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content/notes/10-orientation-sensors.md
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@ -49,11 +49,6 @@ Compass / Magnetometer
- iPhone 4 magnetometer range: ±2mT - iPhone 4 magnetometer range: ±2mT
- Pro tip: prolonged exposure to a fridge magnet decalibrates your phones’ magnetometer for at least a week ;-) - Pro tip: prolonged exposure to a fridge magnet decalibrates your phones’ magnetometer for at least a week ;-)
![field strength examples|300](https://i.imgur.com/00VV74x.png) ![field strength examples|300](https://i.imgur.com/00VV74x.png)
> [!INFO]
> doesn't directly measure north
> measure magentic fielf of earth and aligns with magenetic north
> earth field is very weak so we need sensitive magnetometer
>
![Error around metal/magnetic objects](https://i.imgur.com/YIJAcGS.png) ![Error around metal/magnetic objects](https://i.imgur.com/YIJAcGS.png)
@ -66,6 +61,13 @@ Compass / Magnetometer
- Local discontinuities in magnetic field - Local discontinuities in magnetic field
- Ferromagnetic materials - Ferromagnetic materials
- Power sources - Power sources
> [!INFO]
> doesn't directly measure north
> measure magentic fielf of earth and aligns with magenetic north
> earth field is very weak so we need sensitive magnetometer
> electronic from phone affect sensor but the error can be calibrated out
> balance between what is cheap and what is good enough
> only one degree on freedom (bearing to north)
![gryroscope|300](https://i.imgur.com/VnL5seY.png) ![gryroscope|300](https://i.imgur.com/VnL5seY.png)
Gyroscope Gyroscope
@ -73,13 +75,20 @@ Gyroscope
- Precisely: orientation can be computed from the angular rate that is detected by the gyroscope, expressed in rad/s [deg/s] on 3 axis. - Precisely: orientation can be computed from the angular rate that is detected by the gyroscope, expressed in rad/s [deg/s] on 3 axis.
- Traditional gyroscopes use the e!ect of angular momentum - Traditional gyroscopes use the e!ect of angular momentum
![gyro deg of freedom|300](https://i.imgur.com/q1LjfPD.png) ![gyro deg of freedom|300](https://i.imgur.com/q1LjfPD.png)
![gyro electronic|300](https://i.imgur.com/5Ti80sO.png) ![gyro electronic plane,satellite|300](https://i.imgur.com/5Ti80sO.png)
> [!INFO]
> car, phone, game controller, etc
> measure orientation
> measure change of orientation using angular rate
> use the effect of angular momentum. when you spin something fast, it want to keep that rotation axis
- MEMS (microelectromechanical system) gyro - MEMS (microelectromechanical system) gyro
- Used in most smartphones or mobile/embedded devices - Used in most smartphones or mobile/embedded devices
- Use the displacement of vibrating proof mass to compute orientation (Coriolis effect) - Use the displacement of vibrating proof mass to compute orientation (Coriolis effect)
![MEMS gyro|100](https://i.imgur.com/dzTVCpE.png) ![MEMS gyro|100](https://i.imgur.com/dzTVCpE.png)
![gyro chip](https://i.imgur.com/zVoQ3wM.png) ![gyro chip](https://i.imgur.com/zVoQ3wM.png)
> [!INFO]
> works similar to spinning gyro but uses vibrations instead
Problem: Problem:
- The gyroscope gives us angular rate with a unit of rad/s [deg/s] - The gyroscope gives us angular rate with a unit of rad/s [deg/s]