deg/sec and -8.1 deg/sec. The velocity of joint 1 during the search routine was much less uniform

than that of joint 0.

 At approximately 6 sec (360 ticks) into the routine, as the position of joint 0 increased,

the sliding joint slid about 1 cm in its bearing. This motion was caused by the changing gravity

forces on the slider as the position of joint 0 was increased. This change in the load of joint 1

caused a deviation from the smooth operation of the velocity controller for joint 1. Even though

the velocity errors were quite large when compared to the velocity setpoints, they did not

hinder the successful completion of the fruit search routine. Maximum velocity errors for both

joints 0 and 1 were specified as 40 percent of the desired velocity. This specification was

obviously over extended, but the motion robot was still acceptable for the search routine.

Performance During the Pick Cycle

 The ultimate test for the motion control strategies was performance evaluation during a

pick cycle. A typical pick cycle began with the robot in the home position. The vision system

was checked for a fruit in the image. When no fruit was found in the image, the search routine

was invoked. But, when a fruit was found in the image, the intelligence base proceeded to

remove the fruit from the tree.

 For this evaluation, the actions of the robot were examined during a simple pick cycle

in which the fruit was found without the search routine. The control modes and the motions of

the joints during the pick cycle are presented in Figures 9.24 and 9.25. In Figure 9.24, the control

modes which were used during the entire action and took 3 sec (180 ticks) are shown. When the

intelligence base determined that a fruit was centered in the image, the robot was instructed to

approach the fruit. This approach was conducted using vision control on joints 0 and 1 to

maintain alignment with the fruit while the end-effector was extended towards the fruit under

velocity control of joint 2 (ViViV). When the intelligence base determined that the fruit was

within the pick envelope (63 ticks), all joint motions were stopped under position control (PPP),

and the rotating lip was actuated, grasping the fruit. Once the fruit was grasped (80 ticks), the

slider was actuated under velocity control of joint 2 to retract the end-effector from the canopy