Copter and Rover include a simple “tin can” shaped fence centered on home that will attempt to stop your copter/rover from flying/driving too far away by stopping at the fence or executing a configurable action. The maximum circular distance and altitude (altitude used by Copter only) and the vehicle behavior when the fence is reached can be configured using Mission Planner.
Rover has no altitude actions, but if it reaches the Cylindrical fence boundary in either Steering or Acro modes, it will simply stop and not move beyond it. These are the only modes affected by the fence.
Copter will stop increasing altitude at FENCE_ALT_MAX in Loiter, PosHold, and AltHold modes.
In Loiter mode, it will stop at the horizontal boundaries.
In other modes, it will execute the FENCE_ACTION below if the altitude or boundary is reached.
RTL/HOLD,etc. means it will attempt RTL first, but if it cant’ switch to that mode (ie for RTL, GPS lock is lost), it will attempt to switch to the next,in this case HOLD.
At the moment the fence is breached a backup fence is erected 20m further out (or up). If the vehicle breaches this backup fence (for example if the the vehicle is not set up correctly or the operator takes control but is unable to bring the copter back towards home), the vehicle will execute the FENCE_ACTION again (and another backup fence an additional 20m further out will be created if this is breached again).
If the vehicle eventually proceeds 100m outside the configured fence distance, despite the backup fences, the vehicle will switch into LAND mode (HOLD for Rover). The idea being that it’s clearly impossible to get the vehicle home so best to just bring it down/stop it. The pilot can still retake control of course with the flight mode switches. Like with the earlier fences, another fence is erected 20m out which will again switch the vehicle to LAND (HOLD for Rover), if it continues away from home.
Enabling the Fence in Mission Planner¶
The Fence can be set-up by doing the following:
- Connect your autopilot to the Mission Planner
- Go to the CONFIG/GeoFence screen
- Enable the FENCE: FENCE_ENABLE =1.
The fence can be enabled/disabled by an RC channel, or Mission Command (DO_FENCE_EANBLE), but must be enabled with this parameter first.
- Set FENCE_TYPE = default of “ALL” is fine and will allow you to set up an additional Inclusion and Exclusion Fences , unless you want only a cylindrical fence to be active if a polygon fence has also been loaded. Then you could select “Altitude” or “Circle” or both.
- Set FENCE_ACTION =”RTL or LAND” ,or whatever you wish for a breach action.
- Set FENCE_ALT_MAX to the altitude limit you want (in meters). This is unavailable in Rover.
- Set FENCE_RADIUS to the maximum distance from HOME you want (in meters). This should normally be at least 50m.
Currently Mission Planner does not support the GeoFences menu for Rover, so these parameters must be entered manually.
Rover ignores any altitudes entered, or if a FENCE_TYPE involving altitude is selected.
Enabling the fence with an RC Channel Auxiliary Switch¶
It is not necessary to set-up a switch to enable or disable the fence but if you wish to control the fence with a switch follow these steps:
for firmware versions before 4.0:
- Go to the Mission Planner’s Config/Tuning > Extended Tuning screen and set either “Ch7 Opt” OR “Ch8 Opt” to Fence. These parameters can also be directly set from the Config/Tuning > Full Parameter List screen
alternatively, for firmware versions 4.0 or later, an RCx_OPTION can be set via the Config/Tuning > Full Parameter List screen:
- Use an RCx_OPTION set to Fence
- holding the switch high (i.e. PWM > 1800) will enable the fence, low (under 1800) will disable the fence.
- The minimum recommended fence radius is 30m
- The fence requires the GPS to be functioning well so do not disable the GPS arming check nor the EKF failsafe while the fence is enabled. Conversely if you disable either of these checks, disable the Fence.
- For the best results, ensure RTL is working on your vehicle.
- With the Fence enabled, the pre-arm checks will require you have GPS lock before arming the vehicle.
- If GPS failsafe is not enabled and the Fence is enabled and you lose GPS lock while flying the fence will be disabled.
- If GPS failsafe is enabled and the Fence is enabled and you lose GPS lock while piloting, the vehicle will switch to LAND (HOLD for Rover) because we no longer know the vehicle position and we want to ensure the vehicle never travels far outside the fence. This behavior will occur regardless of the flight mode. If this is not desired, the pilot can retake control by moving the flight mode switch.
- The backup fences are created 20m out from the previous breached fence not 20m out from the vehicle’s position. This means if you choose to override the fence you may have less than 20m to regain vehicle control before the fence switches the vehicle to the FENCE_ACTION again. If you really want to override the fence, you should be ready to switch the flight mode twice or alternatively set-up the enable/disable fence switch.