Phasied HMI and I/O Solution Booosts Productivity
Online Extra for September 2003, Phased HMI and I/O Solution Boosts Productivity
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Phased HMI and I/O Solution Boosts Productivity
What began as a job interview discussion with a prospective employee became an automation upgrade strategy for Michigan Waste Energy.
Dave Harrold, Control Engineering
Recently married and out of a job, Roy Costa applied for a safety coordinator position at the Michigan Waste Energy (MWE) facility in Detroit, Michigan. As the interview morphed into a discussion about obsolete control system problems, Costa articulated a phased solution that began by replacing the obsolete human-machine interface (HMI) with a new application built on National Instrument’s (NI) LabView platform. Costa didn’t get the MWE safety coordinator job; he did get an electrician and instrument technician job where he began making his vision a reality.
Waste to energy
Operated by Covanta Energy Corp . the MWE facility is a refuse de-rived fuel (RDF) plant that began commercial operation in October 1991 and is permitted to re-ceive up to 4,000 tons of municipal solid waste (MSW) per day.
MSW is processed into RDF and burned in two of three available waste-to-energy boilers to produce 720,000 pounds of steam per hour. The site generates up to 68 megawatts of electricity and supplies up to 550,000 pounds of export steam per hour.
Electricity and steam, in excess of what’s used to operate the facility, is sold to Detroit Edison Corp.
Because trash picked up curbside eventually becomes fuel for the waste-to-energy process, a considerable amount of pre-processing is required.
Using three process lines, MWE can turn approximately 250 tons per hour of solid waste into RDF.
Through a series of motor-driven conveyors, trash moves through shredders, trommels (high capacity separators), magnets, packers, and supporting equipment–but not without difficulties. Periodically, oversized materials plug chutes and hoppers. These blockages often cause motors to trip overloads and occasionally damage conveyors, reducing production rates. Furthermore because clearing blockages is labor intensive, time consuming, and hazardous, theadded labor and repair costs can cost thousands of dollars. In addition, MWE’s RDF processing equipment, controlled via PLCs (programmable logic controllers), had an human machine interface (HMI) more than 10-years old. Difficulties in maintaining the obsolete HMI platform prompted the facility to explore alternatives capable of communicating with existing PLCs.
HMI of choice
During his job interview, Costa articulated a phased solution that began by replacing the obsolete HMI with a new application built on National Instrument’s (NI) LabView software.
Costa had used LabView in a previous job and was impressed with its versatility and ability to easily adapt to new requirements. At MWE, Costa began examining the obsolete HMI application only to learn it was poorly documented and written in machine code.
As the application’s complexity revealed itself, Costa began to question if his earlier exposure to LabView, in a smaller, more-specialized application, had jaded his perception of its appropriateness for this application.
“After careful consideration of other HMI software packages, we confirmed that LabView, with the DSC [Datalogging and Supervisory Control] module, was best suited to handle this application, and it provided the customization flexibility this application was likely to require,” Costa explained.
Convinced his vision was achievable on the LabView platform, Costa assembled an offline con-trol system and began the tedious process of reverse engineering the HMI application and implementing equivalent functionality in LabView.
As the LabView application grew, HMI-to-PLC communication read/write times lengthened, eventually reaching unacceptable delays.
After weeks of testing and talking with Covanta Energy corporate staff and NI factory person-nel, the test system was shipped to NI for further evaluation.
NI’s evaluation confirmed the OPC driver had throughput issues and recommended developing a new OPC driver.
Not wanting to wait or become an OPC driver alpha/beta test site, Costa turned to Soogatech’s Software Engineering Group and purchased its HighwayView device driver.
Testing also revealed the application software, as implemented, was contributing to communication performance issues.
As luck would have it, VI Engineering (VIE), an NI Select Integrator Alliance member, was located in nearby Farmington, Michigan. In addition to providing traditional project integration services, VIE provides consulting, standards, tools, and training to help users, such as Roy Costa, develop modular, reusable LabView applications. (See “Software development practices create a bridge to software success” sidebar.)
Following a couple of insightful conversations, MWE issued VIE a time-and-materials contract to help resolve MWE’s application software performance issues.
Mentoring pays off
While Costa attended Vista training, VIE’s Chung-wen Chen used Vista’s good software engineering practices as the foundation for reviewing MWE’s application software and HighwayView driver implementation. With Chen as his mentor, Costa worked through a series of prioritized assignments. As Costa completed each assignment, results were critiqued and evaluated, with some being returned for further work.
