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.

WITTENSTEIN Aerospace & Simulation has been the control loading leader in the flight simulation market for more than a decade. The Company has taken its expertise and applied it to telerobotics, where a user controls an axis or entire vehicle remotely. WITTENSTEIN’s products provide the user with feedback of the remote axis through electrical linking and force control technology.

The main features of the sidestick systems for telerobotics are superior efficiency, compact design, and electric linking with force feedback. These result in smooth operator feel, no need for additional mechanical linkages or hydraulics, and a standard off-the-shelf system solution that utilizes standard wall-outlet power. The robust nature of the WITTENSTEIN systems allow for up to 10 axes per control module.

Sample areas of application for this technology include remote product testing for reasons due to environmental or equipment restrictions.

www.wittenstein-us.com

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.

A group of engineering students, led by Andy Ruina, Cornell professor of theoretical and applied mechanics, announced the robotic record at the Dynamic Walking 2010 meeting on July 9, in Cambridge, Mass.  Ruina leads the Biorobotics and Locomotion Laboratory at Cornell. The National Science Foundation funds this research.

Previously, students in Ruina’s lab set a record for an untethered walking robot in April 2008, when Ranger strode about 5.6 miles around the Barton Hall. Boston Dynamics’ BigDog subsequently beat that record.

One goal for robotic research is to show off the machine’s energy efficiency. Unlike other walking robots that use motors to control every movement, the Ranger appears more relaxed and in a way emulates human walking, using gravity and momentum to help swing its legs forward.

Standing still, the robot looks a bit like a tall sawhorse and its gait suggests a human on crutches, alternately swinging forward two outside legs and then two inside ones. There are no knees, but its feet can flip up – and out of the way, while it swings its legs – so that the robot can finish its step.

Ruina says that this record not only advances robotics, but helps undergraduate students learn about the mechanics of walking. The information could be applied to rehabilitation, prosthetics for humans and improving athletic performance.

Cornell University
www.cornell.edu

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.

With all the discussion about offshore drilling, it should certainly be mentioned that oil well drilling is one of the toughest mechatronic challenges ever.  Constructing and powering drill bits that can cut through rock at depths of up to 30,000 feet has to be on the top ten list.

The first known offshore drilling for oil occurred in Galveston Bay when the early Sharp-Hughes two cone rock bit was first demonstrated in 1909.  Howard Hughes Sr. founded the Hughes Tool Company after buying out Sharp and Howard Hughes Jr. became the wealthiest man in America during the 1950’s.  It is said that every drop of oil produced in America from 1934 to 1951 was produced using a Hughes drill bit.

The drilling industry has produced every possible variation of down hole tool from data gathering equipment to nuclear magnetic resonance detectors which look for defects in the pipe throughout the well casings.

Add to this the complications of drilling under water.  Offshore oil rigs are mammoth machines that sit on “jacks”, like giant adjustable stilts, that are electric motor powered to raise and lower the entire works of the platform.

The oil well is under thousands of feet of water which makes matters even more complicated.  At 5,000 feet of depth, the water pressure represents more than 2,000 pounds per square inch of pressure.

And drilling offshore roughly doubles the cost of producing the oil.

So you have to ask the question; how did we get here?  Why are we drilling further and further offshore and increasing the risk of a disaster?  And I will mention again, that the industry rate of spills has been declining consistently.

The answers are perplexing.  We don’t drill on land because our Congress cannot agree to issue permits.  Democrats in Congress blocked drilling in Alaska on a very small parcel of land that had been surveyed and all the environmental studies had been done.  Ken Salazar, Secretary of the Interior refused to permit Shell Oil to do shale oil production in the remote parts of Colorado after Shell had done all it’s due diligence and spent millions of dollars getting prepared.

Offshore drilling is being pushed further offshore so that the drilling equipment cannot be seen from the shore, and presumably, there would be less environmental impact on local fish and wildlife.  Guess somebody in Congress got that one wrong.

And what about John Hofmeister’s, Shell Oil’s former CEO now turned activitist citizen, who recently commented that the US has oil reserves in Nebraska, Alaska, Texas and off it’s coasts to provide cheap oil and gas for the next 1000 years.  Guess Congress missed that one too.

I am not a fan of gasoline powered transportation.  But I recognize that it is the most economical form of transportation.  The fact of it’s low cost is what has made gasoline powered vehicles popular to the point that consumption has tripled since 1950.

So the real challenge is coming up with something that is lower cost and cleaner.  And there are lots of options to be explored.  If we can get the political issues out of the way.

The Governor of Louisiana has stated that suspending offshore drilling will eliminate thousands of jobs.  The oil spill has ruined fishing in the Gulf Coast for an undetermined period of time.  Denying the permits for shale oil in Colorado cost the country 10,000 jobs.

