More on Motor & Drive integration

The motor and drive combination is a basic building block of motion control.  Each component is useless without the other.  So it’s pretty important to come up with a good definition for what the “system” performance needs are to make sure that you end up where you need to be in your design.

Generally, we go to single source suppliers whose motors and controls are designed to operate together.  This approach guarantees minimum performance levels which the supplier can be held accountable for, and that’s a great thing.  But it usually comes with a huge list of features that will not be used in the application, but which you must pay for anyway.

In the industrial user community this is a great benefit because common environmental conditions such as dust, dirt, oil, or washdown conditions are more difficult to deal with and many products are built to these environmental standatds.  No special precautions are needed to make the equipment work.  And the suppliers warranty their equipment for continuous operation at stated speed, torque and environmental conditions.

But as we migrate into other businesses, machinery builders and equipment manufacturers have to apply the same motors and controls in larger numbers, and the overhead costs of motors and controls designed for industrial use become very expensive and make the cost of machinery less competitive.

In the machinery world, much of the electrical components will be built into control cabinets.  So if the packaging is going to be provided, is an enclosed controller somewhat redundant? Or can the motor speed control be integrated into the motor physically to reduce cost?  This is especially attractive if the cost of cabling a single motor can run 10-20% of the total cost of the motor and control.

There are performance elements that need to be considered in the applications as well.  How should the motor behave at zero speed?  What kind of torque regulation is needed?  What is the exact duty cycle of the application (on time versus off time)?   In these areas of motor and control operation the relationship of the motor to the drive is critical.  The drive electronics must have the ability to regulate current going through the motor without casusing overheating.  Some type of sensor on the motor must provide information about the position of the rotor at fairly high resolution, certainly more than every 120 degrees of rotation as with the common Hall effect sensors.

So as much as we may look at the purchase of a motor and controller as a system, there are a lot of nuances involved in the search process for the right hardware for any given application.  And that is probably one of the more difficult parts of doing motion control applications.

Hexapod Robot Gives 10lbs Of Force For Medical Applications

The miniature hexapod system provides more than 10 lbs of force and motion in all six degrees of freedom.
It can be used for manufacturing and placing of parts requiring very high precision, for microscopy applications or laser and optical alignment

After two decades of experience with the design and production of hexapod robots, PI’s electro-mechanical / piezoelectric six-axis positioners are among the most advanced multiaxis precision motion control systems in the world.

Features and Advantages of the M-810 Miniature Hexapod

• Operation in Any Orientation
• High-Stiffness 6-Axis Hexapod with 5 kg Load Capacity
• Very Compact: 10 cm Diameter, 11.8 cm Height
• 0.2 Micron Minimum Incremental Motion (40 nm Resolution)
• Long Travel Ranges to 40 mm (linear) and 60° (rotation)
• Powerful Controller with Freely Definable Virtual Pivot Point
• High Velocity of 10 mm/s
• Linear and Rotary Multi-Axis Scans

Parallel Kinematics Advantages
Parallel-kinematic motion systems have a number of advantages over standard serial kinematic (stacked) positioning systems:

Virtual Pivot Point: Rotation Around any Point, not unlike the Human Hand
Only one Moving Platform, No Accumulation of Guiding and Lever-Arm Errors
No Moving Cables for Improved Reliability and Precision
Smaller Package Size
Increased Stiffness, Reduced Inertia, Better Dynamics

Smaller Motors and Encoders, Controller & Software Included. The limited space necessitated the usage of new  technologies for encoders, motors and other integrated electronic components.  The M-810 is compatible with PI’s tried and proven hexapod controllers that are supported by windows software and a library of drivers and programming examples for applications such as optical alignment etc.  PI also provides simulation tools for hexapod integration.

PI Hexapods come with load ranges from 2 kg to >1000 kg.

Applications

Precision manufacturing, high precision placement of parts; alignment of optical components & lasers, microscopy applications, neuroscience.

www.physikinstrumente.com

DASH, The Robotic Cockroach, To Save Lives In Haiti

UC Berkeley’s Department of Electrical Engineering is developing mini-robots to help locate earthquake survivors easily, cheaply, and quickly, and without jeopardizing the lives of rescuers.

