How It Works: Linear Resonant Actuators

https://blog.somaticlabs.io/how-it-works-linear-resonant-actuators/

by jakerockland • 10 years ago

47 8 10 years ago

blog.somaticlabs.io

achr2• 10 years ago

The copy repeats itself 20 times... Painful to read.

Hey arch2! I'm sorry you found the post hard to read, thank you though for the feedback. Were you referring to the blog post specifically being repetitive or was there something about our website copy that you found repetitive? We are always trying to improve the content we are putting out.

LeifCarrotson• 10 years ago

I also found the blog post a bit repetitive - not the content itself, which was great, but the sentence structure was repetitive.

It heavily uses sentences of the form "Subordinate clause, independent clause", starting many sentences with one of the words although, since, unlike, or rather. This makes it hard to read after a while.

paulkaplan• 10 years ago

To me it is a combination of repetition and a confusing flow. It feels like it the author kind of discovered the interesting bits as she/he went. But I don't want to be a Criticizing Craig, so here is a (hopefully helpful) breakdown:

“When the voice coil is driven at the resonant frequency of the spring, the entire actuator vibrates with a perceptible force. Although the frequency and amplitude of a linear resonant actuator may be adjusted by changing the AC input, the actuator must be driven at its resonant frequency to generate a meaningful amount of force for a large current.”

Ok, got the basic principle and the key constraint (resonance) in the first paragraph.

“The voice coil remains stationary inside of the device while it produces a vibration and presses against a moving mass. By driving the magnetic mass up and down against the spring, the LRA as a whole will be displaced and produce a vibration.”

The first sentence feels like a repetition of the basic principle, but I get that (together with the second sentence) there is a subtle point being made: the whole assembly vibrates. I'd cut the first sentence or make the comparison more clear: “Although the voice coil is stationary within the LRA, … the LRA as a whole moves.”

The speaker comparison is good for illustrating the resonance constraint, but the conclusion simply repeats rather than expound on the principle. Leading the reader can make the implicit connection more obvious and avoid repetition: “While speakers can be driven at arbitrary frequencies, the physical spring within an LRA imposes a …”

“Rather than directly transferring the force produced by the voice coil to the skin, the device optimizes for power consumption by taking advantage of the resonant frequency of the spring. If the voice coil pushes the magnetic mass against the spring at the spring’s resonant frequency, the device can produce a vibration of higher amplitude more efficiently.”

This paragraph reintroduces resonance, but as an efficiency improvement. It feels repetitive, but there is an important point here that is left as a connection for the reader to draw: Offset rotating masses don't use resonance and draw much more power. I would actually use this in the leader. Instead of introducing resonance as a just a component of the system, make it the key. Instead of “that is DC and this is AC” (the impression I got from the first paragraph, lead with “that uses brute force and this uses a cool property of spring systems: resonance.” The latter is much more interesting, and can help reduce the repetition.

“Although the frequency can be changed, the LRA will typically be operated within a narrow frequency range to optimize its power consumption—if the device is driven at the resonant frequency of the spring, it will consume less power to produce a vibration of equal magnitude”

Repeating the basic principle again. Get rid of this and get right to the next sentence about how you can use a fixed frequency/varying frequency.

Hope this helps!

jessaustin• 10 years ago

The diagram and first paragraph explain the concept as clearly as one could want, without repetition.

bediger4000• 10 years ago

there are two nontrivial challenges to producing a viable implementation: 1) intellectual property

Hey, wait just a moment! Copyright and patents are supposed To promote the Progress of Science and Useful Arts, not hinder them by posing challenges.

kwhitefoot• 10 years ago

Also annoying to have a quote from a patent but not be told when it was granted or when it will expire. Anyway most of these patents are obvious to one skilled in the art. They only survive because no one can afford to fight them and the Patent Office is not very interested in properly examining patents.

Animats• 10 years ago

That's clever. All that complexity leads to lower power consumption, because the device is dynamically driven at its resonant frequency. You could drive it at a fixed frequency, calibrated once at the factory, and avoid patent problems.

How It Works: Linear Resonant Actuators

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