Medical Design Briefs: What are integrated motor drives, and how do they compare with traditional motion control approaches? What advantages make integrated motors a desirable choice?
Brian Taylor: An integrated motor drive solution incorporates a motor controller, a drive, and a motor, all in a single package.
This approach differs from traditional, distributed motion control solutions, where the same components are located in different places: the motor controller sends command signals via cabling to a large electrical panel where the drive is located; the drive amplifies and delivers command signals via more cabling to the motor; and the motor ultimately actuates the load that it was designed to move.
The most obvious advantage of an integrated motor drive solution is that it replaces three or four components with a single, integrated unit, which really simplifies the entire system from a wiring standpoint.
Generating a bill of materials is also greatly simplified. In the past, customers would need to place separate orders for the controller, the drive, and the motor, and then find some way to marry them together with off-the-shelf or custom-manufactured cabling. Now, a customer can handle the same motion control application by ordering a single off-the-shelf component.
Integrated motor drives offer an exceptional means of accomplishing single-axis motion control in industrial applications, in a package that is tight and efficient.
MDB: In applications for medical device manufacturers, are integrated motor drives used predominantly in manufacturing equipment, in finished medical products, or both? How do the characteristics of the motors differ in such varied applications?
Taylor: In our work with medical device manufacturers, we see both distributed and integrated motion solutions being applied in manufacturing equipment as well as in finished medical products. And a lot of the applications that we commonly see on manufacturing lines-the use of peristaltic or syringe pumps for fluid handling, for example-we also see incorporated into finished medical products.
On a typical packaging line for a product like sutures, for instance, there are multiple levels of integrated automation going on to help package the devices. Some motors simply move the products from point A to point B along the assembly line, while others may pick and place products in front of a printer for labeling, or rotate an entire assembly in front of a camera for inspection. All of those movements need to be coordinated and executed with great precision, and integrated motor drive solutions are well suited to carrying out all of those tasks.
Among finished medical products, typical applications might involve systems using peristaltic or syringe pumps to dispense fluids very accurately and very smoothly, for a variety of purposes ranging from drug delivery systems to core lab analyzers.
To meet the specialized needs of device manufacturers-including finished medical products with significant space constraints-we have also provided both dispersed and semi-integrated solutions. When space is at a premium, sometimes a semi-integrated system is just the right solution. In that case, the motor is mounted where it's needed to actuate its intended motion, and then cabled to a drive control package that includes both the controller and the driver. This kind of flexibility is typical of the approach we bring to working with device companies.
MDB: The components of integrated motor drives are designed and tested to work together, so that's one less headache for the client. But when a client needs to have a system that is not integrated, how does Schneider help to make sure that all the pieces will still work together?
Taylor: Balanced design and carefully matched performance are certainly characteristic of integrated motor drives. The systems are intended to work together efficiently, in order to achieve the greatest possible power and speed out of the application load.
Nevertheless, there will always be those customers with special requirements, like a unique motor configuration that is the only one that works in their application. In such a case, our applications group would go to work to understand the electrical values that characterize that motor-its current rating, resistance, and inductance-to make sure that our drive can be optimized to work with that motor. While we are developing a new application, customers often allow us to test their motors with our products, just to make sure they are a good match.
Matching a motor and drive involves a lot more than simply amplifying a signal and applying some voltage and current. Different motors have different winding configurations that can produce greater torque at a lower speed or greater torque at a higher speed; optimizing that performance requires a drive that can address several related electrical components. If we're not providing a fully integrated solution, we need to work closely with the customer to ensure that all of these other factors are taken into consideration.
MDB: In medical products, the use of robotics and automated systems has increased significantly over the past decade. What advances in motor design and technology have been important to this growth?
Taylor: Thinking specifically of advances that we've created, we have come up with a very cool technology that essentially turns an open-loop stepper motor into a closed-loop system, so that it behaves more like a servo system, and doesn't stall.
To create the system, we started with a traditional stepper motor and incorporated an encoder-a feedback device used to track the position of a shaft as it rotates-and married them together with some unique hardware and software.
We are continuing to optimize the performance of this system, which provides closed-loop performance at an affordable price. We are also quite active in taking advantage of the ever-decreasing size of electrical components. We were among the first companies to optimize drive and control circuitry and fit it onto the back of a motor, creating an integrated package. As the physical size of such components continues to shrink, we're working hard to optimize the footprint of our systems, making them suitable for applications where larger motors would be tough fit, while still providing a lot of power.
MDB: What kinds of medical device applications typically make use of integrated motor drives? What roles do the motors play in those products?
Taylor: We've been involved in developing a variety of applications for medical devices and the life sciences community. We're especially proud of our applications for positive displacement pumping systems, where the user needs to actuate a syringe or peristaltic pump in order to dispense a fluid very precisely and very smoothly. The ultimate uses of such systems may be as varied as filling small vials with specimens for downstream testing, or dispensing large volumes of a medication into packaging for onward distribution. The key to our success in this area is a highly evolved micro-stepping drive that makes it possible to electronically divide each physical step of a stepper motor's rotation into 256 micro steps. As a result, the motor doesn't rotate as coarsely as a traditional stepper motor, leading to very accurate pump velocity and extremely smooth dispensing.
