Monday, December 11, 2017

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Machine Vision System improves Ice Cream Production
 

SYSTEMS INTEGRATION: Vision system improves ice cream production

PatMax vision software.
Running the PatMax vision software, specific features of each bag are identified and a pattern score is computed. If an incorrect bag or quantity is loaded by the operator an alarm is sounded and the conveyor is stopped.

Producing around 120,000 to 150,000 liters of frozen confectionary per day during summer, Tip Top (Auckland, New Zealand; www.tiptop.co.nz) is New Zealand's largest supplier. To produce these ice cream products, exact quantities of various powdered ingredients such as milk powder are blended with wet ingredients to ensure consistent flavor and texture.

Since large amounts of ice-cream products are produced, numerous 20kg bags of different ingredients are used to make a single batch. Because of this, the exact number and types of ingredients must be checked to ensure that the correct type and amount of ingredients are added to each hopper prior to the mixing process.

"In the past," says David Berry, Owner of ControlVision (Auckland, New Zealand; controlvision.co.nz), "the type and quantity of ingredients added was performed manually. To do so, an operator would identify and count the type of products as they were loaded onto a conveyor. Since this process is prone to human error, it can result in inconsistencies in the final batch. Should this occur, then the whole batch may need to be reworked, costing time and money."

Although bag handling, conveyors, powder handling and mixing systems had been previously installed by Powder Projects (Hamilton, New Zealand), the company realized that a vision system was required to eliminate any human error in the ingredient handling process. Since Tip Top had already contracted ControlVision to install a machine vision system to check lid placement on ice cream products, the company was asked to develop a system to verify whether the correct type and amount of ingredients were added to each hopper prior to the mixing process.

bags are inspected
After each bag of ingredients is manually placed on a conveyor belt, the bags are inspected for product type and quantity by the vision system.

In the development of the vision system, ControlVision installed a 1392 x 1040 Scout scA1390-17gm GigE camera from Basler (Ahrensburg, Germany; www.baslerweb.com) above the dry ingredient conveyor. Mounted with a 9mm Fujinon lens from Fujifilm (Wayne, NJ; www.fujifilmusa.com), images of the complete field of view of each bag are captured by the camera and transferred over the GigE interface to a panel mounted industrial PC/touchscreen from Cybersys Integration Technology (City Of Industry, CA). To illuminate the bags as they move through the inspection station, ControlVision mounted two banks of white fluorescent lights above the camera.

"Although each variety of confectionary may only use approximately ten different types of dry powder product, between 50 and 100 different 20kg bags of ingredients may be used to produce the various varieties of ice cream produced by Tip Top," says Berry. "Because of this, the system must be trained to recognize over 100 different bags. To accomplish this, the company employed the PatMax geometric pattern matching tool from Cognex (Natick, MA; www.cognex.com).

This pattern matching tool is embedded in ControlVision's VisionServer, a machine vision framework and application development environment. This allows functions such as PatMax to be added as a graphical function block diagram in a sequence of functions that capture process, display and control machine vision processes (see "Vision framework supports multiple software packages," Vision Systems Design, February 2012, http://bit.ly/ztDEvU). VisionServer also provides the HMI for operators to train the system to learn new bag artwork as required.

Using the PatMax algorithm, salient geometric features of each particular bag of ingredients are analyzed and stored in the system's database. "Because the system employs the PatMax pattern matching tool," says Berry, "features within images of flat or wrinkled bags of ingredients can be easily detected." In operation, the system then compares these features against the stored database and returns a pattern matching score that ranges from 0-1. If an incorrect ingredient is added, this score will be lower than a preset score and an alarm will be sounded. This alarm will also occur should too many or too few bags of a required ingredient be loaded on to the conveyor.

To monitor the complete production process, the embedded PC/flat panel is also interfaced to Tip Top's supervisory control and data acquisition (SCADA) system. In this way, the operator can monitor whether the correct type and amount of ingredients are being added for a particular batch and the status of the batch verification system.

According to Tip Top Project Manager Brett Dockery, since the new system has been installed, ingredient mixing accuracy has improved dramatically. "Because the camera captures exactly what has gone into the mix, it is much easier to correct any mistakes than in the past, when we had difficulty in determining which ingredient was missing or wrongly added," he says.

 

Courtesy of Vision Systems Design website.

 

AV Design Matters

DESIGN MATTERS in AV

AV is fundamentally human-centric, so it should not be a surprise that design and design-led engineering is central to the products being developed by the AV market.  Well, surprise – it isn’t.  Part of the challenge for traditional AV companies is they emerged from such a deep area of science and engineering that they haven’t been able to transform themselves from engineering houses to human-centered product companies.  It’s part of the reason all of my readers have heard of Samsung and Apple, but only some are aware of Barco and AMX, which are both very big companies.  To be fair, I’m having conversations with very large AV companies who are aware they need to change how they approach product development and some of them will be successful.

