Medical Device Link.

Originally Published EMDM September 2001

Product Update

Powerful, Compact Motors Drive the Industry

Jamie Graham

The trend is mirrored in devices, which are becoming smaller and more complex.

The Jones Punchline ac/dc series from EADmotors is suited for applications where high power and compact size are important considerations.

As medical products become smaller and more intricate, manufacturers naturally want a motor that is more compact and more specialized. "We are seeing a growing need for smaller, customized motors," says Eddie Hagimoto, head of the international export department at Nippon Pulse Motor Company, Ltd. (Tokyo). Nippon Pulse Motor supplies motors, controllers, and drivers.

To fulfill OEMs' needs, suppliers have to provide a smaller motor that has at least the same amount of power, if not more, as a larger motor. Adding to the conundrum, the electronics accompanying a smaller motor are more intricate and complex than in a larger counterpart. "We are finding that medical OEMs are requiring smaller motors with more integrated electronic functions," says Luciano Antognini, president of Technosoft (Corcelles, Switzerland). Technosoft's IPS150 intelligent step motor drive is compact, can operate in various operating modes, and provides high-level control functions not usually found on step motor cards.

As the quest for smaller motors continues, suppliers try their best to create the most compact solution possible. Maxon Motor AG (Sach-seln, Switzerland) has developed a product with a high resolution for a compact design, and Intelligent Motion Systems (IMS; Lyon, France) has also recognized the need for a more compact, tighter motion control system. "We are trying to provide more power in less space," says Dave Coutu, president of IMS.

R&D Services in Demand

OEMs are also asking for more R&D services than they did in the past. Empire Magnetics (Rohnert Park, CA, USA) president Rick Halstead says most OEMs no longer have an engineering staff, relying instead on suppliers to provide those services. "In general, the value created in a motion control product has shifted away from manufacturing in favour of research and design. We see this trend accelerating, and companies are going to have to merge to meet customers' engineering needs," says Halstead.

The Future of Motion Control

Empire is moving away from high-volume mass production and making the transition to low-volume, precision-engineered products. The company supplies small electric motors, which are custom-made for micromanipulation devices. "We realize that as OEMs seek to differentiate their products from those of the competition, the ability to create new products with proprietary content is critical to their success," says Halstead. The company's most recent offering is the Size 11 medical motor, which features a 1.1-in. diameter, weighs 0.2 lb, and is suited for use with mechanical manipulators in neurosurgery applications.

Ross Goluba, product manager of Industrial Devices Corp. (IDC; Petaluma, CA, USA), says that OEMs want services with their purchase. "Most OEMs aren't familiar with motion control technology, and they need to automate a process," says Goluba. "We help them do this." IDC offers a complete preconfigured electromechanical system. The company performs all the necessary electrical connections between the control, motors, and mechanics, and then labels all the connections. The customer simply plugs the labelled cables into the labelled connectors, and then uses the control's keypad to walk through the initial testing and movement of the system. What trends will define the future of motion control for medical device OEMs? Some suppliers think the key to survival is to provide the most convenient services to OEMs. It seems the going trend in the industry is streamlining—not only the products, but the companies themselves. Many suppliers predict that they will consolidate or form alliances with other suppliers to provide complete motion control systems for OEMs. Tom Toye, project engineer at EADmotors (Dover, NH, USA), says that traditionally OEMs would use several suppliers to create a motion control system, but now EAD is moving to provide all the motion control products an OEM needs. "People are looking for a total systems provider," Toye said. EAD plans to eventually form special labelling agreements with other vendors in order to have access to a wide range of products. EAD would place its own label on the vendors' products under the agreement. Nippon Pulse Motor's Hagimoto agrees that the industry is moving in that direction. He says it is just a matter of time before motion control companies merge into large conglomerates. "I think there will be mass consolidation eventually; so customers can go to one company for everything they need."

Some suppliers disagree with this theory. Jan Bosteels, product manager at Advanced Motion Controls (AMC; Camarillo, CA, USA), thinks the industry will proceed to become more specialized, so companies can carve a niche for themselves. "New advances in computing technologies will continue to allow the entrance of small, innovative players, despite the attempt of large companies to consolidate and acquire other motion control equipment manufacturers," says Bosteels. Though only time will tell what the future holds for the industry, most suppliers don't deny that computing technology is definitely the wave of the future in motion control. The term "mechatronics" has been used to describe the integration of engineering and electronics. Goluba of IDC says mechatronics is a trend that has really caught on in the past five years. Mechatronics is defined by the Institution of Electrical Engineers as "the synergistic integration of mechanical engineering with electronics and intelligent computer control in the design and manufacture of products and processes."