Inventing Industry in the (near) Future

The future of the US economy, and our future as an industrial power will be the result of our cumulative creativity.  New industries will be the result of new ideas, new technologies, new thinking.  It’s gratifying to see programs like the First Robotic Competition getting 215,000 junior high school and high school students exposed to and involved in robotics.  Problem solving, finding solutions, getting their creativity flowing to make a box of parts into a working machine with real world performance.  It will be even more interesting to see what those same kids will be into 5 to 10 years from now as they begin their careers in the many technology pursuits they are likely to follow.

Technology is a major driving force in the economy.  The ability to create whole new industries that have never existed before.

And there is a second driving force, sometimes made less obvious by the flash of the latest technical breakthrough.  Cost.  What is the relationship of cost to the development of industry?  As costs decline volume goes up.  Steel manufacturing per man year of labor increased 500% during a period of intense competition between the US and Japan.  And interestingly, one of the breakthroughs was the creation of the “mini-mill” which could produce specialty steels more cost effectively by making them in smaller batches.  Sometimes the solution is counter intuitive.  The steel industry was all about increasing batch size.  But serving the market with more complex products turned out to be easier with smaller batches, ultimately increasing overall sales and defending the US market to some extent from foreign competition.

Are there other cases where innovation was economically driven?  In the machine tool world the majority of manufacturers develop bigger and more complex machines so that a single machine can handle any operation.  This complexity tends to drive costs up quickly.  So the tendency is to find high performance machine tools costing hundreds of thousands of dollars.  In contrast, the HAAS company re-invented the machine tool business by focusing on making a low cost, high quality machine tool that many shops could afford to buy.  They were one of the first companies to have several models of machine tool in the $50K range.

They did it by concentrating on the economics of a machine tool that was profitable in operation.  That means a machine with a low cost to purchase, low operating and maintenance costs, and sufficient precision to meet the requirements of most operations.   In order to reduce their machine cost they had to develop their own controls platform.  They restructured everything in the design and manufacture of the CNC system to meet the cost objective.

In act, they are so successful, that HAAS is the largest CNC company in the western world.

Many similar situations exist in other industries.  In small plastic parts manufacturing there are a number of breakthroughs that have created lower cost parts in smaller batches based on innovative new tooling systems.  In metal fabrication there are new process like thixotropic molding and metal injection molding that have been developed to lower the cost of metal goods by making parts at lower costs.  These solutions are focused on reducing costs and other barriers to the entre of new products like tooling costs and minimum batch sizes.  And they represent major new markets that were not possible in the past, because they are focused on the economics of the industry they serve.  Decreasing the cost of entry and the cost of part manufacturing opens up new markets

So inventing the future can be technology.  Or as it can be economics.   It’s all innovation.  And it’s all about delivering value.

Step Motor Helps Robot Capture Images in 3D

Michael Comberiate, who manages the Special Projects Initiatives at the NASA/Goddard Space Flight Center, and his team of graduate and undergraduate engineering students build robotic vehicles that are used to test flight avionics, instruments, communications protocols, and approaches for planetary exploration. One project involves developing new communication protocols suitable for the delays encountered in space travel. This research involves the transmission of commands and images between the flight center on Earth and exploratory vehicles roaming various planets. The team works with a robot named Nanook that is outfitted with an imaging system that uses a step motor to help it collect data for 3D images. If Comberiate’s research proves successful, the communication protocols will be used in projects like the Mars Rover explorations, but they could also help solve communication problems here on Earth.

The robotic mothership undergoes testing in Anartica and Alaska while being operational from Maryland.  The current test system runs around $30,000 while the final rover that will be sent to Mars can exceed $100 million.

The Internet, for example, is not suited to a transmission delay of more than 3 seconds. When sending data from say Mars, line of sight transmission can still experience delays of five to ten minutes. Without line of sight, the delay is even longer, often hours.

When a communication protocol experiences a transmission delay, the usual procedure is to try to send the transmission again, from the beginning. This process is not suitable for planetary exploration, thus, the need for a new communication protocol that can handle long delays.

