The Digital Improvement Process in Three Steps

Guest contributor: Marcel Koehler, Bosch Rexroth

Industry 4.0 solutions enable production employees to digitally replicate and implement a continuous improvement process, in order to increase output, improve product quality and reduce costs. But how do I implement a first use-case? How do I ensure the necessary plant transparency? And how do I configure the monitoring and evaluation system? Quite easily – in three steps, with easy to set up tools and tailored support by experienced experts.

20170419_graphic_ppm-process-improvment_en_web

The focus is on people.

There are fundamental principles that were in place long before digitalization. Robert Bosch once said: “People should always strive to improve the existing conditions. No one should merely be content with what they have achieved; instead they should always aspire to do what they do even better.” Today, as in the past, the path to continuous improvement of production processes starts with people. Improving quality, reducing costs or boosting output requires at least one person to design, monitor and readjust the continuous improvement process. This person defines the essential information, keeps track of it, evaluates it, intervenes when necessary and draws conclusions, in order to adapt the process. With the arrival of Industry 4.0 and the Internet of Things (IoT), however, we now have new tools at our disposal. Tools such as IoT Gateway, which collects a variety of data without interfering with the machine logic, as well as the analysis and evaluation solutions associated with it, including the Production Performance Manager, which visualizes and evaluates the data, initiates the required actions to be taken, and simplifies the review and adaptation of the improvement process.

 

Step 1: Workshop in the company

But how do I use these tools? And how do I implement a first exemplary use-case, in order to gradually introduce it? New knowledge is transferred particularly effectively from person to person, just as in Robert Bosch’s time. In line with this principle, an experienced expert comes to the company and demonstrates the typical procedure step by step as part of the Production Performance Starter Kit from Bosch Software Innovations. In the one-day workshop, he explains the digital tools as well as typical use-cases and views the production plant together with the customer. The result of the joint workshop is at least one concrete use-case, including the solution design. The desired benefits will be examined once again and potential hurdles identified. According to the same formula, the customer can later find, develop and implement additional use-cases.

infografik_ENG_16_9_img_w1184_h666The IoT Gateway collects data from various data sources and natively transfers it to the analysis and evaluation software (Production Performance Manager).

Example of a first production performance use-case

A practical example from a concrete workshop: the condition-based monitoring and maintenance of a heat exchanger. If the heat exchanger becomes clogged due to deposits, approximately 1,500 parts become defective and the plant is forced to shut down for two hours for maintenance. An early warning system should be installed, in order to prevent production rejects and unplanned downtimes. A direct measurement of the flow rate in this plant is not possible, however, which is why temperature sensors are installed before and after the heat exchanger. The IoT Gateway, which is also installed in the line, collects the sensor data and transmits it to the Production Performance Manager, where the temperature difference is determined and compared with threshold values in order to indicate contamination. All measured values are visualized centrally for the employees responsible. When the pipes begin to clog, the system transmits a warning signal or assigns a maintenance ticket to the appropriate qualified personnel.

Step 2: Implement yourself with remote support

In the second step of the Production Performance Starter Kit, a senior consultant from Bosch Software Innovations installs the Production Performance Manager via remote access to the customer’s hardware. In doing so, at least one machine is integrated as a prototype, in order to prepare the user for scaling the solution later on. The demo license is valid for three months and up to ten machines are supported. In addition, four days of remote support are included for the Production Performance Manager. Depending on the technical infrastructure, the shopfloor integration can be done in one of three ways: via individual integrators to be programmed, via PPMP-compatible controllers or system-independent integration via the IoT Gateway from Bosch Rexroth, a universal connector that communicates natively in the open source protocol PPMP in addition to other protocols. Via the web-based user interface, the user manages the sensors, defines preprocessing of the collected data if necessary, and configures forwarding to the target system, in this case to the Production Performance Manager.

Industry 4.0 Showcase with IoT Gateway and Production Performance Manager.

