causing only minimum damage to the trees. The knowledge gained from this project is a

beginning for further enhancements of the robot and encouragement toward the final goal of a

production model citrus harvesting machine.

 During the development of this manipulator, some recommendations have become

evident. Because this manipulator was the first prototype, its links were massive and rigid.

Larger and more rigid links were initially designed so that collisions with obstacles during the

tuning and controller design process would not render the robot inoperable. Activation of these

large links required much larger actuators than would be desired in later models. The reduced

inertia of smaller and lighter links would increase the hydraulic natural frequency of the

joints, thereby enabling the robot to achieve the motions necessary for picking fruit with large

and fast motions. The lighter links would also require smaller actuators which would also

result in increased response rates of the manipulator. After increasing the natural frequency

and the response rate of the manipulator, the controllers could be tuned to aid in increasing the

robot's overall efficiency.

 The behavior of the sliding joint could be improved by choosing a different bearing

surface or a different type of mounting arrangement. During the process of this work, the

bushing was changed from nylon to oil impregnated nylon and then to teflon. Each change made

a significant difference in the action of the joint. It is assumed that an even better choice could

be made.

 The technique which was developed for defining the pick envelope could be adapted to

assist in the design process of a more effective picking mechanism. This technique provided a

means for determining the relationship between the end-effector and the fruit for successful

picking. The need of a better picking mechanism has been established. However, all of the

requirements of this picking mechanism have not. A similar concept to that discussed for

determining the picking envelope could expedite the research and testing of a better picking

mechanism.