In their research, Comberiate and his team developed a robot that is being tested at the arctic and that could wind up in the Mars Rover mission. Communicating between their offices in Maryland and the robot at the South Pole is similar to communicating to a roving robot on Mars. The engineers experience satellite synchronization issues with volumes of data as the robot takes digital dot-matrix pictures of objects it finds, similar to what they will experience when transmitting with equipment on another planet. The images are sent to the engineers, who then decide what objects require a closer look. Dot matrix is used because it will transmit faster than a digital camera image.

The robot uses laser-based guidance known as LADAR (Laser Detection and Ranging) to find and take images of objects. It is semi-autonomous and has 3D scanning capability with image stitching.

The laser has a spinning mirror inside that sweeps the beam from left to right, measuring the time it takes to return a pulsed beam of infrared light from an object. The mirror spins four times on each horizontal line and then a step motor raises it up ¼ of a degree in the vertical axis. The laser spins again along the horizontal line, building the image one line at a time. “We scan with a ¼ degree of accuracy left and right, and ¼ degree of accuracy up and down,” noted Comberiate, “which gives us a 3D image. The colors show a low resolution of the distance to every point in the scan, but the computer onboard has about 1000 times more data than shown in the images. These images convey the critical information to the operators on Earth, but take 1000 times less time to send than a typical photograph.”

The 3D scanning provided by the mothership brings back images that show depth of field plus azimuth plus elevation.  The different colors shown in the images depict varying distances from the mothership.

Previous imaging systems could not deliver the needed resolution and the pictures displayed considerable distortion. “We chose the Lin Engineering step motor because it could handle the arctic conditions of -40 below 0 and still deliver smooth motion and hold position,” said Comberiate. “It gives us excellent remote control over the size of each step.”

In the rugged environments, the robot must operate off batteries. “We direct the heat from the electronics to where it is needed throughout the robot and to the batteries to keep them warm. Any motor we choose must be able to handle such environmental conditions.” Comberiate and his team will be continuing their research at the arctic in January 2010.

Discuss this on the Engineering Exchange:

Lin Engineering
www.linengineering.com

Could This Be The Wheel of the Future?

Most typical males constantly worry about our cars.  “Is my oil low?”, “what is that ‘clunk’ing noise?”, “Did my wife put premium unleaded in this like I told her?”, “Why is my ‘check engine’ light on again?”.  They even occasionally check the tires to see if they look low on air, and make sure to change them to studded tires for brutal winters.  But what if you didn’t have to ever change the tire again dependent on the weather? What if you could buy one tire that would be designed to change  to the weather?  Yes, there may be a new kid in town in terms of cars and transportation; the Pumplon wheel could be tire of the future.

The Pumplon wheel, which resembles the shape of a pumpkin, or even a melon depending on its shape (hence the name Pumplon), is designed to change shape to whatever the road conditions call for through a rotary mechanism.

Living in a climate where you get to experience the four seasons to their extreme, you can get wet & rainy springs, 100-plus degree summers, chilly and colorful falls, and blistering cold winters.  If you were to install the Pumplon on your car, according to Pumplon, you would not need to change them for any weather reason or road condition.  Say for instance it was spring-time and there was a heavy rainstorm, by switching the Pumplons to the skinnier shape, it would increase contact pressure, cutting through the water on the road, allowing you to more safely arrive at your destination.  Or if the road is flooded, switch the tires to the widest setting to make the car amphibious.  In the summer, one may just want to hit the highway and cruise with the top down and feel the find in their hair, and for that they would change the Pumplon to the normal, or “ball”-look setting.  For the fall and winter, when you may be trudging through mud or snow (intentionally or not), you will need as much surface area out of my tires as possible.  You would consequently set the tire to its “melon” shape to get as much grip and surface area as possible, hopefully getting yourself unstuck in the mountain, or get you through the snow-packed roads to grandma’s house for Christmas.

With the world “going green”, it has brought about some rather interesting, very innovative ideas and concepts, and this one is no exception. The green benefits can be very numerous, from reducing travel times to increasing fuel efficiency.

