Everything you ever wanted to know about gyroscopes

Although they seem like simple objects on the surface, they can perform some very strange tricks.

When the wheel isn't spinning, gyroscopes are effectively over-engineered paperweights. If you try to stand one up, it will simply fall over (obviously). The key to them is in their spin. 

Perhaps you've played with gyroscopes as a child? Maybe you have a fidget spinner? If so, you'll remember how they can perform many interesting tricks. For example, you can balance one on a string or your finger while it is in motion.

Another noticeable property of them, if you've ever held one, is that it will try to resist attempts to move its position.

You can even tilt it at an angle when suspended from a stand, and it will appear to levitate, albeit while orbiting the stand. Even more impressively, you can lift a gyroscope with a piece of string around one end. 

How do gyroscopes work?

The explanation for this phenomenon is tricky to understand intuitively.  Their ability to seemingly defy gravity is a product of angular momentum, influenced by torque on a disc, like gravity, to produce a gyroscopic precession of the spinning disc or wheel. 

This phenomenon is also known as gyroscopic motion or gyroscopic force, and it has proved very useful for us humans. These terms refer to the tendency of a rotating object, not just a gyroscope, to maintain the orientation of its rotation. As such, the rotating object possesses angular momentum, as previously mentioned, and this must be conserved. Because of this, the spinning object will tend to resist any change in its axis of rotation, as a change in orientation will result in a change in angular momentum.

Another great example of precession occurs with the planet  Earth too. As you know, the Earth's rotational axis lies at an angle from the vertical, which, owing to its angle, traces a circle as the rotational axis itself rotates. While not entirely relevant to this article, the reason for Earth's odd tilt is pretty interesting.

As Newton's Second Law predicts, this effect is enhanced the faster the disc or wheel is spinning. This seems pretty obvious to anyone with a basic knowledge of physics. 

They seem to defy gravity mainly because of the effective torque applied to the spinning disc on its angular momentum vector. The influence of gravity on the plane of the spinning disc causes the rotational axis to "deflect."

This results in the entire rotational axis finding a "middle ground" between the influence of gravity and its angular momentum vector. Remember that the gyroscope apparatus is being stopped from falling toward the center of gravity by something in the way, like your hand, the frame/gimbals, or a table. 

Now, factoring that the gyroscope is being stopped from falling towards the center of gravity by something in the way leads to the fascinating properties we see in these devices.

Gyroscope vs. accelerometer: What is the difference between the two?

To fully answer this question, we must assess how each device works. Since we have covered the gyroscope in some detail above, let's check out what an accelerometer is and how it works. 

The Merriam Webster dictionary defines an accelerometer as "an instrument for measuring acceleration or detecting and measuring vibrations." Great, but that doesn't give us much information. In their most basic sense, accelerometers are electromechanical devices that measure acceleration forces -- hence the name.

These forces can be static (like gravity) or dynamic (caused by moving or vibrating the device). There are various ways to make an accelerometer using the piezoelectric effect or sensing capacitance.  The former consists of microscopic crystal structures that become stressed by accelerative forces and generate a voltage in return. The latter makes use of two microstructures placed next to one another. 

Each has a certain capacitance, and as accelerative forces move one of the structures, its capacitance will be changed. By adding some circuitry to convert from capacitance to voltage, you will get a very useful little accelerometer.

There are even more methods, including the piezoresistive effect, hot air bubbles, and light, to name a few. So, as you can see, accelerometers and gyroscopes are very different beasts.  

In essence, the main difference between the two is that one can sense rotation, whereas the other cannot. Since gyroscopes work through the principle of angular momentum, they are perfect for helping indicate an object's orientation in space. 

On the other hand, accelerometers can only measure linear acceleration based on vibration. However, there are some variations of accelerometer that do also incorporate a gyroscope. These devices consist of a gyroscope with a weight on one of its axes. 

The device will react to a force generated by the weight when it is accelerated by integrating it to produce velocity. 

What are optical gyroscopes? 

Another form of the gyroscope is an optical gyroscope. This device has no moving parts and is commonly used in modern commercial jetliners, booster rockets, and orbiting satellites. 

Using the Sagnac effect, these devices use beams of light to provide a function similar to mechanical gyroscopes. The effect was first demonstrated in 1911 by Franz Harris, but it was French scientist Georges Sagnac who correctly identified the cause. Suppose a beam of light is split and sent in two opposite directions around a closed path on a revolving platform with mirrors on its perimeter. In that case, the beams are recombined and will exhibit interference effects. In 1913, Sagnac concluded that light propagates at a speed independent of the speed of the source. 

