Patent Publication Number: US-8994557-B2

Title: Modular collision warning apparatus and method for operating the same

Description:
TECHNICAL FIELD 
     The invention relates to a collision warning apparatus comprising a positioning receiver, a radio transceiver and an operator information unit. 
     BACKGROUND ART 
     It has been proposed to use GNSS-devices (GNSS=global navigation satellite system, such as GPS) on board of vehicles and other objects, such as cranes, to generate proximity warnings in order to reduce the risk of collisions. Such a system is e.g. described in WO 2004/047047. The system is based on apparatus mounted to the objects. Each apparatus comprises a GNSS receiver, a radio transceiver for wireless exchange of the positional data with the other apparatus, and a display device for outputting proximity warnings. 
     Typically, this type of apparatus is fixedly mounted to vehicles. 
     DISCLOSURE OF THE INVENTION 
     The problem to be solved by the present invention is to provide an apparatus that can be mounted easily to vehicles, as well as a method for operating such an apparatus. 
     This problem is solved by the apparatus and method of the independent claims. 
     Accordingly, the apparatus comprises:
         A positioning receiver for a radio based positioning system, such as a GNSS-receiver, in particular a GPS-receiver. This positioning receiver comprises a first antenna and first analog and first digital circuitry.   A radio transceiver for sending and receiving radio messages to/from other collision warning apparatus. The radio transceiver comprises a second antenna, and second analog and second digital circuitry.   An operator information unit, such as a display device, for issuing collision warnings to the user.   A control unit processing data from the positioning receiver and the radio transceiver ( 31 ) in order to generate the collision warnings.       

     Further, the device has roof mount unit, a cabin mount unit and a digital transmission line:
         The roof mount unit is structured and adapted to be mounted on the roof of a vehicle. It contains the first and second antenna as well as, at least, the first and second analog circuitry.   The cabin mount unit is structured and adapted to be mounted in the cabin of the vehicle. It contains the operator information unit. It may e.g. also contain at least part of the digital electronics of the positioning system, of the radio transceiver and/or of the control unit.   The digital transmission line consists of cabling connecting the roof mount unit and the cabin mount unit. It is adapted to exchange digital data between them and may also carry power.       

     Hence, the roof mount unit is mounted on the roof of the vehicle, and the cabin mount unit is mounted in the passenger cabin of the vehicle. 
     In other words, the present invention is based on the idea that all analog and radio frequency (RF) circuitry is arranged in the roof mount unit, while the communication between the roof mount unit and the cabin mount unit is digital. Since the transmission line between the two units is digital, it is not easily affected by damping, and it does not require extended shielding and can therefore be comparatively thin, such that it e.g. can easily be guided through a slit at the top of the vehicles window. 
     This design is especially suited for apparatus to be mounted on vehicles visiting a safety area. For example, if the vehicles in a mine or large construction site are monitored by an collision warning system of this type, a vehicle visiting the site can quickly and easily be equipped with a collision warning apparatus as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings, wherein: 
         FIG. 1  shows a site under surveillance of a collision warning system, 
         FIG. 2  is a block circuit of a collision warning apparatus, 
         FIG. 3  shows a roof mount unit, a cabin mount unit and a transmission line connecting the two, and 
         FIG. 4  is a sectional view of the roof mount unit of  FIG. 3 . 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION 
     Definitions 
     The term GNSS stands for “Global Navigation Satellite System” and encompasses all satellite based navigation systems, including GPS and Galileo. 
     The term “radio based positioning system” stands for a GNSS or for any other type of positioning system using radio signals, such as a pseudolite system. 
     Introduction: 
       FIG. 1  schematically depicts a site  1 , such as a surface mine or a large construction site, to be monitored by the present system. Typically, such a site covers a large area, in the case of a surface mine e.g. in the range of square kilometers, with a network of roads  2  and other traffic ways, such as rails  3 . A plurality of objects is present in the mine, such as:
         Large vehicles, such as haul trucks  4 , cranes or diggers. Vehicles of this type may easily weigh several 100 tons, and they are generally difficult to control, have very large breaking distances, and a large number of blind spots that the driver is unable to visually monitor.   Medium sized vehicles  5 , such as regular trucks. These vehicles are easier to control, but they still have several blind spots and require a skilled driver.   Small vehicles  6 . Typically, vehicles of this type weigh 3 tons or less. They comprise passenger vehicles and small lorries.   Trains  7 .       

