WO2006018421A1

WO2006018421A1 - Inductive loop detector

Info

Publication number: WO2006018421A1
Application number: PCT/EP2005/053970
Authority: WO
Inventors: Jan Cornelis Arie Dekker
Original assignee: Jade Beheer B.V.
Priority date: 2004-08-20
Filing date: 2005-08-12
Publication date: 2006-02-23
Also published as: EP1628275A1

Abstract

The invention relates to an inductive loop detector (30) arranged to receive first detection signals (D(A)) from a first loop (A) and second detection signals (D(B)) from a second loop (B), a microprocessor (31) and a first output (01), a second output (02) and a third output O(3). The microprocessor (31) is adapted to provide a first control signal (Cl) triggered in response to said first detection signal (D(A)) for said first output (01), a second control signal (C2) triggered in response to said second detection signal (D(B)) for said second output (02) and a third control signal (C3) triggered in response to said first detection signal (D(A)) and said second detection signal (D(B)) for said third output (03). The invention further relates to a detection system (20) and vehicle park employing such a detector (30).

Description

Inductive loop detector

The invention relates to an inductive loop detector ar¬ ranged for receiving first detection signals from a first loop and second detection signals from a second loop.

The invention further relates to a detection system comprising such an inductive loop detector and a vehicle park, such as a parking lot, a parking garage or a parking place, ei¬ ther paid or unpaid and either public or private, employing such a detection system.

Many parking lots have limited space available for parking cars. Frequently money is charged for occupying parking places in said parking lots by cars. Accordingly access and exit of such parking lots should be controlled to avoid unpaid and/or unauthorised usage of the parking places. Access and exit con¬ trol, however, may also be suitable for purposes other than safeguarding payment, e.g. for a private parking place. Access and exit control is typically obtained by employing a vehicle barrier, such as a speed gate, a door, a rising step or a bol¬ lard etc.

These barriers are often activated by inductive loops deployed in a plane which is roughly parallel to the surface of the roadway into which they are embedded or onto which they are provided. An oscillator of a loop detector connected to such an inductive loop generates an alternating signal to provide a de¬ tection field for detecting passing vehicles. A vehicle entering this detection field causes a change of the resonance frequency of the loop which detection signal is detected by the loop de¬ tector. The loop detector subsequently may generate a control signal in response to the detection signal for activating the barrier. Such a loop detector has been disclosed in GB 2 231 188.

Various solutions have been proposed for avoiding vehi¬ cles to accidentally activate the barrier by entering the detection field. Obviously, sufficient space can be left between the parking places and the barrier to prevent vehicles from ma- noeuvring in and out of parking places near the inductive loops. However, this solution is disadvantageous as potential parking place is lost.

As an alternative solution, a combination of three in¬ ductive loops and two loop detectors is employed as displayed in Fig. 2. The first and second inductive loops are connected to a dual channel vehicle detector that is programmed to only acti¬ vate a vehicle barrier if a vehicle approaches the inductive loops correctly, i.e. approach control. The third loop is pro¬ vided at the vehicle barrier and connected to a single loop detector programmed to avoid that the barrier resumes its ini¬ tial position while a vehicle is still in its way, i.e. presence control .

A disadvantage of the latter solution is the complexity of the system as it requires three loops and two detectors. It is an object of the invention to provide a less com¬ plex inductive loop detector and a system using such an inductive loop detector.

This object is achieved by providing an inductive loop detector comprising a microprocessor and a first output, a sec- ond output and a third output, wherein said microprocessor is adapted to provide a first control signal triggered in response to said first detection signal for said first output, a second control signal triggered in response to said second detection signal for said second output and a third control signal trig- gered in response to said first detection signal and second detection signal for said third output.

This object is further achieved by providing a system comprising such an inductive loop detector and a first and sec¬ ond loop arranged to provide said first and second detection signals when a vehicle passes.