We've also had great success in applications for imaging devices such as MRI scanners-another place where smooth, accurate motion and precise spatial positioning are essential.
MDB: Medical products often have extraordinarily high requirements for quality-including reliable everyday performance according to specifications, and long mean times between failures (MTBF). How well do integrated motor drives perform against such criteria?
Taylor: In these kinds of applications, you cannot have a failure-you just can't. So reliability is actually a major reason for adopting an integrated motor drive solution. And part of protecting against failures involves making sure that the performance of the controller, drive, and motor are matched for optimal efficiency.
Traditionally, motors have operated on a fixed current and fixed voltage that have been judged sufficient for enabling the motor to make a move without straining or stalling. But the accuracy of that selection has always been something of a guess, leading developers to build in a little extra capacity, just in case.
Our approach is quite different. Our closed-loop hybrid motion technology regulates system performance so that the motor pulls only the current and voltage needed to make a move. The drive section is optimized to match. Consequently, the motor runs cooler in those applications, which saves on the motor life.
Because our systems have such varied applications, it can be difficult to assign a meaningful field failure rate or MTBF. In some applications, our systems are running 24 hours a day, 365 days a year; in others, the system may be fired up to make a move that takes only a few seconds, and then not asked to move again for another week or two. Nevertheless, taking some assumptions into account, a fairly good estimate for our systems' MTBF is somewhere around 125,000 hours.
We've had recent calls from customers who have asked for assistance with products that we were manufacturing back in the late 1980s. We do our best to respond to those calls, but it does get a little difficult because some of the folks who wrote the software for those older products are no longer on this Earth. Nevertheless, it's a feather in the company's cap to receive calls like that, because it means the product has been out there working away for years and years, without failure.
One of the cool things about our stepper motors is that they make use of brushless motor technology. These aren't like traditional mechanical devices that are always mashing gears back and forth, or running into a physical stop before reversing motion. Instead, we're rotating an electromagnetic field that is generated inside the motor, and applying a force with it; so there aren't a lot of parts that can experience wear. So long as we know what we're doing with the voltage and current that pass into the windings, a properly sized motor should last for quite a long time.
MDB: How does Schneider work with its clients to facilitate preventive maintenance activities or otherwise minimize system downtime?
Taylor: For many of our customers, it is a comfort to know that our manufacturing base in Marlborough, CT, handles all of our MDrive, Lexium MDrive, and MForce products, as well as our older MicroLynx products, which we no longer manufacture but still service and support.Because we have all of the components readily available in a subassembled state, we are able to respond very quickly if a customer calls to report a failure. We can almost always ensure that the customer has an identical product in their hands and functioning the following morning. In a few instances, we have even flown in members of our applications group to help get a customer back up and running.
Of course we also work on agreements with customers, to help them understand their general maintenance schedule and that they have access to replacement products both directly from the factory and through our sales channels.
We also put in place blanket orders that anticipate a customer's build schedule. If a customer typically needs 10 motors a month, for example, we will likely make sure the local distributor has 15 or 20 on hand-just in case something unexpected happens.
MDB: MDrive integrated motors are considered market leaders. What are some of the most challenging medical device applications where MDrive motors have been applied?
Taylor: From a motion control standpoint, most medical device and life sciences applications aren't typically very difficult. The motors and drives must be well matched for their performance requirements, but the software and the motion it controls are usually quite straightforward.
Commanding a motor to rotate at a velocity that will cause a pump to dispense fluid at a specified rate, for instance, requires just a few lines of software code that is saved into the system's nonvolatile memory and runs on power-up.
Setting up the point-to-point motion needed for a scanner is equally easy, requiring just a few lines of code to create the trajectory and specify velocity with an acceleration and a deceleration. The way we've developed our software, it's very simple for customers to write a couple of quick lines of code and get their device up and running.
Where we are more likely to encounter issues is when a motor assembly needs to be positioned in a location that doesn't provide for easy heat dissipation, or when external fluids or cleaning processes are involved. In those kinds of applications, we need to be certain that the correct product is selected. Our MDrive line offers a number of different versions to match most environments, but it's up to us to make sure that our customers choose the right unit for their application.
MDB: Has Schneider Electric Motion USA developed other processing systems that are especially suited for medical device manufacturing applications?A line of Lexium MDrive integrated motors with an ingress protection (IP) rating of 65 has recently been released. What does an IP65 rating mean, and how can products with such a rating be of use to medical device companies?
Taylor: : The International Electrotechnical Commission standard 60529 provides a classification scale for the protection offered by casings and housings. An ingress protection rating of 65 (IP65) indicates that the motor assembly is dust tight, and that water projected on it from a nozzle (with a specific size, volume, pressure, distance, and duration) will have no harmful effects.