     A further type of object within the mine is comprised of stationary obstacles, such as temporary or permanent buildings, open pits, boulders, non-movable excavators, stationary cranes, deposits, etc. 
     The risk of accidents in such an environment is high, specifically under adverse conditions as bad weather, during night shifts, etc. In particular, the large sized vehicles can easily collide with other vehicles, or obstacles. 
     For this reason, the mine  1  is equipped with a collision warning system that allows to generate proximity warnings, thereby reducing the risk of collisions and accidents. 
     The collision warning system comprises collision warning apparatus  12 , one of which is mounted to each vehicle or obstacle. In addition, the system can comprise a central server  13 , whose role is explained below. 
     Collision Warning Apparatus 
       FIG. 2  shows a block circuit diagram of an example of a single collision warning apparatus  12 . The apparatus comprises:
         A control unit  20  having a microprocessor  21 , memory (RAM  22 , ROM  23 ) and interface circuitry  24  as known to the skilled person.   An operator information unit, e.g. formed by a display  26 , for displaying messages and information. For example, display  26  can be a LCD screen and/or can comprise a plurality of light sources suitable to convey two-dimensional images or symbols to the user. The operator information unit can further or alternatively comprise a sound source  27 , such as a loudspeaker or buzzer for emitting acoustic signals.   Two or three radio communication units  30 ,  31 ,  32 .       

     A first radio communication unit  30  is a positioning receiver for a radio based positioning system. It comprises a first antenna  30   a , first analog circuitry  30   b , and digital receiver circuitry  30   c . First analog circuitry  30   b  can e.g. comprise a preamplifier, filters, a mixer and a demodulator. First digital circuitry  30   c  can e.g. comprise circuitry for analyzing the data from the demodulator in order to derive the position of the apparatus. 
     A second radio communication unit  31  is a radio transceiver for sending and receiving radio messages to/from other collision warning apparatus. Advantageously, the second radio communication unit  31  is adapted to directly communicate with the second radio communication units  31  of other apparatus  12 , without the help of any intermediary transmitters. It comprises a second antenna  31   a , second analog circuitry  31   b  and second digital circuitry  31   c . Second analog circuitry  31   b  allows for two-way communication, and therefore, in addition to first analog circuitry  30   b , further comprises a modulator, and outgoing mixer and an outgoing amplifier. Second digital circuitry  31   c  is e.g. structured to error check and decode incoming data and to encode outgoing data. Second radio communication unit  31  is typically a general-purpose non-cellular communication device for sending information from one collision detection apparatus to another collision detection apparatus. 
     A third radio communication unit  32  is optional. It is a cellular phone transceiver, such as a GMS or UMTS transceiver, adapted to send and receive messages through a cellular phone network. Alternatively, or in addition thereto, third radio communication unit  32  may comprise a receiver for communicating through another wireless data transmission network, such as WiFi, WiFi Mesh, WiMax, BigZee, etc. It comprises a third antenna  32   a , third analog circuitry  32   b  and third digital circuitry  32   c . Third analog circuitry  31   b  allows, as second analog circuitry  32   b , for two-way communication, and therefore basically comprises the same type of components. Third digital circuitry  32   c  is e.g. structured to detect incoming SMS messages addressed to the given monitoring apparatus, and error check and decode them, to encode and address outgoing SMS messages, and to handle communication with the cellular network. It may also carry other forms of digital information exchange and/or voice. 
     The various components of the three radio communication units  30 ,  31 ,  32  are known to the skilled person and need not be explained in detail here. 
     Collision warning apparatus  12  advantageously comprises a rechargeable battery  60 . A battery charger  61  comprises circuitry for charging battery  60 . Battery charger  61  can draw power from at least one power source. Such power sources can e.g. be
         a power plug  62  for directly connecting device  12  to an external power supply;   an inductive coupler  63  comprising a coil adapted to generate electrical current from an alternating magnetic field generated by an external primary coil; such inductive power couplers are known to the skilled person; and/or   a solar power supply  64  mounted at the outer surface of device  12  or in a separate unit electrically connected to device  12 .       

