing,modeling,prediction and control.Therefore,relevant research has great challenges.With the development of new technologies such as computer science,robotics,sensor technology,these technologies can be used to assist in automatic cutting.In this paper,an automatic cutting control method of deformable objects based on visual and force feedback is proposed,which is divided into two key parts: deformation prediction and cutting control.The cutting tool can automatically cut along a preset trajectory in the case where the object is deformed.The deformation of objects is predicted by using the optimized Finite Element Method.Through the cutting area division and condensed processing in off-line modeling,the real-time solution order of the model equilibrium equation is reduced,and the online model update rate is accelerated.At the same time,considering that the object model is difficult to obtain accurately and the material characteristics of individuals are different,a fixed camera is introduced and discrete feature points on the surface of the object are selected as image features.The model parameters Young's modulus and Poisson's ratio are estimated online based on visual feedback to improve the robustness of the system to modeling errors.In terms of cutting control,force feedback is used to monitor the force change in the cutting process in real time.By comparing different cutting strategies,the pressing and slicing cutting method is selected to adjust the cutting speed of the vertical axis and reduce the resistance of the tool to achieve smaller force cutting.Based on visual feedback,the object deformation and manipulator motion are monitored,the mapping relationship is derived,and the cutting task is transformed into visual servoing control.Design the controller and prove its stability.Finally,automatic cutting control is realized through the real-time deformation prediction of the Finite Element Model,online planning of the cutting trajectory based on visual and force feedback,tool pose control and multi-point visual tracking.The experimental platform based on Kuka iiwa robot is used to cut sponges and pork liver of different properties.The experimental results verify the effectiveness of the proposed algorithm.