Distance measuring method and apparatus therefor

• US RE35,607 E
• Filed: 01/24/1994
• Issued: 09/16/1997
• Est. Priority Date: 02/09/1988
• Status: Expired due to Term

• Current Assignee: NKK Corporation (JFE Holdings Incorporated)
• Original Assignee: NKK Corporation (JFE Holdings Incorporated)
• Inventors: Kanao, Yoshiyuki, Nagamune, Akio, Tezuka, Koichi
• Primary Examiner(s): Cosimano, Edward R.
• Application Number:
  US08/185,696
• Time in Patent Office: 1,331 Days
• Field of Search: 324/326, 324/327, 324/329, 342/22, 342/124, 342/130, 342/131, 342/145, 364/456, 364/458, 364/561, 367/40, 367/99, 367/100, 367/118, 367/125
• US Class Current: 702/158
• CPC Class Codes: B22D 2/003 for the level of the molten metal B22D11/181 and B22D11/201 take precedence; level indicators in general G01F23/00
• CPC Class Codes: G01F 23/284 Electromagnetic waves
• CPC Class Codes: G01S 13/288 phase modulated
• CPC Class Codes: G01S 13/325 using transmission of coded signals, e.g. P.S.K. signals

Abstract

A distance measuring method and apparatus in which first and second pseudo random signals which are the same in pattern but slightly different in period are generated to obtain a correlation output of the first and second pseudo random signals before transmission thereof as a reference correlation output, and the first pseudo random signal is directly transmitted toward a target or alternatively a carrier wave is modulated by the first pseudo random signal and transmitted toward the target. A correlation output of the signal reflected and received from the target and the second pseudo random signal is detected and the distance to the target is measured from the time interval between the reference correlation output and the received correlation output. Alternatively, the modulated carrier wave reflected and received from the target and the second pseudo random signal are subjected to correlation processing to detect a correlative modulated carrier wave and the correlative modulated carrier is subjected to orthogonal detection by a reference carrier wave thereby obtaining a target detection output. Then, the distance to the target is measured from the time interval between the reference correlation output and the target detection output.

Claims

1. A distance measuring method comprising the steps of:

generating a first pseudo random signal having a clock frequency f₁ ;

transmitting said first pseudo random signal toward a target as an electromagnetic wave signal;

receiving a signal reflected from said target and obtaining a received signal;

generating a second pseudo random signal which is the same in pattern as said first pseudo random signal but having a clock frequency f₂ which is slightly different from said clock frequency f₁ ;

multiplying said first pseudo random signal by said second pseudo random signal to make a first product;

multiplying said received signal by said second pseudo random signal to make a second product;

obtaining a first smoothed signal by passing said first product through a first low-pass filter;

obtaining a second smoothed signal by passing said second product through a second low-pass filter;

generating a first pulse when the value of said first smoothed signal reaches a maximum;

generating a second pulse when the value of said second smoothed signal reaches a maximum;

measuring the time interval between the point when said first pulse is generated and the point when said second pulse is generated, multiplying one half of said time interval by the propagation velocity of said electromagnetic wave to form a first operation value as the product of said multiplication, dividing the frequency difference between said clock frequencies f₁ and f₂ by said clock frequency f₁ to form a second operation value as the quotient of said division and multiplying said first operation value by said second operation value to calculate the distance to said target as the product of said multiplication.

2. A distance measuring apparatus comprising:

means for generating a first pseudo random signal having a clock frequency f₁ ;

means for transmitting an output of said first pseudo random signal generating means as an electromagnetic wave signal toward a target;

receiving means for receiving a reflected signal from said target to obtain a received signal;

means for generating a second pseudo random signal which is the same in pattern as said first pseudo random signal but having a clock frequency f₂ which is slightly different from said clock frequency f₁ ;

a first multiplier for multiplying the output of said first pseudo random signal generating means by an output of said second pseudo random signal generating means;

a second multiplier for multiplying an output of said receiving means by the output of said second pseudo random signal generating means;

a first low pass filter for smoothing the output of said first multiplier and outputting a first smoothed signal;

a second low pass filter for smoothing the output of said second multiplier and outputting a second smoothed signal;

