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.

Linear Feedback Technology (Linear Motion Part 2)

Linear motion is particularly impacted by the choice of feedback.  And for most systems the use of feedback is not an option.  Linear motors, for example, cannot be operated without a feedback device.  And because of the linear motor’s roots in semiconductor manufacturing, the feedback is usually a high resolution linear tape scale.

How much feedback resolution is enough?  Most of the time more resolution is better.  But there is an element of control theory that says if the feedback resolution is ten times greater than the position accuracy that you are trying to measure, the control system can become unstable.  The other side effect of extremely high resolution feedback is the tendency to “jitter” because it is responding to tiny variations in the real world, which the control system will then have to contend with.  So spending extra money for high resolution feedback may cause other problems.

Where should the resolution be put?  Obviously, if you are using a rotary servo motor, just use the feedback on the motor as the linear position reference.  This works when the required resolution is not very high because in all mechanically linked systems, there is lost motion called backlash between the motor and load.  But most motion controllers and many indexing drives contain dual feedback loops, so using an external feedback sensor will produce great benefit in accuracy and repeatability.

The big benefit in using linear feedback is the elimination of mechanical error as part of the control system.  On a project I did a few years ago we were evaluating a special grinding machine that had a 13 foot long lead screw in it.  The customer know the lead screw had wear and error in it, and that was part of the problem that needed to be addressed in rehabilitating the machine.  Instead of replacing or re machining the lead screw, we specified an external linear tape scale feedback.  The results were fantastic.  Accuracy and repeatability were phenomenal and combined with an integrated servomotor system,  led to a 300% increase inthroughput for the customer.  Backlash? What Backlash?

How much distance do we need to sense?  Some linear motors like piezo-electrics  and voice coil motors have very limited stroke lengths.  Similarly, different feedback technologies have scalability parameters such as sensing airgap and length requirements are considered.  Some feedbacks work in the range of 2 to 6 inches in overall stroke length, some are capable of 3 feet, some up to hundreds of meters.

The exception is the stepping motor and leadscrew combination which can be operated without feedback on the assumption that the load is not varying dramatically.  But even the leadscrew and stepping motor needs feedback when the load varies.  Current detection can be used to determine if the motor has stalled, but doesn’t necessarily give you the opportunity to recover position without an external source.  So the extra cost of external feedback is a judgement call based on the accuracy requirement and how “robust” the system needs to be.

The variety of types of linear feedback are equally challenging, and as with most things, must be considered based on cost and performance.  The most popular feedbacks are linear tapescale systems that use reflected infrared beams that are interpolated to achieve very high accuracy.  The classic linear feedback from the machine tool era is the glass scale which uses through beam optics and a grating embedded in glass to product the linear position information.  Check out companies like Renishaw, Heidenhahn and others for details. Information on  Heidenhahn’s latest innovation is featured on the Project Mechatronics website.

Over the last few years there have been a number of magnetic solutions where a magnetized linear scale is interpolated by taking the sinusoidal waveforms produced by Hall sensors or inductors, and digitizing the results.  Integrated circuitry combining Hall effect arrays and functional support to linearize output are now the prevailing state of the art.  Check out NewScale Technologies Tracker product for details on their new offering.

Linear Motion

Electric motors are generally rotating machines.  And over the roughly 100 years of electric motor history, incredible effort has been put into adapting the technology to do an almost infiinite array of tasks.  Which is why it’s kind of ironic that in the industrial world, a significant number of applications require the conversion of rotary motion to linear motion.  And, as with all things mechatronic, there are a variety of ways to solve the problem.

Most often, the first order of business is to couple the motor to a linear mechanism.  The two most common are screw type actuators and belt drives.  Both work well, both have relative strengths and weaknesses.  Screws are very smooth and provide mechanical advantage like a gear reducer, but can add inertia mass and have acceleration limits.  Belts are low mass and high speed but a stiff support system to permit proper tensioning.

