EP2788964B1

EP2788964B1 - Automation system for a movable barrier

Info

Publication number: EP2788964B1
Application number: EP12813512.6A
Authority: EP
Inventors: Paolo Ferron
Original assignee: Nice SpA
Current assignee: Nice SpA
Priority date: 2011-12-05
Filing date: 2012-12-03
Publication date: 2018-08-29
Anticipated expiration: 2032-12-03
Also published as: EP2788964A1; WO2013084136A1; ITTV20110166A1

Description

The invention relates to an automation system for a movable barrier such as gates, doors, traffic bars, and awnings. We will refer to a gate as an example.
Automatic systems for gates are known, as in WO 2010089788 , with a central control unit and various peripheral devices that all communicate with each other wirelessly. The complications of a fully wireless system, especially if it contains safety devices for which the communication must be guaranteed or the system must be set in a safety state, thus stopping any movement, should not be underestimated because the radio transmission that is established between the various components can suffer from disturbances, signal reflections and interferences.
In particular, account must be taken that the characteristics and performances of the channel change over time because the propagation environment changes. WO2010089788 e.g. does not provide a remedy for multiple reflections, so that statistically the system can be at times unsafe because the channel is practically interrupted for a variable period of time. The central unit cannot receive signals from the safety devices and stops any activity.
Experimental tests by the Applicant have shown indeed the hazard and/or the inefficiency of a not very robust system to such disturbances. For instance, one can consider a safety photocell placed near a movable, metal gate. It may happen that the conformation of the gate, together with the objects that surround it, reflects the radio waves transmitted from the central unit along a direct or indirect path, and the sum signal on the receiving antenna can be cancelled out. The signal cancellation is unpredictable, depends on the position of the gate and of all objects, whether fixed or movable, that surround it.
There is, therefore, the problem of ensuring the safety of the system in any operating condition, in particular the problem of ensuring the steady efficiency of the radio channel.
US 2007/0008087 discloses a multi-modulation communication system for remote control able to improve the strength of the wireless communication compared to RF noise by using different modulations (AM and FM).
US 2008/0258870 discloses a communication system between a remote control of a vehicle and a control unit mounted on the same. To reduce consumption the remote control waits for a certain time in which it goes into stand-by mode.
Solving this problem is precisely the object of the invention, defined in Claim 1.
The adoptable signals are not limited to radio signals but may include any technique of wireless transmission, e.g. infrared rays, ultrasound, UV rays and lasers.
By using diversity techniques the above-mentioned problems of uncertainty for the radio propagation are solved. The diversity techniques consist of establishing two or more wireless links between the central unit and the peripheral nodes in such a way that, e.g. for the receiving nodes, it is possible to choose the link that keeps itself above a minimum threshold of quality.
Among the preferred variants we list:

space diversity techniques, wherein in the central unit and/or in the nodes there are installed two or more antennas (and/or two different transceivers) at different positions, obtaining different propagation paths, courses in space; or
frequency diversity techniques, wherein one or each antenna radiates at different frequencies to take advantage of the different frequency responses of the transmission channel. In particular in the central unit and/or nodes a single transceiver can be used by means of which the system transmits/receives at different frequencies, or
time diversity techniques, wherein the signals are transmitted at different times.

