MONITORING ASSEMBLY

Abstract: A monitoring assembly comprising a plurality of sensor modules (11-13), each sensor module comprising at least one sensor (E0, S0) providing an output signal corresponding to a condition being sensed, and a processor (1) for receiving and processing the sensor output signal and for generating an output in accordance with whether or not the condition has been sensed. The processors (1) of each module (11-13) generate outputs of a similar type independent of the sensor concerned.

Description: MONITORING ASSEMBLY The invention relates to a monitoring assembly, for example for monitoring the performance of a machine such as an article processing machine. The invention has particular application to sheet processing machines such as banknote processing. Such banknote processing machines include banknote acceptors, dispensers, sorters and counters . In a banknote processing control system, sensors are required to provide data on the presence and position of notes in the machine and to sense the presence and position of other items such as mechanisms, paper and tape supplies- Several different types of sensing are required, including for example: 1. Sensing of notes moving in the transport. (Track sensors) . Required to accurately detect the front and back edge of a note as it passes at high speed, usually over a small sensing distance. 2. Sensing of notes in a stacking station. (Long range sensing) . Required to detect one or more stationary notes in a pack. Response time is not critical but it is usually over a long sensing distance. 3. Sensing of mechanisms or other items using optical sensors. 4. Sensing of mechanisms or other items using non- optical sensors (eg Hall effect devices/micro switches etc) . The types of sensor used at each location will vary depending upon the most suitable way of carrying out the sensing process. Typically, optical sensors are used to monitor the progress of sheets but other sensors such as magnetic and Hall effect sensors are also used. Typically, the main machine controller interfaces directly with each sensor, the sensing interfaces being specific to the different sensor types and functions. This means that the machine controller must be designed for each specific machine and the combination of sensors required. In accordance with the present invention, a monitoring assembly comprises a plurality of sensor modules, each sensor module comprising at least one sensor providing an output signal corresponding to a condition being sensed, and a processor for receiving and processing the sensor output signal and for generating an output in accordance with whether or not the condition has been sensed, the processors of each module generating outputs of a similar type independent of the sensor concerned. We have devised a modular approach to the use of sensors in which self-contained sensor modules are provided. Each sensor module includes its own processor which interfaces with the corresponding sensor but provides an output signal of a common type (typically indicating a YES/NO condition) to the main machine controller. The main machine controller therefore does not need to be adapted to each type of sensor used, the data appertaining to the sensor type being made available, for example, upon start up of the machine, thus significantly increasing flexibility in the use of such controllers and the ability to add or remove sensor modules as required. Preferably, the sensor of at least one of the sensor modules can be calibrated, the respective sensor module processor being adapted to calibrate the sensor in response to a calibration command. This provides a further useful advantage in that the processor also carries out the calibration process which will vary from sensor to sensor. Again, the main machine controller does not need to take part in the calibration process. The calibration command will typically be generated by the main machine controller but could also be generated within the sensor module processor, for example at a particular time or in response to a start-up condition. Typically, at least one of the sensors comprises a radiation emitter and a radiation detector positioned to sense the passage of an object. Such sensors are particularly convenient for sensing the passage of articles such as sheets where radiation from the emitter is obscured by the presence of the sheet so as to change a voltage in a circuit coupled with the detector, the voltage change being sensed by the processor. In the case of radiation emitters and detectors, the sensor module processor may be adapted to control the operation of the radiation emitter, the processor being adapted to calibrate the sensor by monitoring the apparent response of the radiation detector when the radiation emitter is controlled to emit no radiation whereby a) if the apparent response from the radiation detector indicates to the processor that radiation above a first level is detected, the processor determines that no sensor is present; and b) if the apparent response from the radiation detector indicates to the processor that radiation is present at a level below the first level but above a second level, the processor determines a fault condition. This corresponds to too much ambient emission being sensed or the sensor is faulty. Preferably, c) if the apparent response from the radiation detector indicates to the processor that radiation below the second level is detected, the processor increases the radiation intensity generated by the radiation emitter until the radiation detector indicates to the processor that the received radiation is at a sufficient level to drive the sensor response to a predetermined level . This results in an automatic method for determining firstly whether a sensor is connected to the processor and, if it is, secondly automatically calibrating the sensor. A problem which can arise within article processing machines, particularly sheet processing machines, is that the environment is dusty and dirt can accumulate on the radiation detectors and this needs to be accounted for. Conventionally, this is dealt with by varying the radiation output from the emitter to match the detector distance, sensitivity and cleanliness. This is done on system startup. Once the radiation required has been established, no further adjustment is possible allowing dust build-up during operation to cause problems. Typically, the sensor module processor