This has been changing in recent years with a growing number of mechatronic programs at major universities and wildly popular programs like the First Robotics Competition.  Interest in mechatronics has spawned a wave of contests sponsored by manufacturers to educate young people about the technology and make future customers in the process.  The greater benefit is the number of creative individuals being exposed to the technology in grade school and high school.  Undoubtedly, we will all be the beneficiaries of some new inventions that will be coming in the future.

But there are still some interesting subtleties that arise in motion control.  A common problem is defining coordinated motion.  This is because the precise behavior has to be described BOTH as mechanical objectives and correctly modeled in the control system hardware.

There can be many axes of motion in a particular machine.  But they are rarely coordinated in the absolute sense.  And this is an important distinction to keep in mind during design of the control system.  Most of the axes, maybe 80% of them, will require a start signal to coordinate their operation while the equipment is operating.  Rarely do the axes require time synchronous control.

Want to know the secret?  Simple. Think of a machine that does “Tic Tac Toe” versus one that “Draws a Circle”. Tic Tac Toe can be done with simple Cartesian linear axes with no coordination, other than a start bit and a done bit.  You can have a busy signal if you want to get fancy.

Ever try to draw a circle with an Etch a Sketch?  It is harder than it looks.  Because every tiny point must be coordinated between the two separate sources of motion.

And when you draw a circle, what happens as the time constraint is decreased?  As you go faster the acceleration and inflection points of motion become much more critical.  Generally, this produces increasing error in the actual trajectory.

Which leads to the “Stump the Band” question for would-be mechatronics engineers.  What is the one variable that connects all aspects of mechanical motion and electrical control together?  Time

And there is no end of importance in this fact.

When you try to Draw A Circle, time is absolutely essential.  The incremental change in time, delta-t, will impact how precise the circle is.  And the control system programming and execution will not be of much help in regulating this.  Neither will servo tuning.

For those of you planning a multi-axis system, let me share one further time-oriented thought.  When you have two truly coordinated axes, and they can be anything, a servo following an ac frequency drive (don’t laugh, I did this once and it worked great) make sure that if you are using a PLC that the coordinated axes are on the same control module.

Most PLC’s use a separate processor to run up to 4 axes of motion at a time.  The slave axes have to all have to be on the same module or the backplane update will limit the performance of the motion.  You will see perfect performance up to some speed and then synchronism will be lost because the new position update is going through the backplane and the servo is being commanded to follow old position information.

More on this next time.

The US Department of Defense (DoD) has been seeking a way to reduce the cost of producing cast spare parts. The Advanced Technology Institute (ATI) currently leads several national collaborations that are developing advanced robotics capabilities and implementing both new and existing robotics technologies in response to the DoD’s need.

One collaboration is with the American Metalcasting Consortium (AMC). The ATI-managed AMC partner companies, like Clinkenbeard, are using robotics technologies to support legacy weapon systems; which could help meet the Defense Logistic Agency’s goal of dramatically shorter lead times for the production of legacy weapon systems parts. The patented Clinkenbeard® Toolingless Process proved that it could reduce lead times for military cast spare parts from six to twelve months to six to twelve days.

The results, according to ATI, also demonstrated that the Toolingless Process can reduce capital investment by as much as 35%, reduce individual parts cost by up to 20%, and improve cycle time by 25%.

Lead times often exceed a year because technical data may require reworking, including the development of a solid model of the part. But, even when a solid model is generated first, the Clinkenbeard process can supply a cast part in less than a month. The secret is computer-generated molds with no tooling.

The Toolingless Process consists of machining sand cores and molds, and is accurate. According to the company, this process can reduce the lead-time to obtain development castings by up to 90%. With this process, you can:

• eliminate the need for prototype tooling, depending on project requirements.

• make and test multiple design iterations during product development, from the simple to complex parts.

• reduce the cost of production tooling for one-of and small quantities.

• obtain accurate, prototype parts while large quantity tooling is made.

• eliminate tooling inventory.

• match exact production core materials and chemical levels so that prototype castings emulate production.

• incorporate engineering changes into high-volume production sand cores.

Clinkenbeard developed the sand machining process using CNC machining centers. By using robots with sand machining, company technicians can use the process on much larger molds and cores. Robotic technology will reduce the cost dramatically compared to the same expenditure for CNC machining centers.

