Motor

To rotate the disc, it must be connected to a driving source, such as a motor. They are commonly driven by pulse-width modulation (PWM) generators (though modeled as if driven by linear-gain amplifiers) and provide position information via attached digital encoders. The Maxon Precision Motors Re-35 DC brushed motor meets all of the design requirements when geared to the disc at a load-to-motor ratio of 1:2, and has a form factor on the order of the disc radius.

Key specs

QuantityValueUnits
nominal speed49.5rps
-311rad/s
max (continuous) torque105mNm
max (stall) torque493mNm
max voltage48V
armature resistance11.50Ohm
armature inductance3.16mH
damping coefficient1.22mNm / (rad/s)
torque constant119.00mNm / A
back-EMF constant0.12V / (rad/s)
armature inertia65.5g / cm^2

Key documentation

Notes

We have modeled the motor as powered by a linear gain amplifier, which is uncommon due to power efficiency and cost concerns. Instead, we use a more conventional pulse-width modulation (PWM) generator. We treat the PWM output signal as if it were the equivalent output from a linear gain amplifier, since PWM generators that produce a high-frequency output have approximately the same effect, and mathematical representations of PWM signals are cumbersome.