Bosch 6000 User's Guide download pdf (Page 195)

180

6000 Series Programmer's Guide

Scenario #2: OTF change of distance, where new

commanded distance (D

) is less than the original

distance (D

) that was pre-empted [D

< D

]. In

this example, D

is beyond the position where the

OTF change was entered, however D

can not be

reached with the commanded deceleration. In

steppers, an instantaneous velocity change is

made such that D

can be reached with the

commanded deceleration (in servos, motion is

killed if the new destination cannot be reached

with the commanded deceleration).

Scenario #3: OTF change of distance, where new

commanded distance (D

) is less than the original

distance (D

) that was pre-empted [D

< D

]. In

this example, the position where the OTF change

was entered is already beyond D

. In the event of

an overshoot (steppers only), motion is killed and

AS.3Ø and ER.1Ø bits are set.

(plus overshoot)

Scenario #4: OTF change of velocity. Note that

motion must continue for a longer time at the

reduced velocity to reach the original commanded

distance than if it had continued at the original

velocity (t

> t

On-The-Fly Motion — Sample Application

A manufacturer of three products wishes to produce a “sampler-pak” package which will

contain a few of each of his products. The products all have the same width and length, but

are 3, 4, and 5 inches high respectively. The 3 products are fed from individual lines into a

common conveyor, and arrive at a stacking and wrapping station. At this station, a tray

accepts a product and must have moved down by that product’s height by the time the next

product arrives. This means that each time a new product arrives, the velocity of the tray must

be changed to match the height of that product. Although product spacing will be regular, the

ordering of product type on the common conveyor will be random, due to variations in the

input lines. Also, a finished sampler-pak should contain 5 products or be at least 18 inches

high, whichever occurs first. This means that the total move distance of the tray will be

unknown until the last product arrives. When the last product is stacked, an output is asserted

which will pause the conveyor and start the wrapping process. When wrapping is complete,

the sampler-pak is removed from the tray, and the tray returns to the starting position.

The basic problems in this application are that the move distance is not known until near the

end, and the velocity must change on the fly. As the products approach the tray, they are

detected with a near vertical arrangement of three sensors. Products of heights 3, 4, and 5

inches are detected by 1, 2, or all 3 sensors respectively. Input 1 always detects a product, and

switches last, so that the others will be stable. When each product is identified, the motion

profile is modified accordingly.

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Bosch 6000 User's Guide Page 195

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