The Pumplon wheel is the creation of Osmar Vicente Rodriguez, a native of Brazil, also a professor of industrial design at RCA Innovation.  His intention for creating the Pumplon was primarily for solving transportation problems for farmers in developing countries where the majority of roads are either unkempt and in very bad condition.

How does it work, you may ask?  The secret to the Pumplon is a steel shaft that can expand and retract by means of a rotary mechanism, pneumatic or hydraulic, adjusting rings which makes the wheel deformation wider or narrower.

The material of the tires has been the subject of special consideration. According to Rodriguez, “initially they were steel, but we replaced it with a thermoplastic material, which is easier to produce, lighter and cheaper, and is recyclable. The cover is of vulcanized rubber, similar to that used in tires conventionally, but more flexible to allow changes in size.”

Motion and Software

Rockwell Automation recently had it’s Automation Fair during which a number of new product announcement were made.  The company has announced a collaboration with Dassault Software Systems to create a suite of tools that deal with various applications of industrial automation and manufacturing on the plant floor.  Of particular interest to the mechatronics world is coordination between Solidworks modeling software and Rockwell’s Motion Analyzer.  In addition, Rockwell has made an important ease-of-use connection between the Motion Analyzer which has traditionally been used for sizing motors, and the control system software.

As an experienced user of early version of the Motion Analyzer, I used the software as a tool to analyze tradeoffs between time, torque and inertia to optimize customer machinery and processes in motion control applications.  Good motion control starts with good mechanical design, and there are so many variables and tradeoffs, that it’s often difficult to navigate your way to the best solution.  A good motion analysis tool automates the process so that you can examine an axis requirement and explore several options for how the axis can be optimized.

The results of the Motion Analyzer can be directly integrated into the PLC editor RSLogix.  This is usually an area where there is a major duplication of effort, since everything that you have to program in the control system is data that you have worked with in the Motion Analyzer.  So kudos to the Rockwell team for getting this feature added to the RSLogix suite.

The Motion Analyzer uses information about the Rockwell Automation motors and amplifiers to match inertias to loads and duty cycle requirements to the thermal capability of the equipment.  This is an often overlooked subltety of the equipment, but at the end of the day, it’s all about the amount of heat you can get rid of.  And the duty cycle contains all the critical information about how much energy you need, when you need it, and how long you have to dissipate it.  In addition, I have found that everyone’s idea of thermal modeling is different.  So it pays to do the simulation work at the front end of the design.

But, we always used to joke that we were doing solid modeling anyway.  Everything was a cylindrical object of a certain diameter, length, material density, etc.  So it stands to reason that integration with a 3D modeling system would make sense.  After all, a little step up in capability could lead to a lot better design work from the start. And the ability to link mechanical design at the earliest part of the design cycle, directly to the output at the motor and control system, makes for better outcomes every time.

Big Wind Machines

Recently I had occaision to discuss the merits of wind power with a colleague.  In particular there is a controversy between horizontal axis wind turbines, the giant propeller driven systems you see in advertisements, and vertical wind, which does not have much presence in the marketplace.  The premise is that horizontal systems can take advantage of the large swept area of the propeller blades to generate a great deal of force.  I’m not sure if this is supposed to imply that large swept areas intrinsically convert more kinetic energy from the wind into electricity.  And it is easy to conclude that this is the benefit of horizontal wind turbines.

Except that there is a fundamental mechatronic system at work.  The large propeller turns at low speeds, typically around 18 rpm on average, and there is a massive gearbox that is used to increase the speed of the output to turn a generator at high speed, which is typically where generators are most efficient.  The gear increaser has the effect of also increasing the amount of torque required at the input (propeller) by the gear ratio.  So if the gear increase is 100:1, then the propeller must be size 100 times larger in swept area in order to produce the needed torque to turn the generator.

This actually gets a bit worse since the mass, and it is very substantial, of the gear box itself represnts inertia that is resisting the turning of the blades.  And there is a generator rotor at the end of the gearbox whose mass (massive mass) is now resisting the turning of the propeller by the square of the ratio.  So if the ratio is 100:1, the inertia is increased by 10,000 times.  Even magnetic drag, or the residual attraction of the rotor to the stator, will get amplified in the same fashion, making it a significant force to contend with.

