Doppler effect speedometer

• US 4,914,638 A
• Filed: 02/28/1984
• Issued: 04/03/1990
• Est. Priority Date: 02/28/1984
• Status: Expired due to Fees

• Current Assignee: Industrial Design Laboratories, Inc.
• Original Assignee: Industrial Design Laboratories, Inc.
• Inventors: Milner, Ronald E.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Pihulic, Daniel T.
• Application Number:
  US06/584,432
• Time in Patent Office: 2,226 Days
• Field of Search: 367/89-91, 367/98, 367/902, 367/904, 343/7 PL, 343/8, 343/418, 128/687-690, 128/668, 128/669, 364/561, 455/260, 328/155, 342/103
• US Class Current: 367/90
• CPC Class Codes: G01S 15/60 wherein the transmitter and receiver are mounted on the moving object, e.g. for determining ground speed, drift angle, ground track
• CPC Class Codes: G01S 7/52006 with provision for compensating the effects of temperature
• CPC Class Codes: Y10S 367/902 Speed of sound compensation

Abstract

A speedometer is provided for determining speed by providing a sound signal at a first frequency, receiving a second signal which is the reflection of the first signal, and determining difference in frequency between the first and second signals created by the Doppler Effect. A speech synthesis chip within the speedometer provides a verbal indication of velocity. In this way, a person using the provided speedometer does not have to look at a dial or other visual indicator.

Provided within the speedometer is a heat-sensitive transducer for measuring the air temperature. In this way, the speedometer can take into account the change in the speed of sound with respect to temperature when calculating velocity.

Claims

1. A reflecting Doppler effect speedometer comprising:

means for transmitting a first signal having a first frequency;

means for receiving a second signal having a second frequency, the second signal being a reflection of the first signal;

mixing means for generating a third signal having a frequency responsive to the difference between the frequencies of the first and second signals;

circuit means coupled to receive the third signal for providing a binary signal on a circuit means output, the circuit means output being adapted to change state from a high state to a low state when the voltage on the filter output drops below a first threshold value, the circuit means output being adapted to change state from a low state to a high state when the voltage on the filter output rises above a second threshold value, the second threshold value being greater than the first threshold value;

means for varying one of the threshold values in response to the peak value of the third signal; and

calculating means for calculating velocity in response to the frequency of the signal present on the circuit means output.

2. A speedometer as in claim 1 wherein the means for varying one of the threshold values comprises:

first means for determining the first threshold voltage, the first threshold voltage being determined in response to the negative peak value of the third signal; and

the circuit further comprises;

second means for determining the second threshold voltage, the second threshold voltage being determined in response to the positive peak value of the third signal.

3. A speedometer as in claim 1 wherein the means for varying one of the threshold values comprises:

means for determining the first threshold voltage, the first threshold voltage being a predetermined fraction of the peak value of the third signal.

4. A reflecting Doppler Effect speedometer as in claim 1 wherein the circuit means comprises:

a first diode having an anode and a cathode, the anode of the first diode being coupled to receive the third signal;

a second diode having an anode and a cathode, the cathode of the second diode being coupled to receive the third signal;

a first capacitor having a first terminal and a second terminal, the second terminal of the first capacitor being connected to a constant voltage potential, the first terminal being coupled to the cathode of the first diode;

a second capacitor having a first terminal coupled to a constant voltage potential and a second terminal coupled to the anode of the second diode;

a third diode having a cathode coupled to the cathode of the first diode, the third diode also having an anode;

a fourth diode having an anode coupled to the anode of the second diode and a cathode coupled to the anode of the third diode; and

a first operational amplifier having an inverting input coupled to a constant voltage potential, a non-inverting input resistively coupled to receive the third signal, and an output resistively coupled to the non-inverting input and resistively coupled to the anode of the third diode, the output of the operational amplifier being coupled to the circuit means output.

5. A method for calculating the velocity of a speed measuring device comprising the steps of:

charging a capacitor to a predetermined voltage;

determining the amount of time it takes the capacitor to discharge through a first resistor of known resistance;

changing the capacitor to a predetermined voltage;

determining the amount of time it takes for the capacitor to discharge through a second resistor having a resistance dependent on temperature;

calculating the ratio of the discharge time through the first resistor to the discharge time through the second resistor;

setting a time period in response to the calculated ratio;

providing a doppler signal having a frequency dependant on the velocity of the speed measuring device and the ambient temperature;

counting the number of cycles of the doppler signal occurring in the time period; and

calculating the velocity of the speed measuring device in response to the number of counted cycles.