Step 3: On-site user training

After configuring the infrastructure, one last step remains, in which the employees learn to successfully apply the software. This takes place as part of a detailed user training course with an experienced trainer who comes to the location for one day. After this training, participants are able to gain quick access to machine data via visualization, set up simple automated analyses and evaluations, and define intelligent, data-driven actions based on the results. Following the idea of continuous improvement, they are, as the key stakeholders of their digital improvement process, also qualified to review the actions for effectiveness and efficiency. Thanks to the transparency this provides, the user now has a valuable Industry 4.0 tool for their daily work.

elemente_eng_16_9_img_w1184_h666.jpgElements of the joint starter kit from Bosch Software Innovations and Bosch Rexroth

Gradual scaling after only three months

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After only three months, employees arrive at the decisive point, from which they scale the prepared solution and repetitively connect additional machines and entire lines. As costs steadily decrease, the benefit increases disproportionately in the long run as the transparency gained gradually extends across all bottlenecks. In this manner, the production management of Bosch’s Pecinci plant (Serbia) succeeded in sustainably improving the stability of a complex coating process for wiper arms. The IoT Gateway collects sensor and controller data, such as humidity or paint consumption, and forwards the data to the Production Performance Manager. The software analyzes this data and compares it with defined threshold values, in order to optimize the plant availability of the coating plant, which consists of ten individual stations. A track & trace function, which allows conclusions to be drawn from the finished product about quality-relevant sub-processes, is planned as a follow-up project to the continuous improvement of product quality.

Do not be afraid of software! Try it out now and get started.

With the Production Performance Starter Kit, the hurdles to implementing digital processes for continuous improvement are greatly reduced. Any fears associated with the digital toolkit are completely unfounded. The IoT Gateway and the Production Performance Manager do not require any programming knowledge for daily application. Together with the methodical knowledge and practical support of our experts, companies acquire the knowledge necessary to implement their first use-case, scale the solution and tackle additional improvement projects in only three months. Robert Bosch surely would have relished the idea!

Learn more about the Production Performance Starter Kit in the webcast.

Absolutely Incremental – Innovations in Magnetic Linear Encoder Technology

Guest contributor: Scott Rosenberger, Balluff

Linear encoders – absolute or incremental?  Incremental encoders are simple, inexpensive, and easy to implement, but they require that the machine be homed or moved to a reference position.  Absolute encoders don’t require homing, but they’re usually more expensive, and implementation is a bit more involved.  What if you could get an incremental encoder that also gave you absolute position?  Would that be great, or what?  Read on.

IncrementalEncodersIncremental encoders are pretty simple and straightforward.  They provide digital pulses, typically in A/B quadrature format, that represent relative position movement.  The number of pulses the encoder sends out correspond to the amount of position movement.  Count the pulses, do some simple math, you know how much movement has occurred from point A to point B.  But, here’s the thing, you don’t actually know where you are exactly.  You only know how far you’ve moved from where you started.  You’ve counted an increment of movement.  If you truly want to know where you are, you have to travel to a defined home or reference position and count continuously from that position.

AbsoluteEncodersAbsolute encoders, on the other hand, provide a unique output value everywhere along the linear travel, usually in the form of a serial data “word”.  Absolute encoders tell you exactly (absolutely) where they are at all times.  There’s no need to go establish a home or reference position.

So absolute is better, yes?  If that’s so, then why doesn’t everyone use them instead of incremental encoders?

It’s because incremental encoders typically cost a lot less, and are much easier to integrate.  In terms of controller hardware, all you need is a counter input to count the pulses.  That counter input could be integral to a PLC, or it could take the form of a dedicated high-speed counter module.  Either way, it’s a fairly inexpensive proposition.  And the programming to interpret the pulse count is pretty simple and straightforward as well.  An absolute encoder will usually require a dedicated motion module with a Synchronous Serial Interface (SSI, BiSS, etc.).  These interfaces are going to be both more expensive and more complex than a simple counter module.  Plus, the programming logic is going to be quite a bit more involved.

So, yes, being able to determine the absolute position of a moving axis is undoubtedly preferable.  But the barriers to entry are sometimes just too high.  An ideal solution would be one that combines the simplicity and lower cost of an incremental encoder with the ability to also provide absolute position.

Fortunately, such solutions do exist.  Magnetic linear encoders with a so-called Absolute Quadrature interface provide familiar A/B quadrature signals PLUS the ability to inform the controller of their exact, absolute position.  Absolute position can be provided either on-demand, or every time the sensor is powered up.

