velocity and position control systems as presented in this chapter is tabulated in Table 7.3.

Because of the desire to have very fast pick cycle times, dynamic response times for the

algorithms were required to be kept as short as possible. Another very important criterion of

all of the control systems was that they remain stable during all phases of operation.

 The performance of the vision control system was more critical than that of either

other control mode. The vision control system was required to maintain a steady-state error of

65 pixels or less on joint 0 and 47 pixels or less for joint 1. Maximum phase angles are also

presented in this chapter. These phase angles were used later in defining and tuning the vision

controller. Also, requirements were specified for the amplitude ratio for the vision control

system. Because the worst of the two cases was not distinguishable, both cases were passed on

to the controller design and tuning phase.


Table 7.3. Summary of performance criteria for the velocity, position, and vision control
 algorithms.

 Static Dynamic
 Max. Allowable Max. Allowable
 Steady-State Error Overshoot
 Joint 0
 Velocity Control 40% 45%
 Position Control 0.7 degree (25 bits) 15%
 Vision Control 65 pixels see Figure 7.7
 Joint 1
 Velocity Control 40% 45%
 Position Control 1.1 degrees (12 bits) 15%
 Vision Control 47 pixels see Figure 7.7
 Joint 2
 Velocity Control 10% 25%
 Position Control 3 cm (33 bits) 15%