GB2251151A - Speed detector - Google Patents

Abstract

A speed detection apparatus for detecting the speed of a moving vehicle (10) comprises a radio frequency transponder or transmitter attached to the vehicle and capable of transmitting identification data. The identification data is received by receiver antennae (A, B) in the road surface, decoded in decoders (12, 14) and a time reading attached. Computor device (16) compares the times and calculates a vehicle speed, from a knowledge of the distance between the receivers. The identifications of vehicles exceeding a predetermined speed limit are stored in a memory for downloading. <IMAGE>

Description

SPEED DETECTOR The present invention relates to a speed detection apparatus, which not only measures the speed of a moving object (for example a vehicle) but also uniquely identifies it, without relying on a clear line of sight to the object.

Speed detection apparatus of many kinds are well known. The simplest way of measuring the speed of a vehicle is to time the vehicle over a known distance, for example the distance between two bridges on a motorway.

More sophisticated ways of measuring speed involve radar detectors which measure speed as a function of the Doppler Shift of a radar beam reflected from the moving vehicle.

Other methods involve the use of video cameras which can also measure the speed of a moving vehicle.

However, all of these methods rely on a clear line of sight to the vehicle, most require manned usage, most are unable to identify the vehicle in bad weather. Some require the vehicle to be stopped in order to identify the vehicle.

It is the object of the present invention to mitigate these disadvantages by providing a speed detection apparatus which does not rely on a clear line of sight to the moving object and which can uniquely identify the moving object as well as measuring its speed, thereby allowing unmanned usage.

The present invention provides a speed detection apparatus for detecting the speed of a moving object, which comprises: - radio frequency identification means adapted to be attached to the object for transmitting a unique identification thereof; - stationary interrogation means comprising a pair of spaced receivers, each receiver being adapted to identify the moving object; - timing means connected to each receiver for logging the time that the identified moving object passes each receiver; - calculation means for calculating the speed of the moving object from said time and spacing data; and - memory means connected to the calculation means for storing the identity of the moving object and its calculated speed.

In particular, the transmitter might be a transponder, which only transmits when activated by a signal from the interrogation means.

It is particularly important that the identification means when used on a vehicle be of a tamper proof nature.

Thus, the transmitter, would preferably be encased in a tamper-proof housing having its own internal battery, which would be replaced and the housing resealed at the time of the vehicle's annual roadworthiness inspection.

The precise time at which the two stationary receivers receive each identification is preferably obtained from a single timer.

The timer is preferably capable of giving a time to within at least one hundredth of a second.

Buffering of the information may be provided within the stationary interrogation means.

If so desired, the calculation means for calculating the speed of each moving object should have the ability to differentiate speeds which exceed a predefined limit.

The speed detection apparatus also includes memory means for storing the identification of the moving object together with its speed (and any other relevant data).

This information can either be printed out on a local printer, saved for subsequent downloading, or fed directly into a remote control room.

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings wherein: Figure 1 is a schematic block diagram of a speed detection apparatus, the moving object carrying an identification tag; and Figures 2 and 3 show progress of the object between the two receivers.

Figure 4 is a schematic side elevation showing a vehicle about to pass a further embodiment of the speed detection apparatus according to the invention; Figure 5 is a perspective view showing the vehicle moving between the two spaced receivers; Figure 6 shows the vehicle from above after passing the second receiver; and Figure 7 is a block diagram showing processing of signals from the receivers.

Figures 1 to 3 show an identification tag (e.g. a transmitter, transponder etc) fitted to a moving vehicle. A speed detection apparatus comprising of receiver A mounted in a stationary fixed position at the roadside, and a similar receiver B mounted at a known, stationary fixed distance from receiver A further along the road. A printed circuit board (e.g. a programmable read only memory device) is adapted to receive information from the receivers concerning the presence of a vehicle carrying the identification tag. Knowing the fixed distance between the receivers, it is also capable of calculating and memorising the speed of the vehicle. The printed circuit board also includes a memory for storing information concerning the speed and identity of many vehicles (typically two thousand) ready for periodic downloading.

The speed detection apparatus may be operated as follows: Firstly, the vehicle is fitted with a machine readable identification tag anywhere on the vehicle not subject to interference. On new vehicles, the identification tag would be fitted at the time of registration, and its presence would be checked each year at the annual roadworthiness test.

During installation of the speed detector, the distance between the receivers A and B is accurately set to a predefined distance which is also held in the memory of the printed circuit board, and which is used in the calculations of speed.