How is this possible?  It’s really quite ingenious. You could say that the Absolute Quadrature encoders are “absolute on the inside, and incremental on the outside”.  These encoders use absolute-coded magnetic tape, and the sensing head reads that position (with resolution as fine as 1 µmeter and at lengths up to 48-meters, by the way).  But, during normal operation, the sensor head outputs standard A/B quadrature signals.  Remember though, it actually knows exactly where it is (absolute inside…remember?), and can tell you if you ask.  When requested (or on power-up, if that’s how you have it configured), the sensor head sends out a string, or burst, of A/B pulses equal to the distance between the home position and the current position.  It’s as if you moved the axis back to home position, zeroed the counter, and then moved instantly back to current position.  But no actual machine movement is necessary.  The absolute burst happens in milliseconds.

So, to sum it up, Absolute Quadrature linear encoders provide a number of advantages:

  • Economical: Compatible with standard A/B incremental interfaces – no absolute controller needed
    • No need to upgrade hardware; can connect to existing control hardware
    • Get the advantages of absolute, but maintain the simplicity of incremental; eliminate the need for homing
  • Easy implementation: Simple setup, no (or very minimal) new programming required
  • Accurate: Resolution down to 1 µm, over lengths up to 48 meters

If you’d like to learn more about linear encoders with Absolute Quadrature, go to: http://www.balluff.com/local/us/news/product-news/bml-absolute-quadrature/

cropped-cmafh-logo-with-tagline-caps.pngCMA/Flodyne/Hydradyne is an authorized  Balluff distributor in Illinois, Wisconsin, Iowa and Northern Indiana.

In addition to distribution, we design and fabricate complete engineered systems, including hydraulic power units, electrical control panels, pneumatic panels & aluminum framing. Our advanced components and system solutions are found in a wide variety of industrial applications such as wind energy, solar energy, process control and more.

Is IO-Link only for Simplifying Sensor Integration?

Guest contributor: Shishir Rege, Balluff

On several occasions, I was asked what other applications IO-Link is suitable for? Is it only for sensor integration? Well the answer is no! There are several uses for IO-Link and we are just beginning to scratch the surface for what IO-Link can do. In this blog post I will cover at least 7 common uses for IO-Link including sensor integration.
IO-Link in essence provides tremendous flexibility. Each available IO-Link port offers the possibility to connect devices from hundreds of manufacturers to build a resilient distributed modular controls architecture — that is essentially independent of the fieldbus or network. IO-Link is the first standardized sensor/actuator communication protocol as defined in IEC61131-9.

USE-CASE #1: Simplify sensor integration
Multitudes of IO-Link sensors from 100+ manufacturers can be connected using the simple 3-wire M12 prox cables. No shielded cables are required. Additionally, using IO-Link provides a parameterization feature and anti-tampering abilities- on the same 3 wires. The sensor can be configured remotely through a PLC or the controller and all the configuration settings can be stored for re-application when the sensor is replaced. This way, on your dreaded night shift changing complex sensor is just plug-n-play. Recipe changes on the line are a breeze too. For example, if you have an IO-Link color sensor configured to detect a green color and for the next batch you want to start detecting red color- with IO-Link it is simply a matter of sending a parameter for the color sensor – instead of sending a maintenance person to change the settings on the sensor itself — saving valuable time on the line.
color sensors

USE-CASE #2: Simplify analog sensor connections
In one of my previous blogs, “Simplify your existing analog sensor connection”, I detailed how connecting an analog sensor with single or multi-channel analog-to-IO-Link (A/D) converters can eliminate expensive shielded cables and expensive analog cards in the controller rack and avoids all the hassle that comes with the analog sensors.

USE-CASE #3: Simplify RFID communication
IO-Link makes applications with RFID particularly intriguing because it takes all the complexity of the RFID systems out for simple applications such as access control, error-proofing, number plate tracking and so on. In an open port on IO-Link master device you can add read/write or read only RFID heads and start programming. A couple of things to note here is this IO-Link based RFID is geared for small data communication where the data is about 100-200 bytes. Of-course if you are getting into high volume data applications a dedicated RFID is preferred. The applications mentioned above are not data intensive and IO-Link RFID is a perfect solution for it.

