Sensor and Device Connectivity Solutions For Collaborative Robots

Sensors and peripheral devices are a critical part of any robot system, including collaborative applications. A wide variety of sensors and devices are used on and around robots along with actuation and signaling devices. Integrating these and connecting them to the robot control system and network can present challenges due to multiple/long cables, slip rings, many terminations, high costs to connect, inflexible configurations and difficult troubleshooting. But device level protocols, such as IO-Link, provide simpler, cost-effective and “open” ways to connect these sensors to the control system.

Just as the human body requires eyes, ears, skin, nose and tongue to sense the environment around it so that action can be taken, a collaborative robot needs sensors to complete its programmed tasks. We’ve discussed the four modes of collaborative operation in previous blogs, detailing how each mode has special safety/sensing needs, but they have common needs to detect work material, fixtures, gripper position, force, quality and other aspects of the manufacturing process. This is where sensors come in.

Typical collaborative robot sensors include inductive, photoelectric, capacitive, vision, magnetic, safety and other types of sensors. These sensors help the robot detect the position, orientation, type of objects, and it’s own position, and move accurately and safely within its surroundings. Other devices around a robot include valves, RFID readers/writers, indicator lights, actuators, power supplies and more.

The table, below, considers the four collaborative modes and the use of different types of sensors in these modes:

Table 1.JPG

But how can users easily and cost-effectively connect this many sensors and devices to the robot control system? One solution is IO-Link. In the past, robot users would run cables from each sensor to the control system, resulting in long cable runs, wiring difficulties (cutting, stripping, terminating, labeling) and challenges with troubleshooting. IO-Link solves these issues through simple point-to-point wiring using off-the-shelf cables.

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Collaborative (and traditional) robot users face many challenges when connecting sensors and peripheral devices to their control systems. IO-Link addresses many of these issues and can offer significant benefits:

  • Reduced wiring through a single field network connection to hubs
  • Simple connectivity using off-the-shelf cables with plug connectors
  • Compatible will all major industrial Ethernet-based protocols
  • Easy tool change with Inductive Couplers
  • Advanced data/diagnostics
  • Parametarization of field devices
  • Faster/simpler troubleshooting
  • Support for implementation of IIoT/Industry 4.0 solutions

IO-Link: an excellent solution for simple, easy, fast and cost-effective device connection to collaborative robots.

IO-Link reduces waste due to sensor failures

In the last two blogs we discussed about Lean operations and reducing waste as well as Selecting right sensors for the job and the environment that the sensor will be placed. Anytime a sensor fails and needs a replacement, it is a major cause of downtime or waste (in Lean philosophy). One of the key benefits of IO-Link technology is drastically reducing this unplanned downtime and replacing sensors with ease, especially when it comes to measurement sensors or complex smart sensors such as flow sensors, continuous position monitoring sensors, pressure sensors, laser sensors and so on.

When we think about analog measurement sensor replacement, there are multiple steps involved. First, finding the right sensor. Second, calibrating the sensor for the application and configuring its setpoints. And third, hope that the sensor is functioning correctly.

Most often, the calibration and setpoint configuration is a manual process and if the 5S processes are implemented properly, there is a good chance that the procedures are written down and accessible somewhere. The process itself may take some time to be carried out, which would hold up the production line causing undesired downtime. Often these mission critical sensors are in areas of the machine that are difficult to access, making replacing then, let alone configuring, a challenge.

IO-Link offers an inherent feature to solve this problem and eliminates the uncertainty that the sensor is functioning correctly. The very first benefit that comes with sensors enabled with IO-Link is that measurement or readings are in engineering units straight from the sensor including bar, psi, microns, mm, liters/min, and gallons/min. This eliminated the need for measurements to be scaled and adjusted in the programming to engineering units.