     Battery  60  and the components  61 - 64  can be used to feed power to roof mount unit  40  (described below), display unit  41  (described below) and/or control unit  20 . The various units can also have separate power supply means. 
     Operation of the Apparatus: 
     The operation of the collision warning apparatus  12  can be basically as in conventional systems of this type, such as e.g. described in WO 2004/047047 and need not be described in detail herein. 
     In short, in a simple approach, each device obtains positional data derived from a signal from positioning receiver  30 . This positional data allows to determine the position of the device and is stored in a “device status dataset”. The device status dataset also contains a unique identifier (i.e. an identifier unique to each apparatus or device  12  used on the same site). 
     The device status dataset is emitted as a radio signal through radio transceiver  31 . With the same transceiver  31 , the device receives the corresponding signals from neighboring apparatus or devices  12  and, for each such neighboring apparatus  12 , it calculates the relative distance d by subtracting its own coordinates from those of the neighboring device. 
     Proximity Warnings: 
     Proximity warnings can be generated by means of various algorithms. Examples of such algorithms are described in the following. 
     In a very simple approach, it can be tested if the absolute value of the relative distance d is below a given threshold. If yes, a proximity warning can be issued on display  26  and/or by loudspeaker  27 . This corresponds to the assumption that a circular volume in space is reserved for each object. The radius of the circular volume attributed to an object can e.g. be encoded in its device status dataset. 
     A more accurate algorithm can e.g. take into account not only the relative position, but also the driving velocities and directions of the vehicles. 
     An improvement of the prediction of collisions can be achieved by storing data indicative of the size and/or shape of the vehicle that a monitoring device is mounted to. This is especially true for large vehicles, which may have non-negligible dimensions. In a most simple embodiment, a vehicle can be modeled to have the same size in all directions, thereby defining a circle/sphere “covered” by the vehicle. If these circles or spheres of two vehicles are predicted to intersect in the near future, a proximity warning can be issued. 
     Instead of modeling an object or vehicle by a simple circle or sphere, a more refined modeling and therefore proximity prediction can be achieved by storing the shape (i.e. the bounds) of the vehicle in the dataset. In addition, not only the shape of the vehicle, but also the position of the positioning receiver  30  (or its antenna  30   a ) in respect to this shape or bounds can be stored in memory  22 ,  23 . 
     Other Functions: 
     In addition to issuing proximity warnings as described above, the present apparatus can provide other uses and functions. 
     In one embodiment, which is particularly useful if the device is only temporarily installed on a visiting vehicle as described above, the apparatus can issue a warning when it leaves the site or enters a “forbidden area” of the site. This can e.g. happen when a user of the apparatus forgets to return the apparatus when leaving the site or tries to steal it. 
     This type of warning can be generated by executing the following steps: 
     1) In a first step, control unit  20  obtains the position of the apparatus by means of positioning receiver  30 . 
     2) In a second step, control unit  20  compares this position to a predefined geographical area. This geographical area can e.g. be stored in memory  22 ,  23  and describes the area where the apparatus is allowed to be operated. If it is found that the position is not within the geographical area, the following step 3 is executed: 
     3) A warning is issued. This warning can e.g. be displayed on display  26  or issued as a sound by acoustic signal source  27 . Alternatively, or in addition thereto, the warning can be sent, by means of third radio communication unit  32 , to central server  13 , together with the current position and identity of the apparatus. Then, the warning can be displayed by central server  13  and brought to the attention of personnel that can then take any necessary steps. 
     Another application of third radio communication unit  32  is to send messages from central server  13  to any apparatus or device  12 . Such messages are received by apparatus or device  12  and displayed on display  26  or replayed by acoustic signal source  27 . This e.g. allows to issue warnings, alerts or information to the driver operating the vehicle. 
     Operator information unit  26 ,  27  can also issue further information, in addition to collision warnings. For example, control unit  20  can be adapted to issue, on operator information unit  26 ,  27 , the following further information:
         parameters depending on the location of the apparatus, such as the current position, a local speed limit, a map of the surroundings, or warnings relating to local hazards;   a radio channel to be used for communication;   parameters depending on speed, such as a warning when a speed limit is exceeded.       

