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Control Algorithm for Improved Print Registration

IP.com Disclosure Number: IPCOM000060211D
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 4 page(s) / 73K

Publishing Venue

IBM

Related People

Akers, AL: AUTHOR [+6]

Abstract

Print registration is improved through controlling the effect on character placement of variations in selection, ribbon, and hammer timing with respect to escapement by use of a control algorithm. In some daisywheel print mechanisms, the ribbon move time, as well as the selection move time, may be greater or lesser than the escapement move time. The print hammer time also may vary according to impression force with this being significant if the impression forces required for correction and printing are different. A control algorithm accounts for all these variations by fixing the time from the "end point" of each of the moves to the "hammer impact point" at a constant value.

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Control Algorithm for Improved Print Registration

Print registration is improved through controlling the effect on character placement of variations in selection, ribbon, and hammer timing with respect to escapement by use of a control algorithm. In some daisywheel print mechanisms, the ribbon move time, as well as the selection move time, may be greater or lesser than the escapement move time. The print hammer time also may vary according to impression force with this being significant if the impression forces required for correction and printing are different. A control algorithm accounts for all these variations by fixing the time from the "end point" of each of the moves to the "hammer impact point" at a constant value. The algorithm requires knowing or calculating the move times for each of the escapement, selection, ribbon, and hammer operations and adjusting the relative start times so that all of the moves end at a fixed time with respect to hammer impact. Fig. 1 is a timing diagram of the relation of the various operation times used by the control algorithm with the following definitions: EMT Escape Move Time SMT Selection Move Time RMT Ribbon Move Time SHI Start of Hammer Fire to Impact Time PIOP Previous Impact to Out-of-Plane Time PICS Previous Impact to Cycle Start Time EEI End of Escapement Move to Impact Time ESI End of Selection Move to Impact Time ERI End of Ribbon Move to Impact Time ED Escapement Pre-move Delay SD Selection Pre-move Delay RD Ribbon Pre-move Delay HD Hammer Pre-fire Delay EMT, SMT, RMT, and SHI are specific times required by the print mechanism to perform an individual print operation with these times varying for different print operations. The escapement and ribbon operations can begin when the hammer is still in contact with the printwheel but the printwheel cannot begin its operation until there is no contact with the hammer. PIOP is reset to zero if the time between the print operations is sufficiently long to make it insignificant. PICS specifies the time after the previous hammer fire to when escapement and ribbon operations can begin. As with PIOP, PICS is reset to zero if the time between print operations is sufficiently long. EEI, ESI, and ERI are fixed times and are the same for all print operations although these times are different, as shown in Fig. 1. ESI must be at least as long as the maximum hammer-in-plane to impact time to assure that the printwheel has settled before it is in contact with the hammer. The control algorithm specifies the variable delays ED, SD, RD, and HD so that the times EEI, ESI, and ERI remain constant for any combination of EMT, SMT, RMT, and SHI. The control algorithm is summarized in the following sequences: 1. The moves required for the next print operation are determined. 2. EMT, SMT, RMT, and SHI are obtained for these moves. 3. The following operation cycle times are calculated: E = EMT + EEI S = (PIOP- PICS) + SMT + ESI R = RMT + ERI. 4. The largest o...