With the understanding that the desired performance of the robot could not be met, the

vision controllers were tuned on line to achieve the best possible results. The concentration was

initially placed on tuning the controllers to be able to approach non-moving fruit positioning

the end-effector within reach of the targeted fruit. The controllers were adjusted for tracking

fruit with small motions. This process of tuning the vision controllers continued until acceptable

performance was achieved while picking fruit as a continuous operation in an orange grove.

Adjustments to the controller parameters led to controller gains of 4.0 (D/A word)/pixel and lag

and lead factors of 0.02 sec and 0.01 sec, respectively, as indicated in Table 8.7.


Table 8.7. Final vision controller parameters for joints 0 and 1.

 Kc Ti Td
 Joint (D/A word)/pixel (sec) (sec)
 0 4.0 0.02 0.01
 1 4.0 0.02 0.01

Summary

 For each of the control methods, the lag-lead parameters were determined adjusting

the parameters until the best response of the system was achieved. In all cases, the parameters

were chosen to produce stable systems under all operations of the manipulator. Some sacrifices

were made in the less important areas to address more important requirements of the robot. In

the process of tuning the vision controllers, it was found that the ability to track large, fast

fruit motions was impossible for this manipulator. In this case, the criteria for large motions

could not be met, but the ability to position the end-effector within reach of a targeted fruit

with small or no motion was achieved. A summary of the values which were determined to

provide respectable control of the citrus-picking robot are presented in Table 8.8.

 These parameters for the compensators were used for the robot during actual grove tests

of the robot. With the knowledge that some large fruit motions would not be pickable for this

manipulator, the intelligence base (Adsit, 1989) was altered to cause the robot to either wait

for the motion to settle or to search for another fruit. In conjunction with the intelligence base