Development and evaluation of a pneumatic finger-like end-effector for cherry tomato harvesting robot in greenhouse

This paper presents the development and evaluation of a pneumatic finger-like end-effector for cherry tomato harvesting robot. The end-effector is pneumatically controlled and has the capability of picking cherry tomatoes continuously and steadily. The end-effector is compact in overall structure, which consists of finger-like clamping finger, rotating and telescopic cylinders, and RGB-D camera, etc. Another important feature is that the clamping finger uses a combination of clamping and rotating and has good adaptability in dense operating environments. Further, a hand-picking dynamic measurement system is developed to measure and analyze the applied force and disturbance for simplified picking methods during picking. The hand-picking test shows that both the applied force and the disturbance are smaller for rotating compared to pulling, so the method of rotating is chosen for the design of the end-effector in this study. The field test shows the average cycle time of picking single cherry tomato is 6.4 s. The harvest success rates for pickable cherry tomatoes in different directions are 84% (right), 83.3% (back), 79.8% (left), and 69.4% (front), respectively. The failure cases are analyzed and collision and localization failure are the main causes of unsuccessful picking during picking.