Three-axis gyroscope and accelerometer how to assist the iphone positioning

Last year June 8, the great Apple released the latest http://www.aliyun.com/zixun/aggregation/13260.html "> Generation iphone 4G, the new machine has a lot of hardware upgrades, One of the biggest "three-axis gyroscopes" for gamers!

The first time I heard of this "three-axis gyroscope" is a period of time, occasionally found that Apple players test the ipod touch positioning function, specifically in the "different mobile device positioning offset problem." It's a novelty – because the ipod touch has no GPS and can be positioned, specially researched.
The post study found that this tri-axis Gyroscope is also a great news for our position-positioning enthusiasts, as there is wifi with this gyroscope and accelerometer that can also be positioned, although the positioning accuracy remains to be verified, with less nonsense to say, Let's share my knowledge of the three-axis gyroscope and accelerometer of the iphone.

Explain the gyroscope before all

According to the wiki definition: "Gyroscope is used to measure the angle or maintain the direction of the equipment, based on the principle of conservation of angular momentum." 」

The point of this statement is to measure the angle or maintain the direction, which is why the IPhone 4 is equipped with such equipment. Mechanical gyroscopes – such as the one below – there is a turntable in the middle to detect changes in direction. The IPhone 4 uses a miniature, electronic vibratory gyroscope, also known as a MEMS gyroscope.
It's supposed to be like this. A thing (pictured below) looks like a confidential part of a watch!

Dynamic display diagram of three-axis gyroscope

Note that the middle of the image above is a high-speed rotating golden color of the rotor, because of inertia, it is not affected by external forces to change posture, and the surrounding equipment any change of attitude can be detected, used to determine the rotation of the object in all directions angle.

Here to insert a sentence, we played the gyro as a child, know at a certain speed, you can always maintain a vertical direction.

The most important function of the three-axis gyroscope is to "measure angular velocity to judge the motion state of an object, so it is also called motion sensor", in other words, it can let our iphone know where and where to go (where tightly are or where tightly ' re on)!

Accelerometer is one of the basic measuring elements of inertial navigation and inertial guidance system, the accelerometer is essentially an oscillating system, which is installed in the interior of the moving carrier, and can be used to measure the motion acceleration of the carrier.

The MEMS accelerometer works when the accelerometer acts as an acceleration with an external object (the acceleration of the object is the accelerometer to be measured), and the mass blocks move in the opposite direction by the inertia force. The displacement of mass blocks is limited by springs and dampers, and the external acceleration can be measured by the output voltage.

Accelerometer Working principle diagram

From the application direction of MEMS gyroscope, the gyroscope can measure the angular velocity along one axis or several axes, and can complement the MEMS accelerometer (accelerometer), if the combination of accelerometers and gyroscopes, the designer can better track and capture the complete motion of the three-dimensional space, Provide end users with a more on-site user experience, accurate navigation systems, and other features.

To accurately describe linear (linear motion) and rotational motions (movements with cornering changes), designers need to use both gyroscopes and accelerometers.

the use of gyroscopes alone can be used for high resolution and rapid response rotation detection, the simple use of accelerometers can be used in a fixed gravity reference coordinate system, there are linear or tilt motion, but the rotation movement is limited to a certain range of applications. However, when dealing with both linear and rotational motions, it is necessary to use the acceleration and gyro-meter scheme.

In addition, in order to make the design and fabrication of gyroscopes with higher acceleration and lower mechanical noise, or to calibrate the accelerometer rotation error, some manufacturers will use magnetometer to complete the traditional use of gyroscope to achieve the sensing function, to complete the corresponding positioning, so that the gyroscope surgery industry has specialized. This indicates that the combination of a hybrid gyroscope, accelerometer or magnetic sensor is becoming a trend in the application of MEMS gyroscope technology. Using conventional accelerometers, the user gets either an agile but noisy output, or a slow but purer output, and a combination of an accelerometer and a gyroscope can produce an output that is both pure and responsive.

Accelerometer is one of the basic measuring elements of inertial navigation and inertial guidance system, accelerometer is essentially an oscillation system, installed in the interior of the motion carrier, can be used to measure the movement of the vector acceleration, the use of known GPS measurements and so on the initial speed, the acceleration integral, you can know the speed and location of the carrier information. Therefore, the performance and precision of the accelerometer directly affect the precision of navigation and guidance system.

Outdoor

GPS is used for navigating outdoors where enough satellites can be searched

Indoor

Accelerometer is used to measure the acceleration, combined with the initial speed provided by GPs, can calculate the existing velocity motion distance. A gyroscope is used to measure the change in the turn or slope of a device

In an environment where GPS signals are blocked or disturbed and cannot be positioned, another way of navigating through gyroscopes and accelerometers can greatly enhance the efficiency and accuracy of the positioning navigation. When the iphone is installed with gyroscopes and accelerometers, a large number of handset manufacturers will follow up, which will strongly promote the further growth of lbs services.

Related knowledge:

MEMS

MEMS is the abbreviation of the Microcomputer electrical system (micro-electro-mechanical BAE). MEMS is the name of the United States, in Japan is called micro-machinery, in Europe is called a micro-system, it refers to the batch production, micro-sensors, micro-actuators and signal processing and control circuits, until the interface, communication and power equal to one of the micro-devices or systems. MEMS is developed with the development of micromachining technology and ultra-precision machining technology of semiconductor integrated circuits, and the MEMS processing technology is widely used in microfluidic chip and synthetic biology, so as to carry on the chip integration of biochemistry and other laboratory technology process.

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