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An arduino-based autopilot for Flo

to fix intellisense issues (missing include pinnames.h, or similar) add the following to includepaths in c_cpp_properties.json /Users/bastienGirschig/Library/Arduino15/packages/arduino/hardware/mbed_nano/2.3.1/cores/arduino/mbed/**

Sensing

We take advantage of the intergated sensors in the arduino sense, we can determine the current heading:

  • A preset vector indicates the orientation of the arduino relative to the boat
  • Using the accelerometer, we determine the "down" direction
  • Using the magnetometer, we know the direction of the magnetic field. after removing its vertical component, it points north

Actuation

We're using a motor controller board based on the BTS7960 chip to control an electric oil pump that drives the rudder.

Settings / UI

We plan on using three interfaces for this controller:

  • Built-in LED blink patterns for very basic and reliable 'display'
    • Current mode
    • Missing hardware
    • Catastrophic failures
  • Physical controller(s): LEDs, buttons, potentiometers/encoders, etc...
    • tweak Sensitivity
    • Tracking On/Off
    • Calibrate accelerometer
    • Calibrate magnetometer (how ?)
  • Phone app, via bluetooth

Failure modes

Failure Worst Effect Severity Mitigation
Bluetooth fail Can't use the remote Minor Every critical function accessible through a physical interface
Water damage The pilot cannot function at all Critical Backup arduino with preloaded software + waterproof enclosure
Motor controller fail The pilot cannot function at all Critical Backup motor controller
Logic failure Erratic rudder control Catastrophic "panic button", phisically disconnects electric pump
Bad wire connection Erratic rudder control Catastrophic "panic button", phisically disconnects electric pump
Short circuit Fire Catastrophic Fuse, BTS7960 protection, temp sensor + alarm (?)

CSYS

The inertial sensor and the magnetometer do not have the same coord systems... se we correct them and create our own CSYS: x is in the Arduino card plan, transversal, pointing right if you have USB plug towards yourself y is in the Arduino card plan, longitudinal, pointing towards the side opposite to the USB plug z is perpendicular to the Arduino card, towards the top x y z is a base orthonormee, right handed (standard)

Tips and tricks

Serial.println(pilot.headingError*180/M_PI);

Serial.print(pilot.headingError*180/M_PI);
Serial.print(",");
Serial.print(-90);
Serial.print(",");
Serial.print(90);
Serial.print("\n");

Connections Arduino Vs motor controller

Arduino - motor controller D3 LPWM D4 RPWM D5 L_EN D6 R_EN GND GND 3V3 VCC Motor controller L_IS R_IS are not connected

Arduino Vs start button

Arduino D2 connected to Vin -> pilot ON Arduino D2 connected to GND -> pilot OFF (D2 always connected to GND through 10kOhm resistance, and connected to Vin by switch to be ON)