Secondly, IO-Link masters offer the ability to automatically reconfigure the sensors. Many manufacturers call this out as automatic device replacement (ADR) or parameter server functionality of the master. In a nutshell, when enabled on a specific port of the multi-port IO-Link master, the master port reads current configuration from the sensor and locks them in. From that time forward, any changes made directly on the sensor are automatically overwritten by these locked parameters. The locked parameters can be accessed and changed only through authorized users. When the time comes to replace the sensor, there is only one step that needs to happen: Find the replacement sensor of the same model and plug it in. That’s it!

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When the new sensor is plugged-in, the IO-Link master automatically detects that the replacement sensor does not have the correct parameters and automatically updates them on the sensor. Since the readings are directly in the units desired, there is no magic of scaling to fiddle with.

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It is also important to note, that in addition to the ADR feature, there may be parameters or settings on the sensors that alert you to possible near-future failure of the sensor. This lets you avoid unplanned downtime due to sensor failure. A good example would be a pressure sensor that sends an alert (event) message indicating that the ambient temperature is too high or a photo-eye alerting the re-emitted light value is down close to threshold – implying that either the lens is cloudy, or alignment is off.

To learn more about IO-Link check out our other blogs.

You have options when it comes to connecting your sensors

When it comes to connecting I/O in factory automation settings, there are many options one can choose to build an efficient and cost-effective system. This is one area where you can reduce costs while also boosting productivity.

Single Ended Cables and Hardwired I/O

It is common in the industry for single ended cables to be run from sensors to a controller input card in a centralized control cabinet. And while this method works, it can be costly for a number of reasons, including:

  • Flying leads on single ended cables are time consuming to prepare and wire
  • Wiring mistakes are often made leading to more time troubleshooting
  • I/O Cards for PLCs are expensive
  • Long cable runs to a centralized location add up quickly especially when dealing with analog devices which require expensive shielded cables
  • Lack of scalability and diagnostics

Double Ended Cables and Networked I/O

Using double ended cables along with network I/O blocks allows for a cost-effective solution to distribute I/O and increase up time. There are numerous benefits that come along with this sort of architecture. Some of these benefits are:

  • Reduced cabling — since I/O is distributed, only network cables need to be run back to the control cabinet reducing cost and cabinet size, and sensor cables are shortened since I/O blocks are machine mounted
  • Quicker build time since standard wiring is less labor intensive
  • Diagnostics allows for quicker trouble shooting, leading to lower maintenance costs and reduced downtime

IO-Link

Using IO-Link delivers all of the strengths of networked I/O as well as additional benefits:

  • I/O Hubs allow for scalability
  • Smart devices can be incorporated into your system
  • Parameterization capability
  • Increased diagnostics from intelligent devices
  • Reduced costs and downtime
  • Increased productivity

Inductive Coupling for non-contact connection

Many people are using inductive coupling technology to provide a non-contact connection for their devices. This method allows you to pass both power and signal across an air gap making it ideal for replacing slip rings or multi-pin connectors in many applications. This provides some great options for industry to gain benefits in these areas such as:

  • Reduced wear since there is no physical connection
  • Faster change over
  • Reduced downtime due to the elimination of damaged connector pins

For more information on connectivity and I/O architecture solutions please visit www.balluff.com.

Diversity in factory automation

This blog was originally posted on the Innovating Automation Blog.

Biodiversity is beneficial not only in biological ecosystems, but in industrial factory automation as well. Diversity helps to limit the effects of unpredictable events.

Typically, in factory automation a control unit collects data from sensors, analyzes this data and, according to its programmed instruction, triggers actuators to a defined operation. In most cases, a single-channel structure consisting of sensor, logic and output perfectly fulfills the application requirements. Yet in some cases two-channel structures are preferred to increase the reliability of the control concept.

Clamping control at machine tool spindles

spindle-position-control

To monitor clamping positions of tools in machine tool spindles, several options are possible: Sensors with binary output (e.g. PNP normally open) or sensors with continuous output (e.g. 0..10V or IO-Link) may be installed. The clamping process in many spindles is controlled with hydraulic actuators. This means the clamping force can be controlled by using pressure sensors which control the applied hydraulic pressure in the clamping cylinder.