Add to this situaion a list of systems losses for overall fricitional loss of the bearings and gearbox, parasitic losses for steering and blade pitch adjustments.   Efficiency losses due to long distance transmission of power, that is a by-product of the remote sites that have favorable wind conditions.  It’s a pretty difficult situation to engineer.  And they keep proposing to build them bigger and bigger, hoping that the scale effect will overcome the problems.

All of the vertical wind systems I have seen so far are much smaller due to the fact that smaller rotors can turn at higher speed and power electric generators directly.  The flax axial generator is very popular in do-it-yourself designs that people are experimenting with in their back yards.

But vertical wind can also scale up.  And there are a few companies doing it.  With convertional wind power costing $2/watt, vertical systems could bring that price down very quickly and allow systems that can be installed close to the point of use or in offshore arrays where generation takes place almost 100% of the time.  Unlike the average 31% on the large land based systems.

Now that’s progress, 300% increase in energy generation at lower cost.  Hope it comes to market soon.

Motors and Electronics

I have been involved in the motors and controls industry for quite some time.  Most recently, I worked for a company exploring the possibilities that new generations of RISC based microcontrollers offer for lower cost and improved performance motor applications. This effort has caused me to review all the major motor segments, DC, AC, Brushless and stepping motor, to re-examine my assumptions about what goes on and what brings us to where we are today.

Each motor family has it’s own properties due to the basic physics of the motor’s design.  DC motors which were first proposed by Faraday, actually evolved into workable machines, but electric power was not commonly available.  DC motors are intrinsically variable speed, all you have to do is vary the voltage.

AC motors which came later, proved to be more versatile when AC power distribution became widespread.  AC motors are constant speed and require no control, just a switch to turn them on and off.  As a result of the simplicity of the motor’s construction and implementation, the are very popular and found in lots of applications.

But for every application of a standard motor, there are dozens of applications where there is a need for something a little different.  And oddly, the more rules that we try to apply to how things work in the motor industry, the more exceptions there are to deal with.  The Small Motor Manufacturers Association has a motor family tree with 60+ categories.  And we keep coming up with new ones.

But the really strange thing that keeps coming up is the fact that motor manufacturers are really mechanically oriented.  Motors are machines that convert electricity to mechanical power.  So it makes sense to be focused on how much starting torque there is, what happens the load is stalled and things of that nature.

Ironically, the mechanical focus on motors is often to the exclusion of the control electronics.  Nowadays, all variable speed motors require some type of electronic control, from the variable frequency AC drive to the advanced brushless DC drive.   So for the most part, you buy a motor from one company and controls from another company.  Of course, in the modern marketing era, a lot of companies source the product they are missing and private label it.  But the real expertise may be somewhat harder to get at.

And there’s nothing wrong with this situation.  I just think it’s odd.  Clearly it’s difficult to master two different fields of engineering.  And from the standpoint of the technical competency itself, there would seem to be little in common between power electronics and the electromechanical issues of motor manufacturing.  But there is something of an imperative in the case of electrically controlled motors.  The problem being that the performance of the motor is closely linked to the electronics.

Variable frequency drive suppliers are more apt to be in the motor business, as Reliance, Baldor and some others are.  But in general, motor suppliers and drive electronics suppliers are two completely different activities.  As I have reviewed many of the large market applications, I believe there are opportunities for collaboration that will offer significant improvements in sizem weight, performance and economic opportunities for for cost reduction that would provide adequate incentive for those willing to work toward common goals.

Mechatronics + NASA = New Lunar Rover

Every year, for two weeks in the Arizona desert at Black Point Lava Flow, NASA’s Desert Research and Technology Studies group (Desert RATS) conducts technology development tests in anticipation of lunar exploration. Teams of engineers and geologists from several NASA laboratories as well as a variety of private and academic partners participated in this year’s test, including two key members from ASU’s School of Earth and Space Exploration.

New for this year was an intensive simulated mission during which two crew members, an astronaut and a geologist, lived for more than 300 hours inside NASA’s new lunar wheels, the Lunar Electric Rover (LER). The explorers scouted the area for features of geological interest then donned spacesuits and conducted simulated moonwalks to collect samples. The crew also docked to a simulated habitat, drove the rover across difficult terrain, performed a rescue mission and made a four-day traverse across the rough landscape.

