MEMS Motion Sensors introduction

Magneto-resistance : the resistance increases when the current is in the same direction as the magnetic force and decreases when the current is at 90°to the magnetic force.
unmanned aerial vehicles
Earth's magnetic fields submarines; compasses mobile phones
geophysical surveys
tablet computers
MEMS
M
E
M electrical
S electronic components
-Gyro calibration typical method:
*put the Gyro board on the spinning platform and test zero-rate;
*make sure Gyro spinning axis is perpendicular to the platform;
ironinterference magnetic field is normally generated by ferromagnetic materials with permanent magnetic fields that are part of the handheld device structure. These materials could be permanent magnets or magnetized iron or steel. -A soft-ironinterference magnetic field is generated by the items inside the handheld device. They could be current carrying traces on the PCB or magnetically soft materials. They generate a time varying magnetic field that is superimposed on the magnetic sensoroutput in response to the earth's magnetic field.
magnetometer Static heading angle
The nominal earth magnetic field is on average around 0.5 Gauss, while a small modern permanent magnet can easily give 3000 Gauss!
V 2 V 1
Vo
Magneto-resistance sensor
Symbol
Parameter
Magnetic Measurement Range Magnetic gain setting Magnetic cross-axis sensitivity Maximum exposed field Magnetic self test Magnetic resolution Disturbing field Operating temperature range
*spin the table with known angular rate, like -50dps/+50dps; *collect the Gyro raw data during spinning and get average numbers; *with 3 data points you will be able to determine a gain number for raw data calculation.
Also called Yaw
general test :
*Zero-rate level is the output voltage when there is no angular velocity is applied to the MEMS gyroscope sensing axis. It’s not ratiometric to the power supply voltage and ideally it’s equal to the output reference voltage. *Read the output voltage when the DUT is put still will get the zero-rate level.
Linear acceleration self-test output change
Operating temperature range
Varies from axis to axis
Typical: -30 to +85. Storage range: -40 to 125.
general test flow:
Unit
Note
This factor could be affected by over-voltage, shock(like apply 10000g/0.1ms) or temperature(both storage and operating). Depending on design and manufacturing process Depending on design and manufacturing process Depending on design and manufacturing process Depending on design and manufacturing process Depending on design and manufacturing process
fabrication techniques mechanical optical fluidic
Simple introduction of surface micromachining process:
accelerometer weight per unit of (test) mass g-force
1
2
3
*there are also other tests like self test, zero-g level test, travel range test and axis calibration etc.
Gyroscope angular momentum
angular rate dynamic
You live what you’ve learnt.
MEMS Motion Sensors
Doyong Tang 2013
inertial navigation systems
aircraft
missiles
inertial navigation systems flying vehicles
The relationship between the normalized Mx1, My1 and Mz1 and the magnetic sensor raw measurements Mx, My, and Mz can be expressed as:
Where [M_m] is a 3x3 misalignment matrix between the magnetic sensor sensing axes and the device body axes; M_SCi(i=x,y,z) is the scale factor and M_OSi is the offset caused by hard-iron distortion; [M_si] is a 3x3 matrix caused by soft-iron distortion.
-Prove it’s a linear device
D1 K1
is small displacement
x0
δx
D2 K2
Symbol
Parameter
Linear acceleration, Measurement Range Linear acceleration, Sensitivity Linear acceleration, Sensitivity change vs. temperature Linear acceleration, typical zerog level offset accuracy Linear acceleration, typical zerog level change vs. temperature Acceleration noise density