MEMS Gyroscopes, Smartphones, and Ultrasound

This morning I was reading an article on Ars Technica (great tech website if you don't already read it) about the use of "sonic guns" to disrupt the operation of electronics and gadgets like drones. Here's a simple demonstration video of this happening.

As you can see the toy robot, which balances due to the gryoscopes in it, is quickly confused by the incident sound and ends up moving, then falling over. Why does this happen?

MEMS gyroscopes are Micro-Electrical-Mechanical Systems, essentially a very small structure that's often made by the same processes used to build computer chips, that has combined electrical and mechanical behaviors that are useful to us. In the case of a MEMS gyro, it leads to motion that creates an electrical signal which can be processed to determine rotation. These structures are small enough to be packaged into something smaller than your fingernail, and so can be fitted into compact spaces and consumer goods. Here's a video of a very simple MEMS gyro oscillating.

An image below from UC Davis MEMSLab shows how one small device can detect rotation in all three axes.

You can see that each sensing mode here has at least one "resonant frequency" at which the device naturally oscillates, which means it is very very sensitive to those frequencies. Like finding the right pitch for a glass, you can actually break them by causing them to vibrate at that frequency. Some work here, here, and here shows in more academic detail how the MEMS gyros can be rendered ineffective by ultrasound above around 100 dB. Sound is, after all, just a vibration at a particular frequency - match that sound to the resonant frequency of the gyro and it will play havoc with it.

Here's a drone showing the effect of ultrasound on its behaviour - notice that the transducers used to generate the ultrasound look like Murata devices, very similar in appearance to what uBeam look to be using in their transmitters. (I appreciate the safety precautions this researcher took!)

What this all seems to be pointing to is that high powered ultrasound in the environment can disrupt the activities of more and more of our devices such as drones - what happens if they fly through a high power ultrasound beam? Do they veer off and hit someone? And the smartphones we all use today? Those phones have multiple MEMS sensors in them, and the gyro is what allows you to play games just by tilting your phone. What happens when you direct ultrasound at levels far greater than 100 dB towards a smartphone? The manufacturers know, they spend a lot of time making sure that nothing in the phone vibrates at frequencies that disrupt their operation, but I'm not sure I've seen a study that's been made public.

Those may seem like simple examples, but there are safety considerations. What happens if a safety related system, such as positioning in a vehicle, is disrupted by high power ultrasound? Who is responsible for that? Cars and larger objects can usually shield the gyro to insulate the sound from it, but what about size and weight sensitive devices like smartphones?

If the videos above give an indication, then truly ubiquitous high power ultrasound in the environment is going to be disruptive in more ways than one. Just as well no-one is likely to try to put such loud ultrasound devices out there en-masse.

Dunkirk

Movie review: Dunkirk

Basically - go see it. Great movie. No - fantastic movie. I've found Chris Nolan to be hit or miss - always beautifully filmed, but there are often plot holes you can drive a bus through that most people seem to miss because it all looks so good, and so much is thrown at you that you're overloaded. Inception and The Prestige are the two worst examples of this (so bad I've watched them twice..) while Interstellar has ridiculously awful science it pretends to adhere to, until halfway through it shifts to a "love conquers all" mode and rapidly descends to a giant cauldron of liquid poo in which it revels. Memento gets it right, sticking with a single theme and follows it through, while the first two Batman films are just brilliant (followed by an entertaining but not-as-good third).

Nolan loves to play with time in his films - Inception with its layers and ticking clock, Interstellar with the time dilation due (and ticking clock), Memento and the forward/backward storyline. He does the same in Dunkirk, with three storylines of a week, a day, and an hour in the lives of several Dunkirk participants, all intersecting in parts as they grow closer and closer together - and all through it, a ticking clock (literally) as the soldiers desperately try to get home.

I don't often get drawn in to films, but I found myself tense throughout, and Nolan manages to bring in a lot of tension as you sit on edge waiting for the next thing to go wrong. It's an exhausting film. More though, it gets over the utter powerlessness of almost all the participants, that they're simply statistics and at some point people are going to die, no matter their skill or preparation. This isn't an Arnie action film where the hero saves the day, this is about the horrors of war and how small and insignificant each person is, but also the intense bravery of many of these men in ways that no-one ever would know.

There's a Marie-Claire contributor who has been talking about how it's just a film glorifying war for men. Yeah, this glorifies war like Trainspotting glorifies taking drugs. It's hideous from nearly 80 years away.

