What’s A Gyroscope And Accelerometer Doing In My Mobile Device?
We’ll show you another facet of how it does it’s miracles
The gyroscope is an extremely sophisticated little mechanism, that has found many diverse applications thanks to its ability to provide simplified, accurate measurements of orientation.
A gyroscope is responsible for maintaining balance/orientation and resists change by rectifying any angular displacement, thereby providing stability-control.
Complicated? Well, simply put, it measures angle and judges it’s own orientation so accurately, that it is used to trigger corrections in such angle. Think of it as the Complex Physics version of a magnetic compass.
The gyroscope gained prominence during experiments by a French physicist Leon Foucault, who used it to explain the earth’s rotation. In present day, it is being used for many critical applications such as maintaining the orientation of planes, missiles and spaceships, and more consumer-level applications in smartphones such as enabling gesture control gaming on mobile devices amongst many other diverse implementations.
The gyroscope in it’s simplest form is a rotor on a spin axis, enclosed in a frame to minimize external torques called gimbal and the external gyroscopic frame.
Precession (no, we haven’t misspelt ‘precision’ — that’s a different thing, though etymologically speaking, it may just have it’s origin in Precession!) is the action in a gyroscope that keeps the spin axis oriented even after external forces are applied to disorient the spin axis; so when a deforming force is applied to the spin axis, instead of rotating the axis itself, it rotates the structure surrounding the metallic disc.
In the diagram above we can see that the tilt has not changed the direction of the rotor and has been compensated by the gimbal. The spinning of the rotor means that any change in orientation affects all points on the rotor equally, causing the rotor to spin on a fixed axis.
This is called Precession and it creates a fixed-orientation even after external forces are applied to disorient the spin axis. If an external force is applied, the spin axis transfers the repercussions (hence the English word) of that force to the rotor, which in turn, passes the force to the external framework (gimbal) causing it to rotate at right angles to the initial external force applied keeping the spin axis in form, thereby maintaining the orientation.
Precession, is what keeps the spin axis oriented and thus helps in a number of fields like navigating unmanned aerial vehicles, operating your devices, space shuttles etc and has also been used by a motorcycle manufacturer to invent a 2-wheel bike which uses two gyroscopes to remain upright.
If you mount two gyroscopes with their axles at right angles to one another on a platform, and place the platform inside a set of gimbals, the platform will remain completely rigid, as the gimbals are free to rotate in any axis. This makes the Inertial Navigation Systems (INS) used in unmanned vehicles.
Large gyroscopes are also used to stabilize boats and even satellites during their flight path!
Okay, now that you understand how the gyroscope works, let’s further explore a variant used in your mobile devices.
In our cellphones, the gyroscope used is called micro electro mechanical systems gyroscope (MEMS) gyroscope. This is different from the mechanical one described above, though the principle remains same.
MEMS gyroscopes are compact, and carry small-integrated chips. The sensors register change in angular displacement while a current is generated through the vibrating action of the gyro and transmitted in a viable form to alert the user.
This would be a simple submission of motion-sensing in our smartphones.
A gyroscope in your phone enables it to sense linear orientation of the phone to auto rotate your screen. While the gyroscope takes care of the rotational orientation, it is the accelerometer that senses the linear changes relative to the frame of reference of the device.
Now, an accelerometer is the device used to measure the force of acceleration, whether caused by gravity or by movement.
The mass (M) is attached via a spring (K) and when at rest is in the position “0” (rest). If you pull the frame to the right, the mass will remain stationary for some time and then will move with the motion. This delay is captured and is converted into acceleration.
Consider a housing that suspends a seismic mass from a spring. Depending whether the device goes up or down, gravity will work to produce a displacement that either compresses the spring, or expands it. Depending on the degree and nature of change in the spring, we can tell whether the phone is moving upwards or downwards.
By arranging such an apparatus along all three dimensions in space (one along the x, y and z axes), we can tell what side the device lies on while the gyro takes care of the tilt and angular considerations. The accelerometer senses movement and shift in gravity, making it an ideal tool to accurately capture change in motion and orientation of motion.
Let’s take an example of gaming on WII to understand this further.
When you play golf using the WII controller, the accelerometer captures your swing motion and translates it into an on-screen shot. The acceleration with which you swung the WII controller will be registered into the strength of your swing shot and translated into the distance the ball travels on the green, while the angle of movement will get translated into the direction the ball will travel.
Together the accelerometer and gyroscope can sense the orientation of the device and how fast it’s accelerated. Landscape vs. Portrait? — Our screen orientation preferences, how does the phone sense it to be on its side? The MEMS (micro electro mechanical systems gyroscope) technology integrated in the little chip well seated in the motherboard of the device is the answer.
A tactfully placed housing and mass allows a simultaneous reading in all dimensions and gyro keeps orientation in form. As soon as there is a displacement that indicates there is acceleration in a particular direction, with a vibrating motion caused by the gyro, a potential drop is formed generating a current which leads off into the circuitry to tell the rest of the device how to respond.
This way, the device knows exactly where in space it lies.
Some other places where they come into play are embedded into the gesture controls of your media player (Sony Shake and Samsung Motion Play are two good examples), direction control in gaming — in lieu of using the keypad, the muting of your buzzing phone by simply turning it upside down — all through these two hard-working little electronic gizmos.
So, now you know what goes on inside your device, when you tilt it to grab those coins staring up at you in Temple Run!
So the same technology that’s used in airplanes, guiding the pilot and even the Mars Rover, enabling it to navigate on extraterrestrial land, is what determines how hard you swung your virtual golf club!
Originally published at Chip-Monks.