USE-CASE #4: Simplify Valve Integration
valve manifoldTypically valve banks from major manufacturers come with a D-sub connection with 25 pins. These 25 wires are now required to be routed back to the controls cabinet, cut, stripped, labeled, crimped and then terminated. The other expensive option is to use a network node on the valve bank itself, which requires routing expensive network cable and power cable to the valve bank. Not to mention the added cost for the network node on the valve bank. Several manufacturers now offer IO-Link on the valve manifold itself simplifying connection to 4-wires and utilizing inexpensive M12 prox cables. If you still have the old D-sub connector, an IO-Link to 25-pin D-sub connectors may be a better solution to simplify the valve bank installation. This way, you can easily retrofit your valve bank to get the enhanced diagnostics with IO-Link without much cost. Using IO-Link valve connectors not only saves time on integration by avoiding the labor associated with wire routing, but it also offers a cost effective solution compared to a network node on the valve manifold. Now you can get multiple valve manifolds on the single network node (used by the IO-Link master) rather than providing a single node for each valve manifold in use.

USE-CASE #5 Simplify Process Visualization
Who would have thought IO-Link can add intelligence to a stack light or status indicator? Well, we did. Balluff introduced an IO-Link based fully programmable LED tower light system to disrupt the status indicator market. The LED tower light, or SmartLight, uses a 3-wire M12 prox cable and offers different modes of operations such as standard stack light mode with up to 5 segments of various color lights to show the status of the system, or as a run-light mode to display particular information about your process such as system is running but soon needs a mechanical or electrical maintenance and this is done by simply changing colors of a running segment or the background segment. Another mode of operation could be a level mode where you can show the progress of process or show the fork-lift operators that the station is running low on parts. Since the Smartlight uses LEDs to show the information, the colors, and the intensity of the light can be programmed. If that is not enough you can also add a buzzer that offers programmable chopped, beep or continuous sound. The Smartlight takes all of the complexity of the stack light and adds more features and functions to upgrade your plant floor.

USE-CASE #6: Non-contact connection of power and data exchange
Several times on assembly lines, a question is how to provide power to the moving pallets to energize the sensors and I/O required for the operation? When multi-pin connectors are used the biggest problem is that the pins break by constantly connecting or disconnecting. Utilizing an inductive coupling device that can enable transfer of power and IO-Link data across an air-gap simplifies the installation and eliminates the unplanned down-time. With IO-Link inductive couplers, up to 32 bytes of data and power can be transferred. Yes you can activate valves over the inductive couplers!  More on inductive coupling can be found on my other series of blogs “Simple Concepts for Complex Automation”

USE-CASE #7: Build flexible high density I/O architectures.
IO PointsHow many I/O points are you hosting today on a single network drop? The typical answer is 16 I/O points. What happens when you need one additional I/O point or the end-user demands 20% additional I/O points on the machine? Until now, you were adding more network or fieldbus nodes and maintaining them. With I/O hubs powered by IO-link on that same M12 4-wire cable, now each network node can host up to 480 I/O points if you use 16 port IO-Link masters. Typically most of our customers use 8-port IO-Link masters and they have the capacity to build up to 240 configurable I/O on a single network drop. Each port on the I/O hub hosts two channels of I/O points with each channel configurable as input or output, as normally open or normally closed. Additionally, you can get diagnostics down to each port about over-current or short-circuit. And the good thing is, each I/O hub can be about 20m away.

In a nutshell, IO-Link can be used for more than just simplifying sensor integration and can help significantly reduce your costs for building flexible resilient controls architectures. Still don’t believe it? Contact us and we can work through your particular architecture to see if IO-Link offers a viable option for you on your next project.

cropped-cmafh-logo-with-tagline-caps1.pngCMA/Flodyne/Hydradyne is an authorized  Balluff distributor in Illinois, Wisconsin, Iowa and Northern Indiana.

In addition to distribution, we design and fabricate complete engineered systems, including hydraulic power units, electrical control panels, pneumatic panels & aluminum framing. Our advanced components and system solutions are found in a wide variety of industrial applications such as wind energy, solar energy, process control and more.

How do I make my analog sensor less complex?