In the end, the optimized implementation of the HighwayView driver improved HMI-to-PLC communication read/write performance from more than a minute to four seconds per read and 50 microseconds per write. Additionally, applying Vista techniques and Chen’s specific recommendations, the MWE software application was made more capable, more maintainable, and about 40% smaller.
“Without the patience and wealth of expertise of the VI Engineering staff, especially Dr. Chung-wen Chen, this project wouldn’t have turned out to be the rousing success it has,” said Costa.
Following several months of reverse engineering, implementation, optimization, and testing, the HMI application was ready to debut in the MWE operations center.
With old and new HMIs sitting side-by-side, operators could use the new but had the old as a “just in case” backup.
To enhance operability, dual touch-screen monitors from ViewSonic had been included. Unfortunately, it wasn’t until the last minute that MWE learned ViewSonic didn’t include a dual, touch-screen driver--a problem quickly resolved by ViewSonic’s technical staff.
“For many MWE operators, this was their first exposure to a personal computer. However, the introduction of PCs in the operations center has created an interesting side benefit,” said Costa. “Operators have become so comfortable with the operator interface that many have purchased home PCs. Now they come in with ideas of things we can do to improve our HMI implementations. We never anticipated this HMI upgrade project would also elevate the knowledge of our operators, but everyone is pleased by this added benefit.”
Though the original control system had more than 2,500 I/O points, information for avoiding or minimizing conveyor plugs was limited. For example, when a blockage occurred, the first indication the operator often received was an alarm that a motor had stopped--usually because the motor overload had tripped. By then, a blockage could become more severe or cause damage.
Using NI’s FieldPoint I/O system, Costa added 21 new I/O channels to help optimize plant assets. Seventeen of the new I/O channels monitor amperage and provide alarms when motor cur-rent reaches 90% of the motor’s rated value. Operators are now alerted when conveyor plugs are beginning to happen.
“The addition of these few I/O channels and the operator’s quick response to clear developing blockages has resulted in significant productivity improvements,” said Costa.
MWE’s upgrade project certainly didn’t begin in a typical fashion, staffing selection wasn’t traditional, the HMI selection process was unconventional, and finding a competent integrator to assist was more happenstance than a process. Nevertheless, MWE’s project provides valuable insights, including
While difficult, it is possible to upgrade legacy systems via a reverse engineering process;
Familiarity with a supplier’s software package in one application can create assumptions that may cause you to underestimate efforts required to use that same software package for a dif-ferent application;
Skeptical managers, operators, and even a nemesis or two can be a strong “I’ll show them no matter what” motivator;
Having a new bride with a technical background provides a valuable support system; and
Making purchasing decisions based only on information contained in marketing brochures isn’t a good idea.
With the HMI upgrade project officially online in April 2003, MWE is turning its attention to automation enhancements in the areas of soot blowing and advanced fuel feed-rate control.
Every project team has “stories” to tell. Some of these stories are sad, some are happy, and some shouldn’t be shared.
MWE’s project includes several happy stories, but the story of the project’s origin may well be a first.
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Software development practices create a bridge to software success
No one intentionally sets out to create bloated spaghetti code and/or software with minimum structure or reusability; so why does it continue to happen?
VI Engineering believes the answer lies in an organiza-tion’s failure to recognize the benefits of a comprehensive, well-planned means to organize and continuously improve software-development practices.
Because software development practices depend on many factors, including application characteristics; platform choices; and organizational structure, size, and maturity, the software development strategy used by one organization may not be completely appropriate for a similar organization.
Seeking to improve the quality of National Instrument’s LabView software applications developed for test and measurement, VIE applied principles defined by Carnegie Mellon’s Software Engineering Institute (SEI) to develop Vista.
Over time, the quality of VIE-developed applications using its Vista software development environment became widely acknowledged throughout the NI community.
Responding to requests by clients and other NI integrators, VIE now offers Vista training, tools, standards, templates, and consultation services.
Elements of Vista are:
Reuse productivity strategy;
Technical data management; and
Often software development engineers underestimate the importance and interaction of each element, however research by SEI and others indicate that implementing configuration management tools can increase software quality by as much as 80%.
The same research indicates the implementation of reuse libraries and code sharing can improve development and testing productivity by 20–25%.
Establishing appropriate software development practices, such as Vista, for your company and clients requires engineering and management commitment.
Once committed, it’s important to conduct a needs assessment to ensure areas requiring the greatest improvement are identified and addressed first. For example, just because configuration management and software reuse have produced positive results for others, doesn’t mean those areas are most needed within your organization.
No one intentionally sets out to develop bad software. By committing to the development and application of appropriate software development practices, organizations can remove or minimize uncertainties, thus crossing the bridge to software development success.