The inductive loop detector and system according to the invention enable to perform the approach control and presence control functions employing only two loops and a single loop de¬ tector. Accordingly, complexity of the detection system is reduced thereby diminishing the installation costs. Further, only one loop detector is required which reduces expenses to be made for the system. Moreover, multiple loop detectors may in- terfere with each other, which effect is prevented by the inven¬ tion. It should be noted that the detection system and loop detector can also be employed for detection of other metal ob¬ jects than vehicles. In a preferred embodiment of the invention, the system further comprises a vehicle barrier and said second loop is pro¬ vided at said vehicle barrier. Preferably, this second loop has a shape and/or area different from said first loop. One of the loops may e.g. have a parallelogram shape or a diamond shape. In an embodiment of the invention the second loop is arranged at the vehicle barrier such that a larger part of the area of this loop is at the side of the barrier from which the vehicle ap¬ proaches. Accordingly, the second loop is suitably arranged to have the loop detector to perform both the approach control and the presence control function.

In an embodiment of the invention, the system further comprises an input unit, wherein said input unit is arranged to be activated after triggering of one or more of said control signals. Such an input unit, e.g. a card reader, is inactive if no vehicle is present which reduces chances of fraud at this in¬ put unit .

The invention and advantages thereof will be further illustrated and described with reference to the attached draw¬ ings, which schematically show preferred embodiments according to the invention. It will be understood that the invention is not in any way restricted to these specific and preferred em¬ bodiments.

In the drawings :

Fig. 1 shows a schematic illustration of a parking lot; Fig. 2 shows a schematic illustration of a detection system according to the prior art;

Fig. 3 shows a schematic illustration of a detection system and inductive loop detector according to an embodiment of the invention; Fig. 4 shows a timing diagram of the detection signals and control signals of the inductive loop detector depicted in Fig. 3, and Figs. 5A-5C show alternative embodiments of the loop detector and detection system.

Fig. 1 shows a parking lot 1 with multiple parking places 2 for vehicles 3. The parking lot 1 has an entrance 4 and an exit 5 both barred by a vehicle barrier 6. The parking lot 1 may be multi-storeyed. It should however be appreciated that the invention has alternative applications, such as for garage boxes for only a few cars or for railroad crossings. The vehicle bar¬ rier 6 may be any type of barrier able to block or hinder passage of the vehicles 3 through the entrance 4 or exit 5, in¬ cluding but not limited to a speed gate, a door, a rising step or a bollard.

Parking lots as shown in Fig. 1 are typically employed with a detection system 10 as shown in Fig. 2. The detection system 10 of the prior art comprises a dual channel detector 11 connected to a loop 12 and a loop 13 arranged in the road sur¬ face of the exit 5. The dual channel detector 11 further comprises a first output 14 and a second output 15 to control the vehicle barrier 6. As an example, Never-Fail Systems, Inc. markets a LD200 dual channel detector. Other examples include the PD 230 dual channel detector of Nortech International, VEK M2A, VEK M2B, VEK M2E and VEK M2H detectors of FEIG Electronic GmbH, the IG325/2 detector of Weiss Electronic GmbH and the AGD520 detector of AGD Systems. The detection system 10 further comprises a third loop 16 connected to a single channel detector 17 with a single output 18. As an example, Never-Fail Interna¬ tional markets a LDlOO single channel detector. The above mentioned companies also market single channel detector. The third loop 16 is provided under the vehicle barrier 6. The vehicle barrier 6 typically comprises a control module 7 for controlling the electromotor, the hydraulic and/or pneumatic components to move the vehicle barrier 6. Further, the vehicle barrier 6 may comprise electronics to process the output signals from the outputs 14, 15, 18 of the loop detector 11, 17. In operation, the dual channel detector 11 generates a signal to obtain a detection field above the road surface at the loops 12, 13. If a vehicle 3 exits the parking lot 1 correctly it enters the detection field of the loops 12 and 13 in that se¬ quence. The dual channel loop detector 11 receives a first detection signal for loop 12 and a second detection signal for loop 13 and in response generates a control signal at the out- puts 14, 15 to open the vehicle barrier 6. This function is referred to as approach control. Further, the single channel loop detector 17 also provides a detection field at the third loop 16. The single loop detector 17 outputs a control signal for the vehicle barrier 6 to prevent closing of the vehicle bar- rier 6 as long as a vehicle 3 is in its way. This function is referred to as presence control .

