GB2528755A - Pet door control system - Google Patents

Abstract

A detection system for a cat flap comprises a processor, a light generator and a light detector. Interposing of an animal body disrupts light travelling between the light generator and light detector. A light level value is determined and compared 42 by the processor to a reference value, such that when dirt reduces the light level value so that it falls below a reference value the user is alerted 44 that the system is dirty and should be cleaned. The reference value is calculated from previous light level readings. The processor determines 45 the deviation of the light level from an average of previous light level readings, and if the light level varies by more than an variation allowance then a signal 46 or action appropriate to the presence of a pet in the cat flap is sent or carried out, e.g. an RFID reader is activated to read a chip on the cat.

Description

PET DOOR CONTROL SYSTEM

The present specification relates to a pet door control system, particularly the maintaining of performance of the detection of the presence of a pet.

A popular type of cat flap controls which cats may be allowed to enter by identifjing a unique chip on the cat, usually an RFID chip that may be carried on a fob, or increasingly an implanted RFID chip. The RFID reader is triggered to seek and interrogate an RFID chip by the detection of the presence of a cat in the cat flap tunnel. A known method of detecting the presence of a cat is to transmit a beam of light (for example, using an infra-red LED) across the tunnel, so that the beam hits an optical detector. One configuration is to position the infra-red LED and the optical detector on the upper inner surface of the tunnel, so that when the tunnel is empty, the light beam from the infra-red LED is reflected by the bottom of the tunnel onto the optical detector. The presence of a cat (or other object) changes the amount of infra-red light that reaches the detector. This triggers the cat flap control to seek the presence of an REID chip, and identify it, using an RE transmitter and receiver circuit and aerial -Cats do pick up dust and dirt, and this can rub off onto the infra-red LED, the optical detector and the bottom of the tunnel surface. if sufficient dirt is deposited on either of the components or the reflective surface, the beam of light is completely or partially obscured, and the detector cannot detect a change in the infra red light level when a cat is present. The RFID reader isn't switched on to attempt to read the RFID chip, and this stops the cat flap from working (or the detector erroneously indicates that a pet is permanently present). The user must remember to regularly clean the cat flap to prevent this. Even so, the build up of dust and dirt is a common cause of premature battery depletion, and of customer dissatisfaction.

The object of the present invention is to provide a control element which mitigates these problems.

According to the present invention, there is provided a control element according to claim 1, The invention will now be described, by way of example, with reference to the drawings, of which Figure 1 is a perspective diagrammatic view of the a cat flap; Figure 2 is a diagrammatic view of the components; Figure 3 is a flowchart illustrating the process; The principles of the invention can be applied to many shapes and designs of cat flap, so the cat flap is here illustrated diagrammatically.

I

Referring to figure 1, a cat flap includes an inner frame 10, into which are incorporated an infra-red LED 12 and an infra-red optical detector 13. The inner frame comprises an upper panel 15, a lower panel 16, and two side panels 17, 18. This inner frame forms at least part of a cat flap tunnel, the remainder of the cat flap housing and door not being here illustrated, The infra-red LED 12 and the infra-red optical detector 13 are positioned on the upper panel I S of the inner frame 10. When the infra-red LED 12 is operated in a clean cat flap, without a cat or other object occupying the tunnel of the cat flap, a beam of infra-red light is transmitted from the infra-red LED 1 2 towards the lower panel 1 6, where it is reflected upwards and onto the infra-red optical detector 13, which detects the strength of the light falling on it. The path of the infra-red light beam is illustrated here by an arrow a; however, it will be realised that the infra-red LED 12 need not transmit a tightly focused beam, and further, the reflection from the lower panel 16 may be of a diffuse or scattered nature. Arrow a merely illustrates a possible path for some of the reflected light.

When a cat is present in the tunnel of the cat flap, and the infra-red LED 12 is operated to transmit a beam of infra-red light, the beam is interrupted by the body of the cat, and either absorbed, reflected or scattered so that the amount of infra-red light reaching the infra-red optical detector 13 changes.

Referring to figure 2, the electrical subcomponents of the catflap control comprise a CPU 20, the infra-red LED 12, the infra-red detector 13, the RFTD reader 25, the door latch control 26, and a cleaning indicator 28. This is a purely diagrammatic representation, and it will be realised that the processing and logic functions of the circuitry, and other circuitry components, may be distributed and configured in different but equivalent ways.

Referring also to figure 3, the infra-red LED 12 and the infra-red optical detector 13 may not be operated continuously, but rather an active period of short duration (in the order of a few microseconds), each active period being separated by a passive period (in the order of a few milliseconds). This minimises the energy drain from the battery. This cycle of active and passive phases is well known, and represented here simply by an indication of a pause 32 which is incurred as part of the process steps after the control circuit starts operating 30, and between each repeat of the subsequent sequence of steps.

