robot motor question.

[parisk]

Hi everyone, I am a mechanical engineer student and me and my team have been assigned to make a UGV that is able to deliver at least 5 kg of water at a 60 m distance and return.
My problem comes in the motor selection. We decided to run with 4 motors (one on each wheel).
I used the on-line calculator provided but the results I get are a bit strange. My specs are:
Mass   (max value) 20 kg   
Desired Velocity      0.5 m/s (must not be over: 8 km/h)
Desired Acceleration      0.1 m/s
Expected Efficiency      70%
Incline Angle      2 (max value) degrees
Wheel Diameter      0.176 meters
# of Powered Wheels   4   wheels

I would be really great full if someone could provide some recommendation on a motor. We currently picked: http://www.ebay.co.uk/itm/12V-DC-100RPM-High-Torque-Gear-Box-Electric-Motor-/330758036336?pt=UK_BOI_Industrial_Automation_Control_ET&hash=item4d02b71b70
this one but according to the calculator its not strong enough. Thank you all in advanced.

[mklrobo]

Hello! I can offer my opinion.
I would look at the terrain that the robot has to go. (load conditions)
Hydraulic motors can produce power to the wheel, but too heavy.(smaller, maybe?)
This sound similar to a chemical engineering question, with the power/ load demand.
You could take a motor, then run it in place on a jig & fixture, to determine the total
power demand per m. Or, run the whole model on a jig and fixture to get an idea
of the power consumption.(with load). You could use the Jig & fixture to give a laboratory
guesstimation of what would be needed, as a model. You could then, "tweek" out any
mechanical designs that you have, or mods to the UGV. If you are at a university, the neighboring
students at the electrical department may offer more insight, as they are on sight. Good luck! 

[bdeuell]

My gut says your motor is too small for that size of a robot.

I punched your numbers into the calculator and got the same result (the motor is too small)

Your assumptions for the calculation reasonable for a robot on level ground but I would use a larger incline angle if you plan to run outside.

[Ibaeni]

I would look into motors from an rc store such as hobbyking. There is so many resources regarding motors that are geared towards rc cars. Eventhough you won't be using them for rc, you can learn a lot from them. http://www.hobbyking.com/hobbyking/store/__364__59__Electric_Motors-All_Car_Motors.html

There are definitely strong enough motors from the link above. You'll also be able to find all the electronics necessary to run them. I had to go through the same process while working on a quadcopter. Although we aren't building an rc quadcopter, learning from the rc community was very helpful. Heres a link to our project if you're interested: https://hyperionrobotics.wordpress.com/

[mklrobo]

  Hello!
In regards to your motor calculations, check out
Bdeuell's post on this forum, eletric bicycle, which will provide
lots of calculations to help you with. Keep me posted!.....