Clinkenbeard
www.clinkenbeard.com

American Metal Consortium

http://amc.aticorp.org/

Defense Logistic Agency
www.dla.mil

Advanced Technology Institute (ATI)
www.aticorp.org

Part of the problem may have to do with our use of the word “intelligence”.  We talk about the increasing “intelligence” of processors and particularly about the cost of “intelligent” control dropping to the point where it is suddenly economical to put a microcontroller together with a motor in order to achieve new levels of performance in either energy management or some other critical parameter.  Which opens new performance capability in robot design.

Increasingly, industrial robotics involve the use of vision systems to acquire information about the location and orientation of parts so that the robot system can interface smoothly to the “real world”.  If any of you have been to an industrial trade show and witnessed the Delta Robots making cookies, it is a very impressive sight to behold.  Incredible throughput and accuracy.  And that’s what it’s all about in industry. Higher productivity, improved product quality.

But where is the line between remote control and automatic control?  A remote manipulator for working in the nuclear industry, which was the big application that drove early robots, is a remote servo loop operating a series of servo motors and controls and powering mechanical systems, in order to do work that is dangerous to humans from a safe distance.  The DaVinci medical robot is a phenomenally improved version of the same thing.  A remote controlled robot, guided by direct haptic inputs from a surgeon, and with very sophistical tactile feedbacks, whose end effectors operate a variety of surgical instruments and actually increase the precision and speed with which doctors may perform certain procedures.

Is this a robot? Sure!

When we watch welding and painting robots making cars, we are watching decades of technology development in action.  There has been significant effort to improve the actuator hardware, and probably many man-years of software development to improve our description of the task and its safety and performance constraints in order to create not only reliable, but increasingly efficient machines to do the tasks that humans cannot compete with for productivity.  These are very sophisticated automatic applications, but certainly not autonomous.  The boundaries of the application and the programming for it are very finite.  Again, its about repetition, speed and accuracy.

And, yes, we call these robots, too.

But increasingly, there is discussion about the next frontier of robotics.  Where are the next big apps coming from?  Most of the big robotic companies in Japan and Europe are talking about personal service robots.  You can let your imagination run wild here.  Anything is possible. Certainly the service robot for NASA is interesting because it, again, follows the concept of doing tasks where it is difficult for humans to operate.

Is a Jeep that can be programmed to find a path and drive from one place to another autonomously a robot?  Yes, but we may be pushing the boundaries here just a bit.  These applications fall into the realm of Artificial Intelligence.  The programming and software languages for which were just being described for the first time about 30 years ago.  And at this point we are forced into the debate about what is intelligence.  In addition, are these systems which are capable of “learning” and what is learning exactly?  And more importantly, as all good science fiction movie watchers will ask, can a machine exceed it’s programming?  (See?  I didn’t even start on consciousness yet)

These are all serious considerations for the Future of Robotics which I will pick up further next week.

Obviously, this type of metric will vary wildly depending on how highly automated a particular industry is.  The beverage industry is highly automated and doesn’t have a large employee staff to generate finished products.  But interestingly, the companies that build machinery for the beverage industry have fairly high employment because it takes a combination of technically trained skilled workers to make the machinery that makes the beverage products.

The agricultural economy has grown dramatically with the introduction of machinery to assist in the process. Complex machines have been developed for many applications to increase productivity.  The latest round of enhancements are tilling and planting equipment that uses Global Positioning Satellite information to keep the tractors in a straight line and computer plots of the land to maximize the planting area per acre.  Pretty amazing stuff.

In the automotive area, there are some interesting statistics.  In the ten year period from 1998 to 2008 the industry increased its gross output per employee by 33%.  This is a huge statistic and represents the long term impact of automation on the manufacture of vehicles.  The other interesting statistic is that the average internal price of a car today is the same as that ten years ago.  Given that the US industry has pushed it’s quality to compete with the Japanese cars that were perceived as superior to US in quality, this is an amazing feat.

Of greater interest is the comparison of total vehicle shipments.  The most cars and light trucks ever shipped by the US Auto makers was in the year 2000 when we shipped 17.8 million units according to Ward’s Auto which reports on the car industry.  This feat was almost duplicated in 2005 when 17.4 mil units were shipped.

A relatively stable manufacturing base over the years, the US auto industry hit a disastrous slide in 2008 shipping an anemic 13.49 mil units followed by an even worse 2009 when we shipped 10.6 mil cars and trucks.  This was the year in which the Chinese automakers topped the US manufacturing rate for the first time ever.  A point that the Chinese press made with great vigor in spite of the fact that the majority of Chinese automakers are actually joint ventures with foreign companies, the single original Chinese auto maker being in great difficulties due to poor product quality.

