Motion Trends 2002
How readers use motion technologies is a moving target. Additional findings of an extensive survey of readers of Control Engineering and Design News who use and specify motion control technology are highlighted in a Special Supplement in this issue. Current developments in motion control center on the spread of distributed control architectures and increased integration of components that...
How readers use motion technologies is a moving target. Additional findings of an extensive survey of readers of Control Engineering and Design News who use and specify motion control technology are highlighted in a Special Supplement in this issue.
Current developments in motion control center on the spread of distributed control architectures and increased integration of components that make up the system, including more efficient motors, drive choices, and software advances. Survey results support such trends, in general, but the responses also indicate a traditional lag by industry to adopt the newest technologies.
Leading motion system developers are choosing distributed control architectures over centralized controls. Aerotech Inc. (Pittsburgh, Pa.) has developed an architecture that distributes the motion workload to multiple drives on a high-speed (IEEE-1394) network. 'This type of motion system has the advantage that as the number of axes increases or motion requirements increase, peak performance and synchronization of the system do not degrade,' says Robert Novotnak, Ph.D., division manager of Aerotech's Motion Control Division. Drastically less wiring and components are further user benefits, he explains.
Digital drives, software shine
Versatility of electric drives is evident from the numerous drive types used by survey respondents. (See diagram at right.) The question of digital drives versus analog drives was 'no contest,' with users indicating an 82.1% to 17.9% preference for digital. Also, 55.2% of respondents say they currently use (or plan to use in the next 18 months) integrated motor and drive packages. This good news to manufacturers of combined motor and controller packages has to be tempered by the other side of the coin: 44.8% indicate no current or near-term usage.
Motion system developers apply various types of electric drives. Drive types with lower present usage show relatively larger near-future growth.
Among performance features that users value as very important or important for their electric drives, the top four came in as: accurate positioning (81%), dynamic braking (81%), torque limiting (79.3%), and torque mode operation or control (76.3%). 'Tripless' operation, considered a crucial feature specifically in adjustable-speed drives (ASDs), came in somewhat lower in importance (71%) among 18 performance features. In contrast, CE 's June 2001 Product Focus survey, specific to ASDs, found tripless operation as the most sought-after drive performance feature.
Survey respondents also had other drive-related opinions. Less than half (43.4%) consider an induction servo system-induction motor and flux-vector drive combination-a viable alternative to a traditional electric servo system. Respondents also report that 30% of stepping-motor-based motion systems are currently used in closed-loop mode. This is somewhat surprising because stepping motor and drive systems were designed to run in open loop. Most of them still do. However, in some cases closing the loop is useful, for example, where position verification is desired.
Influence of software is notable in all aspects of electric drive operations-whether in startup, configuration, or maintenance.
'The power to point and click your way to commissioning a system to your exacting needs, without sacrificing performance or dependability, has become a reality with today's electronic drives,' says James Gegg, senior product manager at Yaskawa Electric America Inc. (Waukegan, Ill.). 'Features that previously may have required special factory hardware or firmware modifications are now available on standard drives and amplifiers with more powerful software configuration tools.'
Controllers add value
Users also have several choices available in types of motion controllers (see Special Supplement in this issue). The latest controllers incorporate advanced processors to augment motion-control performance.
When respondents were asked to rate the importance of features they use to select a motion controller, ease of use and convenience came to the forefront. The top five features-rated on mean values of very important (3), important (2), or not important (1)-were: programmable I/O points (2.36), I/O control (2.35), real-time operating system (2.27), applications development software (2.18), and point-to-point positioning (2.16). In this survey, high-technology features rated lower, for example, path/trajectory computation (1.89), adaptive control (1.84), electronic camming (1.82), high-level servo algorithms (1.67), and sinusoidal commutation (1.63).
All feedback methods and divices surveyed show increased usage in the next 18 months but their relative positions are not expected to change over the period.
How about different motion technologies running on each axis? The latest controllers have such capability; and nearly one-fourth of respondents verifies experience in using them. They cite servo motion most often (94.4%), followed by stepper motion (66.7%) and linear motion (63.9%) as available in the same controller. [Note that multiple answers allow exceeding 100%.]
No technology works problem free over its life cycle. Users were asked about this side of motion controllers. The top five 'problem areas' reported were software debugging (57.2%), poor documentation (51.1%), excessive cost (50%), installation complexity (37.2%), and hardware debugging (35%).
Networking has a way to go
This survey indicates that most motion-control systems still operate in standalone rather than networked mode (80% vs. 38%). In part, it illustrates a disparity between available and applied technology in industry. For networked controllers, the distribution of various buses used is discussed in a Special Supplement in this issue.
As for Ethernet in motion control systems, only 28.1% of respondents indicated using it. And Ethernet is often implemented in combination with another bus. Of those using Ethernet, 62% say they combine it with DeviceNet, while 22% do so with Profibus-DP and 16% with Modbus.
Multi-axis motion anomaly
Multi-axis motion control presents an anomaly. While capability and availability of products is growing, the average number of axes actually controlled in a given application is relatively low, according to the survey results. A majority of users (57.7%) say their motion controllers handle just one to two motion axes. And number of users drops quickly as additional axes are added, with only 4.1% indicating their controllers handle more than 16 axes.
At the system level, the median figure reported was three motion axes per application. Virtually all users (93.4%) satisfy their application needs with one to four motion axes.
Chuck Lewin, chairman of Performance Motion Devices Inc. (PMD, Lexington, Mass.), considers the figure of 'one or two' active axes low for a majority of motion controllers used. He cites a recent PMD survey that found the average number of axes was more than three in the motion applications surveyed. Mr. Lewin believes that the discrepancy stems from the difference in the definition of 'controller.' He adds, 'This is despite the fact that each axis may be driven by a one-axis motion 'amplifier,' also known as a controller.'
Don't overlook feedback
Feedback devices serve a vital role in many motion control applications, closing the loop and supplying the information necessary to obtain accurate control. Again, users have a wide choice of feedback methods to apply in their facilities and automation systems (see Feedback diagram). The values shown are for current use and 'new use'-defined as no current use, but planned use in the next 18 months.
About the collaborative survey
Control Engineering, Design News, and Cahners Research collaborated on a landmark Motion Control Trends survey sent to 7,200 subscribers of both magazines in September 2001. Selected survey results, based on 761 completed questionnaires (11% response), are discussed here and in a Special Supplement to this issue. The responses are aggregate to both magazine's readers, representing one snapshot of preferences by users and specifiers of motion control technology.