The default position is that the door of the cat flap is in a locked state 34, The CPU 20 causes the infra-red LED 12 to emit 36 a pulse of infra-red light. At the same time, the output of the infra-red detector 13 is monitored 38. This is indicated as a sequence in figure 3, but of course it will be realised that the infra-red optical detector 1 3 must be active operating and monitored simultaneously with the infra-red LED 1 2 in order to detect any light reflected from the cat or the lower surface 16 of the cat flap.

The infra-red optical detector 13 produces a signal that is related to the intensity of the light it receives, For example, it may be that the iiifra-red optical detector 13 produces a voltage that is proportional to total light received, and the average voltage during the active monitoring period is recorded.

The system first compares the light signal to a value LI. This value may be preset, or may be calculated itself from previous readings (for example taken when the cat flap was set up). If the average light signal falls beneath this value Ll, this indicates that the signal from the infra-red LED 12 to the infra-red optical detector 13 is being attenuated, and it is likely that one or all of the components of the infra-red optical detector 13 and the lower panel 16 are dirty or partially obscured. Based on the light signal falling below the value LI, the system also generates a cleaning alarm value corresponding to the possibility that the cat flap may require cleaning 44. If this cleaning alarm value persists for a prolonged time (for example a period exceeding 10 minutes, necessary to exclude false signals caused by an animal lingering in the tunnel), the system sends a signal to the user indicating that the cat flap may need cleaning.

Light level Ll corresponds to a reasonably clear, unattenuated signal, but not so high that a small amount of dirt will cause the level to be missed and a cleaning requirements signal to be generated too soon after installation or the last cleaning.

In some known systems, such as the cat flap shown in W02011088514A1, the amount of reflected infra-light received by the optical detector is monitored, and an alert signal is generated to alert the user when the light level falls beneath a particular value.

There are a number of difficulties with such an approach. The level of light produced by a batch of infra-red LEDs can vary greatly, with the brightest LEDs sometimes producing 500% of the light output of the dimmest. Often, the quoted output value and tolerance of a batch is actually given in terms of the minimum output levels. However, in some applications, as in this case, using a very bright LED when a cat flap has been optimised for a lower value can also lead to unaccepted variability in the behaviour of units. LEDs can be selected having closer-tolerances, but this makes the LEDs more expensive.

Individual LEDs can also have their brightness adjusted, for example by calibrating each LED or unit and varying a resistor placed in series with the LED. This approach also increases the cost.

A better approach is to compare the detected light against an average or expected value; based on a certain number of previous readings of the total light that is detected by the infra-red optical detector 13.

This in situ calibration avoids the need to and expense of calibrate units for individual LEDs in a factory setting. It also allows environmental factors (the lighting effects of surrounding objects, shade or lack of shade, the colour of the cat flap and so on), to be accounted for. Changes to the cat flap design can be made without having to change hardware or software of the control unit to compensate.

When the unit is first activated and newly installed, the optical system is clean, and stays relatively clean for at least the first three or four weeks. When the cat flap is activated for the first time, the JR LED 12 is activated, and the light value signal from the optical detector is stored. As every light value is received, an average light value is calculated using the initial light value signal (or nominal start value, usually chosen as a low or zero value) and each subsequent light value.

This is carried out for an initial time period, which may typically be set as three to four weeks. A smaller value, for example one third of this value is then permanently stored as a dirty tens va'ue Li These values are retained even in the event of a change of batteries, as even after the customer cleans the unit, it will not be as clean as when the unit is brand new, It will be realised that many other sampling and averaging schemes could be used. Beside taking an average over a set timescale from the units set-up, as described above, the sampling period could start after a set period has elapsed, to allow the conditions surrounding the unit to stabilise.

A more sophisticated method of obtaining a dirty lens value LI is to determine a value of the average ambient light by taking an on-going running or moving average (again, the average being seeded from an initial value of zero or a low set number), The maximum value that this average gets to is then permanently stored as a clean signal reference value, with the dirty lens value Li beiig set at a proportion of the current maximum value (which is usually reached after a few weeks, but depends on the initial value, number of samples etc). This allows ITansitory effects (such as temporary debris in the cat flap, and variations in weather) to be accounted for.

The calculation of the average of a number of values is normally determined by summing all the values, and then dividing the sum by the number of values.

However, this method requires that a large number of values must be stored, and where the maximum average is sought with new values being continually received, this requires the calculation to be carried out on each occasion, and each new result to be compared with the previous maximum value.

Instead of such a method, the system ideally calculates the moving average using an approximation which yields a value very close to the mathematical average.