Linear motion is generally about position, which is fundamentally a different behavior for electric motors. Most motors rotate at high speed, like an 1800 rpm ac motor.  So positioning implies a whole range of properties that are not easily achieved.  While we have achieved a wide variety of solutions for positioning, they are generally much more expensive and complex.  Stepping motors are the  only branch of electric motor technology where position is an inherent aspect of the motor’s operation.  And this fact has made them very popular, especially when linear motion is required.  A typical stepping motor solution is based on a 200 step per revolution motor and a 5:1 pitch lead screw.  This makes the linear motion .001″ of travel per step.  Simple, cost effective.

In many linear motion applications the top priority to is accuracy.  And when the accuracy requirement is higher precision than .001″ or the speeds required are beyond what stepping motors can produce, then other options must be explored.

Linear motors are outstanding in overall performance.  Acceleration, speed and accuracy are excellent and are the way to go where the costs are acceptable.  They use high resolution (generally millionths of an inch) tape scale linear position feedback to achieve the precise positioning required by semiconductor applications.  And this was the early field of use of linear motors.  Once considered an “exotic” solution and very expensive and difficult to apply, the last few years have seen cost improvement and a wider range of applications for the technology.

An emerging technology for linear motion is the piezoelectric motor.  Linear piezoelectric motors are available from a few suppliers and the simplicity and cost effective of this solution is making them an excellent choice for some linear motion requirements.

Most mechatronic solutions for linear motion depend on a feedback sensor to achieve position accuracy.  This makes the linear position sensor a critical component in the design of linear motion systems which I will address in the next post.  There are a number of options and some new technologies available to give designers more choices.

A Key to Successful Production-Integrated Measuring – the Encoder

By Reinhard Kuhn
HEIDENHAIN, Traunreut
Product Manager

An encoder’s coefficient of expansion and its tolerances will play a more significant role in future ISO standards for classifying coordinate measuring machines.

A measuring room offers optimum conditions for precise measurements. But it has several disadvantages including high costs for the room, the machine and temperature stabilization, as well as interruption in the flow of production.

Customers continue to push to install more control over the manufacturing process. Part of this push involves placing the measuring machine spatially closer to actual production, a modification known as production-integrated measurement. Through such a modification, measurement results can go “online” into the control of production and thereby affect the precision of the manufacturing process.

However, the harsh nature of a typical manufacturing environment places new requirements on measuring machines. These requirements either did not exist or were less critical in the sheltered surroundings of a measuring room.

Measuring machines on the shop floor are exposed to changing temperatures and more difficult ambient conditions. Shock, vibrations, and contamination occur often. Manufacturers of measuring machines are responding to these requirements with various designs and approaches. However, all are in agreement on one point: Deviations from the 20° C reference temperature specified in DIN 102 change the length and angle on both the work piece and the measuring machine, and these changes must be mathematically compensated.

KNOWN BEHAVIOR
The defined, reproducible thermal behavior of the encoder is indispensible for accounting for such deviations. The encoder’s coefficient of expansion and its tolerances will play a more significant role in future ISO standards for classifying coordinate measuring machines (see ISO TC 213-WG 10).

Thermal expansion = change of length – an unknown quantity

The coefficient of expansion, or deviations from it, influence the use of encoders on measuring machines. Encoders usually feature measuring standards of steel, glass, or glass ceramic.

The relevant literature provides data for the coefficients of expansion; however the data given differ significantly from source to source. Thus, their utility as a basis for length compensation is limited, as becomes visible in the data for steel, for example. A temperature change of even a few degrees can result in deviations of several micrometers in compensation values calculated from an inaccurate coefficient of expansion.

The scanning heads for the LIDA 400 are a standard size, so they meet all requirements for reading the scales of glass and glass ceramic. Also, the identical cross section of the scales allows the graduation carriers to be exchanged.

