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* failure_injection: improve previously vague motor faulure Reading it again I decided adding the sentance in 4d2170c13ea4d42c5b0b464dbbcbb68fb098cbcc is not clear enough. * docs/safety: add a motor failure detection paragraph The functionality is in my eyes pretty basic but so far completely undocumented so I went through the code and added a paragraph based on questions I received. * Subedit * Apply suggestion from @hamishwillee --------- Co-authored-by: Hamish Willee <hamishwillee@gmail.com>
101 lines
4.2 KiB
Markdown
101 lines
4.2 KiB
Markdown
# System Failure Injection
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System failure injection allows you to induce different types of sensor and system failures, either programmatically using the [MAVSDK failure plugin](https://mavsdk.mavlink.io/main/en/cpp/api_reference/classmavsdk_1_1_failure.html), or "manually" via a PX4 console like the [MAVLink shell](../debug/mavlink_shell.md#mavlink-shell).
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This enables easier testing of [safety failsafe](../config/safety.md) behaviour, and more generally, of how PX4 behaves when systems and sensors stop working correctly.
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Failure injection is disabled by default, and can be enabled using the [SYS_FAILURE_EN](../advanced_config/parameter_reference.md#SYS_FAILURE_EN) parameter.
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:::warning
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Failure injection still in development.
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At time of writing (PX4 v1.14):
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- Support may vary by failure type and between simulatiors and real vehicle.
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- It requires support in the simulator.
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It is supported in Gazebo Classic
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- Many failure types are not broadly implemented.
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In those cases the command will return with an "unsupported" message.
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:::
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## Failure System Command
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Failures can be injected using the [failure system command](../modules/modules_command.md#failure) from any PX4 [console/shell](../debug/consoles.md) (such as the [QGC MAVLink Console](../debug/mavlink_shell.md#qgroundcontrol-mavlink-console) or SITL _pxh shell_), specifying both the target and type of the failure.
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### Syntax
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The full syntax of the [failure](../modules/modules_command.md#failure) command is:
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```sh
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failure <component> <failure_type> [-i <instance_number>]
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```
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where:
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- _component_:
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- Sensors:
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- `gyro`: Gyroscope
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- `accel`: Accelerometer
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- `mag`: Magnetometer
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- `baro`: Barometer
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- `gps`: Global navigation satellite system
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- `optical_flow`: Optical flow.
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- `vio`: Visual inertial odometry
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- `distance_sensor`: Distance sensor (rangefinder).
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- `airspeed`: Airspeed sensor
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- Systems:
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- `battery`: Battery
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- `motor`: Motor
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- `servo`: Servo
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- `avoidance`: Avoidance
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- `rc_signal`: RC Signal
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- `mavlink_signal`: MAVLink data telemetry connection
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- _failure_type_:
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- `ok`: Publish as normal (Disable failure injection)
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- `off`: Stop publishing
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- `stuck`: Constantly report the same value which _can_ happen on a malfunctioning sensor
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- `garbage`: Publish random noise. This looks like reading uninitialized memory
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- `wrong`: Publish invalid values that still look reasonable/aren't "garbage"
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- `slow`: Publish at a reduced rate
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- `delayed`: Publish valid data with a significant delay
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- `intermittent`: Publish intermittently
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- _instance number_ (optional): Instance number of affected sensor.
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0 (default) indicates all sensors of specified type.
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## MAVSDK Failure Plugin
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The [MAVSDK failure plugin](https://mavsdk.mavlink.io/main/en/cpp/api_reference/classmavsdk_1_1_failure.html) can be used to programmatically inject failures.
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It is used in [PX4 Integration Testing](../test_and_ci/integration_testing_mavsdk.md) to simulate failure cases (for example, see [PX4-Autopilot/test/mavsdk_tests/autopilot_tester.cpp](https://github.com/PX4/PX4-Autopilot/blob/main/test/mavsdk_tests/autopilot_tester.cpp)).
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The plugin API is a direct mapping of the failure command shown above, with a few additional error signals related to the connection.
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## Example: RC signal
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To simulate losing RC signal without having to turn off your RC controller:
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1. Enable the [SYS_FAILURE_EN](../advanced_config/parameter_reference.md#SYS_FAILURE_EN) parameter.
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2. Enter the following commands on the MAVLink console or SITL _pxh shell_:
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```sh
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# Fail RC (turn publishing off)
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failure rc_signal off
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# Restart RC publishing
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failure rc_signal ok
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```
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## Example: Motor
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To stop a motor mid-flight without the system anticipating it or excluding it from allocation effectiveness:
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1. Enable the [SYS_FAILURE_EN](../advanced_config/parameter_reference.md#SYS_FAILURE_EN) parameter.
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2. Enable [CA_FAILURE_MODE](../advanced_config/parameter_reference.md#CA_FAILURE_MODE) parameter to allow turning off motors.
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3. Enter the following commands on the MAVLink console or SITL _pxh shell_:
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```sh
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# Turn off first motor
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failure motor off -i 1
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# Turn it back on
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failure motor ok -i 1
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```
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