is adapted to compare the sensor output signal with a threshold and to generate the said output in accordance with the relationship of the sensor output signal with the threshold. This threshold is conveniently defined with respect to previously determined upper and lower limits. For example, the threshold could be determined to be midway between the upper and lower limits. In order to cope with dirt and dust build-up, the sensor module processor is preferably adapted to modify one or both of the upper and lower limits in accordance with received sensor output signals. In this way, continual adaption of the upper and lower limits, and hence the threshold with which the radiation detector output signal is compared, is achieved. In one example, the upper and/or lower limits are modified by the sensor module processor if a predetermined number of sensor output signals fall outside the corresponding existing limit. Thus, the limits are not immediately modified as soon as a single received signal falls outside the limit but only after a predetermined number of such signals has fallen outside the limit. Usually, the predetermined number must occur for successive output signals. Preferably, the processor of each sensor module can configure itself to the requirements of the or each sensor of the corresponding module. For example, the assembly may further comprise a store for storing data to enable the configuring process to be performed. Automatic configuration avoids the need for individually setting up each sensor. An example of a banknote machine monitoring system will now be described with reference to the accompanying drawings, in which :- Figure 1 is a block diagram of a sensor module; and, Figure 2 is a block diagram of part of the banknote monitoring system. The sensor module shown in Figure 1 comprises a micro- controller 1 which may be a hard wired device or a suitably programmed microprocessor. The micro-controller is coupled to two optical emitters E0,E1 corresponding to channels 0 and 1 via respective voltage to current converters 2,3. The two optical emitters E0,E1 are positioned in association with respective sensors SO, SI which are also connected to the micro-controller 1. Typically, the sensor emitter pairs will be positioned on opposite sides of a banknote feed path at laterally spaced positions. As can be seen in Figure 2, the machine controller 10 is connected to a number of sensor modules 11-13 and in practice is likely to be connected to ten or more such modules. It is also connected to a database 30 which stores information relating to the sensors provided with each sensor module. In response to signals received from the sensor modules 11-13, the machine controller 10 controls operation of the machine such as the operation of diverters, stacker wheels and the like via control lines 14-16. As explained above, other sensor modules may be provided with different types of sensor such as Hall effect sensors and the like and may also be used for monitoring the status of certain equipment or the position of movable elements such as banknote stacker wheels. The data defining the type of sensor connected to each module and the detector type operating parameters is made available from the database 30 (Figure 2) connected via the machine controller 10 to the micro-controller 1. The micro-controller 1 and voltage to current converters 2 , 3 are housed on a compact and stand alone printed circuit board (PCB) which is designed to plug into a mother board such as a PC memory board (SIM) . The PCB is reliant on the mother board for its commands and power supplies and as can be seen in Figure 1, the microcontroller is connected to the mother board via an 18 way 2mm pin header 4 which conveys signals from the microcontroller to the central machine controller 10 and receives signals from the machine controller 10 on a calibrate port 5. It also receives the data defining the type of sensor and, as necessary, its operating parameters from database 30 through a mode setting port 6. Turning now to the micro-controller in more detail, typically this is a PIC micro-controller 16c711. This includes A/D converters for converting the voltage signals from the sensors SO, SI directly, and for each emitter E0,E1 an output 7 to control the LED drive current level in response to a "Value" signal, an output 8 to switch ON and OFF the LED currents, and an output 9 to set the current sensitivity range to either cO-lOOmA or cO-lA. The outputs supplied to the machine controller 10 include outputs to indicate that a note is present and also certain error conditions. The PCB operation is controlled by the PIC software allowing a simple hardware implementation. Typically, the signals received from the sensors SO, SI are compared by the micro-controller 1 with predetermined stored thresholds, this process being implemented as software routines operating on digitised sensor data which has been input directly by the A/D converters. A binary output signal is then generated for supply to the machine controller 10 indicative of whether or not a note has been sensed. The LED currents are controlled by a serially commanded current D/A converter. This is implemented as a digipot driving the respective voltage to current converter 2,3 with two range sensitivities controllable by the PIC. The digipot type may be specified to allow storage and recall of the "wiper" position on power up. The resistance of the digipot is changed by the PIC via a serial data port within the voltage to current converter and controlled by the "Value" signal which sends a serial data stream to define the "Wiper" position. It is configured to output 0- 5V to the voltage to current converter 2,3. Each V/I converter 2,3 can be controlled to either provide continuous current or pulsed current depending on the operating mode selected. When operating as a long range sensor the current range is increased and the current is pulsed with a low duty cycle. The current range switching is achieved by the port line 9 via a FET to connect in a resistor which alters the V/I sensitivity. The current is switched ON/OFF by shorting to ground the outputs of the digipot. PIC port lines (AMPSOEN and AMPS1EN) are used directly and are switched between logic low and high impedance. If non-opto modes are used, the emitter current facility may be ignored. The sensor gain is defined by pull-up resistors 20,21 on the PCB which have been found empirically