A growing number of research organizations are developing mechatronic solutions for a variety of applications, including robotics. By integrating the motor into the product design, mechatronic solutions reduce the overall product size and increase efficiency, which always pleases OEMs.

The Bottom Line

What the future holds for motion control is uncertain, but what is clear is that device manufacturers are asking for compact, powerful motors. And suppliers are listening. In the following pages, readers will find profiles of some of the leading suppliers of precision motion control to the medical industry.

Industrial Devices Corp.

"Device manufacturers want a product that is more compact, but provides the same motion control performance as a bulkier product," says Ross Goluba, product manager of Industrial Devices Corp. (IDC; Petaluma, CA, USA). The company's newest product, an ultracompact microstepping drive, can detect a motor stall by monitoring the back electromotive force of the power cable, which eliminates the need for an encoder or resolver.

The Impulse microstepping drive uses a digital signal processor to provide several advanced features. There is a low-resolution step input (25,600 microsteps out) and a tool for eliminating the motor's natural resonance speeds. The smooth rotation of the motor improves the quality of linear motion and also gives the motor more usable torque. More usable torque allows designers either to use a smaller and less costly motor or to decrease the move time, which corresponds to an increased throughput. The motor has a 7.2° range of antiresonance capability and is able to power frame sizes 23 and 34 stepping motors by virtue of its 4 A of available current.

IDC provides a variety of motion control products, including stepper and servomotors, drives and controls, precision positioning tables, rod-style electric cylinders, and linear robotic actuators. The products are used in a broad range of applications, such as scanning technology and pick-and-place systems.

Maxon Motor AG

The MR-encoder adds only 4 to 6 mm to a micromotor, and despite its small size can be given encoder signals to suit the user's requirements. Up to six binary or decimal incremental figures can be selected, which provides a high resolution for the compact design. The encoder supplies up to 1024 pulses per revolution and is unaffected by radial and axial play within mechanical tolerances.

The three sensor channels and complementary signals are integrated on the chip with defined phased difference to facilitate assembly. The modular system of the encoder allows for simple integration with motors from Maxon Motor AG (Sachseln, Switzerland). The company also provides custom-built systems for customers when needed. "We are open to providing specific electronic solutions to a customer," says Michael Schross, an electronics engineer at the firm.

The company specializes in the development, manufacturing, and sales of drive components and systems.

Eppendorf AG

"A great feature of the SMM stepper motor module controller is its microstepping ability, which opens a wide field of special applications," says Jan Eberhard, OEM project manager at Eppendorf AG (Hamburg, Germany). The module combines a motor indexer and an end stage on a 70 x 100-mm PCB.

Using up to 64 steps per full step, the module eliminates resonance problems. High permitted acceleration values, in addition to the reduced size and weight, allow the controller to be fastened near to or on the stepper motor, so that high-frequency leading lines and interference reflections can be kept to a minimum. The module is programmed by an RS-232 interface or via a serial bus system with galvanic signal separation. If the ES bus system is installed, up to 30 modules can be programmed and controlled from one interface. The controller automatically calculates and saves ramps, requiring only a few parameters to program complex functions.

Medical applications for the product include high-precision dispensing units and a range of scientific applications.

Intelligent Motion Systems

A small, powerful motor and driver is suited for designers who want the simplicity of a motor with on-board electronics without the expense of an indexer on each axis. Owing to its integrated electronics, the MDrive 17 motor and driver by Intelligent Motion Systems (IMS; Lyon, France) doesn't have cabling running through the machine. This reduces the potential for problems caused by electrical noise.

"The MDrive 17 will reduce system costs, design time, and assembly time for many applications," says Dave Coutu, IMS president. The drive comprises a NEMA 17 frame size 1.8° motor and a microstepping drive. It accepts up to 14 resolution settings from 1/2 to 256 microsteps per step.

EADmotors

Packing high power into a compact size, the Jones Punchline ac/dc series from EADmotors (Dover, NH, USA) offers efficient, quiet operation. The shunt or universal wound motors operate on a variety of voltages and achieve speeds up to 10,000 rpm.