Fig. 3 shows a schematic illustration of a detection system 20 and an inductive loop vehicle detector 30 according to an embodiment of the invention. The detection system 20 com- prises a first loop A and a second loop B connected to a dual channel inductive loop detector 30. The first loop A and second loop B are arranged in or on the road surface of the exit 5 of the parking lot 1. As an example, the dimensions of loop A are 2 meters in width, i.e. perpendicular to the driving direction of the vehicle 3 and a length, i.e. in the driving direction of the vehicle 3 of 1 meter. Loop B has different dimensions, e.g. a width of 2 meters and a length of 1,75 meters. The second loop B is arranged at the vehicle barrier 6 such that a larger part of the area of this loop B is at the side of the barrier 6 from which the vehicle 3 approaches. The separation between loop A and B in the driving direction is e.g. 0,8 meters. It is noted that the exact dimensions depend on the situation wherein the loops A and B should function.

The loops A and B are connected with cables 21, also referred to as feeders, to the loop detector 30. These feeders 21 may be twisted to prevent the feeders from forming a further loop.

The detection system may further comprise an input unit 22, such as a card reader or ticket dispenser, for receiving in- put information of the driver of the vehicle 3.

The loop detector 30 comprises a microprocessor 31, a memory 32 comprising operating instructions for the microproces- sor 31, a setting portion 33 and three outputs 01, 02 and 03, operated by the microprocessor, for outputting control signals Cl, C2 and C3 for the vehicle barrier 6. The setting portion 33 conventionally employs switches, such as DIP-switches or DIL- switches, or jumpers to set various functions of the detector 30. As an example, these switches or jumpers can be used to set the sensitivity level of the detection field or the duration pulses of the control signals Cl, C2 or C3. Typically such a pulse duration is between 150-250 ms. Variation of the pulse du- ration, preferably in this range, may be relevant for the loop detector 30, as the control electronics 7 for the vehicle bar¬ rier 6 may require longer pulses than 150 ms. The outputs 01, 02 and 03 can be realised in various alternatives, such as relays, transistors or other suitable solid state devices, opto-couplers etc. Typically, the loop detector components are housed in a housing (not shown) . Relays provide universal connection options to the loop detector 30 having such a housing. However, the loop detector components may also be arranged on a printed circuit board without a housing. In such a situation, opto-couplers are typically used for loop detectors 30 to couple the loop detector 30 with the (connector of) the control module 7 for the vehicle barrier 6. It should be appreciated that the loop detector 30 may be part of the control module 7 for the vehicle barrier 6.

Further, the loop detector 31 has an oscillator 34 and a multiplexer 35. The oscillator 34 outputs a signal with a fre¬ quency in the range of 10-150 kHz to provide the detection field above the loops A and B. The multiplexer 31 reduces or elimi¬ nates crosstalk between the nearby loops A and B by connecting the loop detector 30 to loop A and loop B in turns. The loop detector 30 is powered by power supply 36.

Power may be obtained from a DIN-rail socket or can advanta¬ geously be obtained from the power source for the vehicle barrier 6.

The loop detector 30 may employ a 11-pin 86CP11 connec- tor from Nortech International with the following pin lay-out as described in the below table.

In this table, the conventions NC and NO mean 'normally closed' respectively 'normally open' . It is noted that for the invention, the initial state of the relays 01, 02 and 03 is not relevant. The relays 01, 02 and 03 should only change their state, either from NC to NO or vice versa, to provide the con¬ trol signals Cl, C2 and C3. It should further be noted that the change of state of an output not necessarily lasts, but may be only temporarily. Finally, it should be appreciated that other connectors may be used as well. Sometimes, only a connection strip is provided.

Further, the relays 01, 02 and 03 may operate in vari¬ ous modes, such as the modes "presence" and "pulse" generally known in the art. Briefly, in the presence mode, a relay 01, 02, 03 provides a control signal Cl, C2, C3 as long as a metallic object, such as vehicle 3, is over a loop A, B. In the pulse mode, a relay 01, 02, 03 generates a pulsed control signal Cl, C2, C3 , i.e. a control signal of limited duration, either on en¬ try or on exit of the vehicle 3 from the detection field of the loop A, B.

It should be appreciated that the loop detector 30 may have other features, including protection features to protect the detector from high electrical currents, e.g. induced by lightning, and signalling features, such as LED's, to indicate the state of the detection system 20 or the loop detector 30. Also power fail measures, including the provision of a power fail memory, may have been taken.

