We Are the Horses
Thank you for your column, “Lead the Horses to Water” [Mar09, p33; www.ControlDesign.com/horses]. It is engineers like yourself, giving back to the engineering community who keep students like me eager to pursue our education and to learn more than just what the textbooks tell us.
To increase student awareness, put forward examples of students who started their engineering careers early and who are successful. Show students they can start their own businesses and pursue their own unique ideas. They do not realize that an engineer is born and that engineering is a mindset.
Mike Dizor, student,
Jacksonville U., www.jacksonville.edu
Talk About the Passion
One of Jeremy Pollard’s columns about IEC 61131 [“Standards and Guile Lines,” May09, p29; www.ControlDesign.com/guile] recapped his spirited conversation with Beckhoff’s Corey McAtee. That passion is something we could use a lot more of when it comes to doing the right thing for North American manufacturers. One of Hans Beckhoff’s guiding principles (imagine a Westphalian accent here) was “Never do anything in hardware that you can do in software.” I think that single guiding principle says more about how we approach the development of automation products, and it encompasses why we are committed to IEC 61131-3 and even more so now with IEC 61499.
Joe Ottenhof, regional manager
Canada, Beckhoff Automation, www.beckhoffautomation.com
Half-Truths
I read Dan Hebert’s Mojo column [“New Market for Machine Builders,” May09, p13] and was surprised by the suggested list of advantages that hydraulic hybrids have over electric hybrids.
You state the following: “First, hydraulics decouple vehicle power demand from power supply, allowing the gas engine to run at its sweet spot. Second, hydraulic hybrids can run with the gas engine completely shut off. Third, hydraulic hybrids are extremely efficient at capturing braking energy.”
I don’t doubt the validity of the statements above; however, the first two are at least partially true of gas/electric hybrids such as the Prius. It uses a planetary gear where the engine is connected to the planetary carrier while the electric motor and output drive (wheels) are connected to the ring gear. This allows partial decoupling of the engine from the wheels at times when the ECU determines it is appropriate. The vehicle can move at low speeds with only electric motor power, and often the engine shuts off during normal driving to conserve fuel. In addition, the power split between the electric motor and engine is optimized so that the engine is running in its most efficient load and speed range most of the time.
Your third point about brake energy recovery is clearly an advantage, although later in the article you say the opposite, “Gas/electric hybrids capture regenerative braking energy, just like hydraulic hybrids, but with much better efficiency.” What? That has to be a typo.
It could be argued that an engine operated at a more or less fixed speed (hydraulic hybrid) is more efficient than one allowed to operate over a broader rpm range (electric hybrid) does. It just doesn’t appear that a fair comparison between the technologies was offered to the reader.
Michael Sewick, product manager, mobile controls,
ifm efector, www.ifm.com
[Editor’s Note: Yes, that was indeed a typo, Michael. It should have said “poorer.”]
