Research And Implementation Of Strawberry Picking Manipulator

China has become the largest producer and exporter of fruit.Strawberry fruit,as an important economic crop in fruit,has been a fruit loved by people.However,due to the large planting area of strawberry,the shortage of human resources,and the time-consuming and laborious manual picking of fruits,the picking cost has been expensive.The development of strawberry picking robot has been helpful to improve fruit picking efficiency,liberate labor force and reduce cost.Therefore,this thesis has designed a strawberry picking manipulator and a new picking end-effector structure for strawberry in ridge planting environment.The main research contents were as follows:Firstly,Through the field investigation of strawberry planting environment in ridge,the growth environment and physical characteristics of strawberry were studied,and the advantages and disadvantages of mechanical arm structure,rigid flexible end effector structure and different picking methods were analyzed.Complete the overall assembly of the three-dimensional model of the strawberry picking mechanical arm,calculate the driving force of each joint and select the driving element.Based on the stiffness theory and strength theory,the static analysis and simulation of the strawberry picking manipulator under the limit station were carried out,and the minimum deformation of the manipulator was optimized.After optimization,the deformation of the manipulator was reduced by0.8mm,which improved the operation stability of the manipulator and reduced the displacement error of the end effector.Secondly,the kinematics equation and dynamics equation of strawberry picking manipulator were established by improved DH method and Lagrange method.The robot toolbox was used to verify the correctness of the manipulator model.Through the joint space trajectory planning of the picking manipulator with three polynomials and five polynomials,the motion stability of the picking manipulator was verified.Through dynamic simulation,the correctness of dynamic modeling and driving element selection of picking manipulator was verified,which provided data reference for manipulator control.The mechanical equation of vacuum suction cup of end effector,the equation of suction pull motion and the equation of fruit stem cutting motion were established.The factors affecting the suction of the sucker were analyzed.Through experiments,the sucker with a diameter of 25 mm had the best effect on adsorbing strawberries.The motion simulation of the picking end-effector showed that the cutting force was 16.5 N,which could achieve stem cutting.Lastly,complete the mechanical assembly of the picking end effector.The control logic block diagram and electronic control scheme of the picking end effector were proposed.The pneumatic circuit and electrical diagram of the picking end effector were designed,and the selection of the key electrical hardware and the wiring of the electrical circuit were completed.Strawberry picking experiments were carried out in a simulated picking environment.The negative pressure sensor and ultrasonic ranging sensor were used to feed back the test data to realize the negative pressure adjustment of strawberry adsorption with different fruit stems.The experimental data showed that the rapid and non-destructive picking of strawberries can be achieved by adjusting the negative pressure value.One successful picking takes 2s,and the success rate can reach 91.3 %.The test verifies that the structure design of the electric composite drive picking end effector is reasonable,the picking performance is good,and the strawberry can be efficiently picked.