AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Innovation Patent Applicant: Smart Openers Pty Ltd Invention Title: SENSING THE POSITION OF A DOOR The following statement is a full description of this invention, including the best method for performing it known to me/us: 2 SENSING THE POSITION OF A DOOR Field of the invention s The present invention relates to sensing the position of a door. An example of an application of the invention is a door operator for tracking the position of a garage door curtain such as in a roll-up garage door, tilt door or sectional door. The invention also has application in 1o determining the position of a door in a sliding or swing gate such as in driveway gates. This application is a divisional application from Australian patent application number 2008341003 and the is whole of the subject matter disclosed therein is imported into the present specification by reference. Background 20 Domestic and industrial garage doors are known to be provided with motor driven door operator mechanisms to automatically open and close the door. A position sensor is required to determine the position of the door to avoid driving the door beyond fully open and fully closed 25 limits. The position sensor is used to feed back a position of the door to a controller of the door opener. Known door openers use micro-switch position limit switches or shaft encoder counters or optical sensors to determine the door position. 30 A problem with known door operators is if there is an electric power supply failure, and the door is required to be manually opened or closed then there must be a physical disconnection of drive train between a drive motor and the 35 door, as the mechanical advantage of the drive train is too great for a person to overcome by manually holding the door and manually attempting opening or closing. Thus 2948786_1 (GHMatters) P74815 AU.2 3 when electric power is restored it is necessary to make a drive train reconnection if the door opener is to again perform opening and closing. Unless there is direct re engagement of the drive train in the exact same position 5 as when the disconnection occurred, there will be incorrect sensing of the fully open and fully closed positions of the door. Complicated systems have been devised in the past to ensure correct position re engagement and/or suitable adjusting of datums, so that 10 the door will stop at the intended fully open or fully closed positions. There is a need for an alternative arrangement. 15 Summary of the invention According to one aspect of the present invention there is provided a door operator with a door position sensor assembly, said door operator having a motor for 20 providing drive power, a drive train adapted to couple drive power from the motor to a door to cause opening and closing of the door and a controller adapted to control the motor, the sensor assembly co-operating with the controller to stop the door at a set open position and a 25 set closed position, the sensor assembly comprising: an input shaft directly connected with the drive train so the input shaft will be permanently rotated as the door is opened and closed, an active sensor coupled to 30 rotate with rotation of said input shaft and a sensor detector fixedly mounted in proximity to said active sensor to detect the rotation of the active sensor and having a resolution to accurately sense the set open and the set closed positions of the door, 35 the coupling of said active sensor with the input shaft providing less than 3600 relative rotation of the active sensor relative to the sensor detector over a range 294678_1 (GHMatters) P74815.AU.2 4 of full travel of the door greater than the range of travel between the set open and set closed positions so that if the door is manually moved to a position between the range of full travel, the active sensor will 5 relatively rotate with the door movement within a 3600 range, and when motor operation is subsequently required, the controller will be able to determine the position of the door relative to the set open and the set closed positions such that the set open position and set closed io positions do not need to be re-established Brief description of the drawings 15 An embodiment, incorporating all aspects of the invention, will now be described by way of example only with reference to the accompanying drawings in which Figure 1 is a block diagram of a door operator, 20 Figure 2 illustrates an exploded view of an embodiment of a door position sensor for a door operator, Figure 3 illustrates an assembled view of the door 25 position sensor of Figure 2, Figure 4 is a block circuit diagram of an example of a detector for a sensor, and 30 Figure 5 is a schematic conceptual drawing showing use of the sensor with a roller door operator. Detailed Description 35 Embodiments of the present invention relate to a door operator with door position sensor. The door operator has a motor for providing drive power, a drive train adapted 2947881 (GHMatters) P74815.AU.2 5 to couple dive