Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
  • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
  • G01P3/64—Devices characterised by the determination of the time taken to traverse a fixed distance
  • G01P3/66—Devices characterised by the determination of the time taken to traverse a fixed distance using electric or magnetic means

Definitions

• the invention relates to an apparatus for measuring the speed of vehicles in such as traffic checks, and particularly to a sensor device for placing on a roadway.
• the common mehtods for measuring the speed of a vehicle at speed checkpoint is radar measurement and measuring the time required for passage between two points. Radar checks require expensive equipment and specially trained person ⁇ nel for interpreting the measurement results. In spite of this, the uncertainty is great, particularly in dense traffic, and it has often been necessary to rely upon simultaneously photography for interpreting the measurement results. Neither do these steps always allow such reliable measurement that it is accepted by the courts.
• the intention with the method is to measure the time that passes between the instant when a given wheel passes the first hose and the instant when the same wheel passes the second hose. Due to the great distance between the detector hoses, the uncertainty in detection will be great, particularly in dense traffic in several lanes or on a two-way roadway. The probability is then great that several vehicles pass the measuring device approximately at the same time. It may then happen that wheels on different vehicles and not one and the v same wheel on a given vehicle actuate the sensor hoses. In addition, it is difficult to set up a measuring station when the measurement of the measuring distance between both hoses must be made with great precision, and it is important that the hoses are mutually parallel and at right angles to the roadway.
• the object of the present invention is to provide a sensor device which can be quickly laid out with a minimum input of personnel, and which enables speed measurement with great accuracy and great security against measurement errors due to interference between different vehicles.
• a sensor device for measuring vehicle speeds in accordance with the invention includes two elongate sensor devices extending transverse at least one lane on which the vehicle is travelling.
• Figure 1 is a sketch of a roadway provided with speed control equipment
• Figures 2A and 2B illustrate two embodiments of the invention
• Figure 3 illustrates in principle the sequence when a vehicle wheel passes the sensor device
• Figure 4 is a time chart depicting actuation of the sensor devices.
• the reference 10 denotes a roadway on which a vehicle 11 is travelling. Right across the roadway there is a cable containing two sensors 12,13 connected to measuring equipment 14. When the vehicle passes over the sensors 12,13 with a pair of wheels, e.g. 15, the sensors are actuated in rapid succession by the wheel pressure. Since the spacing between the sensors is small (10-100 mm), the probability is very great that it is one and the same wheel which actuates first one sensor and then the other. Let it be assumed that the vehicle speed is 20 m/s (about 70 km/h). and the distance between the sensors is 20 mm, then the interval between the passage of the wheels over both sensors is in the order of magnitude 1 ms. which gives extremely good discrimination between different vehicles.
• the impulses from the sensors are evaluated in measuring equipment 14 which, in a manner known per se, measures the distance between the impulses (tl and t2 in Figure 4) and converts the time difference t to a speed v using the distance s between the sensors.
• the equipment 14 is suitably based on a microcomputer in order to enable the correction of the measuring result in a simple way, taking into account sensor type, temperature variations etc.
• FIGS. 2A and 2B Two different embodiments of a device in accordance with the invention are illustrated in figures 2A and 2B.
• the device according to Figure 2A utilizes flexible, electrically insulated hoses 21,22 filled with a conductive liquid as sensor elements. At both ends, the liquid is in contact with suitable, unillustra- ted conductive terminating plugs. Between the hoses 21 and 22 there is a web 23 which fixes the spacing between them along their entire length. The web 23 is formed such that the spacing is kept constant even when a vehicle wheel passes over it. It may be desirable to reinforce the web 23 with a metal plate, netting or the like.
• a return conductor 24,25 is suitably arranged for each sensor hose 21,22. For example they may be arranged in the web 23 so that the entire measuring equipment 14 can be placed on the same side of the roadway.
• a quiescent current passes through the hoses 21,22 and the associated return conductors 24,25.
• the first hose 21 will be compressed by a wheel.
• the cross-sectional area of the conductive liquid is heavily reduced and the current is decreased heavily or ceases entirely.
• a pulse circuit in the measuring equipment is activated and a counter or other form of time circuit is started.
• a second pulse is generated and the timing circuit is stopped.
• the timing circuit is designed in such a way that once it is started it cannot be actuated for example by the second wheel on the same axle that may pass the same hose a short time afterwards.
• the measured time is converted to a speed with the aid of analogue or digital circuits, known per se.
• Figure 2B illustrates a corresponding device where the sensor elements (12,13) are optical fibres 26,28 bedded into a flexible non-transparent casing 30 in a manner known from cablemaking technology.
• the sensor elements (12,13) are optical fibres 26,28 bedded into a flexible non-transparent casing 30 in a manner known from cablemaking technology.
• return conductor loops 27,29 are suitably placed in the casing 30 so that both transmitting and receiving equipment can be placed on the same side of the roadway.
• the casings 30 are joined together by a stiff web 23 in the same way as illustrated in Figure 2A so that the sensor elements are kept on a constant distance from each other.
• the measuring equipment 14 sends light, which passes through the optical fibres 26,27 and 28,29 respectively, forming two closed loops across the roadway from the equipment 14 and back again to detecting means in the measuring equipment.
• the rapid indication can, if so desired, also be utilized for controlling cameras for identification, and the control of caution signs for indicating acutal speed and the like.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Automatic Cycles, And Cycles In General (AREA)
• Force Measurement Appropriate To Specific Purposes (AREA)
• Traffic Control Systems (AREA)
• Measurement Of Distances Traversed On The Ground (AREA)
• Length Measuring Devices With Unspecified Measuring Means (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20364218

Family Applications (1)

Country Status (5)

Cited By (1)

Citations (5)

• 1986
  • 1986-04-16 SE SE8601740A patent/SE452916B/sv not_active IP Right Cessation
• 1987
  • 1987-04-14 WO PCT/SE1987/000188 patent/WO1987006349A1/en not_active Ceased
  • 1987-04-14 JP JP62502422A patent/JPS63503011A/ja active Pending
  • 1987-04-14 GB GB8726412A patent/GB2196741B/en not_active Expired - Lifetime
  • 1987-04-14 DE DE19873790190 patent/DE3790190T1/de not_active Withdrawn

Patent Citations (5)

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