Motor and Drive Combinations

There is a subtle premise that often escapes us as we talk about motors and the controls that run them.  It is that the motor and controller operate as a package.  In most situations, a customer specification is for input voltage and output torque and speed.  That’s all that is important.  How you get there doesn’t matter a great deal.

But ironically, most motor manufacturers are predominately mechanical engineering centered.  And most drive electronics companies are electronics centered.  And they have very little in common with each other.  Except that their products must work together.  And oftentimes, that’s where the trouble starts.

The drive manufacturer warrants that his drive will produce current and voltage.  But the the motor can have very complex constraints to deal with in response to the excitation of the electronics.  How accurately a 6 step approximation of the sine wave performs, for example, can result in overheating in the motor depending on the loading of the system.  And as the motor winding heats up, the resistance in the motor can change dramatically, especially in the low inductance windings that are common in many specialty motors available today.

Then there are the cabling issues for connecting the motor and drive electronics.  The ac drive industry found out quickly that long wire runs can result in stored energy in the wires themselves.  Standing wave phenomena could cause higher voltages than expected and blow holes in the winding insulation in the motor.

Power semiconductor prices have fallen considerably in the last few years creating situations where it is sometimes cheaper and more reliable to put in parallel devices than to attached single power devices to large heat sinks.  This leads to some serious new options for packaging the electronics.  How about drive circuits in the end bell or junction box attached to the motor?  Actually, some models of the GE ECM motor (now owned by Beloit) are ac fan motors with variable frequency drives and intelligent controls built directly into the motor end bell.  You may have one in your main air handler in the air conditioning system of your home.  I was surprised to find out that I did.

I used to think that thermodynamics of these systems would be impossible to manage.  But the fact is that the drive efficiencies are getting really good.  One team I worked with was producing a 500 Watt brush drive that only shed about 20 Watts of loss at full load.  That’s some incredible efficiency.  So the notion of integrating motors and drive electronics is much more reasonable than it used to be.  And there are stepping motor packages that have been doing it for years.

So where is this all heading?

The fact is that the motor and drive electronics must work together as a package.  There is an increasing need, and an opportunity to create further performance enhancements, by the two technologies working more closely together.  More innovation will lead to better energy efficiency and new design opportunities and a chance to recharge (pun intended) an industry that has been losing share to offshore competition in the last few years.

Scientists Create First-Ever Circuit Powered By Light

For the first time, scientists have created a circuit that can power itself, as long as it’s left in a beam of sunshine. Created by scientists from the University of Pennsylvania, the world’s first photovoltaic circuit could eventually power a new line of consumer devices or even model the human brain.

Right now the creators can only coax minuscule amounts of electricity from their photovoltaic circuits, far too little to power consumer electrical devices, although those amounts could quickly skyrocket.  There are plenty of other ways they say that they can squeeze more electricity from light. Right now only about 10 percent of the photovoltaic circuits on a glass side work. Increasing that number will boost the power output.  Another way to get more power is by turning their 2D structures into 3D structures. Stacking multiple layers of light-collecting and electricity-using circuits would also boost power.

The photovoltaic circuit is a scientific breakthrough, not a technological one. These new circuits will most likely never replace their silicon counterparts.

Photovoltaic circuits could be ideal for other applications, however, such as powering tiny robotic devices or running computer calculations at the speed of light.  Far into the future, these circuits could even be used to set up as artificial neural networks that could model the brain.

At their most basic, computers represent data as on or off, a “0″ or a “1.” Using light instead of electrons, these photovoltaic circuits could store data from, say, one, two, three or four. Each number would correspond to a certain wavelength or color of light — red, green, blue and yellow, for example. To model the human nervous system, each color of light could correspond to a different neurotransmitter, say red for dopamine and blue for serotonin.

The potential applications of the technology are huge, but will take years to develop into any kind of practical equipment.

www.news.discovery.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.

Magnetics 2010 and Motion, Drive & Automation

There is a small industry conference that takes place every year with a lineup of industry experts that is top notch by any standard.  It’s called the Motion, Drive and Automation Conference put on by E-Drive magazine.  This year it is located at the Disney Hilton Resort in Orlando and is taking place on January 28 & 29.   The conference includes a wide range of industry experts from many fields of advanced electric motor design, advanced motor control concepts, power semiconductors and state of the art motor testing system.  There will be a lot of technical and product presentations that showcase leading edge technology in electric motors, precision gear reducers, new technology for motion sensing, and a number of improved power semiconductor devices for the motor control industry.  This is a great place to get up to date on the latest technology that will impact of motor and control technology across many industries over the next few years.

