Nanomechanical computation
Contents
Why nanomechanical logic
- It can be built smaller than nanoelectronics (bound atoms practically do not tunnel away like electrons)
- It is easier to do exploratory engineering about nanomechanics than nanoelectronics. (See: non mechanical technology path).
Basic elements
Differentials
One of the most important things in any computer are wires and forks of them.
The mechanical elements that correspond to simple electrical connections (solder points) are mechanical differentials (that includes planetary gear assemblies and linear versions). The angular speed (corresponding to electrical current) distributes proportional to the loads ([current divider). (Simple splitups of geartrains act like Voltage dividers)
[Todo: add more electrical mechanical analogies]
Testing element (gate)
As in electronic computation a single universal type of logical gate is sufficient to create any 'programmable logic arrays'. (PLA) can be made. See: disjunctive or conjunctive normal form (DNF / CNF)
In a clocked gate the input moves a blocking part in the way of the output (or not). Both are spring loaded. (Instant chain logic gates work differently)
Sequencing mechanism
The analog power-source must somehow be converted in a digital sequence. Too harsh jumps in acceleration may increase power-dissipation.
Quantum dispersion through anharmonic potential (see: coherent states) is probably not to expect even at low temperatures [To investigate!]. A connected nanomechanical system will have a quite high mass in daltons.
Reversible mechanical logic
Reversible mechanics means: whenever an elastic element (a spring) is de-tensioned it must feed back its stored energy into the energy source.
Testing a clocked reversible mechanical gate is done via pulling pushing turning twisting or whatever against a potential steric hindrance obstacle that was put in place (or not) by the precedent gate . As long as the outputs are in use the inputs cannot be removed. If they would be removed all consecutive outputs would snap back - BAD. Thus the testing clock signal must rise like a bar graph display.
This is best done till an appropriate computation result is reached that has way viewer bits than the intermediate computation steps that lead there. This result can then be copied into a storage register and the output deleted. Meaning a view testing springs snap back irreversible and release their energy into the background heat bath.
Finally one let the bar graph clock signal stepwisely recede letting go of the testing gates in reverse order and pushing back the energy into the energy source (e.g. a flywheel). One could say one un-computes the intermediate data garbage.
This hole process is called a retractile cascade
The energy swings back and forth between the energy storage and the many logic gates. Tree like distributed though mechanical differenials.
If the negated bits are always computated in parallel the the energy stored in the springs in the gates when in evaluated state is always the same. Swing overshoot can be made minimal. [Todo: explain in more detail]
In a programmable logic array (PLA) first the gates in the AND-plane and then the gates in the OR-plane must be evaluated in sequence. The results may be fed back into other yet unevaluated parts of the PLA for a second and further rounds.
Drive for retractile cascade
Assuming rotative logic a possible method to generate the "bar graph display clock signal" may be like follows:
A binary tree of differentials to a locked chain of gears (blocked gears or geneva drives may be usable). All gears are spring loaded and only the first one is unlocked. the torque propagates through the differential tree and turns the first gear till the endstop. This in turn unlocks the second gear. Then comes the third and so on and so forth.
Concrete implementations
- reciprocative rod logic
- rotative logic (lower maximum density of logic devices)
- pure flexture/buckling logic
- ...
Benefits of low friction
Mechanical logical gates can either be elements that form instantaneous chains or elements that must be by a testing clock signal. Due to the exceptionally low friction of nanomechanical bearings it should be no problem to make instantaneous chains quite long. Also Differential gear trees with log(n) depth shouldn't pose a problem out of this reason.
Usage as analogous devices
- differentials act as analog adders
- gear ratios act as fixed ratio multiplication
- there's a linkage mechanism for continuous multiplication