to give good sensitivity with optosensors of the type used without over sensitivity to external light. The sensor signal therefore varies between 0V and 5V depending on the illumination level and how obscured it is. This signal passes directly (via filtering) to the U-controller 1 for A/D conversion. Non-opto sensor voltages must be in this range. Each micro-controller 1 issues four types of output signal to the main machine controller 10 which are defined below. NOTEP0 A digital output signal from the adaptive sensor which indicates the presence of notes under the sensor head. It is active in track sensor mode when a note is present under either of the sensor pairs in a track sensor. It is active in long range mode when there is a note present under the sensor pair on channel 0. The meaning of this signal is changed if the ERRORL line is active. NOTEP1 A digital output signal from the adaptive sensor which indicates the presence of notes under the sensor head. It is active in track sensor mode when a note is present under the sensor pair on channel 1. It is active in long range mode when there is a note present under the sensor pair on channel 1. The meaning of this signal is changed if the ERRORL line is active. WARNL A digital output signal from the adaptive sensor which indicates a warning status. The signal is active either if after calibration the opto emitter current is greater than a preset amount or during operation if the working signal amplitude is less than a preset level. If this signal is active the circuit remains in operation. The meaning of this signal is changed if the ERRORL line is active. ERRORL A digital output signal from the adaptive sensor which indicates an error status. This signal is active during all detectable errors including :- Working signal amplitude too small to continue Unable to achieve calibration even at maximum current Systems error - a logical error in the program. As previously mentioned, the micro-controller 1 receives an input signal from the machine controller 10: a calibrate signal which forces a system re-start and recalibration of the sensors. Mode data from the database 30 is monitored on recognition of a calibrate signal and used to define the configuration of the sensor (i.e. whether it is to be a track sensor or a long range sensor) . At start-up and after certain reset conditions, the micro-controller 1 performs a calibration as a software routine which aims to set the level of emitter current so that the sensor voltage is maximised without saturating the receiver. Calibration always operates in pulse mode to protect the emitters from over dissipation. The sensor voltage at zero emitter current is checked. If the sensor voltage is less than a minimum value the sensor is assumed to be not present because the sensor input has intentionally been shorted out to create a "no sensor" condition. If the sensor voltage is above the minimum but less than a maximum there is assumed to be a fault. The emitter current is then increased until the sensor voltage reaches a predetermined level (just avoiding saturation) . This occurs for both channels separately. The calibration current levels are then recorded and used without changing until a further reset occurs. If the sensor is not present calibration still occurs but the current is set to a low level. During calibration the four signals to the machine controller 10 (NOTEP0, NOTEP1, WARNL and ERRORL) are held high. This gives the opportunity to test the indicator lamps. The note present signals drive low when calibration is complete provided there are no calibration errors. (In this case they output the error number) . The calibration routine will generate errors if unable to calibrate or warnings if the calibration is too high. When a sensor module is operated under the track sensor mode, the micro-controller 1 monitors the sensors SO, SI as fast as the software and A/D conversion will allow. Typically this is 50 microseconds per sample. Each channel is sampled in turn. The sample is compared to the current threshold for that channel and in this mode both sensor pairs act as a single logical sensor with NOTEP0 as the main output . Output NOTEP0 is set if either sensor voltage is above its threshold. N0TEP1 is set if channel 1 is above its threshold. Consequently if both sensor voltages are below their thresholds NOTEP0 is reset. NOTEP1 is reset if channel 1 is below its threshold. In the long range mode, response time is not as critical as in track sensor mode and so the sample rate is reduced in favour of pulsing a high current through the LEDs, which requires a "dead time" to prevent over dissipation of the LED components. Typically, each sensor is sampled every 10 milliseconds, each sensor pair acting as an independent sensor. The current for that channel is enabled and allowed to settle for c.l75us. The sample is then converted and the current is disabled. Each channel is sampled in turn. The sample is compared to the current threshold for that channel. Output NOTEP0 is set if channel 0 is above its threshold. NOTEP1 is set if channel 1 is above its threshold. Consequently output NOTEP0 is reset if channel 0 is below its threshold. NOTEP1 is reset if channel 1 is below its threshold. A particularly important aspect of the invention is the ability to adapt the threshold used by the micro- controller for comparison with the received sensor signals. The micro-controller 1 maintains for each channel, values for the current amplitude of the sensors high and low voltages. (Vmax and Vmin) . After sampling a channel the sample is compared to the current values of Vmax and Vmin. If the sample is higher a corresponding channel counter is incremented and if lower it is decremented. On roll over/under of the counter the current values of Vmax or Vmin are adjusted up or down. The new values of Vmax and Vmin are then used to calculate new threshold voltages for each channel, the threshold being set to (Vmax + Vmin)/2. This technique tracks the input signal amplitude and sets the threshold so that it is always in the middle of the signal. This adaption occurs independently for each channel and for both operating modes. Its primary function is to protect against the build up of contamination during running. The adaption process also creates a warning when the working signal becomes small. Finally it will generate an error if the signal degredation becomes too great for continued operation.

