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#26
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more explainations
OK... I'll try to answer some questions and explain some things further.
First of all... the patent. Our management here at Delphi saw the prototype of this design and strongly suggested that we patent this design... not to protect us from other FIRST teams to use, but rather future companies. This will be a Delphi patent, once it goes through it's process. Currently, it is a "record of invention", and we are protected to show it to the public. Natchez is wise. The biggest reason we are looking to protect ourselves is for the use of something like the Segway. Imagine a one-ball balancing Segway. This is exactly why our management wants us to protect it. We currently have an agreement with Segway (of the details, I have no idea) that encourages Delphi to help develop technology for the Segway... so this is a good thing (every Segway has about $400 of Delphi electronics in it). Rickersen2 - you are exactly right... it is the opposite of a mouse. This is the easiest way to explain it. JosephM - you are right also. Your concern about the 2nd level of friction loss is very valid. This is really the biggest hurdle of this design. The fact that the small drive wheel has friction losses to the ball and the ball has friction losses to the floor is not trivial. This makes the "ball drive" definitely not a very efficient mechanism. Our prototype would stop and start because of these losses (and an out of round ball). JosephM - your questions are valid, and you have good points. I appreciate your comments. Katy - the balls dent if we drop them from about waist high, but they have not dented while driving up the ramp. If we ran into a 4x4 at full speed, they might dent... but we have not tried that yet. Ricky - it is great to hear that other people might get on your team by seeing this. If find that suprising, but if it is true, then our goal for this drive base has been achieved.... it's all gravy from here. M.Krass and others - I am not sure what you mean by the stall issue. This device works REALLY well when both small drive wheels are moving. The urethane ball drives nicely at a 45 degree angle, but it drives less efficiently at 0 degrees or 90 degrees. It works, but has less power. Also, at straight forward or backward, the lateral drive wheel does not spin. The main reason we decided to do this was to use the shifting gearbox for the front & back drive direction. Optimally, we would rather use 4 gearboxes (one on each aluminum drive wheel) and have each drive wheel positioned at a 45 degree angle. That way, if both wheels are turning, the robot will go straight forward and backward. But, we could not afford (weight, cost, time, etc.) 4 gearboxes. Thanks for your comments. Dima - good ideas... but FIRST has alot of rules against this. Update #4 was a killer. It really set us back. There is actually a post on the FIRST Q+A forums that says a team should not re-deploy a motor to another subassembly, even if it is the same motor (and not a spare). This ruling is ridiculus, in my opinion. We will abide by the rules, but we will need explainations. For the rest of you: thank you. Come by our pit, and I will introduce you to the guy who came up with the main part of this design: Mark Koors. He told me of this idea last summer and I simply laughed at him. My first concern was the same as JosephM's (the 2 levels of friction issue). But... the more Mark and I worked the issues, the more they cleared up and the simpler the design got. Simplicity - Krass is right... this omnidrive is extremely simple, not only in the mechanics, but especially in the software. No chain linked axis turns, no lookup tables... simple. You who are wrestling with crab drive software/hardware would cry to see how simple this is (yet another reason to patent it). More to come... sorry about rambling. I surely did not heed my own words to be concise. Andy B. Last edited by Andy Baker : 03-03-2003 at 22:49. |
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