Simulate a motor fail with MP and SITL

jimmyEnroute · January 29, 2019, 8:24am

Hi all,

I would like to know if i can simulate a motor fail with MP and SITL.
I would like to try my cutom ardupilot version i have made for an hexacopter. basically, if it detects a motor fail, it stabilize for 15sec and then LAND mode to land the drone.
But i would like to be able to test it with SITL
If someone know if it is possible or know how to do i would be happy.

Thank you

khancyr · January 29, 2019, 8:48am

Hello,

On SITL you have SIM_ENGINE_FAIL that allow you to select the motor you want to fail and SIM_ENGINE_FAIL that is the inverse of the failing percentage (1 == 100% working, 0 = 0% working, 0.5 ==50% working). See the code at

github.com

ArduPilot/ardupilot/blob/master/libraries/AP_HAL_SITL/SITL_State.cpp#L437


}


float engine_mul = _sitl?_sitl->engine_mul.get():1;
uint8_t engine_fail = _sitl?_sitl->engine_fail.get():0;
bool motors_on = false;


if (engine_fail >= ARRAY_SIZE(input.servos)) {
    engine_fail = 0;
}
// apply engine multiplier to motor defined by the SIM_ENGINE_FAIL parameter
if (_vehicle != APMrover2) {
    input.servos[engine_fail] = ((input.servos[engine_fail]-1000) * engine_mul) + 1000;
} else {
    input.servos[engine_fail] = static_cast<uint16_t>(((input.servos[engine_fail] - 1500) * engine_mul) + 1500);
}


if (_vehicle == ArduPlane) {
    motors_on = ((input.servos[2] - 1000) / 1000.0f) > 0;
} else if (_vehicle == APMrover2) {
    input.servos[2] = static_cast<uint16_t>(constrain_int16(input.servos[2], 1000, 2000));
    input.servos[0] = static_cast<uint16_t>(constrain_int16(input.servos[0], 1000, 2000));

jimmyEnroute · January 29, 2019, 9:03am

Thk you for this, but i am quite a newbie with SITL.
Basically, my SITL is already flying and for example in 20m in GUIDED mode, i would like to simulate the motor 6 to stop
How can i do this ?

Because when i type param SIM_* in SITL, i cnt find SIM_ENGINE_FAIL, i only have SIM_ENGINE_MUL

i use the branch Copter-3.4, then i git submodule and run the preinstall script and reload the ~./profile
but in SITL, i cant find the param u said…

EDIT:
It seems than copter-3.4 doesnt have this parameter implemented yet…
Thank you

amilcarlucas · January 29, 2019, 9:44pm

Move to the stable Copter-3.6 branch, or even better use the master branch

peterbarker · January 30, 2019, 8:08am

Parameter probably not available way back then.

master currently has an autotest checking our current behaviour on motor
failure:

github.com

ardupilot/ardupilot/blob/master/Tools/autotest/arducopter.py#L1188




    # wait for disarm
    self.mav.motors_disarmed_wait()
    self.progress("MOTORS DISARMED OK")


    self.progress("Lowering rotor speed")
    self.set_rc(8, 1000)


    self.progress("AVC mission completed: passed!")


def fly_motor_fail(self, fail_servo=0, fail_mul=0.0, holdtime=30):
    """Test flight with reduced motor efficiency"""


    # we only expect an octocopter to survive ATM:
    servo_counts = {
        # 2: 6, # hexa
        3: 8,  # octa
        # 5: 6, # Y6
    }
    frame_class = int(self.get_parameter("FRAME_CLASS"))
    if frame_class not in servo_counts: