Find the Perfect DC Motor for Your Robot: Tips and Tricks for Calculating Torque

[elimenohpee]

Hello

I need a little help here. I need to pick a DC motor to be used on a robot. I'm trying to calculate a minimum torque the motor should be able to produce, but I'm a little confused.

torque = Force * distance = Mass * acceleration * distance

(Ignoring moment of inertia created by the motor's load)

Mass will be the total mass of the robot, distance the radius of the wheels to be chosen. But how do I quantify acceleration?? I can see specifying a maximum speed, but I'm not sure how to account for this.

Or perhaps there is an easier way to calculate the torques I should be accounting for.

Any ideas?

 

[anorlunda]

Simplify it first by ignoring the wheels and rotary motion.

If you have an object of mass m, and you want to accelerate it at rate a, then F=ma tells you the force needed.

But more likely, the motor needs to be sized by the power needed to move the robot at constant speed. That is determined by friction for a flat surface, or to go up an incline, it depends on the mass and angle of incline. I think you can calculate those.

So, step 1, Calculate the power required for the robot physics. Assume 50% efficiency so that the motor size is twice that.

Step 2, make sure that the motor has sufficient torque at zero speed to start motion and accelerate. That depends on motor type. BLDC motors and motor controllers are often used in robotics. Search for a BLDC motor of the required power, then check the data sheet to see the starting torque.