As we exited the film, my wife recounted some stories of her grandfather, who was at Dunkirk. She had interviewed him as part of a school project. He was a remarkable man, I met him when he was in his early 90's, and I would have guessed he was in his 60's. Born in 1912, grew up in a children's home, joined the army when 18, served until the end of WWII, started a welding business then sold it and retired at 65 - got bored and started another one at 67 and ran it until he was 89. He didn't talk about what he did in the war, he even gave all his medals to a local museum to the horror of his family, as he thought no-one would care.

As part of this interview, he described running through the streets towards the beaches at Dunkirk, with men feet away from him being shot dead, and waiting for the evacuation. He was told he was brave but he said he never felt brave, all he did was try to survive. And that, in the end, was much of the point of the film, that these men survived and then later went back to fight again, that these seemingly small acts of what they couldn't see as bravery, mattered.

It also made me think of my wife's great uncle. He was on board the Royal Oak, a British battleship sunk by the Germans at the onset of WWII. Of the ~1200 crew, 833 were killed when it was torpedoed in Scapa Flow at the naval base in Orkney - her uncle, Billy, was one of the men killed. He was 16. Like the Arizona at Pearl Harbor, this site is now a war grave, and we were allowed to scatter the ashes of Billy's sister there. She never got over the loss of her brother. Another young man who tried to do what he could and serve, yet died almost the moment it began. The film reminded me that great feats aren't required to be a hero, that simply volunteering for a role that puts you in harms way for a greater good does that.

All that, so well filmed, and perfectly acted by every one of them, especially Tom Hardy. Never overplayed, just done right.

I'm not sure I've seen a film that conveys the horror and randomness of war, along with the personal sacrifice and bravery of the men who served.

Go see it.

Mount St. Helens National Monument and the US Forest Service

I just spent yesterday at the Mount St Helens National Monument, and wanted to recommend it to anyone who passes through southern Washington or northern Oregon. Not to be missed, the US Forest Service do a great job of keeping it maintained, accessible, and making it educational.

Their budget is around $5.5 billion, which sounds a lot but there are a few things to consider - the maintain nearly 200,000,000 acres of public land (mowing my 0.1 acres of lawn is pain enough...) and nearly 400,000,000 acres of private land, manage forestry and mineral extraction, and then the most visible part to the public - keeping lands and national monuments open and available for education and recreation. That results in an estimated ~$35 billion of economic activity such as tourism. Seems a pretty good return on investment for the country.

Amazingly, half of that budget is spent fighting fires, so when you hear the calls for eliminating various agencies and reducing their budgets, remember that a lot of these agencies are a victim of their own success. Perhaps they should let a few towns burn down now and then to remind people that forest fires can be bad...

I'm only half joking there, because 20 years ago the cost of fire fighting took up 1/6th of their budget and it's been rapidly increasing since. They estimate it's going to double again in the next 30 years.

Changing climatic conditions across regions of the United States are driving increased temperatures— particularly in regions where fire has not been historically prominent. This change is causing variations and unpredictability in precipitation and is amplifying the effects and costs of wildfire. Related impacts are likely to continue to emerge in several key areas: limited water availability for fire suppression, accumulation at unprecedented levels of vegetative fuels that enable and sustain fires, changes in vegetation community composition that make them more fire prone, and an extension of the fire season to as many as 300 days in many parts of the country. These factors result in fires that increasingly exhibit extreme behavior and are more costly to manage. 

The six worst fire seasons since 1960 have all occurred since 2000. Moreover, since 2000, many western states have experienced the largest wildfires in their state’s history. 

In addition, more and more development is taking place near forests—an area referred to as the WildlandUrban Interface (WUI). Increasing densities of people and infrastructure in the WUI makes management more complex and requires more complex and requires more firefighting assets to ensure an appropriate, safe, and effective response that protects lives and property.

We're living with an administration that's trying to remove national monuments, sell off public lands to private only use, and is slashing budgets for departments like this - the FY2018 budget looks to be reduced by nearly $1 billion. The service keeps up with the firefighting - it has no choice - but this is at the cost of deferred maintenance and reducing other activities which support the land and recreation. At some point, this is going to the the US Forest Firefighting Service, and that's all. It may seem a minor thing when we're dealing with other major, immediate, crises, but the US Forest Service provides a critical function for our country, and we need to support it.

