Ultra-sonic distance sensor system and method with correction feature for sensor value
First Claim
1. An ultra-sonic distance sensor comprising:
- an ultra-sonic wave transmitter for transmitting ultra-sonic waves of a given frequency toward an object at regular intervals;
an ultra-sonic receiver for receiving ultrasonic waves reflected by the object and producing a receiver signal having a value indicative of the amplitude of the received ultra-sonic waves;
first means for measuring the elapsed time between transmitting of the ultra-sonic waves by said transmitter and reception of ultra-sonic waves having an amplitude greater than a predetermined level, said first means producing an elapsed-time-indicative signal having a value representative of the measured elapsed time;
second means for detecting the rising characteristics of the receiver signal and deriving a correction value for said elapsed-time-indicative signal value on the basis of the detected rising characteristics of the receiver signal; and
third means for modifying said elapsed-time-indicative signal value in accordance with said correction value, deriving a distance value indicative of the distance to said object based on the modified-elapsed-time indicative signal value, and producing a distance-value-indicative signal representative of the derived distance value.
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Accused Products
Abstract
An ultra-sonic distance sensor system includes means for measuring the elapsed time between transmission of ultra-sonic waves and receipt of the return wave reflected by an object which reflects ultra-sonic waves and the distance to which is to be measured. A correction value is derived on the basis of the rate of change of the signal level of a receiver signal output by an ultra-sonic receiver. On the basis of the derived correction value, the resultant distance value or the measured elapsed time value is corrected to ensure accurate measurement of the distance to the object can be ensured. This allows more precise height control for a vehicle when the distance detector is applied to a height control system of an automotive vehicle.
49 Citations
10 Claims
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1. An ultra-sonic distance sensor comprising:
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an ultra-sonic wave transmitter for transmitting ultra-sonic waves of a given frequency toward an object at regular intervals; an ultra-sonic receiver for receiving ultrasonic waves reflected by the object and producing a receiver signal having a value indicative of the amplitude of the received ultra-sonic waves; first means for measuring the elapsed time between transmitting of the ultra-sonic waves by said transmitter and reception of ultra-sonic waves having an amplitude greater than a predetermined level, said first means producing an elapsed-time-indicative signal having a value representative of the measured elapsed time; second means for detecting the rising characteristics of the receiver signal and deriving a correction value for said elapsed-time-indicative signal value on the basis of the detected rising characteristics of the receiver signal; and third means for modifying said elapsed-time-indicative signal value in accordance with said correction value, deriving a distance value indicative of the distance to said object based on the modified-elapsed-time indicative signal value, and producing a distance-value-indicative signal representative of the derived distance value. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for measuring the distance to an object by means of ultra-sonic waves comprising the steps of:
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triggering an ultra-sonic wave transmitter to transmit ultra-sonic waves at a given frequency towards said object; starting a timer concurrently with triggering of the ultra-sonic wave transmitter; receiving ultra-sonic waves reflected by said object and producing a receiver signal having a signal level proportional to the amplitude of the received ultra-sonic waves; terminating measurement of elapsed time by said timer and producing a timer signal indicative of the measured elapsed time concurrently with production of said receiver signal; detecting signal level variation characteristics of said receiver signal and deriving a correction value for said timer signal value on the basis of detected variation characteristics; modifying said timer signal value in accordance with said correction value; and performing arithmetic operations on the basis of said modified timer signal value to derive a distance value indicative of the distance to said object and producing a signal indicative of said distance value. - View Dependent Claims (9, 10)
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Specification