Arm & Science: Implement motor ramping

[jetkov]

In order to avoid high inrush current when motors are spun up PWM duty cycle ramping needs to be implemented.

Ramping should happen when a motor speed is requested that is significantly different than the current motor speed, if the current speed is near zero. The values of these ranges and the rate of the ramp need to be characterized.

A few guesses to this:

• Ramping only needs to occur if the current duty cycle is less than 10-15% or if the direction of rotation changes. The motor will just start spinning in this range.
• Ramp rate should be slow at first, and can then be quicker proportional to speed.