Electronic Motion Control Reaches for the Sky

KEY WORDS

Motors and motion control

AC/DC drives

Servo and stepper systems

Motion control software

Embedded control

Sidebars: Poetry, sophisticated simplicity in motion

Electronic motion control has become a complex combination of diverse elements—motors, drives, amplifiers, motion controllers, embedded chips, feedback devices, software tools, and more. This vast mosaic of solutions is supplied by hundreds of companies with new entrants expanding the list. Such diversity creates issues and fuels trends.

One classical tradeoff pits single-source solutions—appealing to users with limited experience for implementing a motion system—versus subsystem solutions attractive to those with expertise to optimize all elements. The latter depend on different products working together, which brings up the issue of “open” systems. Changes in control architectures present still another issue. Newer PC-based controls compete with proprietary and PLC-based approaches that were the foundation of motion control. The basic issues are much the same as found in other arenas of industrial control.

A recent study by Automation Research Corp. (ARC, Dedham, Mass.) examines developing trends in general motion control. “Emerging open digital drive and device networks pose a threat to topologies of proprietary suppliers,” says Sal Spada, senior analyst for motion control systems at ARC. So-called “soft logic” providers began the challenge by seamlessly integrating motion and machine logic functions. A common programming and diagnostic environment using PC-bus motion cards is the result. The PC-bus motion controller trend is expected to continue (see diagram) but the next wave of development is coming. ARC calls this “component motion control software integrated directly with the PC.” These changes will take time to develop due to the strong influence of existing systems.

However, some suppliers already offer PC-based motion controllers with hardware-independent software solutions. Among such companies cited by ARC are Advanced Technology Research (Burtonsville, Md.) and Automation Intelligence (Duluth, Ga.), now part of Sanyo Denki of Japan. Real-time extensions to MS-Windows NT is an enabling technology for these suppliers.

Mr. Spada sees two future directions for motion control intelligence—concentration in the drive or as a PC-based software component. The latter favors applications where machine logic control dominates. The alternative path, “distributed intelligent drives [using existing networks] will remain an extremely cost-effective solution, but users adopting this solution are risking a significant switching cost due to the high dependence on the supplier for modifications,” he adds.

Electronic motion control creates a gamut of applications, a sample of which appears in the next article. Perhaps the most visible and dynamic usage of motion control is in the magic world of entertainment (see sidebar). Technology suppliers likewise show diversity.

One source, complete systems

“Complete systems” form the focus of many motion control suppliers. For GE Fanuc Automation (Charlottesville, Va.) its PowerMotion solutions are said to provide that completeness for servo and machine control. “From the motor to the operator interface, engineers incorporate components designed to work together, helping them achieve tighter and easier integration, faster development cycles, reduced costs, and increased reliability,” says Vince Tullo, vice president of PLC Business. GE Fanuc sees its role as a single source for hardware, software, and services for complete motion solutions—from basic, single-axis to sophisticated, multiple-axis control.

Motion controllers designed to best fit OEM users are the product specialty at Galil Motion Control (Mountain View, Calif.). “Our products control between one and eight motors each. Motors may be open-loop steppers or closed-loop servo of brush, brushless, and hydraulic motors,” says Jacob Tal, president. The controllers do sinusoidal commutation for brushless motors and communicate with serial, ISA, PCI, PC-104, VME, and USB protocols.

“Industry continues to embrace brushless technology for improved efficiencies in space, energy, and maintenance,” says Bill Fejes, president of Pacific Scientific, Automation Technology Group (Rockford, Ill.). Following this premise, PacSci focuses on motion control for positioning requirements through expertise in brushless as well as stepper products. These “technologies allows us to cost effectively solve a wide variety of motion control problems,” adds Mr. Fejes. Modular design is part of the approach—for example, PacSci offers multiple plug-in option cards for its new family of brushless servo drives.

At Rockwell Automation (Milwaukee, Wis.), general motion control also takes the route of integrated systems within “comprehensive factory automation control solutions,” rather than just supplying components. Ken Deken, vice president Allen-Bradley General Motion Control, comments, “As a discipline within these solutions, motion control technology achieves maximum value when properly integrated with the overall automation process.”

Motion control at Ormec (Rochester, N.Y.) takes the form of industrial PC-based systems that integrate closed-loop servos with machine I/O devices, human-machine interfaces, and connectivity to popular communication networks for general-purpose factory automation. Examples are in packaging and converting applications. Ormec also cites strength in large systems (over 4 axes) used for high-volume consumer goods production.