power from the motor to a door to cause opening and closing of the door and a controller adapted to control the motor. The sensor co-operates with the controller to stop the door at a set open position and a s set closed position. The sensor comprises an active element connected in the drive train for relative rotation with a detector. The sensor is adapted to determine the rotational position of the active element relative to the detector consequent on opening or closing of the door. 10 Coupling from the drive train to the active element is adapted to cause less than 3600 relative rotation of the active element and detector over a range of full travel of the door and the resolution of the sensor is able to accurately sense the door at the set open position and the 15 set closed position. If the door is required to be manually opened or closed, for example in the event of a power failure, then there must be a physical disconnection of drive train 20 between a drive motor and the door, as the mechanical advantage of the drive train is too great for a person to overcome by manually holding the door and manually attempting opening or closing. Thus when electric power is restored it is necessary to make a drive train 25 reconnection if the door opener is to again perform opening and closing. A user operable clutch is provided for this purpose. The user operable clutch enables a user to manually 30 disconnect the drive train to overcome the mechanical advantage in the drive train and motor which would otherwise prevent the user from manually moving the door in circumstances such as a power failure. The point in the drive train at which the manual disconnection occurs 35 can vary depending on the embodiment and based on the nature of the drive train and cause of the mechanical advantage through the motor and drive chain. 29487861 (GHMatters) P74815.AU.2 6 For example, for a roll up type door, the dominant mechanical advantage is provided by the motor and the associated gears used to reduce the motor speed to the 5 required speed of movement of the door, and to consequently provide the required torque at the door curtain. The above will inhibit a person manually moving the door curtain. 10 In alternative embodiments such as a door opener for a tilt or sectional type door the drive train includes a looped belt or drive chain to which is engaged by a slider attached to the door. The slider moves along a guide track and when engaged with the looped belt or drive chain 15 is driven by the motor to open and close the door. In this embodiment the loop belt or drive chain and the associated reduction drive gear train therefor presents a significant mechanical advantage which must be overcome. 20 If the drive train is disconnected by operation of the user operable clutch and the door manually moved between open and closed positions, the active element will relatively rotate within the sensor with the door movement within a 3600 range and when the drive train is re 25 connected, the controller will be able to determine the position of the door relative to the set open and the set closed positions. This enables the set open position and set closed positions to be re-established from the resolution of the sensor, and the door stopped at those 30 set positions when driven by the motor. An example of a door operator as described above is illustrated in block diagram form in Figure 1. The door operator 100 has a position sensor 110, a mechanical drive 35 assembly 120, and a controller 130. An optional user interface 140, such as a radio remote control can also be provided. The mechanical drive assembly 120 includes 2948788_1 (GHMatters) P74815.AU.2 7 motor 122 for providing drive power, and a drive train 125 adapted to couple dive power from the motor to a door (not shown in the block diagram) to cause opening and closing of the door. The controller 130 is adapted to control the 5 motor and includes a motor controller 132 for executing motor control functions such as controlling the drive speed, direction an input output interface 134 to enable a user to input door open and close commands either manually or via a remote interface 140, and a position 10 determination module 136 adapted to interpret position information accurately from the sensor 110 to stop the door at a set open position and a set closed position. The sensor 110 comprises an active element 115, in 15 this embodiment a polarised magnet, connected in the drive train 125 for relative rotation with a detector 118. The sensor 118 is adapted to determine the rotational position of the polarised magnet 115 relative to the detector 118 consequent on opening or closing of the door. 20 The detector 118 comprises a hall array sensor 150, a digital signal processor 160, a memory 170 and an interface 180 to enable data to be transferred between the door sensor 110 and the door operator controller 130. The 25 detector 118 can be implemented in a single integrated circuit or using discrete components. The hall array sensor 150 is adapted to