The combined usage of both position and pressure sensors controls the clamping status in a better manner than using only one sensor principle. Typically, there are three clamping situations: 1) unclamped 2) clamped without object 3) clamped with object. In tooling spindles, the clamped position is usually achieved by using springs which force the mechanics to hold and clamp the object when no pressure is applied. A pneumatic or hydraulic actuator allows the worker to unclamp the object by providing force to overcome the spring load. Without hydraulic or pneumatic pressure, the clamped position should be detected by the position sensor. When enough pressure is being built up, after a short delay, the unclamped position should be achieved. Otherwise something must be wrong.

The advantage of diversity

By using two different sensor principles (in this case pressure sensing and position sensing) the risk of so-called common cause failures is reduced. The probability of concurrent effects of environmental impact on the different sensors is diminished, thereby increasing the detection rate of failures. The machine control can immediately react if the signals of pressure and position sensors do not match, simplifying monitoring of the clamping process.

Improve Your Feeder Bowl System (and Other Standard Equipment) with IO-Link

One of the most common devices used in manufacturing is the tried and true feeder bowl system. Used for decades, feeder bowls take bulk parts, orients them correctly and then feeds them to the next operation, usually a pick-and-place robot. It can be an effective device, but far too often, the feeder bowl can be a source of cycle-time slowdowns. Alerts are commonly used to signal when a feed problem is occurring but lack the exact cause of the slow down.

feeder bowl

A feed system’s feed rate can be reduced my many factors. Some of these include:

  • Operators slow to add parts to the bowl or hopper
  • Hopper slow to feed the bowl
  • Speeds set incorrectly on hopper, bowl or feed track
  • Part tolerance drift or feeder tooling out of adjustment

With today’s Smart IO-Link sensors incorporating counting and timing functions, most of the slow-down factors can be easily seen through an IIoT connection. Sensors can now time how long critical functions take. As the times drift from ideal, this information can be collected and communicated upstream.

A common example of a feed system slow-down is a slow hopper feed to the bowl. When using Smart IO-Link sensors, operators can see specifically that the hopper feed time is too long. The sensor indicates a problem with the hopper but not the bowl or feed tracks. Without IO-Link, operators would simply be told the overall feed system is slow and not see the real problem. This example is also true for the hopper in-feed (potential operator problem), feed track speed and overall performance. All critical operations are now visible and known to all.

For examples of Balluff’s smart IO-Link sensors, check out our ADCAP sensor.

Imagine the Perfect Photoelectric Sensor

Photoelectric sensors have been around for a long time and have made huge advancements in technology since the 1970’s.  We have gone from incandescent bulbs to modulated LED’s in red light, infrared and laser outputs.  Today we have multiple sensing modes like through-beam, diffuse, background suppression, retroreflective, luminescence, distance measuring and the list goes on and on.  The outputs of the sensors have made leaps from relays to PNP, NPN, PNP/NPN, analog, push/pull, triac, to having timers and counters and now they can communicate on networks.

The ability of the sensor to communicate on a network such as IO-Link is now enabling sensors to be smarter and provide more and more information.  The information provided can tell us the health of the sensor, for example, whether it needs re-alignment to provide us better diagnostics information to make troubleshooting faster thus reducing downtimes.  In addition, we can now distribute I/O over longer distances and configure just the right amount of IO in the required space on the machine reducing installation time.

IO-Link networks enable quick error free replacement of sensors that have failed or have been damaged.  If a sensor fails, the network has the ability to download the operating parameters to the sensor without the need of a programming device.

With all of these advancements in sensor technology why do we still have different sensors for each sensing mode?  Why can’t we have one sensor with one part number that would be completely configurable?

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Just think of the possibilities of a single part number that could be configured for any of the basic sensing modes of through-beam, retroreflective, background suppression and diffuse. To be able to go from 30 or more part numbers to one part would save OEM’s end users a tremendous amount of money in spares. To be able to change the sensing mode on the fly and download the required parameters for a changing process or format change.  Even the ability to teach the sensing switch points on the fly, change the hysteresis, have variable counter and time delays.  Just imagine the ability to get more advanced diagnostics like stress level (I would like that myself), lifetime, operating hours, LED power and so much more.

