Method for estimating flow velocity

• US 5,844,144 A
• Filed: 03/04/1997
• Issued: 12/01/1998
• Est. Priority Date: 03/04/1997
• Status: Expired due to Fees

• Current Assignee: Gordon H. Jennings
• Original Assignee: Gordon H. Jennings
• Inventors: Jennings, Gordon H.
• Primary Examiner(s): BIEGEL, RONALD L
• Application Number:
  US08/810,068
• Time in Patent Office: 637 Days
• Field of Search: 342/194, 73/861.25, 367/87, 367/90, 600/454
• US Class Current: 73/861.25
• CPC Class Codes: G01F 1/663 by measuring Doppler frequency shift
• CPC Class Codes: G01P 5/241 by using reflection of acoustical waves, i.e. Doppler-effect
• CPC Class Codes: G01S 15/58 Velocity or trajectory determination systems; Sense-of-movement determination systems velocity measurement in imaging systems G01S15/8979
• CPC Class Codes: G01S 15/586 using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets
• CPC Class Codes: G01S 15/588 measuring the velocity vector

Abstract

In a Doppler system for determining the average flow velocity of a liquid based on reflection from particles moving with the liquid, and in which system the received signal is subjected to both in-phase and quadrature detection, and is then analyzed into frequency domain in-phase channel amplitude and phase components and quadrature channel amplitude and phase components, an improved method for calculating the average flow velocity, comprising discarding those amplitude components for which the in-phase and quadrature phase components differ from approximately +90 degrees and approximately -90 degrees before using the remaining amplitude components to calculate an average amplitude-weighted frequency that is used in estimating the average flow velocity.

Claims

1. A method for producing an estimate of the average flow velocity of a liquid that includes regions of turbulent flow, for use with an ultrasonic Doppler flowmeter in which a received signal, reflected from particles in the liquid, is detected by an in-phase detector and by a quadrature detector which produce an I(t) signal and a Q(t) signal, respectively, in which the I(t) and Q(t) signals are digitized and converted to amplitude components I_A (f_i) and Q_A (f_i) and phase components I_P (f_i) and Q_P (f_i), where i=1, 2, . . . N, said method comprising the subsequent steps of:

a) calculating, for each frequency f_i, the phase difference Q_P (f_i)-I_P (f_i);

b) assigning a weight of +1 to I_A (f_i) if the phase difference is approximately +90 degrees;

c) assigning a weight of -1 to I_A (f_i) if the phase difference is approximately -90 degrees;

d) assigning a weight of 0 to I_A (f_i) if the phase difference is neither approximately +90 degrees nor approximately -90 degrees;

e) multiplying the amplitude I_A (f_i) by the weight determined in step b), c) or d) to obtain a weighted amplitude (W.A.) corresponding to each frequency f_i ;

f) multiplying the weighted amplitude by the frequency f_i to obtain an amplitude-weighted frequency (A.W.F.) corresponding to each frequency f_i ;

g) repeating steps a) through f) for each frequency f_i ; and

,

h) summing the weighted amplitudes determined in step e) to obtain W.A.;

i) summing the amplitude-weighted frequencies determined in step f) to obtain A.W.F.;

j) dividing A.W.F. by W.A. to obtain an estimate V_E of the average flow velocity of the liquid, where V_E is measured in units equal to the speed of sound in the liquid.

2. In a Doppler system for determining the average flow velocity of a liquid based on reflection from particles moving with the liquid, and in which system the received signal is subjected to both in-phase and quadrature detection, and is then analyzed into frequency domain in-phase channel amplitude and phase components and quadrature channel amplitude and phase components, an improved method for calculating the average flow velocity, comprising:

discarding those amplitude components for which the in-phase and quadrature phase components differ from approximately +90 degrees and approximately -90 degrees before using the remaining amplitude components to calculate an average amplitude-weighted frequency that is used in estimating the average flow velocity.