Analysis Of Robot Grasping Control Modes Based On Viscoelastic Parameters Of Tomato

Application of agricultural robot in picking and sorting fruit and vegetable is becoming more and more popular,the robot end-effector is an important step in grasping fruit and vegetable.Different modes of robot grasping will lead to different mechanical damage of fruit and vegetable.In the process of grasping,the plastic deformation and viscoelastic deformation of fruit were caused by many kinds of loads,such as extrusion and impact,which lead to the current injury and delay injury,whereas the plastic deformation play an overwhelming role on the quality of fruit.Most fruit are viscoelastic,using the model and parameters of viscoelastic to analyze the deformation of fruit,which can provide technical support for reducing and controlling the mechanical damage during the operation and improving the product quality.So,in this paper,the tomato was selected as the operation object,and using the viscoelastic model to express the deformation characteristics of tomato.The plastic deformation was regarded as the indicator of fruit mechanical demage,in order to reduce the mechanical damage of fruit during the robot grasping process,the theoretical analysis of plastic deformation on different grasping control modes of fruit was conducted based on the viscoelastic model and parameters.The main content is as follows:1)The grasping systems of robot were built,and the clamping damage of fruits and vegetables was analyzed in this paper.The tomato was selected as the operation object,and using the Burgers model to express the deformation characteristics of tomato.According to the creep experiment.of TMS-PRO texture analyzer,the viscoelastic parameters k1,k2,c1,c2 of tomato with different maturity were obtained by fitting the creep data through the ORIGIN 8.0 data analysis software,which can provide the parameter for plastic deformation analysis.2)The elastic and plastic deformation of tomato was analyzed based on the Burgers model,three kinds of variations of speed,i.e.,motion with uniform deceleration,deceleration after uniform motion and motion with variable deceleration were selected to indicate different grasping control modes.Using the linear function,Butterworth amplitude square function and exponential function to represent different grasping control modes of end-effector during the real grasping process.3)According to the plastic deformation model of tomato,taking the grasping speed v0=lmm/s and the grasping time,t0=1s of the first grasping control mode as an example,the plastic deformation computational principles of tomato with early maturity was discussed in detail.Then,the mathematical software of Maple was adopted to simulated the robot grasping process on different grasping control modes in regular t0=[1,4]s and v0=[1,20]mm/s of tomato with different maturity,and observe the regularity of force,speed and displacement changed over time,the plastic deformation of tomato was calculated under three kinds of grasping control modes.4)According to the results of plastic deformation of tomato on different grasping conditions which calculated by Maple,the third grasping control model was selected as the optimal grasping strategy based on the minimum plastic deformation.Using the third grasping mode to carry out the grasping control experiment,the simulation results were highly identical with measured results,the correlation coefficient R2 was 0.99,which proved the rationality and feasibility of the third mode as the optimal grasping control mode.This research can offer a reference for robots grasping process optimization.