Obviously we could not have one sensor part number with all of the different light sources but to have a sensor with a light source that could be completely configurable would be phenomenal.  Just think of the applications.  Just think outside the box.  Just imagine the possibilities.  Let us know what your thoughts are.

To learn more about photoelectric sensors, visit www.balluff.com.

5 Ways Flexible Manufacturing has Never Been Easier

Flexible manufacturing has never been easier or more cost effective to implement, even down to lot-size-one, now that IO-Link has become an accepted standard. Fixed control and buried information is no longer acceptable. Driven by the needs of IIoT and Industry 4.0, IO-Link provides the additional data that unlocks the flexibility in modern automation equipment, and it’s here now!  As evidence, here are the top five examples of IO-Link enabled flexibility:

#5. Quick Change Tooling: The technology of inductive coupling connects standard IO-Link devices through an airgap. Change parts and End of Arm (EOA) tooling can quickly and reliably be changed and verified while maintaining connection with sensors and pneumatic valves. This is really cool technology…power through the air!

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#4. On-the-fly Sensors Programming: Many sensor applications require new settings when the target changes, and the targets seem to always change. IO-Link enables this at minimal cost and very little time investment. It’s just built in.

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#3. Flexible Indicator Lights: Detailed communication with the operators no long requires a traditional HMI. In our flexible world, information such as variable process data, timing indication, machine status, run states and change over verification can be displayed at the point of use. This represents endless creativity possibilities.

Powertrain visualisieren

 

#2. Low cost RFID: Radio Frequency Identification (RFID) has been around for a while. But with the cost point of IO-Link, the applications have been rapidly climbing. From traditional manufacturing pallets to change-part tracking, the ease and cost effectiveness of RFID is at a record level. If you have ever thought about RFID, now is the time.

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#1. Move Away from Discrete to Continuously Variable Sensors: Moving from discrete, on-off sensors to continuously variable sensors (like analog but better) opens up tremendous flexibility. This eliminates multiple discrete sensors or re-positioning of sensors. One sensor can handle multiple types and sizes of products with no cost penalty. IO-Link makes this more economical than traditional analog with much more information available. This could be the best technology shift since the move to Ethernet based I/O networks.

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So #1 was the move to Continuously Variable sensors using IO-Link. But the term, “Continuously Variable” doesn’t just roll off the tongue. We have discrete and analog sensors, but what should we call these sensors? Let me know your thoughts!

To learn more about RFID and IO-Link technology, visit www.balluff.com.

 

 

 

External Position Feedback for Hydraulic Cylinders

The classic linear position feedback solution for hydraulic cylinders is the rod-style magnetostrictive sensor installed from the back end of the cylinder. The cylinder rod is gun-drilled to accept the length of the sensor probe, and a target magnet is installed on the face of the piston. A hydraulic port on the end cap provides installation access to thread in the pressure-rated sensor tube. This type of installation carries several advantages but also some potential disadvantages depending on the application.

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Position Sensor Mounted Internally in a Hydraulic Cylinder
(Image credit: Cowan Dynamics)

Advantages of in-cylinder sensor mounting include:

  • Simplicity. The cylinder manufacturer “preps” the cylinder for the sensor and may install it as an extra-cost option.
  • Ruggedness. The sensor element is protected inside the cylinder. Only the electronics head is exposed to the rigors of the industrial environment.
  • Compactness. The sensor is contained inside the cylinder, so it does not add to the cross-sectional area occupied by the cylinder.
  • Direct Position Measurement. Because the target magnet is mounted on the piston, the sensor is directly monitoring the motion of the cylinder without any interposing linkages that might introduce some position error, especially in highly dynamic, high-acceleration / deceleration applications.

