Document stacker with fault detection
View Patent ↗Techniques include sensing electric signals from an actuator during a document stacking operation and determining whether an abnormal event has occurred based on the sensed signals. The techniques may find particular applicability, for example, to document acceptors that include piston-type stackers driven by a direct current motor.
1. An apparatus comprising:
a document stacker including:
a cassette to store documents;
a piston operable to push a document from a pre-storage channel through an aperture into a document storage area in the cassette;
an actuator operable to control movement of the piston; and
first circuitry operable to measure values of signals indicative of a load on the actuator during a document stacking operation; and
second circuitry coupled to the actuator to control operation of the actuator and coupled to the first circuitry, wherein the second circuitry is operable to compare information about the measured values to a reference signal profile that comprises a plurality of different values and to determine whether an expected event has occurred or whether an unexpected event has occurred based on the comparison,
wherein the apparatus operates differently depending on whether it is determined that an expected or unexpected event has occurred.
2. The apparatus of claim 1 wherein the second circuitry is operable to compare an amount of time that elapses between specified values of the measured signals to a predetermined amount of time and to determine whether an expected or unexpected event has occurred based on the comparison.
3. The apparatus of claim 1 wherein the second circuitry is operable to identify an amount of time that elapses from a specified point in the stacking operation to a peak value of actuator load and to determine whether an expected or unexpected event has occurred based on the identified amount of time.
4. The apparatus of claim 1 wherein the second circuitry is operable to identify an amount of time that elapses from a specified point in the stacking operation to a predetermined threshold value of actuator load, and to determine whether an expected or unexpected event has occurred based on the identified amount of time.
5. The apparatus of claim 1 wherein the second circuitry is operable to compare an actual profile of the actuator load with an expected profile and to determine whether an expected or unexpected event has occurred based on the comparison.
6. The apparatus of claim 1 wherein the second circuitry is operable to integrate the measured values of the signals corresponding to actuator load for a specified period of time during the document stacking operation to obtain an integrated value and to determine whether an expected or unexpected event has occurred based on the integrated value.
7. The apparatus of claim 1 wherein the measured signals are indicative of actuator load, and wherein the second circuitry is operable to adjust the reference signal profile based on previously measured values of actuator load.
8. The apparatus of claim 1 wherein the second circuitry is operable to use the measured signals to determine whether the cassette is full or the stacker is jammed.
9. The apparatus of claim 1 wherein the actuator includes a direct current motor.
10. The apparatus of claim 1 wherein the reference signal profile is a curve that represents values of actuator current during different phases of stacker operation.
11. The apparatus of claim 1 wherein the second circuitry is operable to compare an actual profile of actuator current to an expected profile of actuator current.
12. The apparatus of claim 1 wherein the second circuitry is operable to compare an actual curve of actuator current to an expected curve of actuator current.
13. The apparatus of claim 1 wherein the first circuitry is operable to measure values of signals indicative of a load on the actuator by sampling values of current corresponding to the actuator load at different times.
14. The apparatus of claim 1 wherein the reference signal profile represents current values indicative of the expected load on the actuator during different phases of stacker operation.
15. The apparatus of claim 1 wherein the second circuitry is operable to obtain information from the measured values about a transition from one state of the stacker operation to another state of the stacker operation and to compare the obtained information to an expected signal profile.