function roll(degree, duration_ms) {
  board.servoWrite(pwmROLL, degree);
  sleep.usleep(duration_ms * 1000);
}
function yaw(degree, duration_ms) {
  board.servoWrite(pwmYAW, degree);
  sleep.usleep(duration_ms * 1000);
}
function pitch(degree, duration_ms) {
  board.servoWrite(pwmPITCH, degree);
  sleep.usleep(duration_ms * 1000);
}