Ultrasonic distance measuring system
First Claim
1. A distance measuring system, comprising:
- a transducer for generating at a transmit time a transmit pulse towards a surface the distance to which is to be measured and for receiving a plurality of echo signals reflected from the surface and from other surfaces exposed to the transmit pulse;
means for determining a trailing edge time for each echo signal, the trailing edge time being defined as the time at which an amplitude of an echo signal crosses a threshold with a negative slope; and
means for determining a distance value from the transmit time and the trailing edge time of the last of said a minimum amplitude.
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Accused Products
Abstract
A distance sensing system includes an ultrasonic transducer, a transceiver and a microcontroller-based signal processing unit. The transducer periodically generates and directs towards the terrain a dual frequency ultrasonic signal. Echo signals from the ground and/or any intervening crop or trash are reflected back to the transducer and are processed. The system generates amplified and filtered echo envelope signals. Leading and trailing edge times are determined as the times the echo signals cross a threshold value which is a certain proportion of a maximum echo amplitude value. A near distance value is derived from the leading edge time of the first echo which exceeds a minimum amplitude. A far distance value is determined as the trailing edge time of the last echo signal which has an amplitude which exceeds a certain value. Multiple echo time and amplitude values are derived from the maximum amplitude echo. These values are used to prevent echoes which occur after the multiple echo time with less than a certain amplitude from being used in the determination of the far distance value. This far distance value represents the distance to ground and weaker, earlier echoes from trash or crop and later, multiple echoes may be ignored.
31 Citations
19 Claims
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1. A distance measuring system, comprising:
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a transducer for generating at a transmit time a transmit pulse towards a surface the distance to which is to be measured and for receiving a plurality of echo signals reflected from the surface and from other surfaces exposed to the transmit pulse; means for determining a trailing edge time for each echo signal, the trailing edge time being defined as the time at which an amplitude of an echo signal crosses a threshold with a negative slope; and means for determining a distance value from the transmit time and the trailing edge time of the last of said a minimum amplitude. - View Dependent Claims (2)
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3. A method for measuring a distance between a transducer and a surface, comprising the following steps:
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a) transmitting at a transmit time an acoustic signal from the transducer so that the transducer receives reflected echo signals, including an echo signal reflected from the surface; b) determining amplitude and time data for a maximum echo signal having a peak amplitude which is larger than the peak amplitude of all the other echo signals received by the transducer; c) from the amplitude and time data for the maximum echo signal, determining an estimated multiple echo amplitude and an estimated multiple echo time for an echo signal which could result from multiple reflections of the transmit pulse; d) determining whether the amplitude of a particular echo signal exceeds a certain minimum amplitude; e) if the amplitude of said particular echo exceeds said certain minimum amplitude and the particular echo signal was received before the estimated multiple echo time, determining the distance value from the transmit time and a time of said particular echo signal; and f) if the amplitude of said particular echo signal exceeds the certain minimum amplitude and said particular echo signal was received not before the multiple echo time and the amplitude of said particular echo signal exceeds the estimated multiple echo amplitude, determining the distance value from the transmit time and a time of said particular echo signal. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10)
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11. A distance measuring system comprising:
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a transceiver for transmitting a transmit signal towards a surface, the distance to which is to be measured, and for receiving echo signals reflected from the surface; a plurality of amplifiers, each receiving the echo signals, having a different amplifier gain generating a different amplified echo signal; a signal processing unit receiving the amplified echo signals form all of the amplifiers, the unit comprising means for deriving a distance value from the amplified echo signal from a selected one of the amplifiers; and the unit further comprising means for automatically changing said selection as a function of the amplitude of the amplified echo signal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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19. A distance measuring system, comprising:
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a transducer for generating at a transmit time a transmit pulse towards a surface the distance to which is to be measured and for receiving a plurality of echo signals reflected from the surface and from other surfaces exposed to the transmit pulse; means for determining amplitude and time data for a maximum echo signal having a peak amplitude which is larger than the peak amplitude of all the other echo signals; means for, from the amplitude and time data for the maximum echo signal, determining an estimated multiple echo amplitude and an estimated multiple echo time for an echo signal which would result from multiple reflections of the transmit pulse; and means for determining a trailing edge time for each echo signal, the trailing edge time being defined as the time at which an amplitude of an echo signal crosses a threshold with a negative slope; and means for determining a distance value from the transmit time and the trailing edge time of the last of said plurality of echo signals which has an amplitude which exceeds a minimum amplitude and which exceeds the estimated multiple echo amplitude if said last echo signal occurs after the estimated multiple echo time.
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Specification