The 2009 US auto showing is particularly dismal when you consider the “cash for clunkers” incentive which spent $1.4 billion taxpayer dollars to generate 200,000 additional unit sales.  A small showing in the scheme of things even if the market was 10 million units.

Will the US auto market pick back up? Certainly, but not to the former highs of 2000 and 2005.  2009 shipments were off by 40% from the 2005 high, and that is too much of a gap to be easily recovered.  Especially when unemployment continues to be running in the 10% range and higher.

Is there hope?  Yes.  Serious electric hybrids and battery manufacturing for the US automakers will create tens of thousands of jobs in the next couple of years.  Demand for foreign hybrids has been running at over 400,000 units per year, and will likely increase once there are quality US made products available.

States that pay attention to the needs of the industries they provide locations for are States that will thrive with low unemployment and low deficits.

Which is saying a lot.

Some of that economic activity is the obvious stuff.  Jobs.  Making things that are important to the industry.  Like all the silicon ingot, water treatment, chip encapsulation compounds, chemical solvents, and gases that are needed.  And all of those feedstocks require people in their respective industries.

There is also the capital equipment market.  Companies that make machines that make chips.  Machines that grow silicon ingots, machines that slice silicon into thin wafers.  Polishing machines that make the surface smooth enough to create the nanometer sized features that become semiconductors.  Wafer probing machines that do functional testing, dicing machines that slice the wafer into the single chips, wire bonding the bare die into lead frames to we can attach the circuits.  Encapsulation, labeling, testing and packaging the final products.

The Semiconductor Industry Machinery business is estimated to be an $11B activity separate from the sale of chips.  The semiconductor equipment market is still the largest target market for motion control products and mechatronics of any market I know of.  At a close second place would be the electronic assembly machinery market  with it’s pick and place, adhesive dispensers and inspection machinery.

Interestingly, the semiconductor industry also provides trickle down technology.  Hard disk drive spindle motors require the exact same 3 phase brushless drive and control as industrial servo motors.  The difference is that the spindle motor is manufactured in quantities of tens of millions of units.  This allows disk drive manufacturers to explore the ultimate boundaries of cost reducing the technology and introducing new techniques to improve performance.  Much of this technology has migrated to the motion control industry in the way of integrated motor control chips.

The semiconductor industry is now made up of two major markets.  Chips and Solar Cells. The solar cell market is counted separately and does not overlap with traditional semiconductor business.  Many of the companies that make semiconductor machinery have extended their capabilities to the solar industry as a way of diversifying into new markets and making up the lost ground that was experienced in the machinery business.

While Solar is still an emerging industry to some extent, it will continue to drive large segments of the economy. Solar photovoltaics and solar hot water drive a lot of jobs in manufacturing and installation of systems.

What we need in the public policy sector is better understanding of the business needs that these industries require.  Generating enough electricity for these industries to thrive is one requirement.  And most states in the US have failed to bring any new capacity on line over the last 30 years. States that recognize these needs and are willing to meet them are going to be the States that prosper with low unemployment and thriving economies.  And that’s where we all want to be.

Categorizing linear actuators is not entirely straightforward because many categories overlap.  The “motive power” category can be any type of power source, rotary motor or linear motor powered.  Linear motor solutions are much more commonplace in linear actuators today due to declining costs for this technology choice.  But in a linear motor based actuator, the linear motor is both the motive power and the mechanical transmission at the same time.

Categorizing linear actuators by their mechanical transmission style is another approach.  The most common categories are screw type, belt and linear motor.   But the motive power for a screw based actuator could be a stepping motor or a servo motor.  The stepping motor is predominant because of it’s suitability for positioning, but it may be underpowered for some applications where a servo is needed.   So the linear actuator transmission category can have overlaps because of the different motor types that are used in conjuncion with it.

Price seems to be one means of eliminating the ambiguity.  Stepping motor and lead screw combinations are popular because they are economical and maintaining 0.001″ accuracy is very easy.   Linear motor systems are capable of .5 micron accuracy with little or no friction, acceleration and speed that is incredible, but generally the higher performance comes at a higher price.

But in the end, the selection process is best guided by the criteria of the application.  The list is, thankfully, short.  Load weight or force that must be generated, speed, accuracy and life expectancy or number of cycles of operation.  This last is probably the key determinant in system selection.  Long life or high cycling goals lead to linear motors actuators with little or no friction. You have to familiarize yourself with the overall field because the tendency of confusing the technology and the application needs.