If necessary or to enhance the reliability of the system the above techniques can also be used in combination.
Advantageously, the inventive concept is applicable to the central and/or the peripheral devices. If the peripheral devices transmit signals not receivable by the central unit, one can in any event e.g. to safety lock the system after a certain number of failed transmissions. Preferably the system comprises a wireless protocol for the central unit and the peripheral devices according to which during movement of the barrier the central unit transmits, within and with an established period, synchronization signals for the peripheral devices, to which they respond in turn in an assigned time window. The advantage is to create in the wireless network an order and priority of the communications.
Preferably the central unit is adapted to transmit at least two synchronization signals at the same instant or sequentially on relevant different frequencies. In the second case, the peripheral devices are adapted to receive the signals in distinct time windows, thus they have the possibility to correctly receive al least a signal after the interference, usually short and impulsive in nature, is disappeared.
Preferably the central unit is adapted to generate the at least two signals so that they contain an identification data of said frequency and/or of the actual transmission packet. The purpose is to inform the peripheral devices about the type of received packet, so that they do not lose the synchronism and/or the position of the received data within the transmission frame or protocol.
Preferably a peripheral device comprises a timer set to delay the transmission in its own time window by a delay inversely proportional to the delay in receiving one of said at least two signals. The advantage is to maintain constant or approximately constant the transmission instant of the response signal towards the central unit. Preferably the timer is set to activate the transmission in a time window with a constant delay with respect to the beginning of said established period. This allows the temporal constancy of the response signals in the frame.
Preferably, a peripheral device is configured to skip, within said established period, the receiving phase in the time windows subsequent to that in which it has received a valid sync signal. The advantage is to save energy (the peripheral devices are usually battery powered) by removing a useless operative phase in the actual period of the frame.
Preferably a peripheral device is configured to transmit to the central unit an error signal on an emergency channel after a certain number of unsuccessful attempts to receive the synchronization signal in each time window. The advantage is to alert the central unit of a probable malfunction, to which it can react by safely blocking the system.
The invention also contemplates a method as in claim 9.
The method can also contemplate as a phase each programmed action of the central unit and/or of a peripheral device as described herein.
The advantages of the invention will be even clearer thanks to the following description of a preferred embodiment, with reference to the accompanying drawing in which

Fig 1 shows a generic scheme of an automation system;
Fig 2 shows a timing diagram of the protocol of the system.

A plant 10 for automatically moving a gate 12 by means of a motor 14 is composed of a central unit 20, which controls the motor 14 and can be integrated in it, and various peripheral devices 30 (e.g. two photocells, a flashing light, a sensitive edge, a remote control). The communication between the central unit 20 and the peripheral devices 30, and vice versa, takes place without cable connections but through wireless means. Each component/device that composes the plant 10 is part of a wireless network and is identified as a node of the network. Preferably the central unit 20 acts as a "master node" and the peripheral devices as "slave nodes".
The central unit 20 and each device 30 are provided respectively with a radio transceiver 24, 34 and antennas 22, 32 to communicate with each other. Fig 2 illustrates schematically the communication protocol while the gate is in motion (indicated by the arrow F). The protocol is described with two time axes L1 and L2: L1 for the transmitted and received signals by the central unit 20 and L2 for those transmitted and received by the peripheral devices 30.
The protocol has a period T_T, which is divided internally into two intervals T_C and T_D. In the interval Tc the central unit 20 sends to the peripheral devices synchronizing signals while in the interval T_D the peripheral devices respond sequentially, or according to the instructions contained in the received command, to the central unit 20.
During the interval Tc the central unit 20 always broadcasts, one after the other and without overlap, at least two packets 80, 82 containing the same information (e.g. the network address or other data requests) but over different carriers f₁, f₂, for example 0.5 MHz or more far apart in frequency (e.g. f₁ = 868 MHz and f₂ = 433 MHz).
Preferably the frequencies used are relatively close to each other in order to fall within the same frequency band granted for the application (e.g. the band 868.6-869.700 MHz). Moreover, this is advantageous because it allows the use of a single antenna and a single transceiver without having to provide special matching circuits. The double transmission of the command ensures that at least one of the two signals will arrive to the antennas 32 of the peripheral devices 30, without undergoing attenuation by reflections and/or multiple paths.
During the interval Tc the slave nodes 30 tune in by tuning on the first frequency f₁ in a time window 84 simultaneous and synchronized with the packet 80 (sync signal) to receive it. If on the first frequency f₁ the signal or packet is not received or is too disturbed to compromise decoding thereof, the slave nodes 30 tune on the second frequency f₂ in a time window 86 simultaneous and synchronized with the packet 82, which is equal to the previous packet 80. In the absence of noise on the first frequency f₁, consumption in the slave nodes 30 is minimum because the listening time on the second frequency f₂ does not extend.
After receiving the sync signal each slave node 30, or only the polled nodes, transmits within the interval T_D its own answer to the central or master node 20 during an assigned time window, indicated e.g. with 88 or 90. The response signal of the nodes 30 is received by the central unit 20 in the time windows 81.
The precise duration and position of the windows 84, 86, 88, 90 within the interval T_C or T_D is adjusted in the slave nodes 30 by timers. To keep the values of T_D and TC constant a slave node 30 adjusts a timer by setting in it a delay dependent on which window 84, 86 the sync signal 80 or 82 is received in from the central or master node 20. To the reception delay, with respect to the beginning of T_C, the waiting time is added necessary to locate a transmission window 88, 90 always with the same delay with respect to the beginning of interval T_D.
To give greater strength to the system, the packets 80, 82 may comprise: an identification data of the central unit, and/or a network identifier, and/or an identifier of the recipient, a type of command, etc.., a data that identifies the relative frequency of transmission f₁ or f₂ and/or the particular type of packet 80, 82. The purpose is to prevent a node 30 intercepting and misunderstanding a packet 80, 82 during e.g. an initial scan of network installation.
The central unit 20 normally receives with period T_T the answers of slave nodes 30. To limit the bandwidth occupation it is preferable that the central unit 20 transmits the second packet 82 only if it detects a problem in the previous communication (e.g. during the previous period T_T) e.g. because it has not received an answer from a polled slave node.
The system is open to many variations.
In general, one can use two or more antennas for the transmission and reception in the central unit and/or for the transmission and reception in the nodes. Or two antennas connected to a RF switch in the central unit, to send in sequence or simultaneously one same frequency to two different antennas, preferably arranged orthogonally to each other. In any case, the carrier frequency will travel different propagation paths in space and will reach the antenna of the node at least once not attenuated. Another option is the time diversity.

