What is Control – Part 2

While considering the nature of control we tend to focus on the two big issues; hardware and software.  This is very understandable since hardware selection has a lot to do with cost and functionality.  Software has more to do with how we program the hardware to execute the tasks that the control system is intended for.

There is a complex interaction between the two that is often not expressed.  The hardware has “firmware” that defines the exact capabilities of the hardware.  The software is a tool for users to create programs that the hardware executes.  These programs are the embodiment of the useful behavior that the process or machine is intended to accomplish.

So is machine control hardware or software?  It’s both.  The hardware is only capable of executing instructions that we built into it by it’s microprocessor and firmware.  Those instructions are merely a library of possible functions.  The user program calls those firmware functions in an organized manner to accomplish some beneficial result.

There are a couple of really significant issues that are often overlooked.  One is experience.  A lot of experience is required to make good product selections.  The application of control systems involves understanding the application requirements and matching those requirements to specific hardware.  Motion systems that do “high speed registration” for example, require very specific hardware to capture the input signal to define where the registration target is, and then to turn off so that input noise is filtered out.  This is a very specific feature, and if you don’t have it, you generally can’t create it.

Complex control requirements like coordinated motion are both hardware and software dependent.  The simplest example is to draw a circle with two linear axes.  In order to know how to deal with this application the control system must have a dedicated motion controller either as a stand-alone element or embedded within the control architecture.  Most high end PLC’s offer a 4-Axis dedicated controller card that do this.

After all the wrangling is done to get the application and hardware properly scoped out, after all the software development work is done, there is still an aspect of control that is missing from this discussion.  It is the external wiring of power, power protection, and safety systems.  These circuits are separate from the control system hardware and software, and yet embody elements of control that are sometimes necessitated by the hardware itself.

Variable frequency drives and some servomotor drives require time to charge their capacitors.  Most drives has interlocks that will prevent operation until the caps are charged.  PLC processors require a time delay to insure that the I/O devices are powered before the processor “wakes up”.  If not, the processor will immediately fault.  The wiring of emergency stop circuits are physically separate and frequently use reverse power logic, they are energized when “off”, to all detection of broken wires.

All of these behaviors are part of the control system but generally not considered in the early phases of system design.  Yet all are required in order to make safe, working systems.

The Cost of Control

In the computer industry we hear interesting metrics about the ever increasing capabilities of processors and hardware.  That capability is usually measured in a performance metric such as MIPS or Million Instructions Per Second.  We don’t generally talk about capability per dollar spent.  However, the cost of control is a major metric when evaluating control components that go into industrial and commercial machinery.

The cost of control is extremely important in terms of its impact on what is “practical” in the world of production.  Even in medical, military and aerospace systems where cost is often a secondary consideration, the actual cost and performance of a new process or piece of equipment has to be gauged against the benefit that it will produce.  If the benefit is greater in value than the cost, then funds and effort need to be committed to the new project.

There are significant trends in the marketplace that are constantly changing the cost of control.  As we look at the mechatronic arena in particular, recent increasing cost trends for copper wire, lamination steel and permanent magnets have been pushing prices up steadily in the range of 5-6% per year.  This situation is expected to continue.

Recent threats from China about restricting export levels for Neodymium magnets have made magnet pricing very speculative, read high as a kite.  However, Molycorp and others around the world are bringing Neodymium ore into the market and companies like Arnold Magnetics are gearing up to provide finished products without the use of Chinese sourced material.  Good new to those in the motor sector.

On the control side of mechatronics, the power Fet has dropped in cost by 50% in recent years and costs are expected to continue to decline following the traditional cost performance over time that is characteristic of the semiconductor industry.  Add to this the incredible cost performance improvement in embedded microcontrollers used in motor control circuits and you have even more good news for the mechatronic suppliers.

Bandwidth for these controllers now provides motor control that operates in the sub-microsecond range with efficient instruction sets and pre-configured PWM macros to make code creation more efficient.  Typical pricing for these processors is well under $5 making them ideal for a wide range of applications in industry and commercial white goods.  The marriage of low cost motor control cores and reduced cost power electronics should signal declining prices for motor controls for the mid- to high performance applications.  This cost improvement should more than offset the price increases expected in the cost of electrically controlled motors.

