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Spockie-Tech
Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
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@ Tim :
quote:
gyro trys to correct the steering and becuase the gearbox is jammed or broken the bot wouldent move thus making the gyro try harder
I've only had a little tinker with these Gyro's so far, but as far as I understand their behaviour so far, the gyro doesn't sense the bot NOT moving, but only when it moves in a way that was not commanded by the receiver does it apply a correction signal.
So if your receiver is saying "sit still" or "go straight ahead" and the gyro senses a turn, it will apply a correction signal to try and pull the bot back into a straight line, but only for as long as the bot is actively turning. Once the bot stops turning, the gyro will stop applying a correction signal.
So if you push the bot off-line in some way, the motors will fight the turn, but only while it is actually turning, once it settles on the new (wrong) direction, the gyro will stop fighting it and allow it to continue in this way. Of course, if you have traction then the gyro will have pushed the bot back onto line during the turn.
I think you can also get "heading lock" gyro's (heading is the direction you are pointing in airplane-speak), which will continue to apply a correction signal until the gyro is pointed back in the actual direction it was last before the error-movement occured, but I dont think these are typically used in bots.
So, if you did have a dead side on your drive, a normal gyro would fight against it when the uncommanded turn occured, but only for as long as you were trying to go straight, it wouldnt go into a "I'm going to keep trying to drive this dead motor until we're back to where I wanted to go" mode until the IBC fried.
Once you stop trying to go straight, it would stop trying to keep you straight, so in the sense of the load placed on the controller, its not much worse than a system without a gyro would be.
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from what I've seen so far, a Gyro's main advantage is in a 2-wheel drive bot that doesnt have its weight suspended over the wheels. Or maybe if the motors arent exactly equal in timing or power.
If you have a drive-and-skid-plate system (like Scoopy Doo), then the gyro helps keep you on-track when one of the wheels loses traction a bit (due to having less weight on it when the bot is suspended on its other 3 contact points) while going in a straight line.
Without the gyro, Scoopy tends to veer sideways a little when a full-power straight-line charge is suddenly commanded, requiring you to put in a little side-stick to keep it going straight - and you have to be quick on the reactions.. with the Gyro, if you slam the stick forward, it does this for you, and Scoopy just charges straight ahead without any side-input from the driver.
On a 4 Wheel bot like yours, I dont think they would be of much help, since the extra wheels help keep it in a straight line.
It *might* also help in a bot that has a low fricion drive (braking effect) .. like scooter motors, since they tend to "over-steer" and keep rolling in the direction you were turning in my experience.. A gyro should sense this over-steer and automatically apply some "opposite lock" stick to help stop the turn as soon as you let go of the stick..
Rob had a brief go with one on ReBoot on the weekend and didnt seem to like it much, but he's pretty good at driving scooter-driven bots now, and is probably used to automatically applying a little opposite-stick to stop turns promptly. I'd like to try driving something like Reboot with and without one and see what the difference is when you dont have a lot of practice without one.
_________________
Great minds discuss ideas. Average minds discuss events. Small minds discuss people
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Fri Dec 10, 2004 9:40 am |
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Spockie-Tech
Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
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A bit more of an update on my experimentation with Gyro's..
Unless I think of some way to cure it, It doesnt look like the simple Gyro I got to test will be of any use in Inspector General (or any invertible bot). Thats ok, I mainly got it for Scoopy, but why is it so ?
If your Bot is invertible by means of the same wheels poking out of the top of the robot as the bottom, then when you are inverted, the forwards/reverse channel needs to be inverted so forward-stick is still forwards, but the steering stays the same, since the wheels turning direction has reversed, but so has the orientation of the robot, so the two cancel out and the steering is the same as right way up.
Unfortunately, the Gyro doesnt know this, and keeps applying the same correction signals, Activating the IBC's flip input wont help, since 1. its reversing the drive, not the steering. and 2. even if it did invert the steering, you would then have backwards steering.
So it looks like for an invertible bot, you need a Gyro that has remote-shutdown (gain control), so that when the flip is active, the gyro shuts down.
There might be another way to do it, but I havent thought of one so far.. anyone with any ideas ?
_________________
Great minds discuss ideas. Average minds discuss events. Small minds discuss people
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Sun Dec 12, 2004 8:03 pm |
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RoboWars Australia Forum Index
-> Technical Chat
The transmitter was on but not in my hand. I had to hit the kill switch. I suspect that sitting in the sun in the back of my truck caused the problem. But I am really disappointed that the gyro appears to negate the IBCs fail-safes. Would a more expensive gyro not have this problem? Any comments would be welcome.
