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.


energy domains

mechanical gyrator

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

  • a gyrator is lossless but characterized through a resistance value
  • a standalone gyrator cannot be 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
    active negative impedance converters (=transconductor??). wikipedia: negative impedance converter, transconductance, miller theorem