| Tomato robotic harvesting is most difficult due to its feature of several fruits touching each other in one cluster. Vacuum suction system is a vital device for tomato harvesting robot to avoid interference with other fruits in gripping object fruit on same cluster. In this dissertation, systematical analysis and modeling of the running process of a certain vacuum suction system, which has been developed and takes one mini air pump and one vacuum ejector as vacuum generation, is performed. And then control parameters and modes optimization of this newly developed system is finished based on extensive test results, which will be tribute to achieve high success-ratio, high-efficient and energy-saving sucking/pulling to tomato fruits and improve success ratio of robotic harvesting.This dissertation mainly includes the following contents and results:(1) Test study on physical properties of tomato fruits and stems, compression and friction properties of tomato fruits and mechanical properties of tomato stems include pulling, bending and twisting was performed, which provides basic data to device design and control optimization. Then principle design to the end-effector for tomato harvesting robot, type and structure design to the gripper, vacuum suction system and stem laser-cutting device were finished. The end-effector is installed together with a manipulator and a binocular visual system to construct the experimental system of tomato harvesting robot.(2) Considering mechanical relation among the rack, the suction pad, fruit (stem) and plant, a multi-factor pulling force model is constructed based on test results of relation between pull-off force and diameter of the suction pad, relation between pull-off force and vacuum degree and compression property of the suction pad, which discovers the complicated relationship among pulling force and pulling distance, vacuum degree, fruit size, fruit weight, stem length, elastic flexure-resisting stiffness of stem and initial posture and provides theoretical basis to optimal control of sucking and pulling operation.(3) Based on tests results of relation between air supply pressure and vacuum degree, calibration test of vacuum pressure sensor, inflation property of air pump to air tank, air consumption during sucking, blowing and deflating, a continuous inflation-intermittent consumption complex model is built through basic models-primary models-recursion models-pressure-time models gradually which takes air pressure in the air tank as aim index. It describes law of air pressure change in the air tank accurately during sucking and pulling operation and reflects effects on air pressure change in the air tank by different parameters of air inflation and consumption, which provides theoretical basis to hardware configuration and optimization of control of control parameters and modes.(4) Tests of pressure maintenance ability of the check valve, tests of suction response time under air supply control Vs suction control, in exposure Vs closure conditions, in different long time and release response time test have been finished. According to these test results, vacuum suction response model is built, based on which relations among tube length, suction capability and operating performance of the vacuum suction system are analysed and tube length is optimized.(5) One model of actual success ratio in gripping combining success ratio of sucking and pulling with ratio of interference in gripping is built applying probability theory and normal distribution function. Taking this success ratio, working efficiency and energy consumption level as evaluating indicators and laws of force-motion, air pressure change in the air tank and vacuum action response as base, motion parameters and vacuum action parameters in sucking and pulling operation are optimized, and "fruit touch-air supply" control mode to coordinate action of the vacuum system with motion of the rack, "grip-passively release" control mode to coordinate releasing of the suction pad and gripping of the fingers, "inflate-passively stop" control mode to save energy of the vacuum suction system are decided by theoretical and testing optimizing at last.In this dissertation, a systemic optimization process of agricultural equipment is constructed. In view of large difference of features of agricultural objects, a composite indicator to evaluate success ratio of sucking/pulling/gripping operation is constructed innovatively with probability method. Based on all of physical and mechanical properties, parameters of the device, force-motion law, air inflation-consumption law, vacuum response law, optimization to control parameters and modes is finished to achieve high success ratio, high working efficiency and energy-saving sucking/pulling/gripping operation. This study has important theoretical and practical value.
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