detect the angular orientation of the polarised magnet 115 as an 30 analogue signal. The hall array comprises a plurality of individual sensors which are used to sense the distribution of the magnetic field generated by the polarised magnet 115 over the surface of the array and deliver an analogue voltage representation of the magnetic 35 field over the array to the digital signal processor for analysis. The digital signal processor 160 is adapted to receive an analogue detection signal received from the 294878_1 (GHMatters) P74815AU.2 8 hall array sensor 150 and to process the analogue signal. The analogue signal is converted to a digital signal and analysed to determine the angular position and direction of rotation of the polarized magnet 115. This information 5 is output as a digital signal for storage in memory or use by the door operator controller 130. It should be appreciated that the polarised magnet may be substituted with another form of active element 10 adapted to generate a polarised magnetic field for detection by the hall array. Alternative active element and detectors combinations adapted to determine with sufficient accuracy the relative angular rotation of the active element and detector are envisaged within the scope 15 of the invention. The memory 170 is adapted to store an initial position 172, a current position 174 and a direction of rotation 176 of the magnet 115. The initial position can 20 be stored during a door installation process to set a "zero" or reference position for the sensor magnet 115 relative to the hall array 150. The current relative polarized magnet position may be recorded in memory 170 as an initial position 172 in response to an externally 25 applied control signal, for example applied via the controller 130 in response to installation control instructions input by an installer. Typically an installer will cause this initial reference position to be stored with the door in a fully open or fully closed 30 position such that the reference position coincides with a set open position or a set closed position of the door. However, this is not essential as the set open and set closed positions used by the controller 130 may be stored as relative positions to this reference position. An 35 advantage of being able to store the initial or reference position is that the magnet does not have to have its polarity aligned with a predetermined direction, as this 2946788_1 (GHMaters) P74815.AU.2 9 can be awkward or impossible to do during installation particularly if the magnet is provided prefabricated in an element of the drive train 125. 5 Coupling from the drive train 125 to the magnet 115 is adapted to cause less than 3600 relative rotation of the magnet 115 and detector 118 over a range of full travel of the door and the resolution of the sensor is able to accurately sense the door at the set open position and the 10 set closed position. By ensuring that the magnet will rotate less than 360* over the full range of travel of the door which is typically greater than between the set open and closed stop positions, the angular position of the magnet 115 relative to the detector 118 can be translated is directly to a door position relative to the set fully open and fully closed positions. Ensuring that less than 360* rotation will occur can be achieved using appropriate gear ratios between the drive train elements associated with the door and the drive train element carrying the magnet 20 or active element. If the drive train is disconnected and the door manually moved between maximum possible fully open and fully closed positions, the magnet 115 will rotate with 25 the door movement within a 3600 range due to the coupling of the magnet to the drive train. When the drive train is re-connected to the motor, the controller will be able to determine the position of the door relative to the set open and the set closed positions from the sensed relative 30 positions of the magnet 115 and detector 118. This enables the set open position and set closed positions to be re-established from the resolution of the sensor, and the door stopped at those set positions when driven by the motor. 35 An advantage of using a sensor of the type that has an active element which rotates less than 3600 is that no 2948786_1 (GHMatters) P74815.AU.2 10 battery backup is required to ensure the door position is recorded in memory or tracked during a power failure to the door operator. In response to re-establishment of power to the door operator after power failure, the 5 controller is adapted to read a current position from the sensor to determine the position of the door relative to the set open and set closed positions. A further advantage of using an active element and a 10 detector, such as a magnet and a hall array sensor, is that the sensor is not prone to interference due to dust, insects or humidity. Further, as this type of sensor is contactless the sensor is not prone to degradation due to mechanical wear and tear. Thus, the sensor is robust and is suitable