Page 759 - Mechatronics with Experiments

PROGRAMMABLE MOTION CONTROL SYSTEMS 745

Initialize:

Given the process parameters: L_p - part length,
L_3-desired part spacing,
Given algorithmic parameter: V_percent (i.e. 0.9 = 90 %
speed reduction if queue is
full)
Output conveyor speed is electronically geared to the queue
conveyor speed by: V_3 = ((L_p+L_3)/L_p ) * V_2
Where the gear ratio between queue conveyor (master) and
the output conveyor (slave) is: (L_p+L_3)/L_p
Repeat Every Cycle:
Measure, N_1, the part rate,
Calculate queue conveyor speed: V_20 = L_p * N_1
Check queue level and modify V_2 accordingly,
Update speed command to the queue conveyor (V_2)
If V_2 = 0, call homing routine to fill-up the queue
conveyor.
Repeat Loop End

Return
Check queue level and modify queue speed algorithm:
If (Queue is low (PRX-1 and PRX-2 are OFF) and
PRX-3 is ON)
V_2 = V_20 / V_precent
Else if (Queue is High (PRX-1 and PRX-2 are ON )
and PRX-3 is ON )
V_2 = V_20 * V_precent
Else if (Queue is Empty: PRX-3 is OFF)
V_2 = 0.0
Else
V_2 = V_20
End if
Return

Homing Routine:
’ Queue conveyor is empty.
Start input conveyor if it is stopped
Disengage electronic gearing of output conveyor
While (PRX-3 is OFF)
Wait until PRX-1 triggers, then move for L_p distance.
Repeat
Engage gearing of output conveyor
’ On return, queue conveyor is full and all parts are
touching each other.
Return

Position Phase Adjusting Conveyor: Smart Conveyor Slaved to both
the Input and the Output Conveyor In most general form, the smart (also
called shuttle) conveyor must coordinate its motion both with input and output conveyors
at different phases of the motion. In some applications, coordination only to the input or
only to the output conveyor may be sufficient. The smart conveyor acts as a very fast slave