Intro to Inertial Elecia White Logical Elegance, Inc.
Plans 60%: Accelerometer, gyro, magnetometer 30% Navigation is hard 15% Kalman filters, quaternions are awesome 10% Calibration is expensive 8% Summary of sensors, applications, costs
You are here. Intro to Inertial Sensors
Sensors Accelerometers Gyros Magnetometers
Accelerometer
Sensors Accelerometers measure gravity Gyros Magnetometers
Gyros
Gyros Angular Rate Sensors
Sensors Accelerometers measure gravity Gyros Angular rate sensors measure spinniness Magnetometers
Magnetometer
Sensors Accelerometers measure gravity Gyros Angular rate sensors measure spinniness Magnetometers measure north and magnets
Midpoint Quiz! Stickers! Books! Win now! Exclamation points are free!!
Axis
Look! Pretty lights! Accelerometers measure gravity (apples) Gyros Angular rate sensors measure spinniness (gestures) Magnetometers measure north and magnets (compass)
Where am I? Navigation is hard
Accelerometer
Kidnapped and Blindfolded
Position Calculation
Kalman Filter "Basic concept of Kalman filtering" by Petteri Aimonen
Kalman Filter
I Quaternions
Calculate heading
Calculate heading: A+M
Navigation remains difficult. Tactical Considerations
All sensors are temperature sensors, some measure other things as well.
Things to ask sensor vendors
Acronymic Combinations A+G = Vertical gyro, A+M = Tilt compensated compass A+G+M = Attitude heading reference (AHRS) A+G+M+GPS = Fusion navigation solution IMU, IMU with nav library 9DOF – accel + gyro + mag 10DOF – barometric and/or temperature Barometric is for altitude but only good for relative measurements
Cost comparison Prices change pretty rapidly Not recommendations, not exact SensorSpecificPrice BoardPrice (1kq) AccelMMA8451 ADXL345 $8 (Adafruit) $18 $1.20 $4.70 Gyro (Rate) L3GD20H MAX21000 $13$3.18 $2.92 MagHMC5883L MAG3110 $10 $15 $1.55 $0.78 IMUL3GD20H+LM303 LSM9DS0 MPU-9150** $20 $35 $ $5.32 $7.12
Links and books Embedded.fm episodes: 9 (Kidnapped and Blindfolded) 9 43 (A Lot of High-Falutin’ Math) 43 Adafruit 9DOF code (github)github Hackaday.io/elecia for North Star IMU light example Hackaday.io/elecia
Elecia Thank you! Questions?