for use in a typical garage environment prone to dust and insects. The sensor requires an adequate resolution to equate the angular rotation of the magnet to the distance of 20 travel required for the door. The required resolution may vary based on the distance of travel for the particular door application. For example a sensor having a resolution 1024 positions per revolution can determine the magnet's angular position with a resolution of about 0.35* 25 and this resolution may be sufficient for application in an embodiment such as a swing or sliding gate having a required travel distance of travel of 1.5m. This translates to an accuracy of 1.4mm increments. In an alternative embodiment suitable for a 5m high roll-up door 30 the sensor may require a resolution of around 4096 increments in 3600. This translates to an accuracy of 1.2mm increments of the door curtain movements. In practice such accuracy is sufficient for swing or sliding gates, and roll up, lift or sectional doors. 35 A block circuit diagram of an example of a suitable detector is illustrated in Figure 4. The detector 400 29487881 (GHMatters) P74815 AU.2 11 hall array comprises four linear hall sensors 410 which generate a DC output voltage proportional to the strength of the magnetic field incident on the sensor. The four linear hall sensors 410 are arranged symmetrically under 5 the hub 420 of rotation of the polarised magnet 430, such that rotation of the magnet generates four sinusoidal waveforms each having a 90* phase offset from its neighbouring sensors. As shown in Equation 1: HI = asin(a) 10 H2=asin(a+90 0 )=acos(a) H3 = a sin(a + 180)= a(-sin(a)) H4 = a sin(a + 270*)= a(-cos(a)) where: a = peak amplitude o= magnet rotational angle relative to sensor 15 Using differential amplifiers 440 and 450 to amplify the output of opposite sensors, adds the signals to generate two 90* phase shifted signals 460 and 470 having double the amplitude, as shown if Equation 2. 20 H - H3= asin(a) - (-asin(a)) = 2asin(a) H2- H4 =acos(a)-(-acos(a)) = 2acos(a) These two analogue signals can be converted to digital signals for further processing using an analogue 25 to digital converter (ADC) 490, for input to the digital signal processor (DSP) 495 for further processing. The DSP 495 can transform the signals into angle information using the relationship shown in Equation 3. 30 A = arctan( 2asin(a) = arctan sin(a) [3] 2acos(a)) cos(a)) where: A = measured angle 2947861 (GHManers) P74815.AU.2 12 a = peak amplitude o= magnet rotational angle relative to sensor The accuracy of the angle determination and hence the 5 door position determination is influenced by the resolution of the ADC 490 and the capability of the DSP 495. For example using 12 bits enables a resolution of 2 =4096 steps/revolution or 0.087890 per step. 10 An embodiment of a sensor assembly for a door operator is illustrated in an exploded form in Figure 2 and in an assembled form in Figure 3. This embodiment of the sensor assembly 200 comprises a two part housing having a base housing portion 240 for mounting the sensor 15 to a door operator assembly and a top housing portion 250. The polarised magnet 215 is mounted in or to the hub of a first gear 228 which is adapted to couple to a second gear 225 in the assembled sensor 200. The second gear 225 has an axle 226 adapted to be coupled to the drive train when 20 the sensor is mounted in a door operator assembly. Such coupling may be by frictional drive coupling. It can be seen that axle 226 has '0' ring grooves 219 in which respective '0' rings 221 can be received. The '0' rings 221 can, in turn, be received in the hollow interior of a 25 drive shaft of the drive train and frictionally engage with the internal surface of the drive shaft so as to rotate therewith and cause axle 226 to rotate therewith. The frictional drive coupling is desirable as it is an inexpensive means of providing coupling, and it enables 30 easy replacement of the sensor assembly should it be necessary. In that event, bolts (not shown) that pass through mounting openings 227 can be undone and the sensor assembly lifted off so the axle 226 is withdrawn from the hollow interior of the drive shaft in the drive train. A 35 substitute sensor assembly can be substituted by a reverse procedure to the removal procedure and the axle 226 thereof inserted into the hollow interior of the drive 294878_1 (GHMatters) P74815 AU.2 13 shaft in the drive train to pick up rotation drive therefrom. The top housing portion 250 holds the hub of gear 228 s supported for rotation relative to the base housing portion 240 when it is fastened to the base housing portion by bolts 211. The top housing portion 250 has a pair of arms 213 with downwardly extending flanges 214. These flanges 214 locate in 'U' shape openings 217 in the 10 base housing portion 240 into which the hubs of gear 228 locate. The base housing portion 240 therefore provides a bearing support for the worm gear 225, and the top housing portion 250 holds the hub of gear 228 so gear 228 remains meshed with worm gear 225. The detector 218 is provided 15 as a single integrated circuit chip which is mounted on a circuit board which, in turn, is supported on arm 230 which is mounted to the housing base 240, such that the detector chip 218 will be aligned with the magnet 215 in the hub of the first gear 228 in the assembled sensor 200. 