“We are continuously working to meet the challenges of a human outpost on the moon,” says James Rice, faculty research associate in the school and principal investigator of one of the study’s geology traverses. “To meet these challenges, scientists and engineers must conduct hands-on field tests and research here on earth to better prepare and understand the complex challenges that will be encountered on the moon.”

Analogs are conducted to test robotics, vehicles, habitats and in-situ resource utilization in realistic environments that will aid astronauts, engineers and scientists as they define ways to combine human and robotic efforts to enhance scientific exploration. The Arizona desert is well suited for testing technologies and procedures for future human-robotic exploration in extreme environments.

“You have to test hardware and concepts in a real-world environment with real geology, slopes, rocks, dust … and the unexpected,” Rice says. “It can’t be done in a controlled laboratory. The terrain of Black Point Lava Flow contains challenging topography for LER operations and also contains lunar and Mars analog geomorphology and geology.”

Rice was in charge of making traverse routes or paths that the rover and crew followed during the simulation. He had to factor in science objectives, rover driving speed, time for the crew to put on and take off spacesuits before and after geology investigations, and the time required to drive to the next station.

“We had a very detailed timeline from Mission Control that we had to work with to make sure we achieved our science goals,” says Rice, who has been involved with the field tests for about six years. “Sometimes we had issues with loss of communications, equipment or the rover and this caused the whole operation to get behind on the timeline. It was very realistic.”

Kip Hodges, founding director of the school in ASU’s College of Liberal Arts and Sciences, and science team member of Desert RATS, has been involved with this year’s tests on a number of levels. He was the principal scientist of the K10 robot, which was developed at NASA’s Ames Research Center and deployed prior to the simulated mission to identify areas of interest for the crew, and he served in the science “backroom” for the LER human tests.

“The K10 robot was employed in these tests in order to evaluate the added value of robotic reconnaissance of a planetary landscape prior to sending humans into the field for scientific research,” says Hodges. “While the final field test results are not yet in, I think that my collaborators and I are extremely pleased with the exercise and looking forward to further tests. For example, we are also using K10 for follow-up work after human exploration. In that case, our analogue study site is in a bit farther afield: the high Arctic of Canada. Perhaps we’ll also deploy K10 for this purpose next year at the Desert RATS tests.”

New wheels for a new generation of exploration

LER, the next-generation rover, is an all-electric vehicle with 12 wheels. A little bigger than a Humvee, the LER was built for extreme exploration. The frame of this mobile base camp was developed in conjunction with an off-road race truck team, making it able to travel hundreds of kilometers over rugged terrain. Its wheels can move sideways in a “crabbing” motion, one of many features that make it skilled at scrambling over rocks. During the mission, LER was able to climb slopes on the lava flow that the team’s SUV chase vehicles couldn’t handle. Remarkably, the advanced suspension and drivetrain of the LER allows it to perform such feats using only 20 horsepower, an order of magnitude less than the standard off-road vehicles it left in the dust.

If that isn’t enough to make the Apollo-era astronauts envious, LER is also capable of housing two astronauts for up to two weeks with sleeping and sanitary facilities. It is equipped with a time- and space-saving concept called suit ports, designed to allow astronauts to quickly enter and exit their EVA suits via a rear-entry hatch.

“Unlike during the Apollo Program where the astronauts had to drive their lunar rover wearing space suits,” says Rice, “this new manned lunar rover concept with its pressurized environment will allow the crew to drive wearing more comfortable clothing and not be stuck in a space suit.”

NASA has not yet confirmed the technologies that will be used in future lunar missions, but with the successful testing of analogue systems and procedures in simulated environments here on earth, we move one step closer to a sustainable human presence on the moon.

The Desert RATS tests have been held for more than a decade, as engineers from NASA centers work with representatives from industry and academia to determine what will be needed for human exploration of the moon and other destinations in the solar system. It is the culmination of the various individual science and advanced engineering discipline areas’ year-long efforts. This year’s work built on the investigations of previous years and increased the scope and length of the tests.

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