first pulse generating means for generating a pulse when the first smoothed signal from said first low pass filter reaches a maximum;

second pulse generating means for generating a pulse when the second smoothed signal obtained from said second low pass filter reaches a maximum;

measuring and calculating means for measuring the time interval between the point when said first pulse is generated and the point when said second pulse is generated, multiplying one half of said time interval by the propagation velocity of said electromagnetic wave to form a first operation value as the product of said multiplication, dividing the frequency difference between said clock frequencies f₁ and f₂ by said clock frequency f₁ to form a second operation value as the quotient of said division and multiplying said first operation value by said second operation value to calculate the distance to said target as the product of said multiplication.

3. A distance measuring apparatus according to claim 2 wherein:

said first pseudo random signal generating means comprises a first clock generator having the clock frequency f₁ and a first clock-synchronizing type pseudo random signal generating means to be driven by an output of said first clock generator;

said second pseudo random signal generating means comprises a second clock generator having the clock frequency f₂ and a second clock-synchronizing type pseudo random signal generating means to be driven by an output of said second clock generator;

said first clock-synchronizing type pseudo random signal generating means has the same construction as that of said second clock-synchronizing type pseudo random signal generating means; and

the clock frequency f₁ of said first clock generator is slightly different from the clock frequency f₂ of said second clock generator.

4. A distance measuring method comprising the steps of:

generating a first pseudo random signal having a clock frequency f₁ ;

generating a second pseudo random signal which is the same in pattern as said first pseudo random signal but having a clock frequency f₂ which is slightly different from said clock frequency f₁ ;

multiplying said first pseudo random signal by said second pseudo random signal and outputting the correlated code signal as the product of said multiplication;

generating a reference carrier wave;

modulating said reference carrier wave in coded phase by each code of said first pseudo random signal;

transmitting said modulated carrier wave in coded phase toward the target as an electromagnetic wave signal;

receiving a signal reflected from said target to obtain a received signal;

multiplying said received signal by said second pseudo random signal and outputting the phase correlated carrier wave as the product of said multiplication;

respectively multiplying said phase correlated carrier wave by an inphase component (I signal) and by a quadrature component (Q signal) which are extracted from said reference carrier wave, their phases being mutually orthogonal, and respectively outputting both products, the real part and the imaginary part of the orthogonal detected signal;

respectively smoothing said real part and imaginary part of said orthogonal detected signal and calculating the signal absolute value of a composed detection signal from said smoothed two component signals;

passing said correlated coded signal through a low pass filter and outputting the smoothed correlated coded signal;

measuring the time interval between point when said smoothed correlated code signal value reaches a maximum and the point when said signal absolute value of a composed detection signal reaches a maximum, multiplying one half of said time interval by the propagation velocity of said electromagnetic wave to form a first operation value as the product of said multiplication, dividing the frequency difference between said clock frequencies f₁ and f₂ by said clock frequency f₁ to form a second operation value as the quotient of said division and multiplying said first operation value by said second operation value to calculate the distance to said target as the product of said multiplication.

5. A distance measuring apparatus comprising:

means for generating a first pseudo random signal having a clock frequency f₁ ;

means for generating a second pseudo random signal which is the same in pattern as said first pseudo random signal but having a clock frequency f₂ which is slightly different from said clock frequency f₁ ;

a first multiplier for multiplying the output of said first pseudo random signal generating means by the output of said second pseudo random signal generating means and outputting the correlated code signal as the product of said multiplication;

carrier wave generating means for generating a reference carrier wave;

modulating means for modulating the output of said carrier wave generating means in coded phase by each code signal of said first pseudo random signal generating means;

transmitting means for transmitting the output of said modulating means toward the target as an electromagnetic wave signal;

receiving means for receiving a reflected signal from said target to obtain a received signal;

a second multiplier for multiplying an output of said receiving means by the output of said second pseudo random signal generating means and outputting the phase correlated carrier wave as the product of said multiplication.[...]. .Iadd.;

orthogonal signal detecting means for respectively multiplying said phase correlated carrier wave outputted from said second multiplier by an inphase component (I signal) and by a quadrature component (Q signal) which are extracted from said carrier wave generating means, their phases being mutually orthogonal, and outputting respective both products, the real part and the imaginary part of the orthogonal detected signal;