20 The circuit board can be connected in data communication with the door operator controller for transfer of data from the sensor to the door controller. It should be appreciated from the assembly 25 illustrated in Figures 2 and 3 that coupling of the second gear 225 to the drive train of the door operator causes the second gear to rotate when the door is opened or closed which, in turn, causes, rotation of the first gear 228 and the magnet 215 therein. The rotation of the 30 magnet 215 is detected by the detector chip 218 and via the circuit board on the arm 230 and the position information transmitted to the controller. The illustrated sensor assembly represents one possible embodiment of a sensor for a door operator. It should be 35 appreciated that alternative embodiments are envisaged within the scope of the invention defined in the following claims. 2948786_1 (GHMatters) P74815.AU.2 14 Referring now to Figure 5, there is shown a schematic conceptual drawing depicting use of the sensor assembly 240 with a roller door operator. Roller door shutters are s typically wound on and off a drum by power supplied from a DC electric motor 501. The motor, in turn, drives a drive train (not shown) that includes a user operable clutch 503. The user operable clutch 503 typically comprises a lever or similar that a user can grasp to effect 10 disengagement of the drive train with the roller shutter door. Typically, the roller shutter door is wound on to and off a drum (not shown) which is driven by a crown wheel 505. The crown wheel 505 has two protruding fingers 507 that engage with spokes of wheels that define the drum 15 onto which the door curtain is wound. The arrangement is well known in the art. The crown wheel 505 is internally toothed and meshes with a pinion gear 509. The pinion 509 is permanently connected with a drive shaft 511 to rotate therewith. The drive shaft 511, in turn, operably 20 connects within the drive chain through the user operable clutch 503 to the motor 501. Thus, as the motor 501 rotates, it drives the crown wheel 505 which, in turn, drives the wheels which define the curtain drum. The DC motor 501 can have its polarity reversed to cause rotation 25 in the opposite direction. The sensor assembly 240 is received within the hollow interior of the shaft 511 so as to pick-up frictional drive therefrom as previously described. 30 Thus, under normal drive relationship between the motor 501 and the crown wheel 505, the active sensor element in the sensor assembly 240 rotates. The active element rotates less than 3600 for the full range of travel 35 available to the door curtain, as described previously. The position of the door curtain (i.e. the bottom edge of the door curtain), can therefore be determined by noting 2946786_1 (GHMatters) P74815.AU.2 15 the count values from the sensor assembly 240. The count values can be used as described previously to set the open and closed stop positions. 5 If power to the motor 501 should fail, then it is not possible to manually open the door curtain because the mechanical advantage in the drive train is such that it inhibits manual opening or closing. In that event, the user operable clutch 503 can be operated to disengage io coupling with the drive train and the door curtain. In this situation, the crown wheel 505 is still connected with the pinion gear 509 which, in turn, provides drive rotation to the active element within the sensor assembly 240. In this arrangement the active element is always is drive coupled with the door. Accordingly, when power is restored, the user operable clutch 503 can again be operated and drive coupling effected between the motor 501 and the crown wheel 505. In this case, the active element in the sensor assembly 240 will always be able to provide 20 signals indicative of the position of the door curtain. Thus, there will be no slippage or shifting of the end stop positions of the door even if the door has been manually moved. Accordingly, normal operation of the door via the motor 501 can continue. 25 The example shown in Figure 5 is for a roller type door. Other type doors such as tilt doors and/or sectional doors can have a similar arrangement where the sensor element 240 is maintained in drive relationship 30 with the door if a user operable clutch is disconnected to enable manual movement of the door in the event of a power failure. In the claims which follow and in the preceding 35 description, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or 2946786_1 (GHMafters) P74815AU.2 16 "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. 5 It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in any other 10 country. 2940786_1 (GHMatters) P74815.AU 2