In operation, with reference to the signal-time diagram Fig. 4, the oscillator 34 provides signals to loops A and B to obtain a detection field for the exit 5. It is noted that the time diagrams of Fig. 4 depend e.g. on the dimensions of the loops and the length of the vehicle 3. The length of vehicles can be accounted for by employing automatic sensitivity boost generally known in the art. The characteristics of these detection fields have been set by employing the switches of the setting portion 33 and the instructions stored in the memory 32 for the microprocessor 31. The relays 01 and 02 are in the mode "presence" whereas the re¬ lay 03 is in the mode "pulse" . When the vehicle 3 enters the detection field of loop A at time t_lf the loop detector 30 receives a first detection sig¬ nal indicated as D(A) in Fig. 4. At this moment the microprocessor 31 generates a control signal Cl at the output 01 in response to the signal D(A) . It is noted that typically a de- lay of the order of approximately 100 milliseconds is found between the receipt of D(A) and the generation of Cl at the out¬ put 01. As the first relay 01 is set in the mode "presence" , the relay 01 is energized as long as the vehicle 3 is over the loop A, i.e. during the interval between ti and t₄. When the vehicle 3 moves on, subsequently it enters the detection field of loop B at time t₂ to yield a second detection signal D(B) . At t₂ the microprocessor 31 energizes the output 02 to obtain a control signal C2 in response to the second detec¬ tion signal D(B) . As the second relay 02 is set in the mode "presence", the relay 02 is energized as long as the vehicle 3 is in the loop B, i.e. during the interval between t₂ and t₅.

However, as the vehicle 3 is also still in the detec¬ tion field of loop A, the microprocessor 31 further provides a control signal C3 at the output 03. In other words, the third control signal C3 is triggered in response to the first detec¬ tion signal D(A) and the second detection signal D(B) . The relay 03 is set in the mode "pulse", such that relay 03 is energized for only a limited duration, i.e. between t₂ and t₃. The duration of this interval is e.g. in the range of 150-250 milliseconds, dependent on the control module 7.

To provide the approach control as previously described the vehicle barrier 6 is only opened, as shown in the bottom diagram of Fig. 4, if the vehicle 3 first enters loop A and sub¬ sequently loop B. In other words, the vehicle barrier 6 is only opened if output 03 provides a control signal C3. For this rea¬ son, the loop B preferably has an extended loop portion towards the first loop A to open the vehicle barrier 6 sufficiently early.

Further, the vehicle barrier 6 remains open as long as output 02 is energized, i.e. until t₅, to avoid closing of the vehicle barrier 6 with a vehicle present in loop B. Accordingly, the detection system 20 and loop detector 30 enable presence control. Moreover, as output 01 is in the presence mode, drive back security can be provided, which is e.g. important for park¬ ing lots 1 wherein the road of the entrance 4 or exit 5 is sloped. If the vehicle 3 drives back, but remains in the detec- tion field of loop A, the vehicle barrier 6 does not close.

As a special application, if the vehicle 3 enters loop A, the detection signal D(A) may trigger control signal Cl to activate the card reader 22. Accordingly, the driver of the ve¬ hicle 3 may only from that moment on use the card reader 22. Although in Fig. 3, individual lines are shown from the outputs 01, 02 and 03 to the control module 7 of the vehicle barrier 6, it is noted that the detector 30 may have a decision module 40 to process the control signals Cl, C2, C3. In other words, outputs 01, 02 and 03 provide access to the control sig- nals from the microprocessor 31, but these control signals are not necessarily directly available outside the detector 30. Ex¬ amples are shown in Figs. 5A-5C, wherein only some relevant components of the detection system 20 are depicted.

In Fig. 5A, the microprocessor 31 of the loop detector 30 provides control signals Cl, C2 and C3 at outputs 01, 02 and 03. These control signals Cl, C2, C3 are input to the decision module 40. This decision module 40 subsequently makes available a closing signal Cc or an opening signal Co for the vehicle bar¬ rier 6. Obviously, the control module 7 should be able to interpret these signals.

In Fig. 5B, the same arrangement is applied as for Fig. 5A, however, the decision module 40 only outputting one signal for the control module 7 of the vehicle barrier 6. This output is e.g. a presence signal Cp, as long as the vehicle barrier should remain open.