In addition, the Magnetics 2010 Conference will be running concurrently at the same venue.  Magnets are a strategic material without which many motors would simply not operate.  In the ever-changing motor industry, there is always a new design that seeks to make an enhancement over previous solutions, or introduce a new solution to old problems.  Declining prices for Neodymium Iron Boron magnets over the last few years have created a number of novel design shifts which have been instrumental in bringing more varieties of permanent magnet machines into the forefront of motion control and mechatronic technology.  To the point where over the last two years a resurgance of permanent magnet rotor designs have been created to improve the energy denisty and lower the cost of specialty motors in washing machines and air conditioning compressors.

This last development, combined with the forecast increase of hybrid electric car sales coming this year, are expected to increase the sale of permanent magnets by 10-15 percent by 2011.  That’s a staggering jump in a market that is almost exclusively supplied by China.  And there is no assurance that China can meet the forecast production.

The US Department of Commerce usually has a say in the sale of products or businesses to foreign countries that are deemed to be strategic or sensitive technology.  In fact, I got stuck in a situation where my employer was told specifically that we could not sell a CNC controller to a Korean customer.  That’s pretty small potatoes compared to controlling the supply of permanent magnets which influences billions of dollars worth of electric motors manufactured and sold all over the world.  So it strikes me as a little odd that the sale of Magnequench to its current owners, Neo Materials, was completed without a much discussion. leaving the US without a domestic magnet supplier.

There will surely be a lot of discussion about this situation at the conference, and I will be in attendance to get the latest information on the subject.  So look forward to a review of the conference in an upcoming post.

Multi-Touch ‘Resistive’ Touchscreen Controller Chip

As the latest high-tech devices such as smartphones, mobile internet devices and netbooks adopt multi-touch touchscreens to support increasingly sophisticated ‘apps’ and games,STMicroelectronics has introduced a multi-touch ‘resistive’ touchscreen controller chip to optimize the Bill of Materials of the electronics supporting this advanced capability. The STM32TS60 is the first member of ST’s new STMTouch family, which offers a broad portfolio of solutions including multi-touch devices and proximity and touch-key sensors.

The new multi-touch controller detects up to ten simultaneous touches with fingers, nails or stylus, enabling application designers to replace complex menu sequences with more direct and natural user controls. Actions made easier with multi-touch capabilities include browsing and selecting options, handwriting and data entry, arranging and sizing windows, picking up and dragging images, and fast and intuitive game play. Other abilities include drawing pictures, using touch pressure to adjust line thickness.

Employing resistive touch-panel technology, the STM32TS60 controller offers customers a real alternative and complements the recent industry trend for using capacitive touch technology. Resistive technology is a cost effective and mature high-volume solution that has seen dramatically improved performance over the past few years in terms of durability and display transparency. In addition, it easily overcomes EMI (electromagnetic interference) noise issues, which can be an inherent limitation with alternative touch technologies. Resistive technology is already widely used in PDAs and similar touch-enabled devices and the screens are readily available in standard LCD sizes and at competitive prices.

The new chip combines the company’s STM32 microcontroller architecture with PMatrix^TM Multi-Touch technology from ST‘s partner Stantum to achieve fast response times while minimizing system complexity and component count.

The STM32TS60 single-core microcontroller is an added-value solution compared to other expensive multi-core processor or digital signal processors (DSPs) requiring specialized programming expertise.

The STM32TS60’s high EMI immunity makes it suitable for use in multi-function wireless products such as cellphones, notebook PCs, netbooks and mobile Internet devices. Moreover, its low power consumption helps to maximize operating times and recharge intervals, and is a direct benefit of the STM32’s energy-saving design features and ARM® Cortex™-M3 processor conceived for power-sensitive embedded applications. In addition, very-low-power idle mode with ‘wake-up on touch only’ helps further extend mobile battery life.

The STM32TS60 is housed in a 7 x 7mm 144-pin UFBGA package, and is now sampling to lead customers. Volume production is expected for Q2 2010.

www.st.com

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

New, Brighter, Sharper LED Signage

STMicroelectronics recently announced a new series of highly accurate LED drivers with automatic power saving, enabling electronic signage such as road signs, advertising, stadium displays, battery or solar-powered signs and similar equipment to deliver better, high-resolution viewing by ensuring consistent brightness across the viewing area.

The brightness of an LED is closely related to the drive current, usually supplied by a separate driver chip. As each new generation of LEDs produces greater brightness at lower drive current, overall efficiency is increasing but so, too, is the need for more accurate current control. This control is essential to prevent excessively bright or dark areas from damaging the visual effectiveness of signs and screens, which can employ tens of thousands of individual LEDs.

