How’s a Gyro Work?

It wasn’t long ago that a gyro — or gyroscope — was an exotic piece of electronics gear. Most of us only saw them as children’s toys that would balance on your finger. That’s changed, though, thanks to microelectronics. Now your game controller, your phone, and your drone all probably use little ICs that are actually three-axis gyroscopes. Ever wonder how they work and what they do? [RCModelReviews] has a video that covers three kinds of gyros: old mechanical gyros, modern MEMS gyros, and even an exotic laser-based gyro. (YouTube, embedded below.)

Gyroscopes allow you to detect orientation by detecting linear forces on a rotating element. They are used in everything from spacecraft to submarines. The device has many origins dating back to antiquity. But the modern gyro showed up around 1800 or so. The children’s toy appeared in 1917 and is still made today.

Gyroscopes combined with accelerometers can give you a lot of information about a vehicle’s orientation and motion. Combine it with magnetic field sensors and you can even tell your absolute orientation in the Earth’s magnetic field.

Of course, given the source, the video talks mostly about how gyros have changed flying RC vehicles including quadcopters and helicopters. If you ever wondered how they got a spinning disk into those little MEMS gyros, this video will fill you in.

Hard to imagine, but having a gyro in your phone could be a security risk. If you want to see what a $15,000 gyro from the 1960s looked like, you can see that in an earlier post.

25 thoughts on “How’s a Gyro Work?

  1. That’s the point, the meat turns. MEMS inertial sensors don’t rotate so they aren’t gyros. Yes a smartphone and an app probably would get an Apollo spacecraft to the moon and to safely return to earth. I knew a relative who worked on the laser “gyro” back in the early 60’s. At least it’s a ring and photons rotate around the ring, but no meat.

    1. Even the non-MEMS vibrating structure gyros don’t rotate anything…mind you, they are the most precise gyros mankind ever made, many orders of magnitude better then the spinning ones.

      1. >> Even the non-MEMS vibrating structure gyros don’t rotate anything…mind you, they are the most precise gyros mankind ever made, many orders of magnitude better then the spinning ones.

        Sorry, I think that’s false on several levels. AFAIK, there are _NO_ non-MEMS vibrating gyros. Why would you try that, when it’s so easy to build a spinning-wheel gyro?

        Also AFAIK, the king of gyros remains the Honeywell Electrostatically-Suspended Gyro (ESG). The spinning mass is a hollow Beryllium sphere, spinning at some ungodly rate inside an evacuated chamber. In operation, nothing touches the sphere except photons. The sphere is suspended by electrostatic forces (hence the same), spun up by similar forces on electrodes on its surface, and sensed by optical detectors.

        Again AFAIK, the ESG is still the device used in the B-52. It’s drift rate is lower than the proper motion of some stars.

        In operation, they spin up and align the ESG on the ground. Then they shut off the spin “motors,” and carry out the mission while the gyro is slowly spinning down. The vacuum inside is so perfect that it will spin for days.

        You can’t use an ESG on a ship, tank, or fighter plane, because any high-g impact on the vehicle will overcome the electro-static forces suspending the gyro, It will crash into the sides of the chamber, and that means game over.

        But it’s still perfect for the B-52 and whatever follows it.

    2. I don’t think that they will be able to. Maybe, the app will run out of the multiple gigabytes of RAM ot is allowed to use, maybe, some other app will overlay an ad on your screen, and the astronaut will be hours into getting the ad off the screen so he can see stuff and so forth…

    3. Hmm, well the photons don’t rotate, they change direction by virtual of interaction with the fibre reflection/refractive properties ie. Photons are guided by the fibre no rotation takes place as such. Photons travel in a straight line in space-time in vacuo or as directed by change in material properties. Here is a link with some graphic
      https://physics.stackexchange.com/questions/289913/how-does-light-travel-through-an-optical-fibre-of-diameter-less-than-the-distanc
      There are further resources there too. Cheers

    4. >> MEMS inertial sensors don’t rotate so they aren’t gyros.

