Electric Vehicles and Electric Motors

A friend of mine finally got delivery of a Tesla Roadster.  This prompted discussion of the drive train and the fact that Tesla has had to go from two speed transmissions which were failing to a transmissionless drive train.  The ultimate mechatronic challenge, the electric car, is also a challenger in terms of the precise  application of electric motor technology.

But it has to be said that the motor and drive solution for the electric car is not where the problem has to be solved.  Any motor can be made to run an electric car.  What is critical is how you apply it.  The starting conditions require high torque at low speed and the running conditions require low torque at high speed.  So, typically, what looks like a small 5 to 15 horsepower running requirement at full speed, becomes a 150 horsepower starting requirement depending on how quickly you would like to start.  If you want to keep up with a Corvette, it uses 450 HP to start.

And this produces a lot of confusion.  Why not use at 2 speed transmission to help the situation.  Fine, but the ones that are available can’t handle the dynamic response of the electric motor.

Can electronics help this situation?  Interestingly, yes.  There is a control algorithm generally called vector control which allows you to manage the rotor torque and stator torque separately.  By varying the phase angle between the two, like advancing and retarding the timing of a mechanical distributor cap on an internal combustion engine, you get different speed torque curves out of the motor.  COOL!  Is there any downside to this?

Yes.  You need more current to produce more torque.  That doesn’t change.  So you have to be able to supply the current, and you have to be able to manage the heat.  The heat is transitory since you only need the high current during starting, but it is best to have sophisticated software running to keep track of the RMS temperature of the motor.  Lower operating temperatures mean longer life and reduced risk of demagnetizing the motor.

So, yes, you can run an electric car with a garden variety AC motor, and with good electronics, you can make it run fairly efficiently.  With higher efficiency motors, the benefit is increased driving range from a given power source.  High efficiency motors are frequently smaller and lighter weigh, but a weight savings in the motor of 50 or even 100 pounds is not that big a factor in the driving range when the curb weight of the vehicle is 3000 pounds.

Basically, its F=ma.  If you can reduce the mass of the vehicle, you reduce the battery payload required to power the car.  Aluminum space frames, like on the Prowler, have been studied by the car industry and can reduce curb weight by 400 pounds and reduce cost by 10% at the same time.  We need to bring all the mechatronic leverage to the situation that we can, if we are going to make electric cars that make sense.  Before its too late for Detroit.

Energy Equivalence or Not

Among the many issues facing us today is the cost of personal transportation.  To a large extent, modern American manufacturing was built largely on making cars and all the steel, carpet, glass and all the other products that are required in a car.  Interestingly, the electronics sector of our economy, far bigger than automotive, has increased it’s contribution to the modern automobile, but that’s another topic.

There is a lot of material being published about our use of cars and our dependence on foreign oil.  Oil and Gas companies made the decision some years ago that it was cheaper to send tankers of gasoline refined on foreign soil than to ship the crude oil and refine it here.  That was the beginning of the current problem.  Now after many years of disuse, our refining capacity has been mothballed.  What you don’t hear much about is the fact that a lot of that capacity can be brought back within a  year by recomissioning old plants.  Yes, new plants are needed.  Yes, in the short term we need to drill for oil.

But the really strange discussion is around the energy equivalency of various conservation techniques, and the number of barrels of foreign oil that it will save.  Most of the time, these equivalencies are purely theoretical.  The only thing that will save barrels of foreign oil is more fuel efficient cars and driving less.  And by the way, American consumers have been demanding higher efficiency cars since the first Oil Embargo in 1974 when I bought my first Moped and my wife and I went to school and back on a gallon of gasoline a week. Anything else is a political statement, and one that should really be ignored.

It is dis-information to say that using compact flourescent light bulbs is the equivalent of so many barrels of crude oil.  Yes, there is an energy equivalence, but there is no direct connection between the two because light bulbs consume generated electricity.  So there might be a valid statement about how many pounds of carbon dioxide the compact flourescent saves in our national energy picture based on emissions from coal fired power plants.  But even that’s difficult to measure, what percentage of our national energy supply is nuclear?  Doesn’t that mix require that we calculate the CFL bulb CO2 savings as a percentage of the fuel mix that goes into the national power supply?

