Development Of Under-Actuated Manipulator For Apple Picking

Fruit is essential to human life. Fruit Harvest is one of the important links of the agriculture production process while the work of fruit harvest is mostly completed manually in China. In the21st century, the labor shortage of will become increasingly serious in many developed and developing countries. Therefore, the research on fruit picking robot not only can meet the market demand, reduce labor intensity and improve economic efficiency but also has great historical significance to promote agricultural science and technology progress and accelerate agricultural modernization.This project is supported by the National "863" program:"Research on the key technologies of mobile fruit picking robot". One kind of under-actuated manipulator for apple picking was developed and its feasibility was examined through experiments. The main work of the project is as follows:1. Based on the analysis of picking robot development, under-actuated principle and apple picking methods at home and abroad, the shortcomings of the picking mechanism were pointed out; a kind of under-actuated end-effector for apple picking was put forward. The theory and the working principle of under-actuated mechanism were investigated, the static mechanics model of the under-actuated end-effector was established and the main dimensions were determined. MATLAB was used to optimize the design of the fingers. In addition, the static strength of the palm, fingers and other key parts was also examined.2. The3D model of the end-effector was established and the prototype was assembled in the virtual environment of PRO/E. Based on the kinetic and dynamic simulation, the motion characteristics curve of the end-effector was obtained. Then the problems existed in the primary design were revised and the final design was determined.3. Control system of the under-actuated end-effector was designed. Experimental platform with the force sensor and position sensor was built based on the selection of stepper motor, motor drivers, sensors, other components; witch uses AVR as its main controller. The relationship between the clamping force and velocity of the fingers was studied and a stable range of suitable clamping force and the stepper motor speed threshold was then obtained.4. The reliability of under-actuated end-effector was examined through experiments. The results show that:the end-effector has the advantages of simple structure, easy operation, high reliability etc, and it can meet the design requirements.