Potential disadvantages of in-cylinder sensor mounting may include:

  • Sensor Cost. Cylinder-mounted position sensors require a rugged, fully-sealed stainless-steel sensor probe to withstand the dynamic pressures inside a cylinder. This adds some manufacturing cost.
  • Cylinder Cost. The procedure of gun-drilling a cylinder rod consumes machine time and depletes tooling, adding manufacturing cost over a standard cylinder. Refer to additional comments under Small Cylinder Bores / Rods below.
  • Cylinder Delivery Time. Prepping a new cylinder for a sensor adds manufacturing time due to additional processing steps, some of which may be outsourced by the cylinder manufacturer, increasing overall shipping and handling time.
  • Overall Installed Length. Because the sensor electronics and cabling protrude from the back end of the cylinder, this adds to the overall length of the installed cylinder. Refer to additional comments under Small Cylinder Bores / Rods below.
  • Service Access. In case sensor repair is required, there must be sufficient clearance or access behind the cylinder to pull out the full length of the sensor probe.
  • Small Cylinder Bores / Rods. Some cylinder bores and rod diameters are too small to allow for gun-drilling a hole large enough to install the ~10.2 mm diameter sensor tube and allow for proper fluid flow around it. In tie rod cylinders, the distance between the rod nuts may be too small to allow the flange of the position sensor to fully seat against the O-ring. In these cases, a mounting boss must be provided to move the mounting position back past the tie rods. This adds cost as well as increases overall installed length.

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In cases where the advantages of in-cylinder mounting are outweighed or rendered impractical by some of the disadvantages, an externally-mounted position sensor can be considered. The list of advantages and disadvantages looks similar, but reversed.

FINAL Profile transducer - hydraulic frame piercing press_HF
Position Sensor Mounted Externally on Hydraulically-Actuated Equipment

Advantages of external sensor mounting include:

  • Sensor Cost. Externally-mounted magnetostrictive position sensors are typically made from an aluminum extrusion and die-cast end caps with gaskets, saving cost compared to all-stainless-steel welded and pressure-rated construction.
  • Cylinder Cost. The cylinder can be a standard type with no special machining work needed to accommodate installation of the sensor.
  • Cylinder Delivery Time. Since no additional machine work is needed, the cylinder manufacturer can deliver within their standard lead time for standard cylinders.
  • Overall Installed Length. Typically, the external sensor is mounted in parallel to the cylinder, so overall length is not increased.
  • Service Access. The externally-mounted sensor is easily accessible for service by simply unbolting its mounting brackets and pulling it off the equipment.

Disadvantages of external sensor mounting may include:

  • Complexity. The machine designer or end user must provide the means to mount the sensor brackets and the means to position a floating magnet target over the sensor housing. Alternatively, a captive sliding magnet target may be used with a length of operating rod and swivel attachment hardware.
  • Exposure to Damage. Unless guarded or installed in a protected area, an externally mounted position sensor is subject to being mechanically damaged.
  • Space Requirements. There must be enough empty space around the cylinder or on the machine to accommodate the sensor housing and operating envelope of the moving magnetic target.
  • Indirect Position Measurement. Any time a floating target magnet is mounted to a bracket, there is the potential for position error due to the bracket getting bent, flexing under acceleration / deceleration, mounting bolts loosening, etc. In the case of operating rods for captive sliding magnets, there will be some mechanical take-up in the swivel joints upon change of direction, adding to position hysteresis. There is also the potential for rod flexing under heavy acceleration / deceleration – particularly when the rod is acting under compression vs. tension. Take note of the amount of sliding friction of the captive magnet on the sensor rails; some sensor magnet designs offer high friction and stiff resistance to movement that can increase operating rod deflection and resultant position error.

In conclusion, be sure to consider all aspects of an application requiring cylinder position feedback and choose the approach that maximizes the most important advantages and eliminates or minimizes any potential disadvantages. It may be that an externally-mounted position sensor will solve some of the challenges being faced with implementing a traditional in-cylinder application.

For more information about internally- and externally-mounted cylinder position sensors, visit www.balluff.com.

How Hot is Hot? – The Basics of Infrared Temperature Sensors

Detecting hot objects in industrial applications can be quite challenging. There are a number of technologies available for these applications depending on the temperatures involved and the accuracy required. In this blog we are going to focus on infrared temperature sensors.