When a vehicle carrying an identification tag passes in front of receiver A, the identification tag is read by the receiver which decodes the signals and notes the time that these signals were received. This information is relayed to the printed circuit board and stored there in a memory location. The vehicle then passes between the receivers until it comes within the range of the second receiver B. Receiver B reads the identification tag, decodes the signals and notes the time that these signals were received. This information is relayed to the printed circuit board which checks for two identifications which are the same and then uses the difference between times A and B, and the fixed distance, to calculate the speed.

The printed circuit board has the capability to store many parameters including the speeds of vehicles together with other relevant information such as the location of the vehicle, the date and the time. The circuitry needs only one timer from which the receivers can obtain accurate and simultaneous times.

Figures 4 to 6 show a speed detection apparatus comprising a radio frequency antenna A mounted in a stationary position at the roadside, and a similar antenna B mounted at a fixed, known distance (e.g. up to 200 metres) further along the road.

A vehicle 10 travelling along a road with a radio frequency identification tag (not shown) attached to the underside of the vehicle passes over two antennas A and B, which have their receiver coils buried in the road surface.

The radio frequency identification tag operates as a radio frequency transponder, activated only when it comes within range of an antenna. When the vehicle passes over the antennas, the radio frequency identification device is activated using low frequency inductive coupling and sends the vehicles identification to the antennas using its power source.

A suitable radio frequency identification device is a Eureka 411 or 511 electronic transponder tag (Davy McKee (Poole) Stud., Poole, England BH12 5AG) which have a read range of 1 to 1.8m and varying data capacity. The transponder is activated by a 132 KHz signal from the antenna in the road, and then transmits its identification data at 66 KHz.

An alternative identification device (Multicode Vehicle Identification Equipment, Scerasota Automation Ltd., Winchester, Hampshire, S023 7QA) comprises a transponder which is activated by an interrogation signal from the antenna in the road for a period of about 25 ms.

The stationary receiver then listens for an identification signal from the transponder for about 35 ms at the same frequency (about 4500 baud).

Upon receiving the radio frequency signals from the device on the vehicle, decoders 12, 14 respectively will decode the signals into an identification and then join the current precise time (to 0.01 S accuracy) onto the end of the identification. This information is then buffered until requested (Figure 7).

A computor device 16 is adapted to receive information from the decoders. When requested decoder 12 sends the next identification and corresponding time to the device 16 a similar request is now sent to decoder 14 which sends its next identification and time. Device 16 includes a timer, calculator and a memory.

Upon receiving the information, the device 16 separates the identification and corresponding time, comparing the identifications from decoders 12 and 14. If these identifications are equal, the calculator uses the known distance and the difference in times to calculate the speed of the vehicle.

If the identifications are not equal the identification from decoder 14 is held in the memory, while the identification from decoder 12 is checked with any identifications held in memory. If a match is still not found, the device 16 inputs the next identification from decoder 14 and starts the compare procedure again.

It does this a set number of times after which it ignores this identification from decoder 12 and inputs the next identification from decoder 12.

If needed the computor device 16 can distinguish between vehicles which are exceeding the speed limit of the road and vehicles which are not; saving the identification, speed, and other relevant data of the speeding vehicles.

Claims (9)

1. A speed detection apparatus for detecting the speed of a moving object, which comprises; - radio frequency identification means adapted to be attached to the object for transmitting a unique identification thereof; - stationary interrogation means comprising a pair of spaced receivers, each receiver being adapted to identify the moving object; - timing means connected to each receiver for logging the time that the identified moving object passes each receiver; - calculation means for calculating the speed of the moving object from said time and spacing datat and - memory means connected to the calculation means for storing the identity of the moving object and its calculated speed.

2. Apparatus according to claim 1 wherein the radio frequency identification means is a transponder.

3. Apparatus according to claim 2 wherein the transponder is activated by a signal from a receiver at one frequency, and transmits identification data at a different frequency.

4. Apparatus according to claim 2 wherein each receiver transmits an activating signal to the transponder for a fixed time period, and then listens for an identification data signal from the transponder for a subsequent fixed time period.

5. Apparatus according to any preceding claim wherein the spaced receivers comprise loop antennae adapted for location in the road surface.

6. Apparatus according to any preceding claim wherein the timing means comprises a single clock means, adapted to attach a time to the identification data received at the spaced receivers.

7. Apparatus according to claim 6 wherein the clock means is accurate to 0.01 second.

8. Apparatus according to any preceding claim which further comprises selection means for selecting and storing in the memory means only those vehicles whose speed exceeds a predetermined limit.

9. Speed detection apparatus substantially as described in conjunction with Figures 1 to 3 or Figures 4 to 7.