Drive Modes (Differential Rover)
Flight modes (or more accurately "Drive modes" for ground vehicles) provide autopilot support to make it easier to manually drive the vehicle or to execute autonomous missions.
This section outlines all supported drive modes for differential rovers.
For information on mapping RC control switches to specific modes see: Basic Configuration > Flight Modes.
WARNING
Selecting any other mode than those listed below will either stop the rover or can lead to undefined behaviour.
Manual Modes
Manual modes require stick inputs from the user to drive the vehicle.
The manual modes listed below provide increasing levels of autopilot support:
| Mode | Forward speed | Yaw rate | Required measurements |
|---|---|---|---|
| Manual | Directly map stick input to motor commands. | Directly map stick input to motor commands. | None. |
| Acro | Directly map stick input to motor commands. | Stick input creates a yaw rate setpoint for the control system to regulate. | Yaw rate. |
| Stabilized | Directly map stick input to motor commands. | Stick input creates a yaw rate setpoint for the control system to regulate. If this setpoint is zero (stick is centered) the control system will maintain the current yaw (heading) of the rover. | Yaw rate and yaw. |
| Position | Stick input creates a speed setpoint for the control system to regulate. | Stick input creates a yaw rate setpoint for the control system to regulate. If this setpoint is zero (stick is centered) the control system will keep the rover driving in a straight line. | Yaw rate, yaw, speed and global position (GPS). |
Manual Mode
In this mode the stick inputs are directly mapped to motor commands. The rover does not attempt to maintain a specific orientation or compensate for external factors like slopes or uneven terrain!
The user is responsible for making the necessary adjustments to the stick inputs to keep the rover on the desired course.
| Stick | Effect |
|---|---|
| Left stick up/down | Drive the rover forwards/backwards. |
| Left stick centered | Zero forward speed input. |
| Right stick left/right | Yaw the rover to the left/right. |
| Right stick centered | Zero yaw rate input |
For the configuration/tuning of this mode see Manual mode.
Acro Mode
INFO
This mode requires a yaw rate measurement.
In this mode the vehicle regulates its yaw rate to a setpoint (but does not stabilize heading or regulate speed).
| Stick | Effect |
|---|---|
| Left stick up/down | Drive the rover forwards/backwards. |
| Left stick centered | Zero forward speed input. |
| Right stick left/right | Create a yaw rate setpoint for the control system to regulate. |
| Right stick centered | The control system will attempt to maintain a zero yaw rate (minimal disturbance rejection) |
For the configuration/tuning of this mode see Acro mode.
Stabilized Mode
INFO
This mode requires a yaw rate and yaw estimate.
In this mode the vehicle regulates its yaw rate to a setpoint and will maintain its heading if this setpoint is zero (but does not regulate speed).
Compared to Acro mode, this mode is much better at driving in a straight line as it can more effectively reject disturbances.
| Stick | Effect |
|---|---|
| Left stick up/down | Drive the rover forwards/backwards. |
| Left stick centered | Zero forward speed input. |
| Right stick left/right | Create a yaw rate setpoint for the control system to regulate. |
| Right stick centered | The control system will maintain the current heading. |
For the configuration/tuning of this mode see Stabilized mode.
Position Mode
INFO
This mode requires a yaw rate, yaw, speed and global position estimate.
This is the mode with the most autopilot support. The vehicle regulates its yaw rate and speed to a setpoint. If the yaw rate setpoint is zero, the controller will remember the gps coordinates and yaw (heading) of the vehicle and use those to construct a line that the rover will then follow (course control). This offers the highest amount of disturbance rejection, which leads to the best straight line driving behavior.
| Stick | Effect |
|---|---|
| Left stick up/down | Create a speed setpoint for the control system to regulate. |
| Left stick centered | Zero forward speed input. |
| Right stick left/right | Create a yaw rate setpoint for the control system to regulate. |
| Right stick centered | The control system will maintain the course of the rover. |
For the configuration/tuning of this mode see Position mode.
Auto Modes
In auto modes the autopilot takes over control of the vehicle to run missions, return to launch, or perform other autonomous navigation tasks.
For the configuration/tuning of these modes see Auto Modes.
Mission Mode
Mission mode is an automatic mode in which the vehicle executes a predefined autonomous mission plan that has been uploaded to the flight controller. The mission is typically created and uploaded with a Ground Control Station (GCS) application, such as QGroundControl.
Mission commands
The following commands can be used in missions at time of writing (main(PX4 v1.16+)):
| QGC mission item | Command | Description |
|---|---|---|
| Mission start | MAV_CMD_MISSION_START | Starts the mission. |
| Waypoint | MAV_CMD_NAV_WAYPOINT | Navigate to waypoint. |
| Return to launch | MAV_CMD_NAV_RETURN_TO_LAUNCH | Return to the launch location. |
| Delay until | MAV_CMD_NAV_DELAY | The rover will stop for a specified amount of time. |
| Change speed | MAV_CMD_DO_CHANGE_SPEED | Change the speed setpoint |
| Set launch location | MAV_CMD_DO_SET_HOME | Changes launch location to specified coordinates. |
| Jump to item (all) | MAV_CMD_DO_JUMP (and other jump commands) | Jump to specified mission item. |
| Loiter (all) | MAV_CMD_NAV_LOITER_TIME (and other loiter commands) | Stop the rover for given time. Other commands stop indefinitely. |
Return Mode
This mode uses the pure pursuit guidance logic with the launch position as goal. Return mode can be activated through the respective mission command or through the ground station UI.