When do we stop listening to people in Washington, and return to doing what is right locally.   We can fix things on our own.  That’s what Americans do.

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

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.

Similarly, in recent years, there have been a number of significant breakthroughs that offer great potential for the improvement of many current technologies.  But more subtle transformations are taking place throughout the industrial landscape that offer new opportunities yet to be explored.

In many areas of part production, there are solutions that offer reduced cost per part.  The emergence of new CNC’s that are available at the $10,000 level reduces the amortized cost for producing parts by as much as 500%.  Simply put, it you have to produce 1000 parts on a machine tool, the final cost of the part is significantly impacted by the cost of the machine tool.  A $50,000 machine tool will cost $50 per part across 1000 parts.  A $10,000 machine tool will only cost $10 per part.

This economic shift may make it possible to enter a market with an improved price point for an existing product, or create an opportunity to do something new that wasn’t possible because of cost and volume constraints.

In similar fashion the metals industry has consistently worked to developed processes and technology that allow part cost reductions, and more recently, smaller batch sizes for certain applications.  The smaller batch size has the same effect on cost, it lowers the investment cost for improving old designs or coming up with new ones.

The same trend is in place in the controls arena.  Processor technology that used to cost $20. a few years ago is available now for $2-3 and network versions that permit Internet interface are available for around $5.  This makes it practical to embed intelligence and communications in products even if the application is relatively simple.  The low cost is a compelling value in many products.  And in many arenas there are libraries of application code that already exists that may provide 60% or more of the development code for something you are working on.

Energy is still a bit of a limitation.  We don’t have a “Mr. Fusion” nuclear reactor that runs of kitchen scraps.  But things are looking up in this area with lithium based batteries making great strides in energy density.  And there is substantial improvement on the way.

But the real point here is;  Dust if off and Try it Again.  Take those “back of the napkin” sketches you’ve been tinkering with or thinking about and look at them again from the perspective that there dozens of technology improvements out there that will reduce the cost of the product you were thinking about a couple of years ago.  The change in the economics, as amortized cost, or the cost threshold to get your first batch of parts made, are factors that have a huge impact on the feasibility.

It just may be the time for a breakthrough.  A second industrial revolution.

In the car, starting torque requirements can be very high, depending on how fast you want to accelerate.  Running torque, the amount of torque needed to overcome air drag, is very small.   If you want to reach 60 miles an hour in 4 seconds or less, like a Corvette, you will probably need around 450 horsepower.   Cruising on the freeway at 65 miles an hour, constant speed, will probably only require 5 horsepower.

So the power requirements for what appears to be “the same” application can vary wildly, 100 times the power, depending on the circumstances.  That’s where control and regulation come in.   The question being, how fast is the rate of power being dissipated over a small instant in time.  This is the domain of calculus, the first derivative of power over time.  This will determine how fast the control system monitors and updates the value of the power being controlled.  This can also be referred to is as the dynamic rate of the control system, the change in time for the power rate to be measured.

In AC drives, the dynamic response of the drive is a crucial parameter in order to specify the right drive for the application.  Large systems like paper rolls, which can weigh hundreds of pound, have a very slow dynamic rate and a drive for this application should have a dynamic response that is comparable.

Hard disk spindle drives, which have tiny loads and must regulate speed and acceleration based on 2 millisecond seek times, must have extremely fast dynamic response.  The high rate of acceleration requires that torque is regulated in the microsecond range.  Regulating a paper drive with a control designed for hard disks would not only be a waste, but the high response rate in the control would probably lead to instability in the control.

But more complex conditions exist in the real world that must be considered.  What happens when the load is changing?  When you have to palletize beer bottles, every ten cases of beer completes a layer on the pallet.  There are 8 layers to the pallet.  So you start with an empty pallet and end up after 8 identical moves with 3800 pounds of beer.  How do you set the gain?

Either you use an average value equivalent to half the payload weight and live with the results, or you need something that reloads the gain value as the load changes.  Both techniques can be done, both work, but the ideal solution is the second, adaptive gain.  Something that is adaptive, however will require some pretty advanced programming to consider all possible conditions.

And that is the new frontier in robotics.  If robots are to work in human service, they have to be able to operate in a reduced torque mode so that they cannot produce forces that exceed human strength and frailties.  But there are other conditions where the robot’s superior strength can be extremely helpful.  So the current generation of drives will have to incorporate increasingly complex adaptive gain controls in order to make human service robots safe and practical.

Adaptive gain is a discipline that has been talked about for at least a decade in the control community, but it’s been somewhat of a technology looking for an application.  There are the occasional situations where adaptive gain would really be “cool”, but not any widespread applications.  Well, the next great application for adaptive gain will likely be human service robots.  Coming soon to a neighborhood near you.