I tried to build an arduino mobil project (cleaner robot) and i need advises. My robot is quite heavy (2.1 kg) and i think that motors i used aren't sufficiently powerful. I have damaged one of them, certainely because the robot is too heavy...
So far, i used 4 * 6V DC motors (see following link) :
I would like to change for more powerfull motors (2 * 12 V) :
That specs on that gear motor make little sense. Its alleged to do 320 rpm
(about 30 rad/s), and a stall torque of 0.2Nm (converting dumb imperial units to usable SI),
which implies a peak mechanical power of 30 x 0.2 = 6W.
That's not going to happen for long, it will heat up and fry at stall current, but I'd believe about third of
that, perhaps 60mNm continuous at 30 rad/s (well, perhaps 20 rad/s as its under load). So perhaps 1.2W
mechanical is realistic.
Thus 4 motors give about 5W mechanical.
2.2kg on a 10% incline needs about 2W per m/s ignoring friction. But friction in small geartrains and
wheels cannot be ignored - often it dominates. Lets say 5W per m/s is more plausible.
That's still within the power we have to get to 1m/s, so I suspect the gearing/wheel size isn't suitable?
Details of the drivetrain are needed to progress further with analysis. Also what terrain is it designed to
work on? Rough terrain increases torque and thus power requirements. What top speed?
[ Note the procedure is to calculate the torque speed and power requirements first, then choose the motors, not "guess, get the wrong motors, guess again" - all this stuff is easy calculation like choosing resistor values, you just need to know basic mechanics ]
for driving your robot. They even have ones with a motor driver attached, making them easy to control with an Arduino. These motor have HUGE torque. I've personally used them to control robots upwards of 4kgs (I obviously used a motor with lower RPM).
for driving your robot. They even have ones with a motor driver attached, making them easy to control with an Arduino. These motor have HUGE torque. I've personally used them to control robots upwards of 4kgs (I obviously used a motor with lower RPM).
Hi, thanks for your answer.
Ok it seems good ! But i saw that it needs 7 amperes during startup...
In this case, which power supplies can i used ?
Thanks
From the website :
A high-torque DC motor requires high current during startup and during high load or irregular load
conditions. The general rule of thumb to make sure your power supply is adequate for a DC motor is to
make sure it can supply the maximum current required by the motor during stall condition. For RMCS210X
this is 7 Amperes. This doesn’t necessarily have to be its continuous current capability but it should
be able to provide a pulse of 7 amperes during startup of the motor
Till someone's done the calculation who knows? So lets do the calculation:
Allegedly stall torque of motor is 0.2Nm as explained previously, but that's stall torque, so I went
with 0.06Nm instead. With 0.02m radius wheel thats 0.06 / 0.02 = 3 N force, and at 320rpm thats about
0.6m/s top speed (unloaded).
However that's all irrelevant for several reasons:
The motor claims to be 100:1 ratio, with an output speed of 320rpm. That's sounds dubious, I'd expect more
like 100 rpm for that ratio. The details are probably wrong - you'll need to measure the actual performance
of the motor to make sure.
And you have tank-tracks - the highest friction configuration its possible to have... You need to measure
the static friction of your drivetrain to see what the baseline is, that's probably the issue.
Once you know the torque needed to overcome static and dynamic friction in the tracked drivetrain, then
you can progress.
