@nur ‘ω’ (omega) is the angular velocity of the wheel in radians per second, which can be obtained directly from the RPM using 1 rad/s = 9.5492 rpm
Hi,
I am trying to size the motor for a 50kg robotic car. In order to size the motor, I am considering the worst case operating condition in which the car needs to drive along a sloped terrain (like on a banked road) and ride over hurdles of up to 20mm height. Assuming a constant speed of 1 m/s for the car, could you tell me how I should proceed to select and size the motor. I found the following formula to calculate the force required to pull the car over the hurdle :
F = Mg(2rh - h*h) / (r-h) ; r = radius of wheel and h = height of hurdle (assumed as a small step).
Should I consider this force for finding the motor power as P= Fv? or should I use F = Ma + friction to find the motor rating?
Could you please suggest the right method to go about this calculation?
@Aparna This tutorial goes with this tool: https://www.robotshop.com/blog/en/drive-motor-sizing-tool-9698
Regarding the hurdles, you just need to adjust the angle to its maximum. The acceleration is up the incline, which is also worst case.
Hi I am trying to build a Unmanned ground vehicle (UGV) or you can say tha(a Small robot) . I have to make the robot so that it can climb the stairs 2 or 3 steps . Can you suggest me the torque for two motors
There wll be helpful if give me the Robot base which can climb stairs 2 3 steps minimum
Can you please give help me to give the link to buys motor of my specifications and Robot Base of the characteristics so it can climb robot.
@Khaleeq ur rehman Search robotshop.com for products RB-Drr-20, RB-Drr-51, RB-Sdr-64 to get ideas for stair-climbing platforms. You can input the angle between stairs in the tool, but your main issue will be traction between stairs - the robot has to be long enough, which is why tracks are most common. It also needs to be wide enough to turn normally on ground.
Great material rarely found any where
sir i hav four 12v dc geared motor.
i am planning to make a 4wd robot with an expected overall weight of about 6kg.
radius of wheel=5.5cm
stall torque of motor= 26kgcm at 7.5A
no load current=800mA
rpm=60
it is meant to locomote in flat surfaces…maximum inclination-10 degree
is my motor sufficient enough to move the robot.
when i used ur sizing tool it shows torque of nearly 5kgfcm.
@Anu Narayan Excellent. Hope you post the project on the RobotShop Forum. Plug the known values into the tool (except for the torque) and see what torque the tool provides. Hopefully your motors are stronger than what’s needed.
what is this unknown stand for ? a and g… thanks
Sir i have substitute a=0.2 m/s^2, g=9.8m/s^2, theta=20degree I 0.35rads , mass=10kg, radius=0.06m, no of wheel= 2, efficiency=65%, into the torque formula u provide at tutorial. but i got torque equal to 1643.26, compared when i substitute the same value to your calculator, i got 16.726 kgfcm . whats your opinion sir ? Big Thanks for your help.
@Diva Be sure to have your units consistent in all formula. It looks like you combined meters and centimeters somewhere, and there might be a rounding error.
Hi @cbenson,
I calculated a required torque of about 8.8 Nm (1250 oz-in) for my motors, but I struggle with interpreting the result. Does it mean that the rated torque of the geared motor should be greater than 8.8 Nm, or can the rated torque also be e.g. 1.5 Nm (220 oz-in) given that the Nm-RPM-curve shows that the motor will deliver > 8.8 Nm at low speeds? So could for example this motor work out for me (my required RPM is about 80; for low RPM I calculated a torque of ~19 Nm for the motor)? https://www.robotshop.com/en/devantech-24v-49-1-gear-motor-encoder.html
Thanks for the advice!
The 8.8Nm would be the torque needed for the situation you indicated (accelerating up an incline). It depends on you - if that’s a worst case scenario, then you can choose a gear motor which produces that torque at peak power. If that situation is more standard, then that should be the torque at peak efficiency. The motor you indicate can provide around 600oz-in at 80rpm, which seems to be 1/2 of what you need. However, if most of the the time the robot is rolling on a flat surface, it might be fine. It all depends on the values you entered and if that represents a normal or fring case.
@JeanPP Happy to provide some insights. Can you start a new thread / topic here in the forum section and detail what you want to achieve in the project, and what’s been selected or determined?
Is omega (W) found from the max speed under load you want the robot to travel? Or is it the free-spinning rpm of a chosen unloaded motor?
@Zini Welcome to the community. Omega would be the rotational speed under load, after any gear down of the motor(s).
Hi, I’m trying to build an off-road robot from scratch, when comes to motors selection, can I use this calculator to find the required torque for my robot as I saw someone mention this tutorial was for robots on flat surface?
Besides, does the wheelbase and the track width of the robot will also affect the formula, or there were another formulas need to consider?
@Tech49 It’s used for a wheeled robot on an inclined plane. Given that inputting conditions for off road travel are not easy (variety of surfaces and angles), you can use the calculator, but you’ll have to estimate the max angle.
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