View source for Mechanical pulse width modulation

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In an electrical systems when you want to step down from high-voltage-low-current to low-voltage-high-current
(e.g. like you do in your typical smart phone charger) the modern approach is to do pulse width modulation with buck converters.

There seems to be some fundamental impossibility to build a mechanical transmission with a continuously adjustable gear ratio without any friction elements.
(bicycle, drill press)
The trick that pulse with modulation in electrical systems do to archive continuous transmission ratios while keeping losses low is to traverse the region of middle friction and maximal power loss as fast as possible and adjust the output voltage by the duty cycle between zero and movement quenching friction. The pulsating output gets smoothed by energy storage elements like capacitors and inductances.

The same principle could be done by a mechanical analogon in the nanoscale where the energy storage elements are springs and flywheels. One further needs friction clamps and nonlinearizing elements to gain the analog functionality of a transistor. In the macroscale it probably wouldn't work well due to vibrations detrimental to the parts lifetime.

== Related ==

=== energy domains ===

* minimal set of [diamondoid molecular element|DMMEs] analogous to basic universal set of electric parts
* wikipedia: [http://en.wikipedia.org/wiki/Mechanical-electrical_analogies mechanical electrical analogies]
* wikipedia: [http://en.wikipedia.org/wiki/Impedance_analogy impedance analogy]

=== mechanical gyrator === 

* wikipedia: [http://en.wikipedia.org/wiki/Gyrator gyrator]

Allowing to emulate a flywheel (which may be to big) or inertial mass with a spring.
This is analog to the emulation of inductance by capacitance which is used in miniaturisation today (active inductor).

* a gyrator is lossless but charactericed throug a resistance value
* standalone a gyrator cannot by made by passive elements - negative elements would be needed
* negative elements can be either absorbed by the context circuit surrounding it if its suitable or emulated by <br> active negative impedance converters (=transconductor??). wikipedia: [http://en.wikipedia.org/wiki/Negative_impedance_converter negative impedance converter], [http://en.wikipedia.org/wiki/Transconductance transconductance], [http://en.wikipedia.org/wiki/Miller_theorem miller theorem]