Similarly it is a common to talk about the energy equivalence of a battery’s energy storage capacity compared to the energy density of gasoline.  This too, while appearing to be very scientific and logical, is very lopsided.   It ignores the fact that we are really talking about transportation.  The proper context would be that an electric car has an efficiency of 80% to 95% of input energy converted to output of the moving vehicle and an internal combustion engine is only 25-40% efficient in converting gasoline’s stored energy to mechanical motion of the car.  So comparing the energy density of gasoline with the energy density of batteries is out of context and misleading.   And yes, batteries are still not where we need them to be.  But the Lithium technology is a good first step, and it’s being aggressively engineered to improve density even further and bring costs down at the same time.

If the IRS allows 50.5 cents per mile, and the emerging electric cars cost .04 cents a mile to operate, that’s the real cost of technology comparison that counts.

Top 10 Mechatronic Challenges

I recently wrote on the mechatronic challenge of wind power.  Converting wind into mechanical power that can be harnessed for man’s use has been going on since the 9th Century according to Persian historians.  Certainly wind powered grinding of grains has been around in Europe for several centuries and, lest we forget, wind power pumping of water in the United States.  So there is some irony to the cultural “buzz” about wind power at home and abroad, as if the technology were entirely new.  There’s a lot of history, we’re just updating the technology to produce energy in the age of electricity.

Water has been used for power generation as well.  Following a similar path, we learned during the early part of the industrial revolution how to locate manufacturing plants near waterways so we could convert water flow into mechanical power using the water wheel.  This is, in fact the root of all modern motion control.  All the belts and pulleys, cams, gear reduction systems follow from the work done in mechanical engineering from this period of time.  All of the electronic analogs of the mechanical behaviors found in mechanical systems are the functions which we refer to in mechatronics today.

Wind power and water power gave way in the 1800’s to steam power as the improved steam engine of Watt became the standard of energy efficiency, or should I say “cost effectiveness”.  Because the absolute value of technology is in its cost effectiveness.

Still, wind energy poses a huge technology challenge, as witnessed by the number of vairations that exist and new versions that are emerging.  And hopefully improvements will continue to come from the creativity and  imagination of engineers and inventors all over the world.

But what are the other big mechatronic challenges that come to mind?

Transportation certainly ranks in the top 10.  We have seen hydraulic, pneumatic and electric vehicle solutions touted for a variety of uses, personal transport, delivery vehicles etc.  Ballard Energy and General Motors have both been building hybrid and pure electric buses for city transportation systems for several years with some success.  Interestingly, the electric bus is easier to engineer, which seems unreasonable, but the bus has more interior space to put things like batteries and a methanol converter for generating hydrogen for fuel cells.

But there is a great lesson in what appears to be an almost chaotic string of choices in the transportation arena.  One solution will not work for all requirements.  There are many people for whom a 40 mile per day drive cycle is perfect.  The NEV, Neighborhhod Electric Vehicle, is a golf cart type solution that is rated for street usage, and because of its relatively simple performance requirements, is relatively easy to achieve and lowe cost.  As we categorize cars with greater range, the problems get more difficult, and because of the storage limitations of batteries, have only been achievable as hybrids.  But with some hybrid designs reaching 50 and 60 mpg (estimated), these vehicles may be great solutions for other users.  Although, we must consider their cost effectiveness.  If they cannot be introduced at prices well below $50,000 the absolute value of the technology is not very good.

So forget the 15 second soundbyte that will solve the world’s problems.  It doesn’t presently exist.

I would like to hear from any readers about their picks for the Top Ten Mechatronic Challenge.

