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Unread 18-12-2007, 23:04
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WOOPS! shorted the deep cycle batt.
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Re: Torque vs. Speed

The driver can always lean back on the throttle a little bit, you don't want to be stuck in a situation where you need the speed but don't have it. Also a button may be installed to switch the drive from 100 to 80 percent in pushing scenarios.
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Unread 18-12-2007, 23:12
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Re: Torque vs. Speed

You don't need a button to slow down the robot, the robot you're pushing will do that for you

See if you can figure out what this chart is telling you. Notice that torque is zero when speed is 100%.

This is important stuff, it takes a while to understand it, so please take some time to think about it and discuss it more. It's likely a real expert will jump in and point us to a relevant thread, or give a better explanation than I can (I'm a mechanical engineer....)
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Unread 18-12-2007, 23:22
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WOOPS! shorted the deep cycle batt.
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Re: Torque vs. Speed

I believe there is a misunderstanding, are we talking about motor speed or are we talking about the PWM power setting? Because if were talking about motor speed then you are absolutely correct, there is no torque, but if we are talkign about the pwm then its a whole different story.

as for your ability to explain things, i feel your pain, i'm just as bad, i can't explain anything to anyone
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Last edited by eshteyn : 18-12-2007 at 23:28.
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Unread 18-12-2007, 23:54
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Re: Torque vs. Speed

Oh yeah, you're talking about the PWM command signal...I think Hachiban is talking about motor speed...and they are not the same thing.

Hachiban is worried about the motor running at near full power, just because it has been set up to run at near full speed (determined of drivetrain gearing). This is not how it works, the current draw of the motor depends on load as well as well as the speed.

I think he doesn't understand the relationship between torque, speed, current draw, and power. Again, it takes a while to figure out how it works.
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Unread 19-12-2007, 00:05
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Re: Torque vs. Speed

You see our mentor's primary concern was not with the mechanics at all. She was worried that it would be very difficult to run a Victor at 50%.

(apparently they don't like to run at this level or something??.. doesn't really make any sense to me, but then again I'm easily confused by electrical stuff).
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Unread 19-12-2007, 00:14
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Re: Torque vs. Speed

In real life, you will hardly ever have the victor running at 50%....especially if the motors are set up to run at 50% of their no load speed at "normal" driving speed.....

It would help if you did understand the torque/speed/load/power stuff.

You can think of it like driving a car (this might not help if you don't drive a car)...when you drive on the highway, you have the gas pedal pushed just a little bit, but the engine is running at perhaps 50% of it's maximum rpm. You come to an up hill, you have to push harder on the gas pedal just to keep the car going the same speed. You get to a down hill, you have to let off the gas pedal to keep from speeding up more.

When you start from a stop, you have to push the pedal pretty far to get going, and the engine speed changes from slow to faster then slows down again after the transmission shifts, even though all this time the gas pedal is about the same position.

Think of the gas pedal position as the PWM signal, and the engine RPM as the motor speed, and the car's speed as the robot speed.

(This is a bad analogy, but might help you to understand the relationships)

Last edited by MrForbes : 19-12-2007 at 00:21.
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