POSSIBLE METHODS OF ASCERTAINING THE COEFFICIENT OF EXPANSION α
A coefficient of expansion can be measured exactly by a dilatometer, which is a device for measuring thermal expansion. With a well-designed dilatometer it is possible to attain exact data on a material’s coefficient of expansion by measuring a test object and use it to manufacture encoders.  An example is the “alpha measuring station” for measuring the thermal length expansion of bar-shaped bodies. Such a measuring station has been set up at the Physikalisch-Technische Bundesanstalt, Germany’s national metrological institute in Brunswick.

This exactly measured value can then be applied to calculate length compensation. In most cases, companies manage as best they can with data from the literature or the material manufacturer. This makes uncertainty in the result inevitable.

TEMPERATURE AND ACCURACY COMPENSATION
Special care must be taken in setting up a shop-floor measuring machine. Years of experience by the manufacturer result in high reliability and ensure high accuracy in spite of harsh environmental conditions. No compromises in accuracy are made compared with machines in measuring rooms.

Thermal effects must be dealt with through the appropriate know-how, the selection of suitable materials, and providing for thermal requirements. Because temperature increases expand materials to different degrees and these materials take on the surrounding temperature at different speeds, complex calculations are conducted to compensate the effects of temperature and accuracy. A known basis for mathematical compensation is very important—the linear encoder.

Thermally stable encoders are an indispensible prerequisite for basing calculations on accurate measurement data and thereby achieving accurate compensation. The selection of encoder material for shop floor measuring machine is therefore particularly important. While glass or steel scales permit only an approximate value for calculation, the expansion coefficient of 0+/- 0.1 x 10-6K-1 ZERODUR® for glass ceramic scales remains accurate over a large temperature range, and the scales have proven to be durable. The material is used the world over on telescopes, for example, because they place very high requirements on resistance to temperature changes and on distortion-free imaging.

THERMALLY STABLE ENCODERS
The right encoder enhances machine characteristics and contributes significantly to the reliability of the measuring machine. The area of production-integrated measurement is characterized by the following requirements and characteristics:

• Encoders with defined coefficients of expansion
• High accuracy for deviation between compensation points
• Minimal contamination for disturbance-free measurement
• High reliability over a long time period
• Cost-efficient encoders

One type of encoder that meets these requirements is the LIDA 400 exposed incremental encoder. Features include high accuracy and liberal mounting tolerances, high traversing speed, and the small height of the scanning head.

These attributes make it well suited for use on production equipment in automation engineering and the electronics industry as well as for applications on linear drives and in many areas of metrology.

The introduction of new graduation carriers of glass and glass ceramics, such as ZERODUR® and ROBAX®, have expanded the range of applications covered by encoders. They therefore suit applications in shop-floor measuring machines. They are easily installed by the PRECIMET® adhesive film on the back.

The scanning heads for the LIDA 400 are a standard size, so they meet all requirements for reading the scales of glass and glass ceramic (ZERODUR®, ROBAX®). No special scanning heads are needed. Also, the identical cross section of the scales allows the graduation carriers to be exchanged. From the logistical point of view this is a great advantage because the standard LIDA 48 (1 VPP) and LIDA 47 (TTL) scanning heads can be combined with glass ceramic and glass scales as well as with steel scale tapes. The identical carrier cross section of glass ceramic and glass scales make it possible to upgrade existing measuring machines. All designs have the same scanning surface of 14.5 mm², which ensures high tolerance to contamination and generates very clean scanning signals, which can be highly interpolated.

The encoders of the LIDA 400 series have a grating period of 20 µm. They are available in the widely used 1VPP and TTL interfaces and for measuring lengths of up to 30 m (steel) or 3 m (glass and glass ceramic). Traversing velocities up to 480 m/min are possible. The encoders are available with
reference marks as well as integrated magnetic limit switches.