Claims

Automation system (10) for a movable barrier (12) comprising
- a control central unit (20) with at least one wireless transceiver (24) adapted to send and receive radio signals,

- one or more peripheral devices (30) each having at least one wireless transceiver (34) adapted to send and receive radio signals, the central unit and/or a or each peripheral device is adapted to transmit at least two signals with diversity techniques,
characterized by comprising
a wireless protocol for the central unit and peripheral devices according to which during movement of the barrier the central unit is adapted to transmit, within and with an established period (T_T), synchronization signals (89, 82) for the peripheral devices, to which they respond in turn in an assigned time window (90).
System according to claim 1, wherein the transceiver of the central unit and/or a or each peripheral device is adapted to transmit and/or receive through time diversity.
System according to claim 1 or 2, wherein the transceiver of the central unit and/or a or each peripheral device is adapted to transmit and/or receive through frequency diversity.
System according to claim 1 or 2 or 3, wherein the transceiver of the central unit and/or a or each peripheral device is adapted to transmit and/or receive through space diversity.
System according to any one of the preceding claims, wherein the central unit is adapted to transmit at least two synchronization signals at the same instant or sequentially on respective different frequencies (f₁, f₂), and in the second case, the peripheral devices are adapted to receive them in distinct time windows (84, 86).
System according to claim 5, wherein the central unit is adapted to generate the at least two signals so that they contain an identification data of said frequency and/or of the actual transmission packet.
System according to any one of the preceding claims, wherein a peripheral device comprises a timer set to delay the transmission in its own time window by a delay inversely proportional to the delay in receiving one of said at least two signals.
System according to claim 7, wherein the timer is set to activate the transmission in a time window with a constant delay (Tc) with respect to the beginning of said established period.
Method of wireless communication of an automation system (10) for a movable barrier (12), the system comprising a control unit (20) with at least one wireless transceiver (24) and one or more peripheral devices (30) each having at least a wireless transceiver (34),
the transceiver of the central unit and/or a or each peripheral device transmitting at least two signals with diversity techniques characterized in that
the central unit and the peripheral devices communicate in wireless mode by means of a protocol by which, during the movement of the barrier, the central unit transmits within and with an established period (T_T) synchronization signals for the peripheral devices, to which they respond in turn in an assigned time window (90).