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Matched Trajectory Feedback Control of Print Actuator

IP.com Disclosure Number: IPCOM000060303D
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Johnson, M: AUTHOR [+3]

Abstract

Using an electronically programmable feedback controller to match the trajectory of a moving coil actuator to nominal trajectory, both on the impact stroke and the rebound, provides optimum print hammer trajectory with optimum repetition rate. The coil energization profile is adjusted through feedback to provide a trajectory which matches the nominal trajectory, and in which acceleration changes are kept to a minimum by smoothing the breakpoints of the trajectory. The return kinetic energy brings the hammer back to rest by matching the natural bounce motion of the hammer with the selected reference trajectory. Different profiles are available for different character sets or different paper. Fig. 1 illustrates the principle of feedback control.

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Matched Trajectory Feedback Control of Print Actuator

Using an electronically programmable feedback controller to match the trajectory of a moving coil actuator to nominal trajectory, both on the impact stroke and the rebound, provides optimum print hammer trajectory with optimum repetition rate. The coil energization profile is adjusted through feedback to provide a trajectory which matches the nominal trajectory, and in which acceleration changes are kept to a minimum by smoothing the breakpoints of the trajectory. The return kinetic energy brings the hammer back to rest by matching the natural bounce motion of the hammer with the selected reference trajectory. Different profiles are available for different character sets or different paper. Fig. 1 illustrates the principle of feedback control. The conventional driver for a BP1500 print actuator uses a power transistor to switch ON the current through the coil for a fraction of a millisecond. The settle-out time is significant (more than 13 ms), where the rebound trajectory following the backstop impact becomes stronger as the impact force increases. A secondary impact occurs when the impact force is over a threshold. Hence, in the open-loop configuration, the impact force has an upper limit before the secondary impact occurs for a given stroke length. When the feedback control is implemented, the corresponding performance, as shown in Fig. 2, renders a greatly diminished settle-out time (2.5 ms). By optimally choosing the controller gains, the rep-rate data can be pushed to an upper limit dictated by the current-carrying capacity and driver supply voltage constraints. Fig. 3 shows a time optimal tracking t...