sishea/Sumo

Code for my Pololu Zumo sumo robots

Sumo Robot Basics

• Sensors - a device which detects or measures a physical property
  • Digital – reflectance / line sensors
  • Analog – distance sensor
• Controller - a device that manages the behaviour of other devices or systems
  • Reads sensor inputs;
  • Determines action; and
  • Manages actuators.
• Actuators - a device that converts an electrical control signal into mechanical motion
  • Drive motors; Buzzer

Code Overview

The code is created with a very simple state machine and command queue. States and transitions are shown below.

Trigger [Guards] / Activity

State Machine Code Snippet

void checkStateTransition()
{
  // check for transition from or execute the current state
  switch(state)
  {
  case SURVIVE:
    if (!executingCommands) hunt();
 case ATTACK:
    if (edgeDetected) survive();
    else if (!opponentDetected) hunt();
  case TARGET:
    if (edgeDetected) survive();
    else if (!opponentDetected) hunt();
    // check guard
    else if (distance >= CLOSE_RANGE) attack();
  default:  // HUNT
    if (edgeDetected) survive();
    else if (opponentDetected)
    {
      // check guard
      if(distance >= CLOSE_RANGE) attack();
      else target();
    }
  }
}

Command Queue Code Snippet

Commands [Left Speed, Right Speed, Duration]

// Survival Mode - rotate away from the border or evade opponent
void survive()
{
  state = SURVIVE;

  if(sensor_values[0] < QTR_THRESHOLD) turnDirection = 1;
  else turnDirection = -1;

  clearCommands();

  addCommand(-200, -200, 250);

  if (sensor_values[0] < QTR_THRESHOLD && sensor_values[5] < QTR_THRESHOLD)
  {
    addCommand(turnDirection * 200, -turnDirection * 200, 500);
  }  

  addCommand(turnDirection * 200, -turnDirection * 200, 250);
  addCommand(200, 200, 500);
  startExecutingCommands();
}

Tips

• Modify speed, time and distance limits in the parameters
• Change the Trigger / Guard in the state transitions
• Change the commands undertaken in the State Changed activities