Circle will orbit a point located CIRCLE_RADIUS centimeters in front of the vehicle with the nose of the vehicle pointed at the center.
The units are centimeters from AC 3.2 (previously metres). Mission Planner reports the units as cm for all versions of the code.
Setting the CIRCLE_RADIUS to zero will cause the copter to simply stay in place and slowly rotate (useful for panorama shots).
The speed of the vehicle (in deg/second) can be modified by changing the CIRCLE_RATE parameter. A positive value means rotate clockwise, a negative means counter clockwise. The vehicle may not achieve the desired rate if this requires the acceleration towards the center of the circle to surpass the maximum acceleration held in the WPNAV_ACCEL parameter (units are cm/s/s).
The circle rate set above can be dynamically adjusted in flight by two methods. The first is the use of RC Channel 6 if the TUNE option is set to 39, allowing decreasing the rate 50% or increasing it by 100%, at the channel min and max. The other is by enabling the
CIRCLE_CONTROL parameter to allow stick adjustment of radius and speed.
Circle Control Option¶
When enabled, the
CIRCLE_CONTROL parameter allows the adjustment of the circle’s radius and angular velocity, in firmware versions prior to 4.1. In 4.1 and later, the CIRCLE_OPTIONS bitmask parameter controls what actions the pilot can adjust with his sticks and circle mode operation.
When bit 0 is set of the CIRCLE_OPTIONS parameter the pilot can adjust circle’s radius and angular velocity with the control sticks:
- Pitch stick up (reducing RC pwm) reduces the radius until it reaches zero. Think moving forward from an FPV perspective.
- Pitch stick down (increasing RC pwm) increases the radius. Think moving back from an FPV perspective.
- Roll stick right (think clockwise) will increase the speed while moving clockwise, or decrease the speed while moving counterclockwise until reaching zero, at which point it will stop.
- Roll stick left (think counterclockwise) will increase the speed while moving counterclockwise, or decrease the speed while moving clockwise until reaching zero, at which point it will stop. Once stopped (rate 0), releasing the roll stick and pushing it again in either direction will begin moving again in the desired direction. So yes, this allows you to completely change the direction on the fly.
- Roll stick rate changes are inhibited when CH6 tuning knob is set for circle rate.
- All stick changes are inhibited in radio failsafe.(ie if loiter turns was part of a mission that continues when in failsafe)
- The above does not actually change the stored circle_rate or circle_radius parameter. Upon rebooting, any stick changes to rate and radius are gone and it will use the parameter values. So users should not have any surprises with every new flight.
When bit 1 is set of the CIRCLE_OPTIONS parameter the Copter will face the direction of travel as it circles, otherwise, the Copter will point its nose at the center of the circle as it orbits. When bit 2 is set of the CIRCLE_OPTIONS parameter the circle’s center position will set upon mode entry at the current location, rather than on the perimeter with the center in front of the Copter at the start.
The pilot can control the yaw of the copter, but the autopilot will not retake control of the yaw until circle mode is re-engaged.
The mission command
LOITER_TURNS invokes Circle mode during a mission.