The line features easily replaceable brushes and permanently lubricated ball bearings, which significantly increase the life expectancy of the motors. Windings are impregnated with varnish and backed to resist crazing and breakdown, and enclosed housings are available for protection from dirt, grease, and dust.

Model sizes range from 2.8 to 3.6 in. diam, with torque rated at 8 to 40 oz-in., respectively. "We provide high power in a compact size," says Tom Toye, project engineer at EAD. The universal wound models operate on ac or dc current. Single or dual output gearheads can be mounted on either or both ends of a motor, and balanced armatures provide quiet, vibration-free operation.

Options available for specific customer system requirements include, lead wires and exit locations, switches, connectors, shafts of steel or stainless steel in various diameters and lengths with special tooled ends, pilots, and custom mounting in face, foot, or end-bell styles with tapped holes. The series is suited for applications where high power and compact packaging are important considerations. Uses include tape-dispensing machines and medical centrifuges.

Advanced Motion Controls

A new line of digital servo drives can be used in distributed motion applications using the CANopen communication protocol. The products are used in a distributed control architecture, which can be found in medical equipment. "This concept allows improved diagnostics, significantly reduces wiring cost and complexity, improves reliability, and allows for greater flexibility," says Jan Bosteels, product manager at Advanced Motion Controls (Camarillo, CA, USA).

The technology is used to close dc current, velocity, and position loops to control brushed or brushless servomotors. Multiple programmable analogue and digital inputs and outputs enhance interfacing with other devices.

Empire Magnetics Inc.

The Size 11 medical motor is designed specifically for use with mechanical manipulators used in neurosurgery applications. The motor weighs 0.2 lb and features a 1.1-in. diam for applications requiring a compact size. Developed by Empire Magnetics (Rohnert Park, CA, USA), the motor is microstepped to provide 100,000 positions per revolution, and is combined with mechanics to allow surgeons to position instruments within 1 µm.

Constructed with pins and a locator dowel for easy assembly by technicians wearing rubber gloves, the motor is designed to be sterilized with alcohol.

The company supplies motor products, motion control systems, and support services for a variety of applications.

Sonceboz S.A.

"We provide custom-built motion control systems for OEMs," says John Pfister, director of Sonceboz S.A. (Sonceboz, Switzerland). The company's robust, high-precision actuators control physical processes in medical analysis applications. The compact actuators have travel speeds of up to 30 mm/sec and forces as high as 140 N. The 7000-series is suited for functions where the main parameters are small size, integration, power consumption, and price.

The company develops and manufactures mechatronic systems, step motors, and linear actuators according to customer requirements.

Technosoft

A new compact intelligent drive combines step motor control with motion processing, high-level control functions, and serial communication in an economical package. The IPS150 can operate in various operation modes. It can control a step motor open loop in full-step or microstepping mode, and can provide high resolution and high-speed capacity in closed-loop operation.

Because it has compact dimensions and phase current ratings of 3 A at up to 48 V dc, the Technosoft (Corcelles, Switzerland) drive provides high-level control functions and features not usually found on step motor cards. The company's motion language includes a high-level command protocol, which can be used by the host through RS-485/232 serial interfaces. "The high-level language allows you to describe the motion," says Luciano Antognini, company president .

The IPS150 is suited for motion axis control. Intelligent servo drives with other power ratings are also available.

Nippon Pulse Motor Company, Ltd.

"More customers are asking for customized motion control products, and that's what we provide," says Eddie Hagimoto, head of the international export department at Nippon Pulse Motor Company, Ltd. (Tokyo). Allowing for smooth operation of stepper motor control, the PCL-6045 motion control chip can be used in applications ranging from simple to complex multiaxis motion applications. The motor has been used in medical analysis machines, scientific instruments, and biotechnical instruments. The controller offers four-axis independent control in a 176-pin quad flat pack. It supports linear interpolation, circular interpolation, and a combination of linear and circular interpolation.

The chip operates on 19.6608-MHz reference clock input and has a 16-bit pulse rate resolution, 28-bit positioning pulse setting range, and a 24-bit ramp-down pulse setting range.

Other features include damping oscillation control, prebuffer for the next motion control profile, automatic correction of operating speed, backlash correction, and out-of-step detection.

The company provides motors, controllers, and drivers, and can custom build motion control systems to customers' specifications.

Copyright ©2001 European Medical Device Manufacturer