Communications – electrical: acoustic wave systems and devices – Echo systems – Distance or direction finding
Patent
1982-05-25
1985-02-19
Farley, Richard A.
Communications, electrical: acoustic wave systems and devices
Echo systems
Distance or direction finding
367909, G01S 1518, G01S 1593
Patent
active
045009775
DESCRIPTION:
BRIEF SUMMARY
FIELD OF USE
The invention relates to a method for measuring a distance using ultrasonic signals. It also discloses a preferred switching arrangement as well as instruments for carrying out the method on a motor vehicle, such as private cars, buses, trucks, including trailers, tractors, pulling machines and motor-driven agriculatural machines.
Other possible fields of uses are carts and construction machines, such as track-laying planers, loaders and graders as well as all cases involving narrow passages or borders which must be approached accurately.
Another field of use comprises heavy transportation vehicles, mobile cranes, fire fighting and ambulance vehicles as well as military vehicles, such as tanks, armored patrol cars and vehicles for the engineer corps, which make it impossible for the driver to see all contours of the vehicle and, therefore, always require a second man for "guidance".
OBJECT
It is the object of the present invention to provide a dependable, cost-effective installation which may be combined in a variety of ways to suit its use, with whose aid approaching distances from obstacles around the motor vehicle may be measured and indicated to the driver of the vehicle in digital, optical form and/or through acoustic warning signals, or which may selectively and optionally be used to actuate the operating elements of the motor vehicle, such as the gas pedal, the brake and the transmission.
STATE OF THE ART
In the measuring of distances by the ultrasonic (US) echo principle, it is known to emit US-signals produced by a US-frequency generator through a US-transmitter-receiver-transducer. The signals are received by the transducer after reflection from the object to which the distance is to be measured and transmitted to an electronic analyzer for indication, measurement and adjustment.
A great many different devices for receiving and analyzing the reflected signals have become known, which generally have means for counting the received pulses and indicating them in digital form.
Well known companies use open as well as closed ultrasonic transducers as sensors, most of which operate in a frequency range of 30 KHz to 600 KHz and which sometimes reach considerable sound capacities, measured as sound pressure at a predetermined distance and ranges.
They are primarily piezo-electronic sound transducers of ceramic material, such as lead zirconate-titanate, barium titanate, lead-meta-niobate or lithium niobate, in which the sensor, which mostly is pot-shaped, operates simultaneously as sender and receiver.
This is also possible with purely electromechanical transducers which primarily are constituted as plate-shaped oscillators, as rod- or tube-oscillators.
Since 1978, the Siemens company produced a workable ultrasonic transducer (sensor) for echo sounding in the air, which is a combination of piezo-ceramic with a lamda-quarter-resonator of a novel robust bonding synthetic resin with an extremely low acoustic impedance and extraordinary properties. According to information received from the company, these sensors are not sold but are only used in company products!
Depending on the system and the structure and shape, these sensors differ with respect to their specific properties, such as the input voltage, the inner resistance, the capacity, the frequency range, the sound pressure, the degree of effectiveness, the range, the angle of the transmission and receiving channels and also the constancy of the medium in which they are to be used, such as air, gas or water, and the ambient temperature to which they are to be exposed, not the least also with respect to the sensitivity to dirt and precipitation, for example condensation of humidity in the air.
According to the state of the art, they are used in areas where light barriers are also used or where "wireless" signals are to be transmitted over shorter distances, for example control of a television apparatus by means of ultrasonic remote control.
For the purpose of targeted distance measurement in the transmission medium air, ultrasonic dis
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patent: 3742434 (1973-06-01), Leyde et al.
patent: 3766518 (1973-10-01), Rilett
patent: 3793618 (1974-02-01), Plangger
patent: 3842397 (1974-10-01), Sindle
patent: 3852705 (1974-12-01), Backman, Jr. et al.
patent: 4015232 (1977-03-01), Sindle
patent: 4240152 (1980-12-01), Duncan
patent: 4278962 (1981-07-01), Lin
patent: 4326273 (1982-04-01), Vancha
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