New programmable sensor uses ultrasonics.
A new acoustic sensing system for detection, identification, verification, and measurement of parts has been introduced by Cochlea Corp, San Jose, CA.
Called Sonovision , the system-- configured much like an optoelectronic (machine vision) system--can be used for tasks such as measuring flatness, depth of holes, bends in sheet-metal parts, shapes of internal cavities, and the dimensions of odd-shaped parts such as castings and forgings.
According to Dr Shawn Buckley, president of Cochlea Corp and developer of the system, the repeatable accuracy of Sonovision is typically 0.001 for positioned parts.
"We can achieve higher accuracy in certain cases, however,' says Buckley. "For instance, we've been able to measure the flatness of silicon wafers to within one micron. In order to achieve this kind of accuracy, though, we need a flat part and perpendicularity between the sensor head and the part.'
Parts to be measured by the system typically have maximum dimensions of 0.25 to 6.0, but larger objects can be measured with custom sensor arrays.
Speed of inspection can range up to 50 parts/sec.
A basic Sonovision system consists of a sensor head and a microprocessor-based controller. The standard sensor head (see photo) consists of nine small ultrasonic transducers mounted in a grid array on one side of the head. The head measures 3H 5W 2.5D. Other heads are available for localizing the sensing region to small parts or wide parts.
Measuring 5.5 H 17 W 17 D, the controller comes in configurations for table or rack mounting. For on-line operation, the controller has 16 parallel input and output signals as well as one RS-232C serial port. The controller can process signals from up to six sensor heads at once with optional expansion ports and software.
Sonovision can also be operated off-line. The operator then uses front-panel instruments and/or a video monitor.
Power requirements are 200 W for the controller at 115 VAC, 60 Hz; the sensor heads are powered by the controller.
How it works
To program the system, the operator simply positions a part under the sensor head and presses a button on the controller. A transmitter in the head emits ultrasonic waves toward the part; some of the waves echo from the part, return to the transducers, and form an analog picture or signature for the part.
If the part will be presented in any of several orientations, the operator acquires a signature for each of the critical orientations.
The controller digitizes the phase and amplitude data for each orientation, and stores them in memory. Up to 25 signatures can be stored at the same time.
Cochlea Corp now offers units that utilize ultrasonic waves of 20 kHz, 0.5 wavelength, and 40 kHz, 0.25 wavelength. "We'll soon introduce a unit operating at 80 kHz, 0.125 wavelength,' Buckley says. "Generally speaking, the higher the frequency, the greater the resolution.'
In operation, a part approaching the inspection station triggers a sensor that turns on the transmitter. Usually the parts are stopped under the sensor head, but the system can also perform on moving parts. Each action--presence-detection, measurement, inspection, etc--requires just 1/60th sec.
Ideally, the distance between the sensor head and the subject will be fixed at a predetermined distance. This is usually less than 1, but can be as great as 6 for low-resolution measurements.
Measures ID precisely
Buckley reports that beta field-test installations were completed in June of this year, and that several large corporations have ordered Sonovision systems for laboratory and training applications.
Typically the first system costs $30,000 to $40,000. Multiple systems in one facility or for one type of application cost $20,000 or less per system.
"For measuring flatness, the acoustic method is usually more precise than optoelectronic vision,' Buckley says. "Acoustic sensing is also a more accurate method for measuring the depth of holes, the internal dimensions of bores, and deviations from standards.
"If the user wants to measure bends and hole sizes in formed sheet-metal parts, for example, Sonovision would be a good choice.'
Sonovision systems are now available for delivery. For full details, circle E1
Photo: A standard, nine-microphone sensor head sits atop a Sonovision controller. Each controller can process inputs from up to six heads simultaneously.
Photo: There are two ways Sonovision could be used in feeding, inspecting, and sorting. At top, one sensor head coarsely sorts and orients parts as they leave the feeder, deflecting misoriented or bad parts back into the bowl (as shown in the insert at lower right). At left center, a second sensor head accurately inspects the parts and allows only good parts to pass through. In qualification applications, parts usually need not be oriented.
Photo: Schematic shows how Sonovision interfaces through a programmable-logic controller with various automated equipment for sorting, feeding, machining, and handling.
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|Publication:||Tooling & Production|
|Date:||Sep 1, 1984|
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