Orion motion controllers include interfaces for DSP axis control. An MS-Windows 95/NT software development environment provides tools for motion and I/O programming, touchscreen development, and communications.

Recent innovation in the product line widens robotics applications such as material handling. One example is higher capability to coordinate two motion axes via “blend moves” now part of Ormec’s newest version MotionBasic (4.1) software, explains Christopher Englert, technical marketing specialist.

Taking over “many process control functions directly at the machine” describes the focus of Global Drive servo and frequency inverter systems from Lenze Power Transmission (Fairfield, N.J.; Hameln, Germany). Modular, application-specific software supports the hardware. Five current software modules include cam following (for filling, contouring, etc.) and registration (for printing and packaging).

Functions integrated at the machine benefit the user by making process adaptations easier, according to Lenze. The controllers connect to major bus systems and communicate with each other, eliminating “many PLC functions.”

Maturing directions, trends

At API Motion Inc. (Amherst, N.Y.), electronic motion control is regarded as “still a young industry, but showing some signs of maturity.” Only in the past couple of decades has this technology acquired a name and became an industry sector. At the same time, Ken Wyman, vp of marketing & sales at API, reminds us of company consolidations ongoing in this sector—a development expected to continue.

As for trends over the next few years, Mr. Wyman notes, “Ever-more powerful processors, coupled with an increasing demand for digital fieldbuses for motion control, will lead to common use of intelligent drives and motors.” This is also likely lead to “less reliance on host controls, such as CNCs, PLCs, and motion control cards, to handle axis and machine functions, ” he adds.

API Motion and its six subsidiaries supply intelligent step and servo drives, matching motors, feedback devices, gearboxes, and brakes and clutches.

Rockwell’s Mr. Deken, likewise believes that motion control is still an adolescent technology, “with peak productivity still years ahead.” He makes an analogy to PCs, which did not realize their full potential until the infrastructure for integration was in place. Similarly, “motion control’s true value will not be achieved until users begin focusing on process gains,” he says.

As to the future, Mr. Deken adds, “We’ll see more demand for integration, as customers want complete machine control across multiple control disciplines using motion software and hardware to coordinate logic, process control, and operator interface products.”

Galil’s Dr. Tal cites some market demands for improving this technology, for example smoother motion—achieved by linear motors and sinusoidal commutation—and reduced wiring and noise interference, to be solved by networks such as USB, SERCOS, and others.

“Motion control will increasingly be viewed as an integrated part of [total] control strategy, rather than a separate specialty,” says Scott A. Pete, marketing manager at Control Technology Corp. (CTC, Hopkinton, Mass.). “To achieve the performance and information collection objectives of tomorrow,” will further require seamless integration of all factory subsystems—including controls. Mr. Pete refers to such a truly integrated path as “advanced control capability,” made possible by more built-in intelligence and communications capacity.

CTC makes automation controllers and a wide variety of control modules that integrate stepper and servo control, I/O devices, and communications into a single environment. CTC’s Quickstep State Language, used for all control functions, is said to simplify complex automation projects. Quickstep handles multitasking, stepper and servo control, analog and digital I/O points, application communications, and other advanced functions—within one, easy to understand step-based structure. Time for implementation, training, and debug of applications is reduced.

Cost, ease of use are still basic

Many manufacturers echo a common theme of cost reduction and ease of use. Focus for the next few years at Kollmorgen (Radford, Va.) is “to reduce the customers’ total adoption cost.” Kollmorgen is researching new technologies, among them “new motor construction designs for improving speed control through lower (system associated) total harmonic distortion,” says Larry Kingsley, executive vice president of sales and marketing. Examples are new motor commutation and software methods that let users tune their machines more efficiently.

Kollmorgen markets electronically controlled closed-loop drives and motors, and considers its “strength” to be brushless synchronous servo systems. This broad product line offers a common drive platform for four types of brushless servos. Yet, a significant part of sales remains in brush dc servo products such as “servodisc” and “torquer” [motor] technologies, according to Mr. Kingsley.

Higher accuracies and speeds, lower costs, and more flexible physical configuration of systems are customer demands noted at Delta Tau Data Systems (Northridge, Calif.). Among specific trends seen by Curtis Wilson, product specialist, are digital current-loop closure and high-resolution encoder interpolators migrating from high-end to mainstream products —made possible by continuing advances in electronics. Delta Tau makes multiaxis positioning motion controllers for a wide variety of industrial automation applications.

