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?