Guest contributor: Shishir Rege, Balluff

So, you have a (or many) analog sensor in your application or system and they could be 4-20mA signal or 0-10V or even -10- +10V signal strength. You probably know that installing these specialty sensors takes some effort. You need shielded cables for signal transmission, the sensor probably has some digital interface for set-point settings or configuration. In all, there are probably 6-8 at minimum terminations for this single sensor. Furthermore, these expensive cables need to be routed properly to ensure minimal electromagnetic interference (EMI) on the wire. To make matter more complex, when its time to diagnose problem with the sensor, it is always on the back of your mind that may be the cable is catching some interference and giving improper readings or errors.

shieldedCablesOn the other hand, the cost side also is little tricky. You have the state of the art sensor that requires expensive shielded cable and the expensive analog input card (which generally has 4 channels- even if you use single channel), plus some digital I/O to get this single sensor to communicate to your PLC/PAC or controller. You are absolutely right, that is why people are demanding to have this sensor directly on their network so that it eliminates all the expensive cables and cards and talks directly to the controller on express way– so to speak.

Recently, there has been an explosion of industrial communication networks and fieldbuses. To name a few: EtherNet/IP, DeviceNet, PROFINET, PROFIBUS, CC-Link, CC-Link IE, Powerlink, Sercos, and the list goes on. As a machine builder, you want to be open to any network of customer’s choice. So, if that is the case, having network node on the sensor itself would make that sensor more bulky and expensive than before — but not only that, now the manufacturers have to develop sensor connectivity to ALL the networks and maintain separate inventory of each type. As a machine builder, it does put lot more stress on you as well to maintain different Bills of Materials (BOMs) for different projects – most likely – different sourcing channels and so on.

NetworksSo far what we discussed are two extremes; the way of the past with shielded cables and analog cards, and a wishful future where all devices are on the network. There is a middle ground that bridges yesterday’s method and the wishful future without adding any burden on manufacturers of the sensors or even the machine builders. The solution is IO-Link. IO-Link is the first standard (IEC 61131-9) sensor actuator communication technology. There are over 100+ members in the consortium that produce wide variety of sensors that can communicate over IO-Link.

If a sensor has IO-Link communication, denoted by  io-linklogo, then you can connect a standard M12 prox cable — let me stress– UNSHIELDED, to connect the sensor to the IO-Link port on the IO-Link master device. That’s it! No need to terminate connections, or buy expensive hardware. The IO-Link master device typically has 4, 8 or 16 ports to connect various IO-Link devices including I/O hubs, RFID, Valve connectors and more. (see picture below)

DistModIO

All signal communication and configuration now occurs on standard 3 conductor cable that you are currently using for your discrete sensors. The IO-Link master in turn acts as a gateway to the network. So, the IO-Link master sits on the network or fieldbus and collects all the sensors or discrete I/O information from devices and sends it to the controller or the PLC of the customer choice.

When your customer demands a different network or the fieldbus, the only thing that changes in your question is the master that talks to a different protocol.

In my next blog we will discuss how you can eliminate shielded cables and expensive analog cards for your existing analog sensor. Let me give you a hint– again the solution is with IO-Link.

cropped-cmafh-logo-with-tagline-caps1.pngCMA/Flodyne/Hydradyne is an authorized  Balluff distributor in Illinois, Wisconsin, Iowa and Northern Indiana.

In addition to distribution, we design and fabricate complete engineered systems, including hydraulic power units, electrical control panels, pneumatic panels & aluminum framing. Our advanced components and system solutions are found in a wide variety of industrial applications such as wind energy, solar energy, process control and more.

Solving Analog Integration Conundrum

Guest contributor: Shishir Rege, Balluff

These days, there are several options to solve the integration problems with analog sensors such as measurement or temperature sensors. This blog explains the several options for analog integration and the “expected” benefits.

Before we describe the options, let’s get a few things cleared up.  First, most controllers out there today do not understand analog at all: whenever a controller needs to record an analog value, an analog-to-digital converter is required.  On the other end of the equation is the actual sensor measuring the physical property, such as distance, temperature, pressure, inclination, etc.  This sensor, a transducer, converts the physical property into an analog signal.  These days with the advanced technologies and with the cost of microprocessors going down, it is hard to find a pure analog device.  This is because the piezo-electronics inside the sensor measures the true analog signal, but it is converted to a digital signal so that the microprocessor can synthesize it and convert it back to an analog signal.  You can read more about this in a previous blog of mine “How Do I Make My Analog Sensor Less Complex?