Today’s changing requirements on machines such as measuring machines or production equipment in the electronics industry call for encoders that are also capable of meeting these demands. The problem of thermal expansion can be solved by the proper selection of different graduation carriers that are uniformly capable of using the same model of scanning head.  In conjunction with measuring standards of glass and glass ceramic, the new generation of LIDA 400 exposed linear encoders offer ideal properties for accurate measurement even on shop floor and in production-integrated machines.

HEIDENHAIN
www.heidenhain.com

________________________________________________________________________________________

The METALLUR process

HEIDENHAIN has developed a process—known as the METALLUR process—for manufacturing graduations on glass, glass ceramic, or steel.  The quasi-planar graduation structure provides optimum protection against contamination and thereby greatly enhances encoder reliability. The manufacturing processes are environmentally friendly and do not use chemicals such as those generally needed for etching.

Mechatronics on the Trail of Global Warming

By Donna Sandfox

Omron Electronic Components, LLC

A new highly portable mechatronic system to measure harmful pollutant relies significantly on a MEMS flow sensor

Figure 1. Stationary Aethalometers are used throughout the world, but have been too heavy to be truly portable until now.

Carbon dioxide is well known as a major contributor to global warming, and there are many ways to detect and measure it. But it is not the only culprit. Scientist have found that the second most significant contributor is soot, or black carbon. Not only does black carbon contribute to environmental degradation, but these tiny particles also cut short the lives of seniors and sicken children. A recent economic impact study in California’s San Joaquin Valley (The Benefits of Meeting Federal Clean Air Standards in the South Coast and San Joaquin Valley Air Basins, November 2008) has identified the cost of air pollution and estimated it at more than $1,600 per person per year.

Black carbon doesn’t stay in the atmosphere as long as carbon dioxide, so controlling it has the potential to achieve major benefits in the short -term. Some of the major emitters of black carbon are diesel engines plus wood- and coal- burning fires. However, to analytically determine the source of black carbon and recommend effective changes to correct the problem, scientists require instruments capable of measuring black carbon in the field.

Manufactured by Magee Scientific of Berkeley, CA, the Aethalometer, is an instrument that uses optical analysis to determine the mass concentration of black- carbon particles collected from an air stream passing through a filter. However, until recently, these instruments were too large and bulky to be easily moved to a suspected point of origination for black carbon; the smallest device (the AE42) weighed approximately 25 lbs and measured 11 x 12 x 8 in. The instruments collect data from installations located around the world (Figure 1), but these only give scientists local samplings.

To get a complete picture of the black-carbon problem, scientists required a very small portable Aethalometer to easily determine black- carbon readings in almost any location. A reduction in size required some clever engineering and component sourcing.

Figure 2. The AE51 Aethalometer’s designers took advantage of the flow sensor’s port placement by designing the manifold to interface to them directly without tubing.

Aethalometer operation

Aethalometers function by measuring the amount of particulate deposited on a fiber filter by a specific amount of air passing through the filter for a predetermined amount of time. This mechatronic system needed to incorporate mechanics, electronics, and computing in one compact package. One of the major size reduction obstacles to overcome was finding a small, lightweight, highly accurate flow sensor with low power consumption. Having worked with Omron in the past, the engineers from Magee Scientific again called on Omron for a solution to their requirements, and the company recommended its D6F-P MEMS mass flow sensor for gathering the required air samples.

Figure 3. D6F-P flow sensors are individually calibrated before shipping to deliver excellent repeatability results.

Size and power constraints

The body of the D6F-P measures just 10 mm high by 23.3 mm wide by 27.2 mm deep, and with a weight of just 8.4 grams, it fell within the size and weight restraints set forth by Magee. Designed for easy installation, the D6F-P has both the input and output ports on the same side which facilitates the connection of tubing.