At the recent Semicon gathering of manufacturers involved in semiconductor manufacturing, a lot of attention is given to the mechatronic content of machinery.  And as far as I have been able to determine from many different market research projects, semiconductor manufacturing is one of, if not, the largest market for mechatronics every.   So it’s also not a surprise that a lot of vendors come to the Semicon show with their latest and greatest product offerings.

Among the most interesting, Nanomotion continues to extend the reach of piezoelectric linear motors, yet another technology choice within the linear actuator sphere.  Piezo motors have only one moving part, and meet the high precision, high reliability criteria.  With increasing usage, there has been decreasing cost for this unique solution, along with superior position feedback technology and excellent packaging for space constrained applications.

In addition, IKO has released a number of new linear actuator assemblies, both screw driven and linear motor driven.  They are also showing a number of unique 2-axis configurations one of which is the thickness of a tape reel and is targeted to unloading parts for electronic pick and place machinery.

Brilliant examples of manufacturers continuing to integrate mechatronic technology to make it more convenient for the customer.

The robot unit, known as Robolink, was primarily designed for robot developers and laboratories that work with humanoid systems, as well as with lightweight engineering systems for handling and automation. The design was inspired by Dr. Rudolf Bannasch, Managing Director at the Berlin-based company EvoLogics, a high-tech company working in the field of bionics and humanoid robots. He provided both the motivation and developmental support behind this Robolink component.

It consists of a drive-and-control unit, joints in different lengths, and arms in different sizes, including a duct for additional control cables. The jointed arms are made from carbon fiber reinforced plastic and other lightweight materials. At the end of the jointed system is the option to connect to different types of tools.

The drive-and-control unit was purposely designed as a black box. Robot developers have the option to work with pneumatics, electro technology, or hydraulics.

The bionic core of the robot’s skeletal parts is the injection-molded plastic joints. They are controlled through cable pulls that transfer tensile forces, similar to the way tendons function in humans. The cable sheath is held and the inner cable moved. This way, the gripper, shovel, hook—or whichever tool the developer chooses—is moved and operated.

All data cables are routed safely through the jointed arms. The cable pulls are routed through from one joint to the next—just as joints are connected in humans. Only four cables are required for each plastic joint to rotate and swivel freely. These cables convey images, acoustics and forces, which are the artificial senses of humanoid robots.

The cables themselves are made from technical synthetic fibers. The fibers are extremely strong, hardly stretch at all, are resistant to chemicals, and are lubrication-free and wear resistant. When compared to steel, their lighter weight also makes them much more energy efficient.

Since the system is modular, it can be constructed with all kinds of humanoid robot configurations. This ranges from jointed arms, moving ‘digger’ arms, through to four-legged ‘creatures.’ The joints can be easily combined as required.

igus’ development objective was to keep the moving mass as low as possible, so that the actuators can be separated from functioning tools, such as grippers, hands, suction cups, and so on. Particular attention was given to enable quick assembly, as well as the use of tribo-optimized plastics to reduce lubrication needs and weight.

igus
www.igus.com

Occasionally the line between mechatronics as the design of mechanisms in discrete manufacturing and applications that are more process oriented blur the neat categories of the major control disciplines. More and more control system requirements involve the blending of 2 or 3 different types of control into a single architecture.  This creates subtle problems in order to properly architect the system so that the final effects are achieved.

Polishing and grinding, for example, appear to be positioning applications.  A grinding wheel or buffing wheel must be brought into position to make contact with a workpiece.  So the normal control system behaviors must be dealt with in order to achieve position.  But positioning the tool is only the beginning of the process.

How do we measure the process of grinding or polishing?

And most importantly, how do we know when it is done?

The process of grinding or polishing is a matter of torque in the application of the working tool to the workpiece it is in contact with.  Generally through an electric motor that is turning the tool.  By measuring the torque, which is current in the motor, we can know that the actual process is being achieved.  It may require empirical measurement to determine how much torque is required to achieve the proper surface finish, but there is a direct correlation.  Too much current means the tool is buried in the part, too little current and there is no work being done.

But at this point, there is a process that can be controlled.  If the proper torque level is applied through the motor the runs the tool, there is also a corresponding value as the contact is reduced that indicates the completion of the process.

This behavior is completely separate from the position of the tool.  However, if there is reduced contact with the workpiece due to the tool wearing out, that is, the size of the tool has decreased slightly, then the positioning system has to be updated to compensate.

These are simple concepts, but they are often overlooked.  Ironically, there are many applications that require close consideration of the mixed control methods.  Chemical mechanical planarization of silicon wafers suffers from similar difficulties with the need for extraordinary precision in polishing the surface of the wafer.  Do we really know when the process is done or do we just leave it running an extra 20 minutes just in case?

