Intro to Inertial Elecia White Logical Elegance Inc

Intro to Inertial Elecia White Logical Elegance, Inc. Embedded. fm @logicalelegance

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

Intro to Inertial Sensors You are here.

Sensors Accelerometers Gyros Magnetometers

Accelerometer

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

Axis

Look! Pretty lights! Accelerometers measure gravity (apples) Gyros Angular rate sensors measure spinniness (gestures) Magnetometers measure north and magnets (compass)

Navigation is hard Where am I?

Accelerometer

Accelerometer

Kidnapped and Blindfolded

Position Calculation

Kalman Filter "Basic concept of Kalman filtering" by Petteri Aimonen

Kalman Filter

I <heart> Quaternions

I <heart> Quaternions http: //en. wikipedia. org/wiki/Conversion_between_quaternions_and_Euler_angles

Calculate heading https: //github. com/adafruit/Adafruit_9 DOF/blob/master/Adafruit_9 DOF. cpp

Calculate heading: A+M https: //github. com/adafruit/Adafruit_9 DOF/blob/master/Adafruit_9 DOF. cpp

Tactical Considerations Navigation remains difficult.

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 9 DOF – accel + gyro + mag 10 DOF – barometric and/or temperature Barometric is for altitude but only good for relative measurements

Cost comparison Sensor Specific Price Board Price (1 kq) Accel MMA 8451 ADXL 345 L 3 GD 20 H MAX 21000 $8 (Adafruit) $18 $13 $1. 20 $4. 70 $3. 18 $2. 92 HMC 5883 L MAG 3110 L 3 GD 20 H+LM 303 LSM 9 DS 0 MPU-9150** $10 $15 $20 $35 $1. 55 $0. 78 $3. 18 + 1. 76 $5. 32 $7. 12 Gyro (Rate) Mag IMU Prices change pretty rapidly Not recommendations, not exact

Links and books Embedded. fm episodes: 9 (Kidnapped and Blindfolded) 43 (A Lot of High-Falutin’ Math) Adafruit 9 DOF code (github) Hackaday. io/elecia for North Star IMU light example

Thank you! Questions? Elecia White @logicalelegance