Wheel Consideration

by Robert Licari and Anthony Vo

We can take the wheels into consideration for the purpose of finding our desired velocity based upon our calculations.

If our Wheel Diameter (D) is 45 mm, then we can conclude the Radius (R) is as follows:
R= D/2 = 0.0225 m

Now we require a velocity equation that relates velocity to our wheel. For this task, we can employ a basic velocity equation with relation to angular velocity:

V = (R*w)/sin(theta)

Where “w” is angular velocity and our conversion from RPM to rad/s is as follows:

1 RPM = (2*pi )/60 rad/s

The spec that we have four our free-run RPM is 85 RPM @ 6V, which we shall use to find our normal velocity. In tandem with this, our application of the wheel requires that the angle “theta” be 90 degrees, or perpendicular, to our rotational axis, which effectively gives us:

V = 0.0225m * [ 85 RPM * (2*pi/60 rad/s) ]
 =~ 0.2003 m/s

 This equation can be applied to varying Diameter, but, for our purposes, we will use the 45 mm wheel.

 Level 1 Requirement:
— Speed according to the wheel diameter —

 The velocity requirement is defined base on matching the velocity of the standard ROSCO.  To calculate the velocity of the ROSCO, the circumference of the wheels and RPM of the motors is taken into account.  Given the wheel diameter, the circumference of the wheel can be calculated.  After scaling the measurements to meters and seconds, the rover is expected to have a velocity of at least 0.200277 m/s or ~0.2003 m/s.