To provide the enhanced current control designers need, ST has introduced a family of driver chips capable of supplying 16 LED channels with driving capabilities of 3mA to 40mA and bit-to-bit accuracy within ±1%. This accuracy is superior in tolerance to alternative drivers providing comparable drive current. In addition, as a large display may require several thousand drivers, ST’s new devices also provides excellent current matching from chip to chip (±2%) to further enhance visual performance.

The new LED drivers are theSTP16CPP05, STP16CPPS05, STP16DPP05, and STP16DPPS05. In addition to their enhanced current accuracy, they also provide optional features including ST-patented automatic power saving, as well as built-in LED error detection. Available variants allow designers to specify either or both of these value-added features, in a choice of four industry-standard package options.

The patented automatic power saving allows the drivers to turn off independently when no LED drive data is provided. This function delivers two benefits: software design is simplified as no power-save algorithm is required; and power savings are increased as the drivers turn off more quickly than is generally possible under software control.

Error detection helps to improve maintenance and boost productivity for signage operators. If an LED in the display fails, ST’s LED drivers can detect either of the two possible failure modes (short circuit or open circuit) and communicate the failure to a central point. With this information, the system could be programmed to inform field maintenance crews of the necessary replacement parts in advance. In applications such as road signage, where reliability is critical, this feature can enable faults to be repaired quickly and efficiently.

Chips, Chips, Chips

Semiconductor manufacturing is still a little bit like magic.  It’s hard to imagine packing millions of transistor into tiny spaces and creating  cellphones, computers, flat screen television, digital cameras, CD players and so forth.  And the industry keeps pumping out the innovations.

And there are so many technologies, all focused on solving application problems but balancing the economics of development cost and manufacturing scalability.  Where would the Oui or iPhone be without accelerometers that are really inexpensive?  Fax machines without G3 communications chips,  or $49 printers without stepping motor chips and ink jet controls?  All benefits of high volume economy of scale.

Industrial control systems have generally required chip technology, but in numbers of chips considered too small to merit custom designed solutions.  But the Rockwell Control Logix concept breaks the partitioning of applications by applying the same control processor to all kinds of control equipment, variable frequency drives, programmable controllers, HMI’s, you name it.

Is there an ultimate chip?  A chip solution that does everything?  Not really.  But the wizards of the microcircuitry world keep coming up with new architectures.  New approaches to existing applications that offer price or performance attributes that will hopefully trigger lots of new designs that result in breakthrough products.

Recent trade press is buzzing about a new processor that combines the logic solving capability of FPGA (Field Programmable Gate Arrays) with ARM (Advanced Risc Machines).

FPGA excels in the ability solve logic, and has scaled up to massive numbers of gates and tremendous processor speeds to solve enormously complex applications.  Even applications requiring real time operation like motor control can be solved through FPGA with proper attention to detail.   Applications that were considered impossible a few years ago are now within the range of these processors.

But using gate arrays may not be the most efficient way to do motor control.  Hard real time motor control requires a great deal of analog processing to monitor conditions in the real world (like voltage and current) and the ability to respond to dynamic changes through complex programming and mathematical models.  Much easier for ARM processors with super efficient instruction sets and single cycle multiplication and division.  In some designs 16 channels of high resolution A to D converters and direct PWM capabilities.

So combining the two technologies seems like the ideal solution for a huge range of industrial control applications.  And if you get it all in one processor, wouldn’t that be great?

I  can’t wait to see what new product developments take place in the next few years with this kind of processing power available.

Power Supplies Target Medical Applications

A new digitally controlled 300W TDK-Lambda power supply, designed specifically for medical applications, is now available from RS Components.

With a 4kVAC reinforced input to output isolation and other specifications such as an output-to-ground isolation of 1500VAC, the EFE300M meets the rigorous international safety standards of IEC 60601-1 for medical equipment, making it suitable for use in B and BF type medical applications. Regulated DC outputs of 12V or 24VDC are standard and other voltages can be provided.

With a 3-inch x 6-inch footprint with less than a 1U profile (1.6-inch max), the EFE300M can be incorporated easily into designs where space is limited so end equipment can be smaller and cooler. Other features such as a redundant operation capability and a high current standby output make the EFE300M equally suitable for high integrity applications including broadcast, instrumentation, routers, servers and security networks, as well as, ATE, factory automation and mechatronics, says the company.

www.electropages.com

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.

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