Mechatronics and Ignorance

By Richard Comerford,
Editor
Electronic Products

I wish I had a dollar for each time I asked an EE about the use of mechatronics for a development project and got the response, “What’s that?”  And I’m not just talking about IC designers, but about people involved with designing electromechanical systems like disk drives, as well as those who are responsible for developing everything from MEMS to pick-and-place robots.

I find the lack of recognition among the electronics community a bit disheartening. Mechatronics has been around now for several decades, and many universities are now offering courses taught by professors who are dedicated to the discipline. Yet mechatronics has nowhere near the recognition of, say, electronics, or robotics, or bionics, or even hydroponics.

I suppose there may be several reasons for that situation. For one thing, people had actually been using electronic controls for mechanical systems long before the term mechatronics was coined. Things like automatic doors and air conditioners have been around for a long time, as has the pop-up toaster, all of which are examples of simple mechatronic systems.

Robots have been a part of the popular culture for so long that people don’t typically associate them with mechatronics. The discipline of building robots — robotics, which is actually a subset of the field of mechatronics — also predates mechatronics. So everyone thinks they know what you mean when you say “robot,” but I wonder what would happen if you tried dropping “mechatron” into
a conversation.

Another reason for the relative obscurity among EEs of mechatronics may be political. Sometimes, getting engineers from different disciplines to work together is like trying to get the Army, the Navy, and the Air Force to agree on who has the best football team.  As an EE, I can remember how in college we used to disparage civil engineers as “road crew,” mechanical engineers as “gear heads,” and chemical engineers as “stink bombs,” knowing with the certainty of youth that only those who could command the electron to do their bidding were masters of the universe.

I doubt that even today there are many computer scientists or electronics engineers who would be happy to admit that mechanical design is equally as important as their disciplines. And for them to relearn their approach to design with a broader set of tools is by no means an easy process.

Nonetheless, areas that hold the most promise for advancement in the future — such things as haptics, MEMS, and advanced HMI — are inherently mechatronic in nature, and will require interdisciplinary knowledge for success.  Sure, mechatronics may require better PR or an agent who can sell it to Hollywood, but regardless of how successfully it is promoted to the masses, those technologists who are ignorant of it may soon find themselves not only out of touch, but also out of work.

Wind Energy and Mechatronics

By Steve Meyer,
CEO/Senior Consultant
Solid Tech Inc.

What would you put on a “Top Ten” list of the toughest mechatronic applications of all time? The electric car, plug-in or hybrid is certainly on the list.

One application that needs to be on the list is the Wind Turbine. It is a mechatronic challenge because it combines the aerodynamics of rotor design, the mechanics of a gear reduction system, the electromagnetics of an electric generator and the power electronics system for output power conditioning and synchronization to the utility grid system, all of which is designed in the range of 1000 to 4000 hp.

Each portion of the system must be designed in conjunction with the other systems to achieve the overall goals of efficient net power conversion.  Plus, wind turbine hardware has constraints that are different from other forms of equipment.  In addition to efficiency, another top priority of wind power turbines is life expectancy. The manufacturing constraints those priorities create are a nightmare.

Since most wind turbines sit on top of 150 ft tall masts, the systems are also weight constrained.  Other constraints include a second axis of motion that pivots the nacelle that houses the gear reducer and generator.  It can weigh more than 5 school buses. Then, the whole assembly must steer into the wind.  Sounds like fun.

The efficiency of the rotor at a variety of wind speeds is totally an aerodynamic issue. While this not my area of expertise, even with my limited background, it is clearly a problem since wind speeds vary constantly.  The consequence of this dynamic is that the rotor speed cannot be predicted.  Therefore, the electrical system must take a varying input and convert it to dc and then back to
synchronous ac, or control the speed of the rotor and waste some of the input energy.

The gear system requires large-scale, precise machining.  Not so much because there is some accuracy required in the load, but for efficiency and minimal wear.  Only a few companies in the world are able to produce these systems, and the current orders are backlogged to 2011.

Manufacturers have found that wind turbines are more cost effective the bigger they are.  This makes sense on the motor side because power increases with the square of the radius.  But it sure makes everything more difficult.  The mast and cantilever load of the turbine and propellers is huge.