For example, if you want to fmd the average of N values (which in this application, might typically be in the millions, for example S readings a second over a three week period) an approximation is to store the average value of L after N readings LAN, and then each time your get a new value of L the new average value of L after N+l readings can be approximated by LAN l=LAN-LANft +LNI1 This gives a value N times too large, so to fmd the average = LA\/N If N is a binary value 2,4,8,16 16,777,216 etc the calculation is very quick.

Other methods of using weighted values in a running average total are known; Taking an average over a number of weeks ensures that isolated events do not unduly influence the calibrated values. For example, a cat may leave paper or reflective material within the tunnel of the cat flap, temporarily increasing the reflectivity of the cat flap. However, this will usually be noticed or removed after a few days. Taking a large number of readings over a relatively long time period ensures that such events will not skew the calibration for nonial day-to-day use.

If each subsequent reading corresponds to this average, within a certain tolerance DL, this indicates that no object is present in the inner frame 10, whereas a deviation greater than DL indicates that there is an object present.

When a deviation greater than DL is detected the CPU 20 activates the RFID reader 25. If an authorised RFID chip is identified 48, the door latch is released, otherwise no action is taken and after a pause, the I-R generation and detection is resumed again.

Deviation DL is chosen to correspond to a change in signal that occurs when a cat occupies the cat flap. A cat may increase or decrease the infra-red signal, depending on its position and characteristics of its coat.

The actual levels Li and DL will typically be determined after some straightforward experimentation for the particular type of 1-R LED, infra-red optical detector, tunnel material (including the surface treatment, colour etc) and the layout and configuration of the components.

Li and DL need not be constant and could be variable; for example, the user might adjust the levels if it is found that too many cleaning requirement indications are being generated, or the cat is not being routinely detected.

When a signal is generated indicated that cleaning is required, this activates a cleaning required indicator 28. This may conveniently be an LED visible to the user next to a word or symbol conveying the cleaning requirements to the user. It could also, or alternatively, be an audible sound, Many other possibilities will present themselves, such as an LCD display of appropriate words, or an error code that can be explained in the literature accompanying the cat flap.

Rather than activating the cleaning required indicator 28 after the generation of a single cleaning required signal, it may be more effective to register the cleaning required signals and activate the cleaning required indicator 28 when the number of the cleaning required signals exceeds a certain proportion of light level readings being taken, For example, the cleaning required indicator 28 could be activated when five of the last ten readings have generated a cleaning required signal. This minimises the possibility of erroneous activation of the cleaning required indicator.

Once the CPU has activated the cleaning required indicator 28, it can either keep it on until the user initiates a reset function, or the CPU can simply continue to monitor the light levels, After cleaning the light levels will be above LI, so will turn off the clean required indicator.

In some cat flaps, rather than an average light signal reading, and a monitoring of a change of light level, the configuration may be that a comparatively focus beam of light is interrupted, so that the presence of a cat will always result in a lower signal. This system could still be applied in such a case, by changing step 45 as required. In such a system, it may not be necessary to take average readings to determine the expected ambient light levels.

Claims (11)

1. Claims 1. A detection system for a cat flap comprising a processor a light generator a light detector whose output corresponds to the light level arranged so that interposing of an animal body disrupts light travelling between the light generator and light detector a light level value is determined and compared by the processor to a reference value, such that when dirt reduces the light level value so that it falls below a reference value the user is alerted that the system is dirty and should be cleaned and compared by the processor to an variation allowance, such that when a pet causes the light level to vary outside the variation allowance, a signal or action appropriate to the presence of a pet in the cat flap is sent or carried out, the reference value being calculated from previous light level readings.
2. 2. A detection system according to claim I wherein the reference value is calculated from a moving average taken of an on-going sequence of readings.
3. 3. A detection system according to claim 2 wherein the reference value is calculated from the maximal value of the moving average.
4. 4. A detection system according to claim I wherein the reference value is calculated from a number of readings taken over a set period.
5. 5. A detection system according to claim 4 wherein the set period starts from the initial readings of the detection system.
6. 6. A detection system according to any previous claim where a single light level reading is compared to the variation allowance.
7. 7. A detection system according to any previous claim wherein the variation allowance may be changed.
8. 8. A detection system the variation allowance represents a range whose upper and lower limits are equally spaced about an average of the light value readings.
9. 9. A detection system according to any previous claim wherein the output falling below the reference value triggers the indicator.
10. 10. A detection system according to any previous claim wherein the further action carried out on detection of a pet in the cat flap, is the initiation of an RFID reading means.
11. 11. A detection system according to any previous claim wherein the user is alerted to the cleaning requirement by means of a sound sial,