4 ms·

The invetor's slides say that the only time the analogy breaks down is with ungrounded capacitors, though its unclear to me what exactly that means (I don't rea

The invetor's slides say that the only time the analogy breaks down is with ungrounded capacitors, though its unclear to me what exactly that means (I don't really feel like thinking too hard about it). See slide 17 http://www-control.eng.cam.ac.uk/~mcs/lecture_j.pdf http://www-control.eng.cam.ac.uk/~mcs/lecture_j.pdf There are actually a few different analogies you can make between electrical/mechanical devices. See the top table "Key Concept: Analogous Quantities". This is part of the reason why I don't feel like thinking too hard about what the inventor means when he says the analogy "breaks down" with ungrounded capacitors. http://www.swarthmore.edu/NatSci/echeeve1/Ref/LPSA/Analogs/ElectricalMechanicalAnalogs.html http://www.swarthmore.edu/NatSci/echeeve1/Ref/LPSA/Analogs/E... The inventor has created a "new analogy" where the inerter is a capacitor. I read your post as saying the old analogies don't work. Is that correct?

colanderman 16y ago
The point you're making is orthogonal to the one I was making: the force ~ voltage analogy breaks down at KCL/KVL (as well as ungrounded inductors), while the force ~ current analogy breaks down only for ungrounded capacitors. "Ungrounded capacitors" refers to capacitors which do not have at least one terminal connected to the reference voltage (ground). These break the force ~ current analogy because with that analogy, capacitors, which are two-terminal devices, are analogous to flywheels, which are one-terminal devices. The velocity (voltage) of the second terminal is effectively zero. Your reading of my post is close to correct. The force ~ voltage analogy is incorrect however you look at it because KCL and KVL don't hold. The "old" force ~ current analogy does hold except for the case of ungrounded capacitors, which the replacement of flywheels with inerters remedies.

colanderman 16y ago

The point you're making is orthogonal to the one I was making: the force ~ voltage analogy breaks down at KCL/KVL (as well as ungrounded inductors), while the force ~ current analogy breaks down only for ungrounded capacitors. "Ungrounded capacitors" refers to capacitors which do not have at least one terminal connected to the reference voltage (ground). These break the force ~ current analogy because with that analogy, capacitors, which are two-terminal devices, are analogous to flywheels, which are one-terminal devices. The velocity (voltage) of the second terminal is effectively zero. Your reading of my post is close to correct. The force ~ voltage analogy is incorrect however you look at it because KCL and KVL don't hold. The "old" force ~ current analogy does hold except for the case of ungrounded capacitors, which the replacement of flywheels with inerters remedies.