Comments on: Miniature balancing robot

By: Jonathan

Jonathan — Tue, 12 Aug 2008 20:55:04 +0000

I must agree, the higher the robot the better. So batteries must be at the highest point. Try it with a short and a long broom stick (i mean te tool ur mom uses to clean the house) on ur hand. the longest stick will be the easiest to maintain in balance. The more weight at a higher point, the higher the inertia of the broom (robot) will be. So the slower it will fall. Which makes it more easy to balance the robot.

By: dan

dan — Mon, 11 Aug 2008 18:14:54 +0000

Raising the center of gravity will create a longer pendulum arm and a more easily controlled system because of the longer time constant.

Try it yourself:
Try balancing a 12" ruler on your hand, then try balancing a yardstick. If you're feeling really cocky, then try balancing a toothpick. You'll get the idea ;)

By: Ken

Ken — Mon, 11 Aug 2008 17:50:33 +0000

The best thing to do would be to find your local engineering college and enroll in their class on signal processing and system control. Then enroll in their graduate-level class on feedback control systems because I’d be surprised if anyone got this working reliably without some advanced control theory underlying it all.

By: Wwhat

Wwhat — Mon, 11 Aug 2008 17:41:02 +0000

I don’t get those ‘lower the center of gravity’ remarks, the whole thing is about balancing, if you want stability you could just add 2 more wheels, or no wheels and a flat surface, the point it balancing and the imbalance of the basic setup is part of it.

By: sweavo

sweavo — Mon, 11 Aug 2008 13:26:25 +0000

yes. Lowering the CoG is not necessarily a good idea in a dynamic equilibrium system. Ideal CoG depends on the speed and acceleration at the wheels and the sensitivity of the tilt sensor. You need to tune it accordingly. Higher needs better sensing but is more forgiving of coarse motors. Lower will allow slower motors but they need to react a lot quicker.

By: salva

salva — Mon, 11 Aug 2008 11:02:47 +0000

if u lower the center of gravity it will perform way better. other than that good job. i would like to see the same thing but with a lower center of gravity.

By: Derek Anderson

Derek Anderson — Mon, 11 Aug 2008 08:10:28 +0000

It looks like the creator is trying to avoid any kind of microcontroller. Still, it would be relatively trivial to add an L293DD, 555 timer, and a potentiometer for variable pwm motor control. The tricky part would be getting past the motor’s deadband (motors have a +-5% or similar pwm where they don’t do anything). Still, it would be better than a bang-bang controller.

By: matt

matt — Mon, 11 Aug 2008 06:44:38 +0000

I thought the high center of gravity helped to maintain stability. This is because more weight doesn’t change direction as quickly as less weight, allowing for more time to get the wheels up under it but the simple tilt sensor doesn’t allow for it to catch up properly.

By: sumguy

sumguy — Mon, 11 Aug 2008 05:26:43 +0000

I wouldn't think it'd be very hard to replace the switch with a potentiometer to the feedback proportional rather than bang/bang. Then it'd even be possible to add another potentiometer ahead of that one to control the speed and yet another after it for steering.

something like
speed rheostat
|
vdd --tilt sense pot -- vcc
|
steering pot___
| \
vdd--motor 1 -vcc |
vdd-- motor 2 -- vcc

By: max

max — Mon, 11 Aug 2008 05:18:40 +0000

SUIT SONG 43 FUCK YEAH

By: andrew

andrew — Mon, 11 Aug 2008 04:36:03 +0000

I am surprised it works as well as it does, given that it’s essentially a bang-bang controller with a very shitty motor! Wow, I never would have thought it’d work.

By: octel

octel — Mon, 11 Aug 2008 03:57:57 +0000

wow, that poor thing looks like it’s having a seizure :(