As software companies enter the AV market, a focus on the user experience is being brought to bear into a problem space that is usually driven first by standards, video codecs and hardware constraints, and last by design. Getting this mix correct is difficult for any company, and I’ll admit, we struggle with getting it right as well. That’s why I found yesterday’s article in Fast Company so interesting. The article was written by Hartmut Esslinger, the founder of Frog Design, Inc. and one of the leading designers in the world. He is recognized as the force that helped put a culture of “design first” at Apple.

hartmut - design first
I’m very familiar with Frog since my brother was a senior UX designer there for many years, and I got to see some of Frog from the inside during the overwhelming and exciting dot-com era (think SXSW parties that today are just not possible). I’d like to think being aware of the design community as a separate-but-equal partner of technology gave us a leg-up on entering the collaboration arena (not to mention hours of consulting time from my brother).

Esslinger makes some very good points.  If you work in the AV space and are responsible for helping set direction for your company in any way, then read the article and ask yourself how your company envisions, designs, and builds products that people love.  The point is quite simple.  Design and user experience should drive products, not engineering. Esslinger further drives this point home in his new book, Design Forward.

As a technologist (not a designer), it took me several years to fully accept this approach, and encouraging others to embrace the methodology is an ongoing process.  Esslinger points out the danger of allowing design considerations to fall or be placed at the mercy of engineering, and I think the rewards for adopting a design-first strategy are huge.  In a market where we are focused on building products to be looked at, listened to, and now interacted with by our customers, the benefits are probably even greater.

 

Courtesy of Mersive Technology Blog & Chris Jaynes

 

"The Basics" AV Design: Part 1 Transmission Line Impedance
 

AV Design "The Basics" Impedance Part I Transmission Line (Characteristic) Impedance 

BY: Sam Davisson, Director of Engineering at SJD Engineering Group

Courtesy of: sdjeg.net

 

Impedance has been the most requested subject since I started the “Basic’s” series. So I thought it about time to address it. Problem is, no one actually mentioned what area of impedance they were confused about and was looking for clarification on. Perhaps some are wondering why when you measure across the center conductor and braid of a 75ohm coax cable you don’t read 75ohms. Or how in the world you would ever know if a connector was a 75ohm connector or one of the 50ohm variety? Does all that mumbo jumbo have anything to do with audio amplifiers and the speaker connected to it.

Every signal input, and every output, has an impedance, this "impedance" represents the relationship between voltage and current which a device is capable of accepting or delivering. Electricity is all about the flow of electrons in wire. "Voltage" is a measure of how hard the electrons are pressing to get through, it’s like water pressure in a pipe. "Current," measured in amps, is a measure of the rate at which the electrons are flowing. It’s like the gallons-per-minute flow in a pipe. Total power delivery, in an electrical circuit, is measured in watts, which are simply the volts multiplied by the amps. A number of watts may represent a very high voltage with relatively low current (such as we see in high-tension power lines) or a low voltage with very high current (such as we see when a 12-volt car battery delivers hundreds of amps into a starter).

An output circuit can’t supply just any combination of voltage and current we want. Instead, it’s designed to deliver a signal into a specific kind of load ("load," here, simply meaning the device, such as the TV input that the signal is being delivered to). The "impedance" of the load represents the opposition to current flow which the load presents.

The impedance of the load is expressed in ohms, and the relationship between the current and the voltage in the circuit is controlled by the impedance in the circuit. When a signal source sees a very low-impedance circuit, it produces a larger than intended current; when it sees a very high-impedance circuit, it produces a smaller current than intended. These mismatched impedance’s redistribute the power in the circuit so that less of it is delivered to the load than the circuit was designed for, because the nature of the circuit is that it can’t simply readjust the voltage to deliver the same power regardless of the rate of current flow. What happens in an impedance mismatch between a source and load; power isn’t being transferred properly because the source circuit wasn’t designed to drive the kind of load it’s connected to. In some electronic applications, this will burn out equipment. A radio transmitter must be able to deliver its power into an antenna load that presents the proper impedance or it will self-destruct, and an audio amplifier can possibly be destroyed by attaching it to speakers of the wrong impedance.

Hopefully that is a rare occurrence. So why do we really care about impedance mismatches? The reason is that when impedances are mismatched, the mismatch causes portions of the signal to reflect. This can happen at the source, at the connectors, at any point along the cable, or at the load and when a portion of the signal bounces backward down the line, it combines with and interferes with the portions of the signal that follow it. This is why, in the case of a impedance mismatch your audio quality suffers. With digital video these reflections can cause a "sparkle" effect in your picture or a complete loss of picture.

So, when I say that the input impedance of HD SDI input jack is 75 ohms, that’s what I mean. But what does it mean to say that the impedance of the cable between the source and display is 75 ohms?

Well, first, it doesn’t mean that the cable itself presents a 75 ohm load. If it did, the total load would now be 150 ohms, and you’d have an impedance mismatch. Furthermore, if the cable itself constituted a 75 ohm load, that load would be dependent on length. So a cable twice as long would be 150 ohms, a cable half as long would be 37.5 ohms, and so on. In case it’s not obvious by now, another thing that it doesn’t mean is that the resistance of the cable will be 75 ohms. Resistance, which also confusingly happens to be measured in ohms, has nothing to do with characteristic impedance, which can’t be measured by using a VOM.