Now let’s review the options available:

  1. The classical approach: an analog to digital converter card is installed inside the control cabinet next to the controller or a PLC. This card offers 2, 4, or even 8 channels of conversion from analog to digital so that the controller can process this information. The analog data can be a current measurement such as 0-20mA or 4-20mA, voltage measurement such as 0-10V, +5- -5V etc., or a temperature measurement such as PT100, PT1000, Type J, Type K and so on.  Prior to networks or IO-Link, this was the only option available, so people did not realize the down-side of this implementation.  The three major downsides are as follows:
  • Long sensor cable runs are required from the sensor all the way to the cabinet, and this required careful termination to ensure proper grounding and shielding.
  • There are no diagnostics available with this approach: it is always a brute-force method to determine whether the cable or the actual transducer/sensor has the issue. This causes longer down-times to troubleshoot problems and leads to a higher cost to maintain the architecture.
  • Every time a sensor needs to be replaced, the right tools have to be found (programming tools or a teaching sequence manual) to calibrate the new sensor before replacement. Again, this just added to the cost of downtime.
  1. The network approach — As networks or fieldbuses gained popularity, the network-based analog modules emerged. The long cable runs became short double-ended pre-wired connectors, significantly reducing the wiring cost. But this solution added the cost of network node and an additional power drop.  This approach did not solve the diagnostic problems (b) or the replacement problem above (c ). The cost of the network analog module was comparable to the analog card, so there was effectively no savings for end users in that area.  As the number of power drops increase, in most cases, the power supply becomes bigger or more power supplies are required for the application.
  2. The IO-Link sensor approach is a great approach to completely eliminate the analog hassle altogether. As I mentioned earlier, since the sensor already has a microprocessor that converts the signal to digital form for synthesis and signal stabilization, why not use that same digital data over a smarter communication to completely get rid of analog? In a nutshell, the data coming out of the sensor is no longer an analog value; instead it is a digital value of the actual result. So, now the controller can directly get the data in engineering units such as psi, bar, Celsius, Fahrenheit, meters, millimeters, and so on. NO MORE SCALING of data in the controller is necessary, there are no more worries of resolution, and best of all enhanced diagnostics are available with the sensor now. So, the sensor can alert the controller through IO-Link event data if it requires maintenance or if it is going out of commission soon.  With this approach, the analog conversion card is replaced by the IO-Link gateway module which comes in 4-channels or 8 channels.

Just to recap about the IO-Link sensor:

  1. IO-Link eliminated the analog cable hassle
  2. IO-Link eliminated the resolution and scaling issue
  3. IO-Link added enhanced diagnostics so that the end users can perform predictive maintenance instead of preventative maintenance.
  4. The IO-Link gateway modules offers configuration and parameter server functionality that allows storing the sensor configuration data either at the IO-Link master port or in the controller so that when it is a time to replace the sensor, all that is required is finding the sensor with the same part number and plugging it in the same port — and the job is done! No more calibration required. Of course, don’t forget to turn on this functionality on the IO-Link master port.

Well, this raises two questions:

  1. Where do I find IO-Link capable sensors? The answer is simple: the IO-Link consortium (www.IO-Link.com) has over 120 member companies that develop IO-Link devices. It is very likely that you will find the sensor in the IO-Link version. Want to use your existing sensor?  Balluff offers some innovative solutions that will allow you bring your analog sensor over to IO-Link.
  2. What is a cost adder for this approach? Well, IO-Link does a lot more than just eliminate your analog hassle. To find out more please visit my earlier blog “Is IO-Link only for Simplifying Sensor Integration?

 

cropped-cmafh-logo-with-tagline-caps1.pngCMA/Flodyne/Hydradyne is an authorized  Balluff distributor in Illinois, Wisconsin, Iowa and Northern Indiana.