In the next several years, Mr. Wilson foresees “continual ferment and shakeout” in integrating motion systems. “Dozens, or even hundreds, of digital interface protocols among different parts of a motion control system are vying for market share as users try to simplify system wiring and configuration,” he adds.

” ‘Openness’ will be the key word in the future, with controller platforms rapidly becoming PC-based, providing easy, ‘open’ accessibility to multiple vendors,” says Sun Y. Kim, senior product engineer at Mitsubishi Electric Automation Inc. (MEA, Vernon Hills, Ill.). “However, there is no agreement on the definition of open, and this will not likely change in the near future.” In the interim, Mr. Kim suggests picking a “complete solution provider… as the safest and most logical choice.” Understandably, he places Mitsubishi Electric in that category.

Looking ahead, Ormec sees faster processors driving PC and DSP technologies toward more visibility in industrial control applications. Other developments mentioned are:

Connectivity will become increasingly important, especially in Ethernet- and TCP/IP-based applications; and

Remote development, maintenance, and reporting will become commonplace for motion control applications.

Of chips, DSPs, and ICs

Texas Instruments DSP Digital Control Systems Group (DCSG, Stafford, Tex.) is keen on digital signal processing (DSP). “We expect to see 1.5 billion brushless motors in 2001, DSP solutions will be commonplace in many, if not all, of these motor control applications,” says Christophe Chene, worldwide marketing manager for TI DCSG. He thinks that “innovative architectures and economies of scale” position TI to push DSPs into wide embedded control applications. Affordability of DSPs is necessary to make that happen.

Mr. Chene cites some product examples. For high-performance, TI offers the popular TMS320C32 floating-point DSP at $9.95 in any quantity. TMS320C242, a fixed-point DSP optimized for high-volume appliance usage, is priced below $4 in OEM quantities. To allow designers to explore new dimensions in motor control, there is TMS320F241—with a 20-MIPS DSP core, motor control peripherals, a CAN controller, and flash memory on chip.

Analog Devices Inc.(Wilmington, Mass.) notes the progress made by motor controls “from analog ICs to embedded digital solutions,” thanks to the availability of low-cost microcontrollers and DSPs. Today, digital processing makes motor control cost-effective and energy-efficient in applications ranging from high-end industrial robotics to domestic appliances. Analog Devices provides 11 embedded fixed-point, 16-bit DSP motor controller ICs optimized for motor type and industrial or appliance usage.

As a provider of IC-level motion control, Performance Motion Devices (PMD, Concord, Mass.) is at the other end of the solutions spectrum. Chuck Lewin, PMD’s president, puts the cost of motion control ICs generally at $100 or less, making them a “cost-effective means of assembling a motion system.” Alternative “box” or motion card approaches can run to 10 times higher or more, he says.

Besides cost, “motion ICs give designers a high level of control over the final shape, size, and features of the resultant controller,” says Mr. Lewin. Benefits of this approach are smaller unit sizes, less wiring between elements, and higher reliability.

Mr. Lewin notes several trends as motion control is pushed into the “Internet era.” Among them are:

Wider acceptance of digital current control in amplifiers;

More smart amplifiers with on board motion processors; and

For controllers, increased use of distributed networks (e.g., CAN, Ethernet, SERCOS, and DeviceNet).

However, he cautions that lack of standards holds back fast adoption of distributed networks specifically for motion control.

Steps in motion

Intelligent Motion Systems (IMS, Marlborough, Conn.) sees the small motor market as one of the fastest growing areas within the motion control industry. The small motor market will reap benefits in the next few years, as companies switch to electric motion control for improving production efficiency, says IMS.

IMS specializes in the design and manufacture of very small microstepping drivers and stepper motors. For example, the IM483I, a 4-amp microstepper, measures just 2.75×3×1.2 in., including a built-in indexer. Its Lynx motion control system interfaces with stepper and servo drives; the modular design promotes distributed control. Price, performance, and package are stressed.

Oriental Motor USA Corp. (Torrance, Calif.) is a mechatronics motion company offering a broad range of small ac induction, stepping, and brushless dc (bldc) motors, and their associated drivers for precision automation. Gearheads and brakes are combined in the various motor-driver packages. Oriental’s motion solutions comprise fixed speed, variable speed, torque control, and position control (open loop) from 1 to 200 watts. Typical users are in medical, semiconductor manufacturing, and factory-floor applications.

Both ac and bldc variable-speed controls carry the Oriental Motor brand, while the 2- and 5-phase hybrid step motors (under the Vexta brand name) and associated drivers provide precise positioning and smooth velocities using microstepping techniques.

Software and soft logic

Software companies and their developments have a growing presence in motion control.

