Control Engineering's E-News Letter for Embedded Control - February 2002

06/04/2002


In this issue:


 

Control in February Control Engineering

If you don't receive the print version of Control Engineering, the February issue should be posted online within a week of this newsletter. Check out the article on controllers. Dave Harrold and I have been discussing controller hardware in a pair of articles. In this article, I summarize a paper by C. K. Gollapudi and D. M. Tilbury of the University of Michigan Engineering Research Center for Reconfigurable Machining Systems (ERC). 'Familiar and Emerging Logic Control Frameworks' surveys several methods of logic for machine control.

Some of the goals of the ERC include studying and recommending improvements for configuration tools for discrete logic control systems as well as studying open architecture controllers. As the authors state in the paper, 'Ideally, good software tools should lower the cost contributed by logic control elements in setup, maintenance, and operation, and should increase the human efficiency factors related to control at all stages of its life cycle.' The ERC is trying to bring some of the academic rigor to discrete logic that is a staple of process control.

The entire paper will be posted in pdf format with the February issue. Take a look and let the authors and me know what you think. Watch for more work from ERC and check out the program at erc.engin.umich.edu .

 

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Programming feedback from readers

Last month I asked if you thought that good programming practice was being lost. Here is a sampling of the responses with names omitted to protect the innocent. Most seem to be using Ladder Logic or other IEC 61131 language. Some use C/C++ and there was some response for flow chart software.

Biggest concerns were thinking through the system before coding and documenting the program.

'One of my biggest gripes was that a lot of programmers would not break down the code into sections or files. There is nothing more frustrating than a program with 300 networks all rolled into one segment or an entire program in one file.'

'At the company I work for, we have developed best practices for structuring PLC programs and writing code to help ensure that the programs are consistent and easy to read.'

Troubleshooting something written in a scripting language is almost impossible.

'I think the two biggest reasons good programmers go bad are tight deadlines and last minute changes.'

One reader suggested a book that has helped him for years, 'Techniques of Structured Program Design' by Edward Yourdon (1975). I couldn't find it on Amazon.com, but there are several others by him you may want to check out.

'I realize that there is an ongoing debate as to the future of ladder diagram programming vs. higher level programming but not enough concern has been given to the maintenance of an industrial machine. Maintenance personnel are intimately familiar with relay logic...'

'What has served me well throughout my career, and what I increasingly think is lacking in the field of programming, is a thorough and structured approach to program design and development. While this mentality was certainly encouraged during my formal schooling, it's my observation that to some extent this is more of a personality trait than something that can be taught.'

'A complicated ladder program can be easy to follow, if all of the documentation features are put to good use, including address, instruction, and rung comments. I have seen programs where these same features made the program almost impossible to follow, because the programmer and service people did not correct the documentation to match program changes that were made.'

Is this a topic that should be tackled in a future Control Engineering article? Any more thoughts on good programming practice? Let me know at gmintchell@cahners.com .

 

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New semiconductor companies

Two new semiconductor companies have just appeared over the Control Engineering horizon.

Cyan Technology ( www.cyantechnology.com ) based in Cambridge, England has developed a 16-bit flash microcontroller. Why 16-bit? The company saw a gap in the market between 8-bit low-power microcontrollers and high-performance 32-bit ones. Its 16-bit product is developed to be low-power consumption and low heat. Not only is the product less expensive than higher end ones, its low power and heat output enable lower system cost and extended battery life for such products as intelligent sensors or hand-held, connected HMI devices. The product combines a core with communications processor, MMU, four serial ports, modem support, IrDA support, and many more peripherals.

Xyron Semiconductor ( www.xyronsemi.com ) has ZOTS, that is, a 'zero overhead task switch' that is an integrated hardware interrupt and task-switch management mechanism. With it, all internal and external interrupts are directed to the RTOS hardware, which manages information for each task. Tasks can be initialized for different priorities, can ramp at different rates and can be managed and monitored on each clock cycle. The company essentially puts software into hardware so that current microprocessors can run applications faster..

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Programming tools

SoftIntegration ( www.softintegration.com ) has released 'Ch' version 2.1. Ch is a superset of C with C++ classes and a C interpreter. Ch has built-in graphical support, generic mathematics functions, and computational arrays for linear algebra and matrix computations, 2D/3D graphic plotting, and advanced high-level numerical functions for linear systems, differential equation solving, integration, non-linear equations, Fourier analysis, etc. Ch for Windows has collections of UNIX utilities including vi, ls, awk, sed, grep, cp, find, etc.

I have not yet had an opportunity to try it, but if you have intensive mathematics requirements, you might give it a try. Let me know how it works. I'll try to give it a try later.

Another tool you might want to look at is from eclipse.org ( www.eclipse.org ). I have downloaded and installed the application for Java 2. I have just looked at the IDE and will try writing some programs in the next month. If you write any Java, this looks like something to consider. The organization also has released a tool for C++ in Linux.

The eclipse.org Consortium was formed to deliver new-era application development tools. Industry leaders Borland, IBM, Merant, QNX Software Systems, Rational Software, RedHat, SuSE, TogetherSoft, and WebGain form the initial eclipse.org board of directors. These companies plan to release Eclipse Platform compatible product offerings.

In the Eclipse Platform, code access and use is controlled through the Common Public License, which allows individuals to create derivative works with worldwide re-distribution rights that are royalty free.

Speaking of tools, I saw a demo last week of GE Fanuc's new IDE for machine control program development, Cimplicity Machine Edition. It has a Visual Studio look and feel and allows you to program in IEC 61131 languages (ladder, SFC, list), do custom function blocks, save blocks of code for reuse, and write first then target the platform (PLC or PC) required by the project. Looks good. GE Fanuc is found on the Web at www.gefanuc.com .

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Cool embedded products in brief

STX 15 series from CyberResearch ( www.cyberresearch.com ) are compact form factor, NEMA 4/12 rated PCs with four COM ports, two USB ports, and a 10/100BaseT port all built in.

Eight new modules in the Allen-Bradley Point I/O family from Rockwell Automation ( www.rockwellautomation.com ) four digital modules, two voltage analog modules one input and one output, a two-channel isolated thermocouple input module, and a two-channel RTD input module.

Baumer Electric ( www.baumerelectric.com ) introduced a line of 18 mm tubular inductive proximity sensors with analog output. The company states the linearized output is accurate to one micron.

Hyde Park's ( www.hpsensors.com ) 30 mm ultrasonic proximity sensors offer a range from 8-in. to 26-ft. Functionality selections include NO or NC NPN and PNP outputs, complementary NPN or complementary PNP outputs, a variety of response times, and default window setup limits.

Acces I/O ( www.accesioproducts.com ) model 104-AIO12-8 12-channel analog multifunction I/O card for PC/104 allows users to precisely configure the board to the application's requirements.

Ferrous-only proximity switch from ifm efector ( www.ifmefector.com ) features multi-coil design for improved reliability in sensing steel targets in aluminum machining applications. 4500-S from CSI division of Emerson Process ( www.csimeansreliability.com ) enables continuous monitoring of rotating equipment in applications requiring 12 or fewer signal channels including two tachometers and two I/O relays.

WinSystems' ( www.winsystems.com ) PPM-TX PC/104-Plus single board computer has a -40 to 85 deg C operational temperature range and includes four serial ports, 10/100 Ethernet port, and Intel 166 MHz Tillamook PentiumMMX processor.

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