On a practical level, of course, companies rarely specify their components according to such classification scales or ratings. What actually happens is that a company describes the environmental conditions in which their motor will be expected to operate, and we use the ratings as a guide to determine what level of product will be needed under those conditions.
We actually design our assemblies to perform well past their ratings, but we also work closely with our customers to make sure we understand their needs. A company that starts off by asking about assemblies with an IP65 rating may actually need a product that is rated IP67 or IP69.
On the other hand, companies that aren't asking about any particular IP rating and don't express any specific environmental concerns will likely be in pretty good shape with one of our standard products.
MDB: How are integrated motor drivers controlled? What types of communications interfaces do MDrive products use?
Taylor: We work hard to ensure that the components we produce can communicate properly with all of the external equipment and machinery that they are a part of. In the past, all of our MDrive products always used serial-based communications. But for our new line of Lexium MDrive systems we have added an EtherNet option, and this has really opened us up to the market. In these products, EtherNet is the hardware used for communications.
With this new generation of products, we supply a version of EtherNet/IP that we have tested and certified through the Open DeviceNet Vendors Association, an organization that certifies the implementation of protocols used to communicate with other third party-devices. We also supply Profinet, an EtherNet-based communications protocol for third-party manufacturers such as Siemens; and Modbus TCP, an open-systems EtherNet-based communications protocol for companies and devices that don't use a more proprietary language.
We also provide our own software language in two versions: MCode, which can be used to communicate serially; and MCode TCP, which is used to communicate via the EtherNet. Finally, we also provide CANOpen as a means of communicating to our devices from a CANOpen master.
In short, we supply a lot of different languages and connecting options for communicating with our components over a network.
MDB: How does your organization work with medical product developers to meet design and manufacturing challenges for new devices and diagnostic systems?
Taylor: We are especially good at working with companies that are in the earliest stages of designing a new product. For us, that could literally mean that the product design is represented by a blank sheet of paper. Connecting with companies at such an early stage enables us to understand what they are hoping to achieve, and to speak from the standpoint of what solutions will meet their needs.
Our standard product offerings include a wide range of options-our MDrives, Lexium MDrives, MForce products, M series motors, and linear actuator devices-so oftentimes an off-the-shelf solution will fill the bill.
But if a standard product isn't the right fit, we still have many ways that we can help a company meet its needs. In fact, about 55% to 60% of what we do involves some level of customization-which could mean customizing a standard product or even creating a totally unique custom product from the ground up. We have a full set of hardware, firmware, and software design engineers who work on our products, and all of their development and integration work is done right in our factory.
My applications team interfaces with those engineers about new opportunities on a daily basis. When we get requests that are outside of our standard product offerings, that doesn't mean the show is over. That's actually when the fun starts, because then we get to create something unique and totally custom for that customer that will be theirs moving forward.
MDB: What kinds of concerns do the developers of new medical products typically ask about?
Taylor: Both medical device and life sciences customers struggle to figure out how much of their project they want to perform in-house, and how much of it they are willing to put in the hands of outside vendors.
With our experienced engineering staff, it often makes sense for us to help a customer develop an entirely new product from scratch. But some customers may decide to develop their own control board, for instance, and attempt to match it up with our drives and motors.
That's a decision that should lead to a discussion about sustainability, because it is very difficult to maintain control of all the components that reside at the board level of a complex medical device system. And without that control, the manufacturer may soon be unable to deal with the complexities that come with component obsolescence, model variations, and subsystem mismatches.
Standard products may address many of these concerns. But when they don't, customization is usually the next and safest option for companies that recognize the importance of product sustainability.
In the same vein, medical device clients often express concern about product updates-and especially about the potential for unapproved changes to system firmware. To address that concern, we make sure that manufacturers are able to lock the firmware on their devices so that it never changes.
We keep product firmware and software available via our website. Any time we make a change-whether it is to add a previously unavailable function or to correct a program bug-we make sure that there is a change order in place. This enables each customer to see and feel it for themselves and decide whether they want to make that firmware or software upgrade in the field.
For those who decide to upgrade, we make the process very simple. Our hardware and software design provides the tools needed to execute an upgrade, and the upgraded firmware or software is available via our website. So companies don't have to worry about sending product back to us, or paying to have it upgraded by a factory technician.
MDB: When companies want to lock their system's firmware and prevent changes to the system, is that typically driven by regulatory concerns-needing to make sure that features already approved by FDA or another agency don't somehow evade change control?
Taylor: Absolutely. The regulatory paperwork required of our customers is monumental. And once a product has received marketing authorization, any change to the documented components or part numbers belonging to the system can mean lights out for the manufacturer, who may have to repeat much of the premarket review process all over again.
When we have designed and tested a product for a particular application, it typically doesn't make sense to impose running changes on the product that might force customers to seek reauthorization. Moreover, such changes in firmware or software aren't necessary for a legacy device, because the updated features aren't within the set of intended uses for which the product is authorized, and therefore they won't be used.
Although we may make changes to a product because we found things that could be enhanced, we recognize that the users of legacy systems must still have access to an unchanged and locked version of their firmware.