When I say that the characteristic impedance of a cable is 75ohms, or 50, 110, 300, or what-have-you, what I mean is that if we attach a load of the specified impedance to the other end of the cable, it will look like a load of that impedance regardless of the length of the cable. The object of a 75 ohm cable is simply to "carry" that 75 ohm impedance from point A to point B, so that as far as the devices are concerned, they’re right next to one another. If we take a hundred feet of 300-ohm television twin-lead cable, solder it to RCA connectors, and stick that in between the display and an an analog device, the load, as "seen" by the analog device, will not be 75 ohms. How bad the mismatch is, and what the consequences of it are, will depend on a variety of factors, but it’s fair to say that this sort of mismatch needs to be avoided.

Transmission line impedance is critical in some applications, and not so critical in others. In analog (line level) audio, impedance has become a non-factor as designers of these circuits dispensed with the idea of matched impedance’s completely and use what is called voltage matching instead.

The idea here is to engineer the equipment to have the lowest possible output impedance and a relatively high input impedance. The difference between them must be at least a factor of ten, and is often much more. Modern equipment typically employs output impedance’s of around 150ohms or below, with input impedance’s of at least 10kohms or above. With the minuscule output impedance and relatively high input impedance, the full output voltage should be developed across the input impedance.

Relatively high-impedance inputs such as these are called bridging inputs. They have the advantage that several devices can be connected in parallel without decreasing the impedance to any significant degree. The voltage developed across each input remains high and the source does not need to supply a high current. As an example, a mixing console output is feeding two tape machines. Each machine now has an input impedance of 30kohms. Connecting two in parallel will only reduce the combined input impedance to 15kohms, which is still substantially higher than the 150ohm output impedance of the console. Therefore the input voltage will be virtually unaffected. I calculate a loss of 0.04dB. Even connecting a third device to the output, the impedance would only fall to 10kohms and the level would fall by a further 0.05dB, which would not be audible. Because bridging inputs make studio work much easier, the idea of voltage matching is now employed universally in line-level audio equipment, irrespective of the actual reference signal levels used.

Back on topic now, the behavior of cables changes as signal frequencies increase. This is so because as frequency increases, the electrical "wavelength" of a signal becomes shorter and shorter. As the length of a cable becomes closer to a large fraction of the electrical wavelength of the signal it carries, the likelihood of significant reflections from impedance mismatch increases. The whole cable can resonate at the wavelength of the signal, or of a portion of the signal, and the impact on signal quality will be anything but good. Many signals are complex, occupying not a single frequency, but a whole range of frequencies. This is why we so often speak of the "bandwidth" of a signal, and so a mismatch will affect different parts of the signal differently.

Because the effects of impedance mismatch are dependent upon frequency, the issue has particular relevance for digital signals. Where analog audio or video signals consist of electrical waves which rise or fall continuously through a range, digital signals are very different. They switch rapidly between two states representing bits, 1 and 0. This switching creates something close to what we call a "square wave,", a waveform which, instead of being sloped like a sine wave, has sharp, sudden transitions. Although a digital signal can be said to have a "frequency" at the rate at which it switches, electrically, a square wave of a given frequency is equivalent to a sine wave at that frequency accompanied by an infinite series of harmonics, that is, multiples of the frequency. If all of these harmonics aren’t faithfully carried through the cable and, in fact, it’s physically impossible to carry all of them faithfully, then the "shoulders" of the digital square wave begin to round off. The more the wave becomes rounded, the higher the possibility of bit errors becomes. The device at the load end will, of course, reconstitute the digital information from this somewhat rounded wave, but as the rounding becomes worse and worse, eventually there comes a point where the errors are too severe to be corrected, and the signal can no longer be reconstituted. The best defense against the problem is, of course, a cable of the right impedance: for digital video or SPDIF digital audio, this means a 75 ohm cable like Belden 1694A; for AES/EBU balanced digital audio, this means a 110 ohm cable like Belden 1800F.

Fortunately, for most applications, it’s very easy to choose the right impedance cable. All common analog video standards and HD SDI use 75ohm cable, as do coaxial (unbalanced) digital audio connections. If you have balanced AES/EBU type digital audio lines, you’ll want 110 ohm AES/EBU cable. There are a few others you may bump into, however, and it’s good to be aware of them. RG-58 coax, such as is often used for CB or ham radio antenna lines and CATV, is 50 ohms, not suitable for video use. Twin-lead cable, the two wires separated by a band of insulation that used to be the most common way to hook up a TV antenna is a 300 ohm balanced line.

Connectors have impedance, too, and should be matched to the cable and equipment. Many BNC connectors, especially on older cables, are 50ohm types, and so it’s important to be sure that you’re using 75 ohm BNCs when connecting video lines. RCA connectors can’t quite meet the 75 ohm impedance standard because their physical dimensions just aren’t fully compatible with it, but there are RCA plugs which are designed for the best possible impedance match with 75 ohm cable and equipment.

Coming Impedance Part II, Speakers, Amplifiers and Nominal Impedance

 


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