JPH02278181A - Temperature compensating method for ultrasonic range finder - Google Patents

Abstract

PURPOSE:To enable an accurate distance measurement to be performed without delay even when an external temperature suddenly changes by constructing an ultrasonic range finder such that a temperature compensation is conducted by using a temperature change detected by measuring a unit distance by an ultrasonic wave. CONSTITUTION:The space propagation time To of an ultrasonic wave signal for which the signal transmitted from an ultrasonic wave generator 10 is propagated through a unit distance lo and received by an ultrasonic wave receiver 11 is counted by a counter circuit 13 to be fed to an arithmetic circuit 7. When the circuit 7 is given the time To from the circuit 13, the circuit 7 calculates a temperature correcting compensating value alpha and stores it. On the other hand, a time Tx for which an ultrasonic wave signal P fed from an ultrasonic wave generator 2 is reflected from an object 1 to be measured and received by a receiving circuit 5 via an ultrasonic wave receiver 4 is counted by a counter circuit 6. When given the time Tx from the circuit 6, the arithmetic circuit 7 calculates a distance Xo to the object 1 by using a sonic velocity at a reference temperature to and corrects the value of the distance Xo with the correcting value alpha. As a result, the measured value of the distance to the object to be measured can be corrected without delay.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a temperature compensation method for an ultrasonic distance measuring device.

[Conventional technology]

Unmanned vehicles that use storage batteries as a driving power source are self-contained vehicles that use ultrasonic distance measuring devices to measure the distance to guiding walls on both sides of the driving path, and process this distance information to correct the driving route. There is a car coming in.

FIG. 2 shows a block diagram of this type of ultrasonic distance measuring device, where 1 is an object such as a guiding wall, 2 is an ultrasonic transmitter, and the transmitter circuit 3 periodically sends a voltage. Driven by the signal, it emits an ultrasonic signal P toward the object 1 . Reference numeral 4 denotes an ultrasonic receiver that receives the reflected wave R of the ultrasonic signal P from the object 1, converts it into an electrical signal, and inputs it to the receiving circuit 5. 6 is a counter circuit which receives a timing signal and starts counting at the same time as the transmitting circuit 3 sends out the electrical signal, receives the timing signal at the same time as the receiving circuit 5 receives and detects the signal, and stops counting. , the count value Tx is sent to the arithmetic circuit 7. Reference numeral 8 denotes a temperature sensor, and the measured temperature value t is converted into a digital value by an A/D conversion circuit 9 and supplied to the arithmetic circuit 7.

In this configuration, the ultrasonic signal P transmitted by the ultrasonic transmitter 2 is reflected from the object 1, and until the reflected wave R is received by the ultrasonic receiver 4, the spatial propagation time Tx of the ultrasonic signal P is
(sec) is measured by the counter circuit 6, and the calculation circuit 7 calculates the distance iX (m) to the object 1 using the following equation (1), where the speed of sound is v (m/S).

X=V-T・ ・ ・ ・ ・ ・ ・
・ ・ ・ ・ ・(1) Note that the sound speed V is affected by the outside temperature, so after measuring the atmospheric temperature L0C with the temperature sensor 8 and calculating the sound speed using the following equation (2), the above (
Temperature compensation is performed by performing distance calculation according to Equation 11.

V=331+0.6Δt・・・・・・・・・・・・(2)
[Problem to be solved by the invention] In this way, conventional methods have been able to directly measure the outside temperature and use the measured value to eliminate distance measurement errors caused by temperature changes. However, in general, the responsiveness of the temperature sensor 8 is not good (about a few minutes).For this reason, if the outside temperature changes rapidly, the output of the temperature sensor 8 does not follow this change quickly. , time delays occur and erroneous measurements are unavoidable, especially in the case of unmanned vehicles, as they are moving.
This was an important problem because repeated measurements at the same point could not be made and errors could not be corrected.

The present invention has been made to solve the above problems, and provides a temperature compensation method for an ultrasonic distance measuring device that enables accurate and quick distance measurement even when the external temperature changes rapidly. The purpose is to

[Means to solve the problem]

In order to achieve the above object, the present invention provides a second ultrasonic receiver that simultaneously transmits signals, in addition to the original ultrasonic receiver that performs object distance measurement.
an ultrasonic transmitter, a second ultrasonic receiver facing the second ultrasonic transmitter at a unit distance and receiving the output of the second ultrasonic transmitter, and transmitting the output. A temperature compensation system is provided to calculate a temperature correction value by measuring distance based on the time from the time to reception and the speed of sound, and the temperature compensation is performed using the temperature correction value.