But all that engineering has to be done inside a cost envelope.  According to the Danish Wind Energy group, a typical 600 kW system costs around $450,000.  Installation costs will be $135,000, making the initial cost $585,000.  If the unit produces 1,500,000 kWh hour a year at 0.05/kWh it generates $75,000 that year minus an average maintenance cost of $6,750.  At a cash flow rate of $68,250 a year, it will take 8.4 years to break even, not including discounted cash calculations.

You can play with the numbers on line at the Danish Wind Energy website.  The US utilities are regulated in how much they can get for power.  At 0.10/kWh the payback is 4.2 years.  But what if the wind estimates are too high?  That’s a lot of money.

The public policy question is how much government funding is going in to this arena?  Is the Federal or State government offering subsidies to facilitate the adoption of the technology?  If so, shouldn’t we be getting a discount on our electric bill if taxpayer money is used?

Footnote: The Global Wind Energy Council in Brussels reports that installed capacity for wind power worldwide was up 28.8% last year with the US increasing its base by over 50% and edging out Germany as the leading user of wind power in the world.  Interestingly, China, often accused of being one of the most environmentally irresponsible countries, is the No. 4 user of wind power in terms of installed base with similar growth over last year.  Maybe some things are headed in the right direction.

Energy Stimulus Debate

As “We the People” wait for Congress to do something to stimulate the economy we are flooded with information about “Green Initiatives” as part of the stimulus strategy.  And its really easy to get dragged along with the tide of enthusiasm.  After all, the electric car has languished in the shadows for over 70 years since the Baker company closed its doors.  So the idea of re-inventing even a small part of the automotive industry in the US is very appealing during a difficult period in our history.

We all share the concern that unemployment is up and many areas of the economy are slow.  But let’s be sure that when the government says its going to spend our money, that the decisions are based on sound strategy.  Maybe government spending money that it doesn’t currently have isn’t such a great idea. Read more

The Tools, They are a Changing’

(regarding the title, just think Bob Dylan’s “The Times They are a Changin”)

Just as Computer Aided Design, CAD, has revolutionized the design process, it is growing in capability and impacting many other arenas of engineering. The first major extensions to CAD were integration of Finite Element Analysis, the ability to analyze loads on the parts being created.  And certainly, if the design software can model the complex aspects of loading, then animation of part motion can’t be a far reach.  And that’s the case today. Read more

Mission: Efficiency

Think-tank for mechatronics and miniaturization

How do machinery and equipment manufacturers keep up with worldwide competition? With (energy) efficient solutions! “Mechatronics, miniaturization, piezo technology and systems technology are catchwords which aren’t just pointing the way towards more efficiency in emerging business areas like photovoltaic”, says Dr. Eberhard Veit, chairman of the board of directors at Festo AG.

Read more

Does More Simulation Mean Companies Profit More From Its Use?

BOSTON, MA — Increasing product complexity combined with the ever pressing market pressures to develop these products faster and cheaper requires new ways of exploring product performance. A recent report by Aberdeen Group, a Harte-Hanks Company (NYSE: HHS), “Engineering Evolved: Getting Mechatronics Performance Right the First Time,” finds that an increasing number of companies are responding with an “early and often” approach to the use of simulation tools. According to Aberdeen’s research, it’s a response that’s getting results, including an average savings of $332,673 and 118 days for complex products. To obtain a complimentary copy of the report, visit: http://www.aberdeen.com/link/sponsor.asp?cid=5359.
Read more

Progress In Europe

The SPS Drives show in Nuremberg Germany is one of the best attended shows in the world.  And one of the reasons why has to the with the outstanding technical effort and preparation that all the vendors put forward.  Demonstration systems are sophisticated and perform flawlessly.  Exhibitor personnel are all very professional and technically astute.  And multi-lingual which is great for me because my German is almost non-existent, so its great having so many people able to bridge the gap. Read more

Next Page »