      Not so. The key is: you don’t have to rotate 360° to be rotating. You get the same effect by rotating through a much smaller angle, but doing it over and over — i.e., vibrating.

      Most flying bugs have two pairs of wings, like a dragonfly. Butterflies are an exception — their front and back wings have merged.

      But the common housefly has a brilliant adaptation. It’s back pair of wings have atrophied down into little club-like appendages called halteres. These haltares vibrate exactly like MEMS gyros, and for the same reason. Flies have great attitude control. In short, nature developed the MEMS gyro roughly 60 million years before we mere humans figured it out.

    5. >> Yes a smartphone and an app probably would get an Apollo spacecraft to the moon and to safely return to earth.

      Not sure about that. The Apollo spacecraft was 1960’s technology, but after all, they were not exactly operating on a tight budget. They would have — and did — use the best wheel gyros MIT could produce. The accuracy of a MEMS gyro is orders of magnitude lower.

  2. Back in the 80s, prototypical hacker Forest Lancaster wrote that the world demanded a $5 rate gyro (a single axis rate gyro was around $600 in 80s $). The point of his statement was that there were so many potential applications for a cheap gyro that someone was going to HAVE to bring the price down. I’d say he did well as a futurist.

    1. bstriggo, are you sure about that name? I remember Forrest Mims and Don Lancaster, both prolific experimenters and writers, but no Forest Lancaster.

      Not at all impossible, of course. I’m sure there must be many Forest Lancasters scattered around the world. Just wondering if you meant one of the famous ones.

    2. Didn’t really happen, in the conventional supposed “demand creates supply” way. We all had to wait until microchip fabrication technology advanced far enough to carve MEMS gyros out of silicon. A brand new, disruptive technology, rather than just gradually improving the process for old macro-mechanical gyros.

      That said, gyros, and related intertial sensors, are still the main demand for MEMS devices. Though mostly in games consoles and mobile phones (for no important reason) are where they mostly end up, rather than aeroplanes or whatever.

      And yeah you probably mean Forrest M Mimms. He was more a general-purpose experimenter, I think Don Lancaster mostly did electronics and computer stuff.

  3. You don’t even need the mag sensor to get your orientation to the Earth’s axis. I worked on aircraft inertial nav (INS) back in the day that worked this out while sitting on the ground. As soon as the internal gyros spun up (ionized gas gyros at the time) they begin to experience a tilt up in the east as the earth rotates beneath them. Once you’ve established east/west, north/south is easy. Gyros were also used to stabilize aircraft compass by smoothing out erratic magnetic changes. The magnetic input is used to correct the gyro compass but is limited to 2 degrees a minute. You needed a knob to get the compass approximately correct as the magnetic input would take 45 minutes to correct a 90 degree initial error. When powered down the gyros lost their orientation so when powered up again the compass would start up randomly pointing anywhere.

    1. Yes, exactly right. A lot of aircraft systems store their location data before shutting down and use that as a starting point when coming back online. That’s why it takes so long to align the nav platform if the aircraft gets moved in an unpowered state.

      1. You definitely would have to compensate for declination, but perhaps not how you’re thinking.

        Runway headings, VOR radials, and heading instructions from air traffic control are all given relative to magnetic north. If you only had an INS that provides true north, you’d need to do the conversion.

        Even very sopisticated planes with advanced instrumentation will have a magnetic compass for backup. And normally, the directional gyro will be set to display magnetic heading.

  4. Thanks for the article. I knew how a gyro worked… But always wondered (but never researched it) how it was done electronically in such a small package. I fly fixed wing R/C (prop and ducted fan) and never needed one, but my son always used a gyro in his helis.

  5. bstriggo, are you sure about that name? I remember Forrest Mims and Don Lancaster, both prolific experimenters and writers, but no Forest Lancaster.

    Not at all impossible, of course. I’m sure there must be many Forest Lancasters scattered around the world. Just wondering if you meant one of the famous ones.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.