     Furthermore, control unit  20  can have an “alert mode”, which can be activated by a user, e.g. by pressing an alert button on a keyboard  29  and/or by voice control. It can e.g. be used to indicate that the person using the apparatus is in need of urgent help or needs all activity around it to be stopped immediately. The device status dataset comprises a flag indicative of whether the device is in alert mode. Another apparatus or device receiving a device status dataset that indicates that the sender is in alert mode may take appropriate action. For example, the central control room operator can be informed, closeby machinery can be shut down, etc. 
     The present system can also be used for generating automatic response to the presence of a vehicle or person at a certain location. For example, when a pedestrian vehicle with an apparatus  12  approaches a gate, such as actuator-operated door  36  of building  9 , that door can open automatically. Similarly, an entry light can switch to red or to green, depending on the type of object that an apparatus  12  is attached to, or a boom can open or close. This can be achieved by mounting a receiver device to a selected object (such as a door, a gate or an entry light). The receiver device is equipped with a radio receiver adapted to detect the proximity of monitoring devices. When the receiver device detects the proximity of an apparatus  12 , it actuates an actuator (such as the door, gate, boom or entry light) after testing access rights of the object attributed to the apparatus. For example, the actuator may be actuated depending on the type of the object that the apparatus is attached to. This type is transmitted as part of the device status dataset of the apparatus. 
     Acceleration Detector 
     In an advantageous embodiment, apparatus  12  comprises an acceleration detector  28 . This acceleration detector  28  can be used to reduce the energy consumption of the apparatus. Since first radio communication unit  30  (positioning receiver) is one of the major power drains, first radio communication unit  30  can have a “disabled mode” where it is not operating and an “enabled mode” where it is operating. When control unit  20  detects an acceleration by means of acceleration detector  28 , it puts first radio communication unit  30  into its enabled state to obtain the current position of the device. Otherwise, it puts first radio communication unit  30 , after a predetermined amount of time, into its disabled state. In addition to this, to account for the unlikely event that no acceleration is measured even though the apparatus  12  is moving, control unit  20  can be adapted to put first radio communication unit  30  into its enabled state at regular intervals in order to perform sporadic position measurements. 
     In addition or alternatively to switching first radio communication unit  30  between a disabled an enabled state, other parts of apparatus  12  can be switched between an idle and an active state in response to signals from acceleration detector  28 . In general terms, apparatus  12  can have an “idle state” and an “active sate”, wherein, in said idle state, apparatus  12  has a smaller power consumption than in said active state. Control unit  20  is adapted to put apparatus  12  into its active state upon detection of an acceleration by acceleration detector  28 , while the apparatus is e.g. brought back to its inactive state if no acceleration has been detected for a certain period of time. 
     Apparatus Design 
     The physical design of the apparatus  12  is shown in  FIGS. 3 and 4 . It comprises a roof mount unit  40 , a display unit  41  and a digital transmission and power line  42  connecting them. 
     As mentioned above, roof mount unit  40  is structured and adapted to be mounted to the roof of a vehicle. It can e.g. be equipped with an attachment (in the following called the “first attachment” for distinguishing it from a similar attachment of cabin mount unit  41 ) adapted to mounting the roof mount unit to the vehicle roof in quick and simple manner. The first attachment can e.g. be a clamp or a suction cup, but advantageously it is a magnet  43  ( FIG. 4 ), in particular a permanent magnet, of sufficient strength for affixing roof mount unit  40  to the steel roof of a vehicle. 
