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# Printer Carrier Optimum Move Algorithm

IP.com Disclosure Number: IPCOM000047406D
Original Publication Date: 1983-Nov-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 4 page(s) / 52K

IBM

## Related People

Dyer, S: AUTHOR [+3]

## Abstract

The carrier move algorithm discussed herein increases system throughput by minimizing the time required to perform a tab or carrier return in a typewriter or printer. Typically, a carrier move is made either at a given low speed or at several speeds depending upon the distance of the move. The move distance determines the move speed since ramp-up distance and stopping distance are dependent upon steady-state speed. Thus, for this type of algorithm the carrier never reaches maximum speed (and thus shortest move time) except for very long moves. The algorithm described achieves the shortest possible move times by always accelerating toward the maximum move speed. The move is optimized in time by always accelerating to the maximum speed possible for the length of move while still decelerating to a stop by the stop point.

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Printer Carrier Optimum Move Algorithm

The carrier move algorithm discussed herein increases system throughput by minimizing the time required to perform a tab or carrier return in a typewriter or printer. Typically, a carrier move is made either at a given low speed or at several speeds depending upon the distance of the move. The move distance determines the move speed since ramp-up distance and stopping distance are dependent upon steady-state speed. Thus, for this type of algorithm the carrier never reaches maximum speed (and thus shortest move time) except for very long moves. The algorithm described achieves the shortest possible move times by always accelerating toward the maximum move speed. The move is optimized in time by always accelerating to the maximum speed possible for the length of move while still decelerating to a stop by the stop point. This optimization is possible since deceleration is closed loop, providing a tightly controlled deceleration, and since an equation calculated during acceleration defines when the deceleration profile is intersected so that deceleration can begin. The system discussed is illustrated in Fig. 1. The scheme for determining velocity may be that described in
[1] in which clock pulses between fixed distance emitters are counted to determine inverse velocity. The deceleration scheme is preferably that described in [2]. The closed-loop deceleration scheme set forth in [2] is the key to making this move algorithm work well over the range of system parameters. The closed-loop deceleration describes a tightly controlled deceleration path via an equation that relates distance from stopping point to the desired velocity at that distance. Then a velocity error can be calculated at each position point and used to control the deceleration path, as shown in Fig. 2.

In Fig. 2, velocity is a linear function of time described by VELOCITY = VELss - Mt1 (Note: linearity is not necessary except for convenience.) where M = slope of the velocity profile; VELss = steady-state velocity intercept. The final stop in Fig. 2 occurs after a low speed plateau which compensates for variability in the deceleration profile. Fig. 3 illustrates the defined deceleration profile from Fig. 2 as a function of distance. This profile is nonlinear since position is the integral of the previously linearly defined velocity. In Fig. 3, DIS = Distance from the start of the defined decel profile at the VELss intercept to the present position.

DIST = The total distance of the defined decel profile.

DIS can be calculated by DIS = DIST - Present Position. For the defined deceleration profile, the relationship between DIS and COUNTS (clock pulses between encoder pulses) can be used to calculate the velocity error during closed-loop deceleration. This relation is plotted in Fig. 4. The defining equation is

(Image Omitted)

where

1

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NE = The number of encoder pulses between which

clock pulses are counted

K1 = Constant refle...