SU767810A2 - Device for measuring car speed - Google Patents

Description

one

. The invention relates to the field of instrumentation and can be used to monitor the parameters of traffic flows for the purpose of recording and controlling traffic. .-.- ,. , -. .. - five

A device for measuring the speed of movement of automobiles is known. St. 632958, containing an inductive loop sensor, a generator, a frequency-dependent circuit, a differentiation unit, an amplitude detector, a memory unit, a resolver unit, and a recording unit.

Determining the speed of individual cars with this device gives the g 15 only partial information about the controlled traffic flow.

The aim of the invention is to expand the functionality of the device for measuring the speed of motor vehicles so that it can also be used to measure the current value of the average speed of a given set of cars.

This goal is achieved by introducing a delay element, a pulse shaper, a first electronic key, a low-pass filter, and a second electronic 30 into the known device for measuring the vehicle NIN speeds.

2

the key, with the input of the delay element connected to the output of the differentiation unit, and its output connected to the input of the pulse former connected to the second inputs of the electronic switches, and the first electronic switch connected in series, the lower frequency filter and the second electronic switch are connected between the output of the decision unit and the second input of the registration block.

The block diagram of the device is presented

in the drawing.

The device contains an inductive loop sensor 1, which is included in the circuit of the generator 2 connected to the input of the frequency-dependent circuit 3 connected to the inputs of the amplitude detector A and the differentiation unit

5, the outputs of which are connected to a series-connected memory unit

6, a decisive block 7 and a register 8, with the first electronic cell connected in series between the output of the decisive block 7 and the second input of the register 8; the lowpass filter 10 and the second electronic key 11 are output.

Differentiating 5 through a sequential delay element

12 and the pulse shaper 13 is connected to the second inputs of both electronic switches 9 and 11.

The device works as follows. .

When driving a car over an inductive loop sensor 1, its inductance changes, therefore the frequency of generator 2 changes. The frequency-dependent circuit 3 converts the change in frequency of generator 2 into an analog pulse, the shape and amplitude of which depends on the geometric parameters, the direction of motion relative to sensor 1 and on vehicle speed. The vehicle speed is determined by the normalized value of the derivative of the front pulse of the analog pulse, i.e.

V Kfe where A „is the amplitude of the analog pulse

m

sa;

g - {- is the k-maximal value of the derivative,. K. is a coefficient that takes into account the dimensionality of A and S values.

To obtain the values of A and S, the analog impulse is fed to differentiation unit 5 and amplitude detector 4. These values are stored in memory unit 6, from where they are entered, c into decisive unit -7, which implements the above reduced speed function. In the 8 pb registration block the end of the computational operations, the speed values are recorded. When a differential value appears at the output of the block. The next value of 2 is activated. Delay element 12 triggers and sends a signal to the pulse driver 13 with a delay sufficient for the computational operations . The pulse shaper 13 generates a pulse width ration, during which the input of the low-pass filter 10 is connected to the output of decision block 7 with the aid of an electronic switch 9, and the output of the filter 10 is disconnected from the second input of the recording unit 8 with the electronic switch 11. Thus, at the input of the filter 10 low frequencies are formed in duration: pulses with amplitude, corresponding to the speed and the next passing over the inductive loop sensor of the car.

The low-pass filter performs the operation: the current smoothing of the amplitude of the normalized pulses according to the algorithm:

 ; f (S) ds, LCV (f)

gl j

de (f operator of the current smoothing rate as a function of time; c.d n duration of the smoothing interval;

V (Sj is a study of the realization of a function V (-t), whose argument is denoted by the letter g.

4Q The value of T is determined by the constant time parameters of the filter and when

. Tcr l-u-t, -,

where dg is the duration of the normalized pulses at the output of the former 13;

And - the specified number of vehicles in the studied population. The low pass filter 10 performs 20 a function of the current averaging of the velocity of the group consisting of automobiles. This is accomplished by switching the input circuit of the filter 10 with an electronic switch 9, as a result of which the smoothing process is not affected by low-duration, the pauses between the moments of passage of the inductive sensor by individual vehicles. 2Q During these pauses with

the electronic key 11, the output of the low-pass filter 10 is connected to the recording unit 8, which is used to register the current value

average speed, for the time required for registration.

after the fixing of the new values of speed and its average value in the recording unit 8, the values of A and S are reset in the memory block 40, than the device is prepared for the new work cycle.

Claims (1)

Invention Formula Device for measuring the speed of movement of cars on the aut. ev 632958, so that, in order to expand the functional capabilities by measuring the average flow rate of cars, the first electronic key, the low-pass filter and the second electronic key included between the output of the block solver and the second input of the recorder, a delay element connected to the output of the differentiation unit, and a pulse shaper f to take {6 dkb rb It is connected to the output of the delay element, and the output to the second inputs of electronic keys.