signal absolute value calculating means for respectively smoothing said real part and imaginary part of said orthogonal detected signal and calculating the signal absolute vale of a composed detection signal from said smoothed two component signals;

a first low pass filter for smoothing the correlated code signal outputted from said first multiplier and outputting smoothed the same signal; and

measuring and calculating means for measuring the time interval between the point when the output of said first low pass filter reaches to a maximum and the point when the output of said signal absolute value calculating means reaches to a maximum, multiplying one half of said time interval by the propagation velocity of said electromagnetic wave to make a first operation value as the product of said multiplication, dividing the frequency difference between said clock frequencies f₁ and f₂ to make a second operation value as the quotient of said division and.Iaddend.

multiplying said first operation value by said second operation value to calculate the distance to said target as the product of said multiplication.

6. A distance measuring apparatus according to claim 5, wherein said orthogonal signal detecting means comprises:

a first distributor for extracting a part of the output of said carrier wave generating means;

a hybrid coupler for receiving an output of said first distributor and converting the same to generate said I signal and Q signal wherein their phases are mutually orthogonal;

a second distributor for dividing said phase correlated carrier wave outputted from said second multiplier into an R₁ signal and an R₂ signal;

a third multiplier for multiplying the I signal outputted from said hybrid coupler by the R₁ signal outputted from said second distributor; and

a fourth multiplier for multiplying the Q signal outputted from said hybrid coupler by the R₂ signal outputted from said second distributor.

7. A distance measuring apparatus according to claim .[.6.]. .Iadd.5.Iaddend., wherein said signal absolute value calculating means comprises:

a second low-pass filter and a third low-pass filter for respectively receiving the the real part and the imaginary part of the orthogonal detected signal outputted from said orthogonal signal detecting means and subjecting them to band limitation of the same frequency range as said first low-pass filter;

first and second squaring devices for respectively receiving the output of each of said second and third low-pass filters and separately performing a squaring operation thereon; and

an adder for adding the outputs of said first and second squaring devices.

8. A distance measuring apparatus according to claim 7, wherein said distance measuring apparatus is arranged on an upper part of either one of a melting reduction furnace, converter and blast furnace to measure any one of a slag level, molten steel level and charged raw material level.

9. A distance measuring apparatus according to claim 6, wherein said distance measuring apparatus is arranged on an upper part of either one of a melting reduction furnace, converter and blast furnace to measure any one, of a slag level, molten steel level and charged raw material level.

10. A distance measuring apparatus according to claim 5, wherein said .Iadd.orthogonal signal detecting means comprises:

a first distributor for extracting a part of the output of said carrier wave generating means;

a hybrid carrier for receiving the output of said first distributor and converting the same to generate said I signal and signal wherein their phases are mutually orthogonal;

a second distributor for dividing said phase correlated carrier wave outputted from said second multiplier into two signals, R_l signal and R₂ signal;

a third multiplier for multiplying the I signal outputted from said hybrid coupler by the R₁ signal outputted from said second distributor; and

a fourth multiplier for multiplying the Q signal outputted from said hybrid coupler by the R₂ signal outputted from said second distributor; and

further

wherein said .Iaddend.signal absolute value calculating means comprises;

a second low pass filter and a third low-pass filter for respectively receiving the real part and the imaginary part of the orthogonal detected .Iadd.signal .Iaddend.outputted from said orthogonal signal detecting means and subjecting them to band limitation of the same frequency range as said first low-pass filter;

first and second squaring devices for respectively receiving the output of each of said second and third low-pass filters and separately performing a squaring operation thereon; and

an adder for adding the outputs of said first and second squaring devices.

11. A distance measuring apparatus according to claim 10, wherein said distance measuring apparatus is arranged on an upper part of either one of a melting reduction furnace, converter and blast furnace to measure any one of a slag level, molten steel level and charged raw material level.

12. A distance measuring apparatus according to claim 5, wherein said distance measuring apparatus is arranged on an upper part of either one of a melting reduction furnace, converter and blast furnace to measure any one of a slag level, molten steel level and charged raw material level.