In addition to distribution, we design and fabricate complete engineered systems, including hydraulic power units, electrical control panels, pneumatic panels & aluminum framing. Our advanced components and system solutions are found in a wide variety of industrial applications such as wind energy, solar energy, process control and more.

Decentralized Control Systems to the Rescue

Guest contributor,  Bob White, Kollmorgen

Less Cabling, Smaller controls cabinet, Less heat…wow, that’s all great stuff.  I can achieve this all with a decentralized solution? Absolutely – and even more! 

Decentralized Control Architecture means shifting the motion control drives from the crowded cabinets, and moving them near to the motors – out on the machine where the action is.  Immediately you can see that this can reduce the size of the controls cabinet, moving all of those drives out onto the machine – but how do I see these other advantages?

Decentralized ArchitectureIt’s not JUST about moving the drives out onto the machine, near or integrated with the motors, but also how you design your entire control system.  Think about a conventional Centralized Control Architecture – all of your drives, power supplies and other I/O are jammed into a large cabinet and cables are run to each motor – and since we are talking conventional, this likely means multiple cables (power and feedback for each motor). So in a decentralized solution, the motor, feedback and fieldbus communication needs to be run through a single cable, and the control architecture  allows communications to function over the fieldbus loop.

So thinking about it that way, with an 8 axis machine – Control cabinet 5 meters from the initial motor, and subsequent axes 3 meters apart – this adds up quickly to almost 250 meters of cabling (Power and Feedback) using a centralized approach.

Centralized vs Decentralized ImageImagine now – A decentralized solution, drives located within a meter of the motor they are driving – you cut cabling down to a mere 35 meters!  Do the math – an 86% reduction!  Throw in extended I/O and your savings jumps to almost 90%  SO – Point 1 – Substantially reduced cables cost – not just from the mere reduction in cable length, but in reduced costs associated form cable management trays and even the labor to run the cables.

But there’s more (or do I mean less).  Smaller cabinet, less electronics, means less heat to dissipate – electronics usually don’t like the heat, so they tend to get some cool air, provided by some nice air conditioning system.  Less heat, less need for an expensive air conditioning unit, AND less energy consumption.

One other element not so readily apparent with a good decentralized design – flexibility!  Designing with a decentralized drive architecture in mind from the start opens up new possibilities.  This allows more flexibility in modularization.  We’ll cover this modularization concept in a follow on blog topic next time…

All of these advantages help the OEM build a more efficient machine, with less components, reduction in assembly time, and more flexibility in design – improving the marketability of the machine.  End users enjoy the lower cost of ownership and increase reliability – and potentially space savings on their factory floor.

Decentralized Machine Vision

cropped-cmafh-logo-with-tagline-caps.png

CMA/Flodyne/Hydradyne is an authorized  Kollmorgen distributor in Illinois, Wisconsin, Iowa and Northern Indiana.In addition to distribution, we design and fabricate complete engineered systems, including hydraulic power units, electrical control panels, pneumatic panels & aluminum framing. Our advanced components and system solutions are found in a wide variety of industrial applications such as wind energy, solar energy, process control and more.

What is a Capacitive Sensor

Guest contributor:  Jack Moermond, Balluff

Capacitive proximity sensors are non-contact devices that can detect the presence or absence of virtually any object regardless of material.  They utilize the electrical property of capacitance and the change of capacitance based on a change in the electrical field around the active face of the sensor.

Capacitive sensing technology is often used in other sensing technologies such as:

  • flow
  • pressure
  • liquid level
  • spacing
  • thickness
  • ice detection
  • shaft angle or linear position
  • dimmer switches
  • key switches
  • x-y tablet
  • accelerometers

Principle of operation

A capacitive sensor acts like a simple capacitor.  A metal plate in the sensing face of the sensor is electrically connected to an internal oscillator circuit and the target to be sensed acts as the second plate of the capacitor.  Unlike an inductive sensor that produces an electromagnetic field a capacitive sensor produces an electrostatic field.

The external capacitance between the target and the internal sensor plate forms a part of the feedback capacitance in the oscillator circuit.  As the target approaches the sensors face the oscillations increase until they reach a threshold level and activate the output.