     Roof mount unit  40  comprises a housing  44 , which has a flat base  45 , which comes to rest on the vehicle&#39;s roof. It has a base section  46  and a head section  47 , with base section  46  being located between base  45  and head section  47 . As can best be seen in  FIG. 4 , first attachment or magnet  43  is part of base section  46 . Further, base section  46  comprises a set of batteries  48  for supplying power to the components in roof mount unit  40  and in some embodiments also to the display. On the other hand, first, second and third antenna  30   a ,  31   a ,  32   a  are mounted in head section  47 . The circuitry of head unit  40  is arranged on two printed circuit boards  50 ,  51 , either in base section  46  or head section  47  or both. This design has the advantage that the heavy components of roof mount unit  40 , in particular the batteries  48 , are mounted close to the vehicle&#39;s roof, while the light components, namely the antennas, are located further away from the roof, which reduces the risk of toppling while improving signal reception by the antennas. 
     The circuitry on circuit boards  50 ,  51  comprises at least the first, second and third analog circuitry  30   b ,  31   b ,  32   b  of the radio communication units  30 ,  31 ,  32 . 
     A metal plate  52  is arranged between the antennas  30   a ,  31   a ,  32   a  and the circuit boards  50 ,  51  for shielding the antennas from electric noise from the circuitry on the boards. 
     Cabin mount unit  41  comprises a second attachment  55 , such as a clamp or suction cup  56 , adapted to mount unit  41  within the passenger cabin of the vehicle, in plain view of the driver, such as to the dashboard or windshield. It further comprises display  26  and sound source  27  in addition to any user operated controls. 
     Typically, control unit  20 , which processes the signals from the communication units  30 , generates the proximity warnings therefrom, and controls the operation of display  26 , is arranged in cabin mount unit  41 . The first, second and third digital circuitry  30   c ,  31   c ,  32   c  of the radio communication units  30 ,  31 ,  32  can be arranged in roof mount unit  40 , cabin mount unit  41  or partially in both. 
     In an alternative embodiment, all or part of control unit  20  may also be located in roof mount unit  40 , with cabin mount unit  41  e.g. only comprising the circuitry for driving display  26 . 
     The whole apparatus may be powered by the batteries  48  of roof mount unit  47 . Alternatively, cabin mount unit  41  may be equipped with its own batteries or be provided with an adaptor for drawing power from the vehicle. In yet another embodiment, the batteries  48  in roof mount unit  41  can be dispensed with if power is supplied through the cables of transmission line  42  from cabin mount unit  41  to roof mount unit  40 . 
     Transmission line  42  is a wire-bound transmission line having sufficient number of cables for transmitting the signals and, if necessary, a shielding. 
     Digital transmission line  42  can be wire-bound, i.e. be formed by one or more wires. In some embodiments, the transmission line  42  may also be a wireless link, such as a Bluetooth link. 
     Signal Strength Triangulation: 
     Under adverse conditions, e.g. when one or more satellite signals are blocked, e.g. by obstacles, first radio communication unit  30  (positioning receiver) of a given apparatus  12  may not be able to derive its position, or the determined position will be inaccurate. Also some of the apparatus at the site may not be equipped with a first radio communication unit  30  at all. 
     Therefore, in order to further improve the reliability and versatility of the system, apparatus  12  can be equipped to perform a “signal strength triangulation” as described in the following. This triangulation allows to determine the mutual positions of several apparatuses at least approximately, even if one or more of them is unable to determine its position based on GNSS signals. The principles of this signal strength triangulation are described in the following. 
     The radio signal emitted by second radio communication unit  31  has a strength S that decays as a function of distance r. This decay can be approximated by a decay function d(r) with
 
