Motor Torque (gains)

[archiver]

Posted by Alex at 2/15/2001 3:35 PM EST


Engineer on team #405 from Richmond Community High and Infineon Technologies.



Hi All,

I have a Q about increasing the current to the motors. We are using a van door motor connected to an "arm" the pushes down the bridge. We need to get a little more "umph" from our motor. Is there a parameter (gain) that I can adjust to increase the torque? Are the gains defaulted at 100% to begin with?
We are also physically cutting off 4" from the arm to decrease the resistance to the motor. TIA

Alex

[archiver]

Posted by Ken Leung at 2/15/2001 4:26 PM EST


Student on team #192, Gunn Robotics Team, from Henry M. Gunn Senior High School.


In Reply to: Motor Torque (gains)
Posted by Alex on 2/15/2001 3:35 PM EST:



I am not so sure you can increase the current to the motors, because there are certain rules that limit what kind of circuit breaker you can use on the motor. Those circuit breakers are already limiting how much current you can have on the motor. Plus, this is just another way of making sure people don't max. out the power of motor if they have the engineering skills to, or have the resources to afford to replace motors, but also, it's a simple rule to prevent unnecessary damages to the motors.

As most teams do, you should look into adding mechanical modification to the output of the motors, instead of changing around current and electronics. Usually most teams gear the motor's motion slower so that they can get more torque out of them. Remember, Power = force x velocity or torque x angular velocity.

By cutting off 4" from the arm, you already increase torque quite a bit.

About The relationship between torque/speed/power/current, I know that there is a linear relationship between torque and current, and that the more current you have, the more torque you can get. The linear relationship between torque and speed is the exact opposite.

As for the relationship between power and torque, all I know is that at the beginning when you have an increase of torque, you also have an increase of power. But then it reaches to a mid point where power output have a change of zero, and start decreasing until a point where you have maximum torque but really little power, meaning very little speed (stall torque). All I know is that you want to keep your range of torque in the interval where your power is at maximum or near the maximum.

You should really look at the power point presentation in the white paper section by Michael Ciavaglia and Joe Johnson about all these. That is if you haven’t do so…

I am sorry I can’t offer much help here because I only know about characteristic of motors, and can’t really apply that knowledge to making the situation. If you already when through those presentations already, then assume I didn’t say anything. Can someone please help out here?

[archiver]

Posted by Joe Johnson at 2/15/2001 5:33 PM EST


Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.


In Reply to: Motor Torque (gains)
Posted by Alex on 2/15/2001 3:35 PM EST:



The van door motors have plenty of power to move the bridge around in a reasonable timeframe.

What you probably need is more ratio from the motor shaft to the arm.

I don't know if you can do anything at this late date but if you can get more turns of the motor shaft for the same travel of the arm, but if you can it will give you the "umph" you seem to want.

Good luck.

Joe J.

[archiver]

Posted by Tim Gates at 2/15/2001 10:38 PM EST


Engineer on team #288, RoboDawgs, from Grandville High School and X-Rite/Delphi.


In Reply to: Motor Torque (gains)
Posted by Alex on 2/15/2001 3:35 PM EST:



Last year we used the van door motor on a rather lengthy arm and had enough torque when under the goal to lift(not on purpose) the goal up and damage the playing field. As a matter of fact, in one instance we chewed the teeth off of a fairly heft set of gears with the van door motor. You have to give up a little speed to get the torque. Our ramp would not stay tipped unless we were within 1" of the floor. What is your ramp doing when you slowly rotate it until it tips on its own?

[archiver]

Posted by Alex at 2/16/2001 4:26 PM EST


Engineer on team #405 from Richmond Community High and Infineon Technologies.


In Reply to: Motor Torque (gains)
Posted by Alex on 2/15/2001 3:35 PM EST:



Joe,

You are right. We are working on a mechanical solution. Thanks,

Alex


: Hi All,

: I have a Q about increasing the current to the motors. We are using a van door motor connected to an "arm" the pushes down the bridge. We need to get a little more "umph" from our motor. Is there a parameter (gain) that I can adjust to increase the torque? Are the gains defaulted at 100% to begin with?
: We are also physically cutting off 4" from the arm to decrease the resistance to the motor. TIA

: Alex