6. A reflecting Doppler effect speedometer comprising:

means for transmitting a first signal having a frequency;

means for receiving a second signal the second signal being a reflection of the first signal, the second signal having a second frequency;

mixing means for generating a third signal having a frequency responsive to the difference between the frequencies of the first and second signals;

a voltage controlled oscillator having an input terminal, the voltage controlled oscillator being adapted to provide a signal on an oscillator output terminal, the signal on the oscillator output terminal having a frequency responsive to the voltage present at the input terminal;

frequency comparator means having a first input, a second input and an output the first input coupled to receive the third signal, the second input coupled to the oscillator output terminal, the output providing a fourth signal having a first voltage if the frequency of the signal on the first input is greater than the frequency of the signal on the second input, the fourth signal having a second voltage if the frequency of the signal on the first input is less than the frequency of the signal on the second input;

calculation means for calculating velocity of the speedometer, the calculation means being coupled to the oscillator output terminal, the calculation means calculating speed in response to a signal present on the oscillator output terminal;

a capacitor adapted to store charge, one terminal of the capacitor being coupled to the input terminal of the voltage controlled oscillator, voltage present at the input terminal being determined by the change stored on the capacitor; and

resistance means for charging and discharging the capacitor at different rates, the resistance means comprising a first resistor coupled between the output of the frequency comparator means and the one terminal of the capacitor and further comprising a second resistor coupled in series with a diode, the series coupled second resistor and diode coupled in parallel with the first resistor.

7. Apparatus for measuring velocity comprising:

a signal source for providing a first signal;

a receiver for receiving a reflection of the first signal;

signal means for providing a second signal having a frequency indicative of the difference in frequency between the first signal and the reflection of the first signal, the signal means providing the second signal on a signal output;

temperature means for calculating temperature;

a microprocessor having a signal input coupled to the signal output, the microprocessor also being coupled to the signal output, the microprocessor also being coupled to the temperature means, the microprocessor being adapted to count the number of cycles of the second signal during a predetermined time period, the microprocessor altering the duration of the predetermined time period in response to the temperature, the microprocessor calculating the velocity of the apparatus in response to the number of counted cycles;

wherein the temperature means for calculating temperature comprises;

a capacitor for storing change, the capacitor having a first terminal coupled to a constant voltage source and a second terminal coupled to a sensing input of the microprocessor;

a first resistor coupled to the second terminal of the capacitor and a first output of the microprocessor;

a temperature-sensitive resistor coupled to the second terminal of the capacitor and a second output of the microprocessor, the microprocessor being adapted to charge the capacitor, permit the capacitor to discharge through the first resistor, the microprocessor sensing the voltage present on the second terminal of the capacitor, the microprocessor counting the number of machine cycles between the time the capacitor starts to discharge through the first resistor and the time the voltage present at the second terminal of the capacitor reaches a predetermined threshold, the microprocessor being adapted to charge the capacitor again and permit the capacitor to discharge through the second resistor, the microprocessor being adapted to count the number of machine cycles between the time the capacitor starts to discharge through the second resistor and the time the voltage present at the second terminal of the capacitor reaches the predetermined threshold.

8. A reflecting Doppler effect speedometer comprising:

means for transmitting a first signal having a first frequency;

means for receiving a second signal, the second signal being a reflection of the signal, the second signal having a second frequency;

mixing means for generating a third signal having a frequency responsive to the difference between the frequencies of the first and second signals;

a variable oscillator adapted to receive an input signal, the variable oscillator providing an oscillator output signal having a frequency response to the input signal;

frequency comparator means coupled to receive the third signal and oscillator output signal for providing a fourth signal having a first value if the frequency of third signal is greater than the frequency of the oscillator output signal, the fourth signal having a second value if the frequency of the third signal is less than the frequency of the oscillator output signal;

calculation means for calculating velocity of the speedometer, the calculation means being coupled to receive the oscillator output signal, the calculation means calculating speed in response to the value of the oscillator output signal;

accumulator means for providing an input signal to the variable oscillator in response to the fourth signal, the accumulator means adapted to increase the value of the input signal at a first rate in response to the fourth signal having a first value and to decrease the value of the input signal at a rate different from the first rate in response to the fourth signal having a second value.

9. Apparatus for measuring velocity comprising:

a signal source for providing a first signal;

a receiver for receiving a reflection of the first signal;

signal means for providing a second signal having a frequency responsive to the frequency of first signal and the frequency of the reflection of the first signal;

temperature means comprising;

(a) a capacitor for storing charge, the capacitor having a first terminal coupled to a constant voltage source and a second terminal;

(b) a first resistor having a first terminal coupled to the second terminal of the capacitor and having a second terminal; and

(c) a temperature-sensitive resistor having a first terminal coupled to the second terminal of the capacitor and having a second terminal;

control means for charging the capacitor, discharging the capacitor through the first resistor, sensing the voltage present on the second terminal of the capacitor, determining a first discharge time for the capacitor to discharge through the first resistor until the voltage present at the second terminal of the capacitor reaches a predetermined threshold, charging the capacitor again, discharging the capacitor through the temperature-sensitive resistor, sensing the voltage present on the second terminal of the capacitor, determining a second discharge time for the capacitor to discharge through the temperature-sensitive resistor until the voltage present at the second terminal of the capacitor reaches the predetermined threshold; and

calculating means having a signal input coupled to receive the second signal, and coupled to the control means, for calculating the velocity of the apparatus in response to the number of cycles of the second signal during a time period, the time period being varied to compensate for temperature in response to the values of the first and second discharge times.