Difference between revisions of "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 | 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 | + | (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. | There seems to be some fundamental impossibility to build a mechanical transmission with a continuously adjustable gear ratio without any friction elements. | ||
Revision as of 18:49, 21 January 2015
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 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. In the macroscale it probably wouldn't work well due to vibrations detrimental to the parts lifetime.