 S ( r )= S   0   ·d ( r ).  (1)
 
For example, d(r) can, in far field approximation, decay with a negative power of r, i.e. d(r)=r − n, with n being 2 or larger.
 
     In the following, it is assumed that a first apparatus A and a second apparatus B know their positions p A  and p B  and receive a device status dataset with a signal from a third apparatus C. The signal from apparatus C is lacking position information because apparatus C is unable to determine its position p C . However, first apparatus A is able to measure the signal strength S CA  of the signal that it receives from third apparatus C, and, similarly, the second apparatus B is able to measure the signal strength S CB  that it receives from third apparatus C. If the distance between apparatus A and apparatus C is r AC  and the distance between apparatus B and apparatus C is r BC , the following set of equations applies:
 
 S   CA   =S   0C   ·d (| p   C   −p   A |) and
 
 S   CB   =S   0C   ·d (| p   C   −p   B |),  (2)
 
with S 0C  being the original signal strength (i.e. the signal strength at zero distance) of apparatus C. Assuming that the vertical coordinates of the positions of all three apparatuses are equal (the devices are on a flat terrain), or assuming that the surface of the terrain is known (i.e. the vertical coordinate of an apparatus is a known function of its horizontal coordinates), and assuming that S 0C  is known as well, the set of two equations (2) has two unknowns, namely the horizontal coordinates of the position p C  of apparatus C. Hence, in that case, the position p C  can be basically calculated from the measured signal strengths S CA  and S CB . Hence, any apparatus that knows the positions p A , p B  as well as the signal strengths S CA , S CB  measured by apparatus A and apparatus B, can obtain an estimate of the position p C  of apparatus C.
 
     There may, however, be more than one solution to the set of equations (2), and, since the function d(r) will never be able to accurately reproduce the signal decay in arbitrary terrain, the solution of (2) may be inaccurate. To further improve accuracy, it is advantageous to generalize the case to N devices measuring a signal from a “third” apparatus j, in which case the signal strength S ji  received by apparatus i from apparatus j is given by
 
 S   ji   =S   0j   ·d (| p   j   −p   i |)  (3)
 
with i=1 . . . N and N&gt;1. The equations (3) can be solved in approximation while minimizing the error in each equation using adjustment calculus, which allows to obtain a more accurate estimate for position p j  if N&gt;2, and to allow for variations of S 0j .
 
     Hence, at least a subset of the apparatuses  12  can be designed to calculate the position p j  of a “third” apparatus j if the device j does not deliver its position in its device status dataset. For this purpose, at least some or all of the apparatuses  12  should be adapted to broadcast the identities j and the signal strengths S ji  of the signals received from other apparatus j by including this information in their device status dataset. Advantageously, the device status dataset of an apparatus i includes the identities j and the signal strengths Sji for of all (or at least part of the) apparatuses j that a signal was received from. The identity of the third apparatus j and its signal strength S ji  can then be used by any other apparatus for estimating the position p j  of apparatus j. 
     Further Notes 
     Memory  22  in apparatus  12  can also be used for storing the trajectory of the apparatus while it is being used, alarms issued during said trajectory, and/or other significant information for later retrieval and use, in particular e.g. for mining process analysis and improvement, statistical hazard analysis, etc. 
     The apparatus  12  can also use CORS data, in particular CORS data received by means of third radio communication unit  32 , in order to improve the position measurement derived from the signals of first radio communication unit  30 . CORS (Continuously Operating Reference Stations) data is provided by stationary reference stations located in or close to the site and allows to correct a position derived by GNSS signals, as described e.g. at www.ngs.noaa.gov/CORS/cors-data.html. 
     While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.