Control Engineering

Paul Grayson

Proportional Response
April 25, 2008

Power steering kit.

HYDRAULIC STEERING
For tractors and other vehicles like AIM's AGV WENDY DARLING that already have hydraulics power available onboard, hydraulic steering is a reasonable option. The photo shows an example of how quickly the power steering can be installed. The cylinder rod end clamps on the drag link. The two U bolts loop over the hardened steel frame of the truck to hold the bracket in place. All that is needed to complete this picture are the hoses and the computer controlled steering valve. A few days ago Sun Hydraulics sent me a post card about their Electro-hydraulic Proportional Valves with on-board electronics. This valve looks like it has some interesting characteristics, I will let you know what I find out in the next few days when the data sheets show up and I get a chance to chat with the people at the factory about what it can and can not do.

REVERSE ENGINEERING
As you might guess from the topic, today I spent the day working on hydraulics, making hoses to replace damaged ones, snaking the new ones through complex turns within the machines I was working on. One of the control lines of the thirteen that work a Ditch Witch back hoe got a hole in it. Another was one of the nest of hoses on a Ransomes Greens mower which was the supply line to one of the cutting head raise/lower cylinders. Repairing machinery is quite an education. To begin with when you walk up to a machine to be repaired, you are looking at another engineers answer to a series of complex questions. The trick is to look at it and see if you can recognize all the answers and then work backwards to what the questions were that produced this design. Did the person before you use "best practices"? Do you agree that this is a workable solution to the problem? What short cuts were taken? This all starts with what you have learned from text books about routing houses, alignment, strain relief, flow rates, pressure drops, and speed then goes show me where the design failed - because it has been brought to me for repair. Given enough hours, all designs will eventually fail, given a lot of hours and repirs, there will be a long series of failures in a machine's lifetime. The question then becomes is it the same failure every time or something different? Is there a pattern forming? What needs to be changed to improve reliability? That was my first shift job and continued on to my second shift job which is working as a volunteer Team Leader on AIM's US Army truck, WENDY.

WENDY
My work on hydraulics continued on my Second Shift Job as I searched catalogs in the AIM Technical Library and hydraulics company web sites looking for what parts I can use to make a hydraulic after market steering system for the 400,000 vehicles that the US Army needs to convert to driverless operation as soon as possible and before 2015. While the silence from the other teams may mean that they are working on solving the problem in secret, I can't be sure of that. To keep the pressure on I must keep working toward getting the US Army the guidance and control system they need as soon as possible. I do it just a bit more publicly that most people would. Here is a start on a hydraulic steering system. 



Basic hydraulic steering control, additional elements can be added to refine the design.

READER CHALLENGES COMMENTS
It is good that companies are becoming interested in being "green", that it is now fashionable. Perhaps that interest will expand into being concerned about fellow US citizens. Robert Bass, one of this column's readers took exception to my repeating, what I had heard, that there is a long haul truck driver shortage. He blames me and other media for perpetuating the myth that there is a driver shortage when in fact he is a long haul truck driver out of work, along with at least 6,000 others he knows of on the driver internet forums. A quick search of http://www.everytruckjob.com/ shows 2,518 companies looking for drivers. This discrepancy or mismatch, while not a traditional engineering problem, is puzzling to me. What is wrong here and how do we fix it? Would helping these two US citizen groups solve their mutual problem be any less important than being environmentally friendly? Color(s) could be assigned to being US citizen friendly - perhaps "red, white, and blue"?

2007 DARPA URBAN CHALLENGE

Urban Challenge support vehicle with crane, vise, and tools.
GO ROBOTS !

Paul F. Grayson - Chief Engineer
AMERICAN INDUSTRIAL MAGIC, LLC
Racing to build technology that saves soldier's lives.
390 4-Mile Rd. S.
Traverse City, MI 49686-8411
(231) 946-0187, (231) 883-4463 Cell
pgrayson@aimagic.org
AIM: http://aimagic.org
Robot Club: http://tech.groups.yahoo.com/group/robotcluboftraversecitymi/
CE Magazine: http://www.controleng.com/blog/1180000318.html

Posted by Paul Grayson on April 25, 2008 | Comments (0)