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Valen
Experienced Roboteer
Joined: 07 Jul 2004
Posts: 4436
Location: Sydney
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I'm thinking perhaps some of my issue is I haven't re-timed the motors, and as I speed up I run out of top speed on one side before the other making the bot spin out. I don't really want to re-time them as it looks like it makes the whole back of the motor weaker.
It also lacks the speed of cobra which is :-<
I'm thinking of upping the voltage, to get more top speed, but I need some form of current limit. I was also thinking of adding some system so that the sticks control wheel speed not power.
2 birds one stone, glue a teensy magnet to the back of the motor shaft, put a rotary hall effect sensor on there and we can sense motor RPM, rather than directly measuring current (another thing that can fail, and hard to do at hundreds of amps of PWM) just infer the current from battery voltage and motor RPM, then limit the signal going into the TZ85's to stay under some magic number that keeps the smoke in the motors.
Not as good as actual current sensing but easier to pull off I think. _________________ Mechanical engineers build weapons, civil engineers build targets
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Fri Oct 16, 2015 7:45 am |
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Valen
Experienced Roboteer
Joined: 07 Jul 2004
Posts: 4436
Location: Sydney
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I thought about using a gyro, and I'll leave room to add one, but it feels like if the wheels are both going the same *distance* (even better than RPM, as error won't accumulate) then most of the error should be taken out and you won't need to worry about the errors a gyro would introduce.
Though I guess a gyro would perhaps help counter spinout, hmm I'll have to think about that some more.
@nick
I was hoping to use something like
http://ams.com/eng/Products/Position-Sensors
for the sensing, but even with just a regular hall sensor you get 2 pulses per motor RPM which after the gear reduction should be pretty good, (also I've learnt from the mill backlash between motor and sensor is the debil for PID loops lol)
I'm going to look at making NC2 as well, victory through superior numbers.
NC2 would be brushless drive, which kinda solves the whole "sensing motor position" thing for you to some extent. And of course moar powah.
I was really hoping glen could have a drive of NC before the arena was packed up but we ran out of time. Anybody have an idea how to test drive a pushy bot without eating the wheels on concrete? _________________ Mechanical engineers build weapons, civil engineers build targets
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Fri Oct 16, 2015 4:37 pm |
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