Magee engineers made clever use of this feature, designing their new AE51 Aethalometer so that the sensor ports would mate directly to their manifold, without the need for tubing (Figure 2). Since this miniature Aethalometer was to be battery powered, current consumption was a concern. The D6F-P proved to be very efficient, drawing a maximum of only 15 mA while operating on 5 Vdc.

Accuracy and repeatability

The AE51 relies on calculating the exact amount of air, driven by a blower incorporated in the device for a given time. Therefore the flow sensor would have to be very accurate. The D6F-P’s flow range/ pressure range of +1.0SLM (+0.84 in H2O) with an accuracy of ±5% F.S. maximum and ±2% F.S.

typical would deliver the precise flow readings Magee required to obtain reliable measurements.

Additionally, since the sensors are individually pre-calibrated at the factory for high repeatability, Magee Scientific’s finished device adjustment and test time was kept to a minimum (Figure.3). Durability was also a concern since the AE51 would have to take multiple readings, but the sensor’s MEMS technology has been proven to deliver a long life with excellent repeatability.

Figure 4. A patented dust segregation system with dual centrifugal separators ensures that the sensing chip remains clean.

In the real world

Since the AE51 is designed to measure black- carbon particulate in areas of known high concentration rates, the sensor had to be reliable in these dirty, real- world environments. Measurements would need to be taken at busy traffic intersections, bus stops, industrial sites, and coal-burning power plants.

The AE51 would also be used in remote areas of the world where use of wood fires to cook and heat is common. Although the filter used to measure the density of the black carbon is in front of the sensor’s inlet, if any particles that got past were to effect sensor operation, measurement accuracy would be compromised.

Figure 5. The reduced size of the hand-held AE51 is obvious when compared to the rack mount AE22 Aethalometer behind it.

To prevent that occurrence, the D6F-P design uses a patented dust segregation system (DSS). The DSS in the flow path incorporates dual centrifugal chambers, in which particulate matter follows in the outer path away from the MEMS sensor chip regardless of the flow direction. Thus there is practically no degradation in sensor performance over the lifetime of the system.

Keeping the MEMS sensor chip clean lets Magee guarantee a long life for their Aethalometer without worry about black-carbon build- up harming the device’s performance (Figure 4).

The A51 Aethalometer (Figure 5) is so small that it can be strapped to a user’s belt, enabling the user to become the instrument’s legs and freeing the user to do other work while the meter is gathering information. It can also be tethered to weather balloons for upper atmosphere readings. Another potential application would allow the device to be carried by those whose health might be affected most by inhaling large amounts of black carbon. The AE51 would alert them to areas that have high concentrations of this toxic material.

Omron Electronic Components, LLC

www.components.omron.com

Controllers Help Astronomers Peer into the Universe

In mechatronics applications control is most often paired with motion. The following motion control system works with other components to deliver the required movement precision to research the Universe.

Photo by: Laura Hatch lauriehatch.com

Astronomers working for University of California Observatories (UCO) are creating the first comprehensive survey and map of the distant universe. Called the Deep Extragalactic Evolutionary Probe (DEEP), the team uses twin 10-m W.M. Keck Telescopes located in Hawaii, the Lick Observatory on Mount Hamilton in California, and the orbiting Hubble Space Telescope (HST).

The telescopes collect the light that stars and faint galaxies emitted more than 14 billion years ago. Detecting and analyzing this light requires an approach that includes a complex compliment of mechanical, electronic and optical instruments, along with sensors and software.

One of the key components of the Keck II telescope is the Deep Imaging Multi-Object Spectrograph (DEIMOS). Able to magnify the telescope’s capacity by a factor of seven for faint-galaxy optical spectroscopy, DEIMOS features:
• An optical beam camera with advanced optics and three 13-in. diameter calcium fluoride crystals lenses
• A “slitmask” system that allows observation of 140 galaxies simultaneously
• The largest spectroscopic charge-coupled device (CCD) detector of its type ever made (5-in.2, contains 67 million pixels)
• Sophisticated software for rapid setup and flexure compensation to keep the mirrors stable and aligned to prevent images from moving about on the detector. Conventional spectrographs that suffer from severe flexure make calibration and data reduction difficult.

