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# Algorithm for Magnetic Sensing of Print Actuator Dynamics

IP.com Disclosure Number: IPCOM000060239D
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 59K

IBM

## Related People

Sri-Jayantha, M: AUTHOR

## Abstract

Calculating hammer impact force and contact-time from position information derived from a magnetic pickup eliminates the need for separate sensors for position and impact force measurement. It is becoming common in the manufacture and servicing of impact printers to measure the flight time and impact force of a hammer. Position and velocity measurements are mandatory for feedback control of impact printers; the same measurements can be used to predict the remaining variables, such as impulse force, flight time, and contact time. Sensor-based data can be extended to provide the hammer flight- time by predicting impact parameters using momentum principles. Consider Fig. 1. The print hammer is deposited with two magnetic strips A and B separated by a known distance "d.

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Algorithm for Magnetic Sensing of Print Actuator Dynamics

Calculating hammer impact force and contact-time from position information derived from a magnetic pickup eliminates the need for separate sensors for position and impact force measurement. It is becoming common in the manufacture and servicing of impact printers to measure the flight time and impact force of a hammer. Position and velocity measurements are mandatory for feedback control of impact printers; the same measurements can be used to predict the remaining variables, such as impulse force, flight time, and contact time. Sensor-based data can be extended to provide the hammer flight- time by predicting impact parameters using momentum principles. Consider Fig. 1. The print hammer is deposited with two magnetic strips A and B separated by a known distance "d." As the hammer moves past the stationary magnetic pickup, the linking flux induces two voltage spikes A and B as the hammer moves in the forward direction and two voltage spikes (not shown) as the hammer rebounds. The time duration between the two spikes provides a measure for velocity computation; computed velocity is subsequently converted into impact force information using the momentum equation. The typical hammer displacement time history is shown in Fig. 2. When the hammer mass to spring stiffness is high enough for the hammer to assume linear free-flight trajectories, the velocity of the hammer prior to and immediately after impact can b...