Some families of processor have native CAN or Ethernet communications interfaces with multi-threading software to guarantee that high priority instructions in the motor control code will not be impacted by messaging from outside applications.  Network technology is providing fast, and in some cases, deterministic forms of Ethernet like EtherCat making the servo network the control architecture.   This approach to the network demands of high performance control reflects a general shift to low cost, high reliability platforms that are ready to transform the controls landscape in the mechatronic arena.

It’s an interesting time to be in the controls business.

Motion Control and Communications

I used to caution customers, actually I preferred to talk customers out of the idea of using control networks with motion control applications.  But having been around motion control, now mechatronics, for 30 years, a lot of things have changed.  In fact, the whole game has changed.

Motion control has always been challenging to control systems because it is the hardest of hard real time applications.  But our notion of time has changed.  The processors that manage electronically commutated motors operate at 50mHz with incredible code efficiency, requiring nonosecond precision oscilloscopes to measure events.  Considering that we used to be thrilled at the prospect of controlling things in the microsecond world, I’d say that’s game-changing (another over-used catch phrase).

So corresponding changes in the communications realms shouldn’t be a surprise.   Though I think that we hadn’t even invented Ethernet 30 years ago.  But ignoring that detail, we’ve seen Ethernet technology bloom from a mere megabit per second to Gigabit Ethernet.  Bandwidth is not a problem.  And with universal adoption of the technology by business and telephone communications systems, the cost of the physical layer and connectors have dropped to incredibly low levels.  As you would expect.

In fact, Ethernet is so cost effective, it’s starting to take over the industrial control landscape.  To the point where Ethernet connectors are available for dust tight and wash down environments.  That’s pretty extreme for a consumer grade communications platform.  But that’s wasn’t my primary point.

The dilemma for applying a communications protocol to motion control is it’s ability to move data faster than the synchronous control of the motor.  So industrial networks, even at a few megahertz, can’t keep up.  Particularly when there are two axes of motion which must coordinate their relative motion at the update rate of their position feedback sensors.  And in the case of linear motors with extremely high resolution tape scale encoders, you can end up in situations where the feedback is running 20 mHz.  So good luck coordinating 2 or 3 linear motor axes.

But, of course, we do this kind of thing every day.  With micro controllers.  But not with networks.  But what if you could?  It’s coming soon.  IEEE-1588 is a time synchronous version of Ethernet that permits precise coordination of data movement over Ethernet.  And it’s compatible with existing Ethernet networks.  Sounds like a pretty good deal.  And that makes it a workable solution for coordinated axes of motion control.  It’s been tested at a technical university in Zurich Switzerland.  And like good solutions, may have many other applications.  Look for it in new motor control products coming soon.

Tips for the Control Side of Mechatronics

The ACOPSOSmulti cooling system is available in standard, feed-through and water-cooled versions.

By Leslie Langnau, Managing Editor
Design World

In mechatronic projects, the focus is often on the mechanical and electrical aspects of a system as engineers concentrate on throughput, speeds, accuracy, and so on.  How these system goals affect the desired control selection may not be addressed until too late to make changes. Mechanical engineers do their part, then electrical engineers do their part, then, the controls engineers must make it all work.

In addition to finding ways to improve the communication and interaction of the various engineering disciplines, there are other design aspects that affect controls to keep in mind. Robert Muehlfellner, Director Automation Technology, B&R Industrial Automation Corp., offers a few. Read more

Energy Stimulus Debate

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

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

Sartorius Introduces ProBatch+ Software

Goettingen, Germany – The Sartorius ProBatch+ software used in conjunction with the Sartorius X-Family, Combics Pro, and other PLC controllers offers the user efficient management of original raw material and recipe data. The powerful ProBatch+ software program allows for visual presentation of the running process and enables all batch procedures to be both visually monitored and easily controlled.
Read more

Control Considerations in Mechatronics

PAC hardware can be used in multiple domains, including logic, motion, drives, and process control. And the software programs all control and monitoring tasks of multiple domains. This feature enables the programs to “flow” as the requirements of the application dictate.