SYNERGISTIC ENGINEERING
The multiple detectors on each Keck telescope, the DEIMOS spectrograph, and other related instruments require precise motion control of a number of elements, including filter wheels, focusing, apertures and positioning stages. Barry Alcott, development engineer at UCO, has been specifying Galil motion controllers for more than 15 years to handle the motion control tasks.

Alcott used Galil’s RIO Pocket PLC to automate portions of the Hamilton Spectrograph system, the first cross-dispersed spectrograph installed at the Lick Observatory. It operates by having light fed to a grating that sends it in one direction and then immediately feeds it to a prism that disperses it at a 90° angle for very high-resolution spectra.

Alcott configured the multiple I/O points of the controller to automatically control four pneumatic stages used for moving an iodine cell into a beam, opening a light port, moving a mirror into a beam, and opening a mirror cover. The controller’s logic control ensured proper event sequencing. Communication between the controller, the motion system and the I/O points is handled through the built-in Ethernet port.

“I was able to put together this control system in under two weeks. By automating the control of these functions, our astronomers can remotely control the telescope instruments from a home base,” said Alcott. “They no longer need to come to the Mount Hamilton Observatory to adjust the instrumentation.”

Multiple Galil Motion Controllers enable astronomers to precisely control the movement of giant telescopes from a home base.

In addition to the RIO upgrade, the Hamilton Spectrograph was fitted with Galil’s DMC-4080 Accelera Series motion controller.  The dual-loop position mode is used specifically for sub-micron, precise positioning and guidance of the correct light wavelength onto detectors. The dual-loop position data come from a 0.01-m resolution encoder that is placed on the stage and an
auxiliary encoder placed on the motor.

Additional upgrades using Galil controllers are in process at the Mt. Hamilton location.  The 68000 MPU based system of the Kast spectrograph is being replaced with a pair of DMC-4080 controllers. Additionally, a spectrograph is being built for a new remotely operated 2.4 m Automatic Planet Finder (APF) telescope that will be used to search for extraterrestrial planets.  Keck I’s flagship optical spectrograph, the High Resolution Spectrograph (HIRES), uses Galil controllers for precise velocity work in its search for extraterrestrial planets.

PEERING INTO THE DARKNESS
While the Lick Observatory sits atop the summit of 4200-ft Mt. Hamilton in the Diablo Range east of San Jose, CA, the W.M. Keck Observatory is positioned at the 14,000-ft summit of Mauna Kea, a dormant volcano on the Big Island of Hawaii. Its Keck I and Keck II are considered to be the world’s largest optical and near-infrared telescopes, each capable of collecting four times more light than the world-renowned Palomar 200-in. (5-m) telescope located in San Diego, CA.

Astronomers use multiple telescopes from several locations, including the Hubble Telescope, to survey and map the distant universe.
Photo courtesy of University of California Observatory.

Each of the Keck telescopes is equipped with a mirror 33 ft in diameter and composed of 36 hexagonal segments pieced together in a mosaic pattern. Keck I has been in operation since 1993 while the Keck II was commissioned in 1996.

According to a UCO data report, the beginnings of 8- to 10-m astronomical telescope development began at UCO/Lick, with the genesis of what eventually became the Keck telescopes. UCO/Lick faculty member Jerry Nelson designed the unique Keck mirrors, while UC Santa Cruz Professor Steve Vogt is credited for designing and building Keck I’s flagship optical spectrograph, the High Resolution Spectrograph (HIRES).

A second spectrograph at the Keck Observatory, the Eshelette Spectrograph and Imager (ESI), features Galil’s DMC-1500 motion controllers and was recently shipped and commissioned by the UCO/Lick team. DEIMOS, which also features the DMC-1500, represents the third and most advanced optical spectrograph built by UCO/Lick.