“A single integrated programming and execution platform” is what Steeplechase Software (Ann Arbor, Mich.) calls its motion offering—Visual Logic Controller (VLC). Machine logic and motion control are combined in VLC using one database, one programming language, and one PC-based hardware platform.

“Complex, multiaxis coordinated motion configuration is as simple as filling-in-the-blanks; no need for separate proprietary programing languages,” says Steeplechase. Once filled out, these motion function blocks can be used directly in a flowchart or ladder- logic program. VLC is said to greatly reduce design, debug, and maintenance time associated with typical motion control applications. It’s part of the brave new world of soft logic.

Software companies continue to add motion capabilities to their products. One example is ASAP Inc. (Chagrin Falls, O.), with a recent toolkit called Motion Direct that allows quick interfacing of various motion control cards to its flagship PC-based ASIC-Control Suite. In June 1998, ASAP announced that Motion Direct supports Galil motion cards.

Summarizes PMD’s Mr. Lewin, “As hardware controller products begin to look more and more alike, software-based factors such as ease of use, open architecture support, autotuning, and performance monitoring will become distinguishing product features.”

Meanwhile, hardware isn’t sitting on the sidelines. At least two companies now offer complete servo systems—controller, amplifier, servo motor, and encoder—all in one compact unit. Animatics Corp. (Santa Clara, Calif.) has its SmartMotor line available in five sizes: NEMA frames 17, 23, 34, 43, and 56. Meanwhile, QuickSilver Controls Inc.’s (Covina, Calif.) SilverMax product packs similar components into a servo motor form factor (NEMA 23 and 34). Space and installation time savings are the ultimate user benefits.

Poetry, sophisticated simplicity in motion

While novelty entertainment is the norm in Las Vegas, “Masquerade Show in the Sky” breaks new ground with its precise coordination of technical elements and systems.

The $25 million interactive audience attraction at the Rio Suite Hotel & Casino combines live performers, animatronic figures, ceiling drops, and precisely synchronized lights and sound performed on various stages—as well as on five floats suspended from the ceiling. The floats emerge from a retractable wall inside the casino area and glide along an overhead track at 3 ft/sec, as spectators view the parade from eye level along a balcony and from the casino floor below. The 12-minute show is performed every two hours.

Inherent technical logistics of coordinating lights, sound, live performers, moving sets, and more than 50 other automated effects require a sophisticated, yet flexible control system. To deliver the reliability and accuracy required for this project, the Rio Hotel teamed with Scenic Technologies (New Windsor, N.Y.) to create an automation control system to handle the complex requirements of positioning, timing, and movements.

The project challenged Scenic’s design team. Each float—with its own on-board lighting and sound and individual editable cue lists—has to run separately, yet simultaneously.

Scenic Technologies developed a system that uses Stage Command, its proprietary software package, along with 16 Allen-Bradley motion controllers and two A-B PLCs (5/80)—from Rockwell Automation (Milwaukee, Wis.)—for primary system control. Stage Command is a PC-based human-machine interface with Ethernet communication to PLCs and motion controllers.

The show uses three “levels” of motion control. Ten dc servo drives and motors in the 5-hp (3.7 kw) range control a variety of functions (64 servo axes), such as shuttle and track diverter switches. These orient the track to “line up” power continuity for the floats as they move along the track (no trailing cables used).

Five ac drives and five 10-hp, 3-phase A-B induction motors (one per float) propel the floats. Velocity feeedback comes from a motor-mounted encoder, while two encoders on each float supply position feedback, explains John Hennessey, a vice president at Scenic. Another 16 dc regenerative drives and dc motors provide the higher power needed for ceiling drop movements and various animated effects.

All on-board electronics, including motion controllers and Remote I/O stations are embedded into the carriage of the floats. Allen-Bradley PLCs, located in the control booth above the casino floor, provide overall system monitoring and feedback. DeviceNet-compatible sensors, placed every 10 ft around the track, detect the floats’ proximity. Sensors report to the main control via Remote I/O and Ethernet, while HMI and PLC commands travel the same path down to the floats.

“The motion controllers were easily integrated into our Stage Command platform and delivered the control functionality and flexibility we needed for this application,” says Michael Paulin, a vice president at Scenic. “The motion control modules’ I/O capabilities plus analog output and encoder input also proved extremely valuable.”

In the world of entertainment, concepts and ideas must be quickly transformed into reality. For “Masquerade Show in the Sky” it took just 13 months to go from little more than an artist’s sketch to poetry in motion.

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