Critical to any mechatronics system is the control. One of the newest controllers is the programmable automation controller. Here are tips on selecting one for your specific application.

By Kelly Downey,
Electrical Engineer
Opto 22

Industrial applications continue to increase in complexity, requiring controls that can integrate multiple systems that incorporate discrete, motion control, and process tasks and that can gather, process, and transmit real time data to company databases. Programmable automation controllers (PACs) can be one choice for managing this complexity because they combine the capabilities of several traditional control and monitoring systems. Typically, they have features found in programmable logic controllers (PLCs), distributed control systems (DCSs),remote terminal units (RTUs), and personal computers (PCs).
Even so, control manufacturers offer PACs with varying capabilities. Thus, there are several considerations to keep in mind with your selection. Read more

Networks and Control

Network technology has changed dramatically. Speeds that would have seemed unimaginable ten years ago are off-the-shelf these days. And with the speed a lot of bottlenecks have disappeared. With the possible exception of motion control applications.

Networks for motion are still a in category by themselves. Sercos has gone through major evolution to its current level, Sercos III, to continue to hold its position as the top performing motion network. Other implementations of Ethernet, EtherCat, Powerlink and others bring the high bandwidth available in Ethernet and add features to the network to insure its performance for motion control applications.

But the network technology momentum continues. There is a specification from IEEE, 1588 Protocol, which adds hard real time to Ethernet by clocking to make sure that messages get where they are supposed to be WHEN they are supposed to be there. This feature creates a level of determinism that has long been a stumbling block to more broad acceptance of Ethernet in the industrial community, possibly eliminating any serious impediment to using Ethernet for motion.

The controversy is usually around the question of “What is Real Time?” How fast is fast? Well, its usually whatever is fast enough for your specific application. But that doesn’t really help control system manufacturers when developing solutions for a broad audience. So its nice to find that the technology migration is starting to resolve some of the basic issues with respect to motion control, with something more broad than a vendor specific solution.

Even the Open DeviceNet Vendors Association seems to be exploring the potential of IEEE 1588 as their Common Industrial Protocol as a platform for bringing the legacy networks of manufacturers together as an overall solution. This is a very significant effort, one that has been difficult to achieve, that many users need help with. Operating a manufacturing or process plant is hard enough without having 3 or 4 different networks to maintain, and worse still, exchange information across different platforms.

My guess is the cost pressure of inexpensive Ethernet components will continue to push manufacturers toward finding similar solutions. But is sure would bring everyone along more quickly if the competition among control system providers were balanced with an option that everyone can find acceptable. IEEE 1588 is certainly a possibility worth considering.

Motion and Communication

I used advise people working on motion control never to make a communications layer part of the application. There were too many things that could adversely impact the motion. But communications have gotten a lot faster, and there is a tendency to think of speed as the issue. Not really.

Motion Networks are a breed apart, Sercos, Firewire, USB and many proprietary solutions are offered in today’s marketplace. Claims are made about, not surprisingly, speed. And determinism. That’s the tricky part. Guarantee the message got there when it was supposed to.

And its kind of the same problem for PLC’s doing motion control. Yes, its true that most applications do not require tight coordination between two or more axes. So its perfectly reasonable to put the motion in the PLC and let it referee when independent motion axes start. It leads to the assumption that everything is fine no matter how many axes and if any are coordinated, synchronized or registered to a moving target. Read more

The Continuing Evolution of Mechatronics

It began as the integration of mechanisms with electronics. Since then, mechatronics has evolved, and for all practical purposes, includes nearly every engineering discipline.

By Andy Urda, Director Channel & Industry Marketing

Yaskawa Electric

In 1953, Yaskawa Electric began its active role in advancing technology in the field of motion control when the company introduced its servo motor line, the Minertia® Motor (named for minimum inertia). These servomotors made rotation exact to the proportion of conduction. Due to their very low inertia, they handle extremely fast starts and stops. Originally, they were applied to electrical actuators for the control of mechanical arms. Today, they are also found in many industrial automation applications. Yaskawa’s signature phrase of the late 1960’s and early 1970’s was “Mochintrol,” which was created from the combination of motor, machine, and control. Mochintrol became a registered trademark for the company in 1971. Read more