In addition to the three spectrographs, Alcott said that the UCO’s Atmospheric Dispersion Corrector (ADC) was built using a Galil DMC-2200 controller for the Keck I telescope. “This essentially helps to improve the differential refraction of the telescope as seen by the existing cassegrain instrument.”

A CLOSER LOOK AT HISTORY
Sandra Faber, a UCO astronomer, UOC professor and a founder of the Keck Observatory, said, “A great telescope like the Keck allows us to explore the River of Time back toward its source. Keck will allow us, like no other telescope in history, to view the evolving universe that gave us birth.”

In fact, UC Irvine scientists recently announced that with the aid of data obtained from the Keck telescope, they have discovered the minimum mass for galaxies in the universe: 10 million times the mass of the sun. “By knowing this minimum galaxy mass, we can better understand how dark matter behaves, which is essential to one day learning how our universe and life as we know it came to be,” said Louis Strigari, lead author of this study and a McCue Postdoctoral Fellow in the Department of Physics and Astronomy at UCI.

Galil
www.galilmotion.com

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.

Materials and Motion

Most motor sizing programs deal with time and torque analysis.  The traditional tradeoff is more torque for less time.  As an aside, the increase in electric motor torque comes with increased motor inertia, so it’s not for free.  And the motor costs are always a factor.

But this assumes that inertia is fixed.  And that’s an OK assumption as long as the assumption is made consciously.  Because, it’s only an assumption for the convenience of doing a time/torque tradeoff analysis, not reality.

The fact is that there are lots of options on inertia, whether the mechanism is new or existing.  If the parts are existing, you know what your starting parameters are.  But the real issue is to NOT ignore the options.  There’s a lot of performance bandwidth to be had by exploring materials and inertia options.

Here are some typical material properties; steels are approximately 7.86gm per cubic centimeter.  Good old steel, cheap, strong, dense.  Typical strength is 50-60kpsi without getting into the exotic alloys.   This is where most mechanical designs start because of steel’s low cost.

Machinable grades of aluminum alloys are routinely available in the 30-40kpsi range.  And the density is only 2.7gm/cubic centimeter.  Roughly one third of steel.  That means only 1/3 the inertia.  And only 1/3 the amount of torque needed to achieve a given motion.  So even though aluminum costs three times as much as steel, the cost of the motor to drive the load is reduced significantly.  In addition, most machine shops can run aluminum parts twice as fast, so it costs less to machine.  A lot less.  So at the end of the day, even though we could start the comparison of steel versus aluminum at direct material cost, that comparison wouldn’t take into account all the benefits.

Then there are the engineering plastics which have gotten better over the years.  Polycarbonate, for example, has strength in the range of 10-13kpsi with density of 1.3gm per cubic centimeter.  Half the density of aluminum, good strength and very inexpensive.  So in some cases, you could use more polycarbonate volumetrically to replace aluminum and reach comparable strength requirements while reducing inertia at the same time.

This is all based on common off the shelf materials.  The  options get even more interesting when you start exploring more exotic materials.

Titanium is a great alternative to steel when high strength and light weight are required.  But it’s expensive material to buy and because it is so hard, the machine costs are typically much higher than steel.  But when you have to have it, you have to have it.  And I have had projects where we needed the inertia advantage, and the premium paid for the material made possible some applications that couldn’t have been done any other way.

A friend of mine developed a material called AlBeMet, a blend of aluminum and beryllium.  The beauty of this material is that it has the strength of titanium at the weight of aluminum, beryllium being much harder and lighter than aluminum.  Beryllium doesn’t alloy well, but that’s the part the folks at Brush Wellman were able to get done.  And the results are phenomenal.  Again, it is expensive material, but you don’t need much of it to get the job done.  And where strength and light weight is needed, this stuff is incredible.

But the real point is, keep your options open when working on mechatronic designs.