There’s always room for improvement.  And some of the recent control system innovations are delivering significant performance that should be considered as we pursue new applications.

One of the most complex parts of the automobile is the transmission, which is a multistage gear reducer that “tunes” the speed range of the engine to the desired speed range of the vehicle at power levels of several hundred horsepower.  What makes this so extraordinary is that the workings are almost entirely automatic.  And the gearbox life expectancy is huge.  I just sold a 15 year old car and it’s transmission system is still working perfectly.

Manufacturing processes associated with gear manufacturing have evolved to help deal with the various demands for performance at lower costs.  The traditional method of gear cutting using machine tools generates accurate parts, but metallurgists found that the grain of the metal cut by machining caused weakening of the gear tooth.  Powder metallurgy had been progressing to the point where it was more cost effective to mold gear profiles in sintered powdered metal and do only finish surfacing with machining processes.  Later improvements in the process include the ability to load higher strength materials where needed in the design to produce higher strength parts at lower cost.

But as load requirements increase, all of the performance issues are magnified.  And unique environmental conditions can play a part as well.  In the current design of horizontal wind turbines, the gear box design is a critical component.  The gear requirement at 2.5 megawatts is certainly a challenge, but adding the need for precision and and durability to survive 25 years of operation make the task incredibly difficult.

There are a couple of subtle aspects to gearbox operation that need to be considered.  One is reversal stress.  How does one calculate reversal stress?  It’s the absolute value of the power, two times the power for simplicity, divided by the time period of the reversal.  This is usually a really big number.  And as the time allowed for the reversal decreases, the number goes up.

It doesn’t matter if the application is a servo motor system on piece of machinery or a gear increaser on a wind turbine.  The situation is the same.  It’s just more expensive when it’s a 30,000 pound reducer that’s 180 feet above the ground on a pole.    But the principles are all the same.

Keeping the machinery running is a tough task regardless of the field.  But monitoring the mechanical systems is key place to start.  Next generation gear boxes will likely include electronics to monitor the loading and condition of the gearbox to prevent catastrophic failures.

Accuracy in machining of the bearing parts and lubrication technologies have become incredibly sophisticated.  Some of the latest innovations include the use of  ceramics rolling elements instead of metal on metal contact, and whole new classes of fluorine based lubricants that survive incredible temperatures.

There are a number of applications where conventional bearings are not usable.   The inherent vibration of bearings may be unacceptable.  Creation of particulates can be a problem in some situations.  The alternative is fluidized bearings.  Fluidized bearings are designed using precision flat surfaces with grooves that allow oil to form a film between the moving parts.  So the parts are literally riding on a layer of oil, no contact between moving parts.

Fluidized bearings have successfully taken over the spindle drive motors on hard disk drives, which is a really tough application, 10,000 rpm and starting and stopping in 2ms.  On the opposite end of the power spectrum, I worked with a company that makes machines that make the cans for beer.  The machines form the can body using impact extrusion with a 75 horsepower drive and a massive inertia flywheel.  The linear motion of the forming tool runs on fluidized bearings.  Very cool stuff!

But what do you do when conventional bearings won’t do it, and even a fluidized bearing won’t work?  The ideal fluid is air.  And thanks to some really creative engineering at New Way Air Bearings, the superior performance of air bearing is available as an off the shelf technology.

New Way Air Bearings are based on a porous carbon media that allow air to flow through it at a controlled rate so that a cushion of air is formed on the face of the media.  Parts are suspended on 5 millionths of an inch.  And there is no contact, so there is no wear, no particulates, no lubricant.  Pretty awesome stuff.

Air bearings are available, from stock, in rectangular pad forms, round journals and radial designs.  You can see a great animation of the radial air bearing used in MRI machines on the company’s website.  Medical imaging depends on extremely precise motion and NO vibration.  A perfect application for air bearings.  New Way has also done a number of applications in the semiconductor arena that combine air bearings and vacuum barriers in the same assembly.

One of the great subtleties of bearings is their concentricity.  There are many applications in cutting and shaping operations where the active tool is rotating at high speed to shape a desired part.  But slight errors in the rotary precision of the tool become exaggerated at high speeds.  But with air gaps of 5 millionths of an inch, and the high stiffness of the air bearing, extraordinary truing of the rotating shaft is built in.

And I suspect there are dozens of other applications possible.  Especially as the standard bearings are very reasonably priced.