[Effect]

In the present invention, the unit distance is measured by ultrasonic waves, and the temperature change is calculated from this measurement value to correct the actually measured distance between objects, so if there is a change in the speed of sound, the temperature correction of the measured distance can be made without delay. will be held.

〔Example〕

Hereinafter, a practical example of the present invention will be explained with reference to the drawings.

In FIG. 1, 10 is a second ultrasonic transmitter,
It receives an electric signal from the transmitting circuit 4 and oscillates an ultrasonic signal in synchronization with the ultrasonic transmitter 2.

Reference numeral 11 denotes a second ultrasonic receiver 11, which faces the second ultrasonic transmitter 10 at a unit distance eo (<<X) and converts the received ultrasonic waves into electrical signals. and sends it to the second receiving circuit 12. Reference numeral 13 denotes a second counter circuit, which receives a timing signal and starts counting at the same time as the transmitting circuit 3 sends out the electrical signal, receives the timing signal and stops the counting at the same time as the receiving circuit 12 receives it, The count value TO is sent to the arithmetic circuit 7.

In this configuration, the spatial propagation time TO of the ultrasonic signal emitted by the ultrasonic transmitter 10 after propagating the unit distance eo until it is received by the ultrasonic receiver 11 is counted by the counter circuit 13. , are given to the arithmetic circuit 7. When the calculation circuit 7 receives TO from the counter circuit 13, it calculates the distance i6t ff, and calculates and stores the temperature correction value α.

1o 2 On the other hand, the time Tx from when the ultrasonic signal P sent out from the ultrasonic transmitter 2 is reflected by the object 1 to when it passes through the ultrasonic receiver 4 and is received by the receiving circuit 5 is counted by the counter circuit 6. When the calculation circuit 7 receives the time Tx from the counter circuit 6, it calculates the distance Xo to the object 1 using the sound velocity vo at the reference temperature LO, and corrects this value using the correction value α.

X = αXXO (4) In this way, in each measurement cycle, in each measurement cycle, the unit distance β0 is ultrasonically measured, and the temperature change with respect to this unit distance is calculated. Min E/f! o is detected and this value is used to correct the object distance Xo measured by ultrasonic waves at the reference temperature, so even if a change occurs in the speed of sound, the measured value of the distance between objects is corrected at the same time. It turns out.

The above-mentioned unmanned vehicle is equipped with a plurality of ultrasonic ranging devices, and the temperature compensation system including the second ultrasonic transmitter 10 and the second ultrasonic receiver 11 is equipped with each ultrasonic ranging device. May be used commonly for devices.

Furthermore, in the above embodiment, the second ultrasonic transmitter 10 is caused to emit in synchronization with each emission period of the ultrasonic transmitter 2;
The transmission period may be increased.

〔Effect of the invention〕

As explained above, the present invention has a configuration in which a unit distance is measured by ultrasonic waves to detect a temperature change, and this temperature change is used to perform temperature compensation, so that even when the outside temperature suddenly changes, Since temperature compensation is performed without time delay, accurate distance measurement is possible, and it is particularly suitable for a distance measuring device for an unmanned vehicle or the like that measures distance while moving.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional ultrasonic distance measuring device. 2-ultrasonic transmitter, 3-transmission circuit, 4-ultrasonic receiver,
5-receiving circuit, 6-force counter circuit, 7... arithmetic circuit,
10-second ultrasonic transmitter, 11-second ultrasonic receiver, 12--second receiving circuit, 13-second counter circuit.

Claims (1)

[Claims] It has an ultrasonic transmitter that periodically emits ultrasonic waves to a target object, and an ultrasonic receiver that receives reflected waves of the ultrasonic waves from the target object. In an ultrasonic distance measuring device that measures a distance between objects based on It has a second ultrasonic receiver that faces the second ultrasonic transmitter and receives the output of the second ultrasonic transmitter, and includes a temperature compensation system that measures the distance based on the time from transmission to reception of the output and the speed of sound. ,
A temperature compensation method for an ultrasonic distance measuring device, characterized in that the distance between the objects is corrected using the measured value measured by the temperature compensation system.