Posted by Gary Bonner.
Other on team #433, MINT, from Mount Saint Joseph Academy and Pew Foundation.
Posted on 9/5/2000 4:49 PM MST
Is there a significant difference in the efficiency of the drill motor spinning clockwise vs. counterclockwise? On our 2000 Robot, which had a tank-drive setup, we had to scale the output of one motor when the robot was going forward, and the other motor going when it was going backward. Is this typical?
Posted by Nate Smith.
Other on team #66, GM Powertrain/Willow Run HS, from Eastern Michigan University and GM Powertrain.
Posted on 9/5/2000 9:52 PM MST
In Reply to: Motor Spin Direction posted by Gary Bonner on 9/5/2000 4:49 PM MST:
: Is there a significant difference in the efficiency of the drill motor spinning clockwise vs. counterclockwise? On our 2000 Robot, which had a tank-drive setup, we had to scale the output of one motor when the robot was going forward, and the other motor going when it was going backward. Is this typical?
I’ve noticed this same thing in the machines that I’ve worked on…and I remember seeing other teams comment on it here before…your best solution, rather than scaling, is find a way where the motors can be positioned so they are both going the same direction when going forward or reverse.
Nate
Posted by Thomas A. Frank.
Engineer on team #121, The Islanders/Rhode Warrior, from Middletown (RI) High School and Naval Undersea Warfare Center.
Posted on 9/12/2000 1:40 PM MST
In Reply to: Re: Motor Spin Direction posted by Nate Smith on 9/5/2000 9:52 PM MST:
: : Is there a significant difference in the efficiency of the drill motor spinning clockwise vs. counterclockwise? On our 2000 Robot, which had a tank-drive setup, we had to scale the output of one motor when the robot was going forward, and the other motor going when it was going backward. Is this typical?
: I’ve noticed this same thing in the machines that I’ve worked on…and I remember seeing other teams comment on it here before…your best solution, rather than scaling, is find a way where the motors can be positioned so they are both going the same direction when going forward or reverse.
Hello All;
Yes, there is a difference in efficiency depending on with direction the drill motors turn. They are constructed (timed) to provide more power when rotating in the direction that one uses to drill/drive screws IN. We’ve measured about a 20% difference between the directions of rotation.
Nate is right, it is best if you can set things up so that the motors are ‘matched’, rather than trying to trim things in software. But, when all else fails…
Tom Frank
Posted by Joe Johnson. [PICTURE: SAME | NEW | HELP]
Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.
Posted on 9/12/2000 9:32 PM MST
In Reply to: Re: Motor Spin Direction posted by Thomas A. Frank on 9/12/2000 1:40 PM MST:
I have sat and watched this conversation over and over again over the years.
I will be honest with you folks, we have NEVER bothered with such subtleties.
Drive time trumps all. Give your drivers time with the machine and they can undo all sorts of nasty nonlinearities and asymmetries.
I don’t know if we are just too ignorate to know better or if other teams have too much time on their hands to worry about these things.
These FIRST games are not games of 1 and 2 % improvements. Look for the main problem. Solve that.
Free advice from Dr Joe.
Joe J.
Posted by Lora Knepper.
Other on team #419, Rambots, from UMass Boston / BC High and NASA, Mathsoft, Solidworks, Analog Devices.
Posted on 9/13/2000 1:20 AM MST
In Reply to: Much ado about not much posted by Joe Johnson on 9/12/2000 9:32 PM MST:
: Drive time trumps all. Give your drivers time with the machine and they can undo all sorts of nasty nonlinearities and asymmetries.
Joe,
As a driver for 3 years, I agree with you! As long as your drivers are given ample time with the machine, they should be able to compensate (I know I got yelled at more than once for complaining that the motors were running differently! ‘Compensate then! That’s your problem!’). The key is to work out the big bugs, and let the drivers get used to the unique ‘personality’ of the machine…and keep in mind that time with the drive train is not enough…the CG and behavoir of the machine changes with eveything else added on.
Lora
Posted by Nate Smith.
Other on team #66, GM Powertrain/Willow Run HS, from Eastern Michigan University and GM Powertrain.
Posted on 9/13/2000 9:44 PM MST
In Reply to: Yes, drivers should compensate posted by Lora Knepper on 9/13/2000 1:20 AM MST:
: : Drive time trumps all. Give your drivers time with the machine and they can undo all sorts of nasty nonlinearities and asymmetries.
: Joe,
: As a driver for 3 years, I agree with you! As long as your drivers are given ample time with the machine, they should be able to compensate (I know I got yelled at more than once for complaining that the motors were running differently! ‘Compensate then! That’s your problem!’). The key is to work out the big bugs, and let the drivers get used to the unique ‘personality’ of the machine…and keep in mind that time with the drive train is not enough…the CG and behavoir of the machine changes with eveything else added on.
While I agree that to some point, driver compensation will be necessary, no matter what your design(I know it still was for us,) I’m still an advocate of minimizing the need for compensation as much as possible. As much as we try, the majority of teams that I’ve talked to at some point during my time with the competition still admit that they wish they had been able to get more driver practice time, and some teams make design changes right up until it goes into the box, so there may be changes that effect the performance of the system. Also, as much as they practice in the comfort of their own school, driving at an actual event, in front of who knows how many people, is a completely different experience. I saw my first matches from the field as a volunteer at Great Lakes last year, and being that close to the action puts you into an entirely different mindset than being in the stands. Watching teams as they were setting up to compete, I could tell that some of the drivers were still nervous, even during practice matches. With all this running through their head, it is almost too easy to forget that you have to push the stick slightly to the left and forward if you want the machine to go straight. So, any help that can be given, be it through creative software(in PBASIC? Yes, it is possible…) or a compensation built into the machine itself, will do nothing but help you in the long run…
Nate
Posted by Joe Johnson. [PICTURE: SAME | NEW | HELP]
Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.
Posted on 9/14/2000 5:02 AM MST
In Reply to: Drivers can always use a little help… posted by Nate Smith on 9/13/2000 9:44 PM MST:
…So, any help that can be given, be it through creative software(in PBASIC? Yes, it is possible…) or a compensation built into the machine itself, will do nothing but help you in the long run…
Not necessarily. If your team and your engineers in particular are spending time working out this ‘improvement’ rather than fixing your lift mechanism or even worse, such changes are being stolen from drive time, your team will be farther behind in the long run!
Finally, I am pretty confident that most teams with this ‘my robot wont drive straight’ illness have issues unrelated to the variations in motor power output between CW & CCW (wheel alignment, weight distribution, wire lead lengths, drive mechanism variations, etc.).
For what it’s worth.
Joe J.