Claims: CLAIMS 1. A monitoring assembly comprising a plurality of sensor modules, each sensor module comprising at least one sensor providing an output signal corresponding to a condition being sensed, and a processor for receiving and processing the sensor output signal and for generating an output in accordance with whether or not the condition has been sensed, the processors of each module generating outputs of a similar type independent of the sensor concerned. 2. An assembly according to claim 1, further comprising a central monitor coupled to the sensor modules for receiving the outputs from the processors. 3. An assembly according to claim 2, wherein the central monitor is connected to or forms part of a machine controller for a machine whose performance is monitored by the or each sensor. 4. An assembly according to any of the preceding claims, wherein the sensor of at least one of the sensor modules can be calibrated, the respective sensor module processor being adapted to calibrate the sensor in response to a calibration command. 5. An assembly according to any of the preceding claims, wherein at least one of the sensors comprises a radiation emitter and a radiation detector positioned to sense the passage of an object. 6. An assembly according to claim 5, wherein the radiation emitter generates optical radiation. 7. An assembly according to claim 5 or claim 6, when dependent on claim 4, wherein the sensor module processor is adapted to control the operation of the radiation emitter, the processor being adapted to calibrate the sensor by monitoring the apparent response of the radiation detector when the radiation emitter is caused to emit no radiation whereby a) if the apparent response from the radiation detector indicates to the processor that radiation above a first level is detected, the processor determines that no sensor is present; and b) if the apparent response from the radiation detector indicates to the processor that radiation is present at a level below the first level but above a second level, the processor determines a fault condition. 8. An assembly according to claim 7, further comprising: c) if the apparent response from the radiation detector indicates to the processor that radiation below the second level is detected, the processor increases the radiation intensity generated by the radiation emitter until the radiation detector indicates to the processor that the received radiation is at a sufficient level to drive the sensor response to a predetermined level. 9. An assembly according to any of the preceding claims, wherein each sensor module processor is adapted to monitor the output signal from the or each associated sensor at regular, spaced intervals. 10. An assembly according to claim 9, wherein the intervals are substantially 50 microseconds. 11. An assembly according to claim 9 or claim 10, when dependent on any of claims 5 to 8 , wherein the sensor module processor causes the radiation emitter to emit radiation at the said intervals. 12. An assembly according to any of the preceding claims, wherein the sensor module processor is adapted to compare the sensor output signal with a threshold and to generate the said output in accordance with the relationship of the sensor output signal with the threshold. 13. An assembly according to claim 12, wherein the threshold is defined with respect to previously determined upper and lower limits. 14. An assembly according to claim 13, wherein the sensor module processor is adapted to modify one or both of the upper and lower limits in accordance with received sensor output signals. 15. An assembly according to claim 14, wherein the upper and/or lower limits are modified by the sensor module processor if a predetermined number of sensor output signals fall outside the corresponding existing limit. 16. An assembly according to any of the preceding claims, wherein the processor of each sensor module can configure itself to the requirements of the or each sensor of the corresponding module. 17. An assembly according to claim 16, further comprising a store for storing data to enable the configuring process to be performed. 18. An article processing machine comprising a transport system for transporting articles along a processing path; a machine ' controller for controlling operation of the transport system; and a monitoring assembly according to any of the preceding claims for monitoring the location of articles along the processing path, the machine controller being responsive to the monitoring assembly to control the transport system. 19. A machine according to claim 18, wherein the articles comprise sheets, the sensors being adapted to detect the passage of the sheets.

Inventors: COTTRELL RONALD ALEC, COTTRELL, RONALD, ALEC
Applicants: COTTRELL RONALD ALEC, RUE DE INT LTD, COTTRELL, RONALD, ALEC, DE LA RUE INTERNATIONAL LIMITED
Application year: 2000
Main classification: G05B19
IPC codes: G05B19