New Assistance Machine Aids Strawberry Pickers PDF Download

California is the nation's leading producer of strawberries. In 2013, California's strawberry industry harvested more than 2.3 billion pounds of strawberries (88% of the U.S. production) at a value of $2.6 billion. Labor for manually strawberry crops can contribute up to 63% of the production cost and picker availability is low due to the harsh working conditions. Prior attempts to build robotic harvesters have not resulted so far in effective, cost-efficient machines. An alternative to complete mechanization is machine-aided harvesting. In an effort to improve picker efficiency and working conditions, a team of inexpensive, relatively small, harvest-aiding mobile robots is being developed at the University of California - Davis, which will aid human pickers by transporting fragile crops from the pickers to loading stations at the edges of the field. The robots aim at significantly reducing pickers' non-productive walking times, which can take up to 20-30% of their working time. This thesis focuses on the design of the carrying tray for the flat of strawberries to maintain strawberry quality. The PSD of the harvest-aid robot chassis was measured and it was found that the most dominant frequencies in the PSD curve were 8-11 Hz for traveling speeds of 100 cm/s, 150 cm/s, and 200 cm/s. It was found that using viscoelastic material alone was not sufficient to attenuate vibrations. A two parameter isolator was developed consisting of a compression spring and viscoelastic block. This design proved successful in reducing vibration amplitude. In addition to being designed to reduce damage to strawberries, the tray has been designed to be easy and safe to use by the picker. This work also presents a dynamic model to predict the power spectrum density (PSD) of an isolator design, with the input to the model being chassis acceleration. Model output was compared to experimental data for model validation. The results indicate that the simulation model is similar to the PSD curve of the tray over uneven terrain, therefore the model can be used as a tool to design alternative isolators for later iterations of the isolation system design. In total, the tray design provides a safe and quick interface for the user, protection for the product, and the potential for increased yields for field owners. Together with the rest of the robot, this design will contribute to a safer, more efficient harvest for strawberries.