On a happier note, the trip into the Mt St Helens Monument was fun. Stop at the visitors center about 5 miles in from I-5 for the educational side, then drive up about 50 more miles to the observatory for some fantastic views of the volcano.

There are a ton of trails and other parts of the monument to access, we barely scratched the surface. Try and go if you're ever in this part of the world, and support the US Forest Service whenever you can, we all rely on them for way more than most realize.

Picking on the Little Guy

If you don't like politics, stop reading. For those who have to live in this world...

Anytime a politician or those in power target the poor, the powerless, minorities, and those who have no means of defending themselves, then take a close look because they are most likely either looking for a scapegoat or trying to deflect and distract from something else. 

No-one should be singled out based on gender, sexual orientation, religious choice, race, socio-economic class or anything similar. Any country that is diverse in its population and works to integrate, not separate, will be stronger because of it. Moreover, a country that looks after the weakest of its citizens is a society that will be just to everyone.

Authoritarian regimes get their start with scapegoats from small groups outside the mainstream. We should have zero tolerance for any such discrimination from our government. The recently tweeted 'trans ban' is exactly such an action. If someone meets the physical and mental requirements for the military, or any other role, they should not be discriminated against.

As an example you have likely already seen, I give you Kristen Beck, a transgender Navy SEAL. Kristen seems like exactly the type of warfighter we want, and wouldn't let things like 'bone spurs' get in the way of serving. Her quote sums up the entire situation perfectly:

It's a leadership issue, not a transgender issue.

America is better than this, and such divisiveness can't be allowed to stand. What is happening right now is not normal, and we can't allow it to become that way. To those who don't care about such people, let me make this pretty clear - Donald Trump doesn't care about you, or your tax cuts, or your coal mining job, or whatever you thing you can get from dealing with the devil, and one day you will be the target, no matter how white or male or Christian you are. Defend the little guy, and you're defending yourself.

Oh, and it's just the decent thing to do.

uBeam Withdraw Claims of Wirelessly Charging TVs?

It seems someone at uBeam might read my blog, and has updated a recent posting claiming that TVs can be charged wirelessly. Their page for a recent job ad read:

uBeam is an innovation that will breed innovation. Ubiquitous wireless power will lead to a world with smaller batteries and thinner, lighter devices. With wires virtually eliminated, TVs can sit in the middle of a room cord-free and light fixtures will become “stick-on” without the need for routed power. uBeam is also a universal standard, making those bulky travel adapters a thing of the past. Imagine charging your phone, laptop or even your hearing aid virtually anywhere, without any effort. This is life powered by uBeam.

uBeam have made these claims before, such as in a panel discussion, Oct 2016, the CEO explicitly states TVs can be charged wirelessly with ultrasound, and a previous incarnation of the company website that explicitly states flat screen TV charging. The current company website still carries images showing TVs and other high power devices, so while not stated, it does seem to be implied they can be powered - hence my question as to whether it's a claim the company still stands by.

In a blog post here, I laid out the case why I believed this was near impossible/impractical due to a wide range of considerations. Well, it seems they may have accepted my carefully laid out argument, and have now changed their claims in that page:

uBeam transmits power over the air to wirelessly charge electronic devices. the company seeks to enable a world where device charging is a seamless and untethered experience. It will be the Wi-Fi of energy.

While apparently it's too difficult to do a grammar check on three sentences, it's good to see that they appear to have accepted that my argument is correct, and that it is utterly impractical to charge TVs wirelessly with ultrasound. They even noticed that it's not a universal standard and removed that statement, given the explicit ultrasound limit in most of the world would at best result in about 3 mW at a phone, enough to charge in around 3 months of it being switched off. Oh, and that standards usually have to be run through Standards Association like the IEEE and take years of input from a large committee.

This is the latest in a list of reduced deliverable or performance claims from uBeam such as 'faster than a wire' down to 'trickle charge' style rates, charging through your pocket, mass production in 2016 that never materialized, and claims of efficient and powerful transducers in 2015 that the Chair of their Technical Advisory Board apparently never saw.

Are they withdrawing their claim of wirelessly charging TVs with ultrasound, or simply saving that surprise for later? No one has stepped up to challenge my assumptions or working, and I am still happy to discuss that with anyone who cares to. As you can see, "Arguing the Point" in the manner I suggested seems to work, though I'm getting the feeling it's working better when I blog than when I worked there.

You're welcome, uBeam!