He also discovered that despite the beams being within a closed loop, the beam traveling in the same direction of rotation arrived at its starting point slightly later than the other one. According to Encyclopedia Britannica, "As a result, a “fringe interference” pattern (alternate bands of light and dark) was detected that depended on the precise rate of rotation of the turntable."

The right-hand rule

Scientists tend to use what is called the "right-hand rule" to visualize this. To do this, take your right hand and make a right angle. Then you can stretch your fingers out along the radius of the wheel. If you curl the end of your fingers in the direction of the spin, your thumb will be pointing toward the angular momentum. The wheel's axle will be the direction the entire spinning wheel "wants" to move in. 

This video gives us a pretty simple explanation using a suspended bicycle wheel.

Applications of Gyroscopes

The interesting properties of gyroscopes have provided scientists and engineers with some fascinating applications. Their ability to maintain a particular orientation in space is fantastic for some applications.

Slap on some sensors, and you've got a recipe for usefulness. With that in mind, here are some great examples of the use of gyroscopes in our modern world.

1. You'll find plenty of gyroscopes in aircraft

In modern aircraft, inertial guidance systems use these relatively simple devices. They have a suite of spinning gyroscopes to monitor and control the orientation of the aircraft in flight. Spinning gyroscopes are kept in special cages that allow them to keep their orientation independently of the orientation of the aircraft. 

The gyroscope cages have electrical contacts and sensors that can relay information to the pilot whenever the plane rolls or pitches. This lets the pilot and guidance systems "know" the plane's current relative orientation in space.

2. The Mars Rover has a couple of gyroscopes, too

The Mars Rover also has a set of gyroscopes. They provide the Rover with stability as well as aid with navigation. They also have applications in drone aircraft and helicopters, in providing stability and helping with navigation. 

3. Cruise and ballistic missiles use gyroscopes as well

Another interesting application of gyroscopes is for the guidance systems of cruise and ballistic missiles. Used to automatically steer and correct roll, pitch, and yaw, gyroscope sensors have been used for this purpose since the German V-1 and V-2 missiles of World War 2. 

Typically, missiles will carry at least two gyroscopes for this purpose, with each gyro providing a fixed reference line from which any deviations can be calculated. One reference tends to include the spin axis of a vertical gyroscope. 

Pitch, roll, and yaw deviations can be readily measured from this axis. Gyroscopes also found their way into gunsight stabilizers, bombsights, and platforms for carrying guns and radar systems onboard warships. 

4. Gyroscopes can also be found in orbital spacecraft

Another interesting application of gyroscopes is for the inertial guidance systems of orbital spacecraft. Such small craft requires a high degree of precision when it comes to stabilization, and gyroscopes are perfect for the job. 

Some larger and heavier devices, called momentum wheels or reaction wheels, are also employed for altitude controls of larger satellites. 

5. Part of Star Wars: Return of the Jedi was filmed using gyroscopes

A device called a "Steadicam" was used to film certain scenes in Star Wars: The Return of the Jedi (as well as in many other movies). This device, used with several gyroscopes, held the camera stable when filming the background shots for the famous speeder bike chase on Endor. 

Invented by Garrett Brown, he operated the rig to walk through a redwood forest, running the camera at one frame per second. When the footage was sped up to 24 frames per second, it gave the impression of a high-speed journey through the trees. 

Today, Steadicam's descendants are a common feature of many movie productions.

6. Your phone might have one too

Gyroscopes have also found their way into various consumer products over the last few years. Including them within handheld devices, like smartphones, allows for a highly accurate way to determine movement in a 3D space. 

Modern smartphones typically combine gyroscopes with accelerometers to provide excellent directional and motion-sensing. Notable examples include the Samsung Galaxy Note 4, HTC Titan, iPhone 5s, etc. 

Modern game consoles also tend to include some form of gyroscope too. From the Wii Remote to various Playstation 3 and 4 peripherals, gyroscopes have opened up an entirely new way to play computer games. 

7. Lest we forget drones

Yet another interesting application of gyroscopes in our everyday lives is drones. For these devices to fly perfectly they require gyroscopes, among other devices, to hover and fly level. Modern commercial drones use three- and six-axis gyro stabilizers to provide navigational information to the flight controller, making drones easier and safer to fly.

And that's all, folks. 

Despite their simplicity in design, they have become essential pieces of kit for anything from ocean-going ships to the Space Shuttle and, of course, helicopters.

Gyroscopes are incredible, even if you don't realize they are there. Amazing to think that such a simple device can have such interesting and varied applications. While relatively simple devices, they have fantastic properties that scientists and engineers have exploited to make our world a little bit better. 

Plenty of online retailers exist if this article has sparked your imagination and you want your gyroscope. How on Earth could you refuse?