SU1377794A1 - Device for measuring speed of excavating-transport and agricultural machines - Google Patents

Abstract

The invention relates to a measurement technique and can be used for contactless measurement of the speed of slow moving machines operating under conditions of strong vibrations. The purpose of the invention is to improve accuracy. The device contains a transmitter 1, a receiver 2, r-3, a synchronous detector 4, a low-pass filter 9 and a recorder 11. G-r 3 contains a crystal oscillator 12 and frequency dividers 13 and 14. In order to improve the accuracy of the device serially connected bandpass amplifier 5, comparator 6 and frequency converter to voltage, as well as synchronizer 8 and signal level converter 10 are entered. For normal operation of the device, the frequency difference Af f, -fj (f is the frequency of the sounding signal coming from the transmitter 1 located on the machine; f - frequency signal, n 3) is selected so that the arbitrary speeds and vibrations of the machine ensure that the condition uf 2V / Cfcse / is satisfied, where V is the speed of the machine; C is the propagation velocity of the probe radiation. This makes it possible to exclude a quadrature channel from the receiving path while maintaining the possibility of determining the direction of movement of the machine. 2 Il. i SL

Description

figure 1

The invention relates to a measurement technique and can be used for contactless measurement of the speed of slow moving machines operating under conditions of strong vibrations.

The purpose of the invention is to improve accuracy.

FIG. 1 shows the structural electrical circuit of the proposed device; in fig. 2 illustrates embodiments of a frequency to voltage converter and a synchronizer.

The device contains a transmitter I, receiver 2, generator 3, synchronous detector 4, bandpass amplifier 5, comparator 6, frequency-to-voltage converter 7, synchronizer 8, low-pass filter 9 (LPF), signal level converter 0 and recorder P, the generator contains a crystal oscillator 12 and dividers J3 and 14 frequencies.

The frequency to voltage converter (Fig. 2) contains a pulse shaper 5 including triggers 16 and 17 ,. a logic unit 18 and a switch 19 including keys 20 and 25. The synchronizer (Fig. 2) contains a threshold unit 22 and a sawtooth generator 23.

The device works as follows.

Transmitter 1, located on the machine, emits a probe signal with a frequency f, directed at an angle d To the ground surface. This signal after reflection from the ground surface is received by receiver 2, which is also located on the machine. In accordance with the Doppler law, the frequency of the received signal is equal to

IV „, (1- со8.),

where V is the speed of the machine; C is the speed of propagation of the probe, radiation (e.g., ultrasound). This signal is fed to the input of the synchronous detector 4.

After frequency conversion, filtering and amplification in a band-pass amplifier 5 and its zero-sampling in a comparator 6, a sequence of square pulses is formed, the frequency of which is equal to

ten

15

20

25

2V F f, (H- Icos) -f, +

2V2V

+ - f, coso l + - f coso /,

L.Vj

where f is the frequency of the signal coming from the generator 3 to the input of the synchronous detector 4.

With a stationary machine, the frequency of following these pulses is constant and equal to FO uf. When the car moves forward or backward, the pulse frequency F is respectively increased or decreased due to the term 2V / Cf, cosd. For normal operation of the device, the frequency difference, -fj, is chosen so that, at any speed of movement and vibrations of the machine, the condition df 7 2V / Cf cosol is met. This makes it possible to exclude a quadrature channel from the receiving path while maintaining the possibility of determining the direction of movement of the machine.

Pulses with frequency F, i.e. with the period following T, arrive at the counting input of the trigger 17 of the driver 15 pulses. On the leading edge of these signals, the trigger 17 is triggered and sets a high potential level at the D input of the trigger 16. After the arrival of the nearest leading edge of the frequency pulse fо at the counting input of the trigger 16, the latter goes into the single state and returns the trigger 17 to the initial state by the input R and sets the zero potential level to the D input of the I6 trigger. By the next leading edge of the frequency pulse f, the trigger 16 returns to the zero state, and the driver 15 of the pulses 45 transitions to the initial state before the next leading edge of the pulse sequence arrives at frequency F.

Thus, with the arrival of the front of the pulse sequence with a frequency F, a pulse of a fixed duration equal to the period of the pulse frequency fg is formed. The pulses of a fixed 55 duration directly and through the logic block 18 (operating in the considered case in the inverter mode) are fed to the computer inputs

35

40

mutator 19. In the presence of a pulse, switch 20 key 19 is opened and a 4-C reference voltage source is connected to the input of low-pass filter 9. In the absence of a pulse, the input of the low-pass filter 9 through the switch 21 of the switch 19 is connected to a common drive.

Thus, the voltage at the input of the lowpass filter 9 is

tt tt - Uor.if

by, op 7- - 7 + year

+ V

2Uon f 1 COScC

After subtraction in the converter 10 of the level from the output voltage of the filter 9 of the lower frequencies of the constant component U j, 4f / fo, the voltage is obtained

„„ Uon f2Uon fi COSol ,,

Uftbr U6b, x.- - f-p-V

 BBH 6blX

 KV

which, up to a constant scale factor K, corresponds to the actual speed of the vehicle. If necessary, this voltage in the level converter 10 can be further amplified and filtered.

The signal applied by receiver 2 after reflection from a statistically rough ground surface has a strong parasitic amplitude modulation. At certain points in time, the signal level at the input of the comparator 6 is insufficient to trigger it. In this case, the individual pulses of the pulse sequence disappear at a frequency F. To increase the measurement accuracy, the synchronizer 8 detects these points in time and switches the frequency converter 7 to the voltage in the third state, which ensures the preservation of its output voltage. This is done as follows. The output voltage of the low-pass filter 9, proportional to the frequency F, is fed to the input of the sawtooth generator 23. The slew rate of the output voltage of the sawtooth generator 23 is proportional to the ratio of the output voltage of the filter 9 to the bottom

Q

five

five

0

5 0 5 0 5

These are the frequencies to the resistance of the resistor (Fig. 2). The trigger level of the threshold unit 22 is selected so that, in the presence of a regular pulse sequence with a period of T, the trigger of the threshold unit 22 does not occur, and the synchronizer 8 does not affect the output signal of the sensor.

With the disappearance of individual pulses and a corresponding increase in the period t T, the threshold unit 22 is triggered and the logic level 18 receives a high potential level. This leads to the simultaneous closing of both switches of the switch 19, and the previous voltage level is maintained on the capacitor of the low-pass filter 9. After the arrival of the next pulse with the frequency F, the key 20 of the switch 19 is opened, the discharge of the integrating capacitor in the sawtooth generator 23 occurs and then the processes in the device are repeated.

Claims (1)

With a sufficiently slow change in period T, a synchronous change occurs in the rate of rise of the output voltage of the Sawtooth generator 23 and the corresponding adjustment of the synchronizer 8 reveals sharp deviations of the period following the output pulses of the comparator 6 from the change in the average period value. Invention Formula A device for measuring the speed of the earth-moving and agricultural machines, containing a series-connected receiver and a synchronous detector, the second output of which is connected to the first output of the generator, the second output of which is connected to the input of the transmitter, a low-pass filter and a recorder, precision increases, serially connected bandpass amplifier, comparator and frequency converter to voltage, the first output of which is connected to the input of the lower clock filter from the synchronizer and signal level converter whose output is connected to the input of recorder, the third output of the generator is connected to the second input of the frequency converter in the voltage, a third input and a second output of which are respectively connected to the first output and the first the synchronizer input, the second input of which is connected to the output of the low-pass filter and the input of the signal level converter. /five I I 3 18 uz.Z iUon 19 x 20 4a U8b / j (.3 -o