Capacitive sensors have the ability to adjust the sensitivity or the threshold level of the oscillator.  The sensitivity adjustment can be made by adjusting a potentiometer, using an integral teach pushbutton or remotely by using a teach wire.  If the sensor does not have an adjustment method then the sensor must physically be moved for sensing the target correctly.  Increasing the sensitivity causes a greater operating distance to the target.  Large increases in sensitivity can cause the sensor to be influenced by temperature, humidity, and dirt.

There are two categories of targets that capacitive sensors can detect the first being conductive and the second is non-conductive.  Conductive targets include metal, water, blood, acids, bases, and salt water.  These targets have a greater capacitance and a targets dielectric strength is immaterial.  Unlike an inductive proximity sensor, reduction factors for various metals are not a factor in the sensors sensing distance.

The non-conductive target category acts like an insulator to the sensors electrode.  A targets dielectric constant also sometimes referred to as dielectric constant is the measure of the insulation properties used to determine the reduction factor of the sensing distance.  Solids and liquids have a dielectric constant that is greater than vacuum (1.00000) or air (1.00059).  Materials with a high dielectric constant will have a longer sensing distance.  Therefore materials with high water content, for example wood, grain, dirt and paper will affect the sensing distance.

When dealing with non-conductive targets there are three factors that determine the sensing distance.

  • The size of the active surface of the sensor – the larger the sensing face the longer the sensing distance
  • The capacitive material properties of the target object, also referred to as the dielectric constant – the higher the constant the longer the sensing distance
  • The surface area of the target object to be sensed – the larger the surface area the longer the sensing distance

Other factors that have minimal effect on the sensing distance

  • Temperature
  • Speed of the target object

Sensing range

A capacitive sensor’s maximum published sensing distance is based on a standard target that is a grounded square metal plate (Fe 360) that is 1mm thick.  The standard target must have a side length that is the diameter of the registered circle of the sensing surface or three times the rated sensing distance if the sensing distance is greater than the diameter.  Objects being detected that are not metal will have a reduction factor based on the dielectric constant of that object material.  This reduction factor must be measured to determine the actual sensing distance however there are some tables that will provide an approximation of the reduction factor.

Rated or nominal sensing distance Sn is a theoretical value that does not take into account manufacturing tolerances, operating temperatures and supply voltages.  This is typically the sensing distance listed in various manufactures catalogs and marketing material.

Effective sensing distance Sr is the switching distance of the sensor measured under specified conditions such as flush mounting, rated operating voltage Ue, temperature Ta = 23°C +/- 5°C.  The effective sensing range of capacitive sensors can be adjusted by the potentiometer, teach pushbutton or remote teach wire.

Hysteresis

Hysteresis is the difference in distance between the switch-on as the target approaches the sensing face and switch-off point as the target moves away from the sensing face.  Hysteresis is designed into sensors to prevent chatter of the output if the target was positioned at the switching point.

Hysteresis stated in % of rated sensing distance.  For example a sensor with 20mm of rated sensing distance may have a maximum hysteresis of 15% or 3mm.  Hysteresis is an independent parameter that is not a constant and will vary sensor to sensor.  There are several factors that can influence hysteresis including:

  • Sensor temperature both ambient and heat generated by the sensor being powered
  • Atmospheric pressure
  • Relative humidity
  • Mechanical stresses to the sensor housing
  • Electronic components utilized on the printed circuit board within the sensor
  • Correlated to sensitivity – higher sensitivity relates to higher rated sensing distance and a larger hysteresis

How to determine a capacitive sensor’s sensitivity

Capacitive sensors have a potentiometer or some method to set the sensor sensitivity for the particular application.  In the case of a potentiometer, the number of turns does not provide an accurate indicator of the sensors setting for a couple of important reasons.  First, most potentiometers do not have hard stops instead they have clutches so that the pot is not damaged when adjusted to the full minimum or maximum setting.  Secondly, pots do not have consistent linearity.

To determine the sensitivity of a capacitive sensor the sensing distance is measured from a grounded metal plate with a micrometer.  The plate is grounded to the negative of the power supply and the target is moved axially to the sensors face.  Move the target out of the sensing range and then move it towards the sensor face.  Stop advancing the target as soon as the output is activated.  This distance is the sensing distance of the sensor.  Moving the target away and noting when the output turns off will provide the hysteresis of the sensor.

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