Every object with a temperature above absolute zero (-273.15°C or -459.8°F) emits infrared light in proportion to its temperature. The amount and type of radiation enables the temperature of the object to be determined.

In an infrared temperature sensor a lens focuses the thermal radiation emitted by the object on to an infrared detector. The rays are restricted in the IR temperature sensor by a diaphragm, to create a precise measuring spot on the object. Any false radiation is blocked at the lens by a spectral filter. The infrared detector converts radiation into an electrical signal. This is also proportional to the temperature of the target object and is used for signal processing in a digital processor. This electrical signal is the basis for all functions of the temperature sensor.

There are a number of factors that need to be taken into account when selecting an infrared temperature sensor.

  • What is the temperature range of the application?
    • The temperature range can vary. Balluff’s BTS infrared sensor, for example, has a range of 250°C to 1,250°C or for those Fahrenheit fans 482°F to 2,282° This temperature range covers a majority of heat treating, steel processing, and other industrial applications.
  • What is the size of the object or target?
    • The target must completely fill the light spot or viewing area of the sensor completely to ensure an accurate reading. The resolution of the optics is a relationship to the distance and the diameter of the spot.

  • Is the target moving?
    • One of the major advantages of an infrared temperature sensor is its ability to detect high temperatures of moving objects with fast response times without contact and from safe distances.
  • What type of output is required?
    • Infrared temperature sensors can have both an analog output of 4-20mA to correspond to the temperature and is robust enough to survive industrial applications and longer run lengths. In addition, some sensors also have a programmable digital output for alarms or go no go signals.
    • Smart infrared temperature sensors also have the ability to communicate on networks such as IO-Link. This network enables full parameterization while providing diagnostics and other valuable process information.

Infrared temperature sensors allow you to monitor temperature ranges without contact and with no feedback effect, detect hot objects, and measure temperatures. A variety of setting options and special processing functions enable use in a wide range of applications. The IO-Link interface allows parameterizing of the sensor remotely, e.g. by the host controller.

For more information visit www.balluff.com

Put Out the Fire

Every time I enter tier 1 and tier 2 suppliers, there seems to be a common theme of extreme sensor and cable abuse. It is not uncommon to see a box or bin of damaged sensors along with connection cables that have extreme burn-through due to extreme heat usually generated by weld spatter. This abuse is going to happen and is unavoidable in most cases.  The only option to combat these hostile environments is to select the correct components, such as bunker blocks, protective mounts, and high temperature cable materials that can withstand hot welding applications.

Example of bad bunkering. Sensor face not protected. Plastic brackets and standard cables used.
Example of bad bunkering. Sensor face not protected. Plastic brackets and standard cables used.

In many cases I have seen standard sensors and cables installed in a weld cell with essentially zero protection of the sensor. This results in a very non-productive application that simply cannot meet production demands due to excessive downtime. At the root of this downtime you will typically find sensor and cable failure. These problems can only go on for so long before a culture change must happen throughout a manufacturing or production plant as there is too much overtime resulting in added cost and less efficiency. I call this the “pay me now or pay me later” analogy.

Below are some simple yet effective ways to improve sensor and cable life:

Example of properly bunkered sensors with bunker block and silicone wrapped cable
Example of properly bunkered sensors with bunker block and silicone wrapped cable
  • Apply flush sensors vs. non-flush sensor in fixtures
  • Bunker the flush sensors to protect the face of the sensor (Let the bunker block take the spatter)
  • Apply sensors with special coatings to combat weld spatter
  • Apply sensors with steel faces for added insurance against contact damage
  • Apply high temp cables such as full silicone high durability offerings
  • Protect cables with silicone tubing and high temperature weld jackets
  • Wrap cables with weld repel tape to insure spatter will not penetrate the ends of the cable

If these simple steps are followed, uptime and efficiency will result in increased productivity with immediate improvements and positive results.

For information on welding improvements visit our website at www.balluff.us.