In Fig. 5C, the loop detector 30 is identical to that shown in Fig. 3. A decision module 40 is applied intermediately between the detector 30 and the control module 7 to convert the control signals Cl, C2 and C3 of the outputs 01, 02 and 03. Evi¬ dently, the decision module 40 may be implemented at the control module 7. It should be acknowledged that the present invention is not limited to the above-described embodiments, since the func¬ tion of the loop detector 30 according to the invention can be achieved in many alternative ways, including both digital and analogue solutions, all of which fall under the scope of the in- vention. A gist of the invention relates to adding a third output to a dual channel loop detector, e.g. the LD200 of Never- Fail, the PD 230 of Nortech International, the VEK M2A, VEK M2B, VEK M2E or VEK M2H of FEIG Electronic GmbH, the IG325/2 detector of Weiss Electronic GmbH or the AGD520 detector of AGD Systems and adapting the microprocessor to provide control signals at the three outputs allowing to fulfil both the approach control function and the presence control function. A further gist of the invention relates to providing a system comprising a loop detector and detection loops of different arrangements, i.e. di- mensions and/or shapes.

Further, it should be appreciated that the invention can also be applied for other type of sensors or detectors than inductive loop detectors, e.g. magnetic field detectors, pneu¬ matic, hydraulic detectors or optical detectors. A magnetic field detector generates a signal on a substantial variation of the earth magnetic field as a consequence of e.g. passing of a metallic object, such as a vehicle. For pneumatic detectors, pressure pulses are detected when objects pass over air tubes. For hydraulic detectors, pulses are generated when objects pass over liquid filled tubes. Optical detectors detect variation of optical properties of optical fibre cables when vehicles drive over.

Claims

1. An inductive loop detector (30) arranged to receive first detection signals (D(A)) from a first loop (A) and second detection signals (D(B)) from a second loop (B) , a microproces¬ sor (31) and a first output (01) , a second output (02) and a third output (03) , wherein said microprocessor (31) is adapted to provide a first control signal (Cl) triggered in response to said first detection signal (D(A)) for said first output (01), a second control signal (C2) triggered in response to said second detection signal (D(B)) for said second output (02) and a third control signal (C3) triggered in response to said first detec¬ tion signal (D(A)) and said second detection signal (D(B)) for said third output (03) .

2. The inductive loop detector (30) according to claim 1, wherein at least one of said first, second and third outputs are relays and/or optocouplers .

3. The inductive loop detector (30) according to claim 1 or 2, wherein said loop detector (30) further comprises a de¬ cision module (40) for receiving said control signals (Cl, C2, C3) and outputting further signals (Cc,Co;Cp) on the basis of said control signals (Cl, C2, C3) .

4. The inductive loop detector (30) according to one or more of the preceding claims, wherein said microprocessor (31) is adapted to trigger said first, second and/or third control signal as a pulse signal .

5. The inductive loop detector (30) according to claim

4, wherein said detector is adapted to vary the duration of said pulse signal, preferably in the range 150-250 milliseconds.

6. A detection system (20) comprising an inductive loop detector (30) according to one or more of the preceding claims and a first and second loop (A,B) arranged to provide said first and second detection signals (D(A) ₇D(B)) when a vehicle (3) passes.

7. The detection system (20) according to claim 6, wherein said system further comprises a vehicle barrier (6) , said vehicle barrier being controllable by or via said first, second and third control signals (C1,C2,C3) .

8. The detection system (20) according to claim 6 or 7, wherein said system further comprises a vehicle barrier (6) and said second loop (B) is provided at said vehicle barrier (6) .

9. The detection system (20) according to claim 6, 7 or 8, wherein said second loop (B) has a shape and/or area differ¬ ent from said first loop (A) .

10. The detection system (20) according to one or more of the claims 5-9, wherein said system further comprises an in¬ put unit (22) , wherein said input unit is arranged to be activated after triggering of one or more of said control sig¬ nals.

11. A vehicle park (1) comprising a detection system (20) according to one or more of the claims 5-9.

12. A detector (30) , such as a magnetic field detector, a pneumatic or hydraulic detector or an optical detector, ar¬ ranged to receive first detection signals (D(A)) from a first detection arrangement (A) and second detection signals (D(B)) from a second detection arrangement (B) , a microprocessor (31) and a first output (01), a second output (02) and a third output (03) , wherein said microprocessor (31) is adapted to provide a first control signal (Cl) triggered in response to said first detection signal (D(A)) for said first output (01) , a second control signal (C2) triggered in response to said second detec¬ tion signal (D(B)) for said second output (02) and a third control signal (C3) triggered in response to said first detec¬ tion signal (D(A)) and said second detection signal (D(B)) for said third output (03) .