ARK Flow MR Open Source Optical Flow and Distance Sensor¶
The ARK Flow MR Open Source Optical Flow and Distance Sensor is an open source optical flow sensor including a Broadcom AFBR lidar which uses the CAN protocol to communicate with the autopilot. This can be used to improve horizontal position control especially in GPS denied environments. Next Generation of the ARK Flow, designed for mid-range applications.
Specifications¶
Sensors
Wide working distance from 80mm to infinity
No focal length calibration required
Auto detection of challenging conditions, such as checker boards, stripes, glossy surface and yawing
Automatic switching of Operation Mode
40mW IR LED built onto board for improved low light operation
Typical distance range up to 50m
Operation of up to 200k Lux ambient light
Laser Opening Angle of 2° x 2°
Connections
Two Pixhawk Standard CAN Connectors
4 Pin JST GH
Pixhawk Standard Debug Connector
6 Pin JST SH
Power Requirements
5V
86mA Average
90mA Max
Other
USA Built
NDAA Compliant
4 Pin Pixhawk Standard CAN Cable
LED Indicators
Where to Buy¶
The sensor is available from ARK Electronics.
Connection to Autopilot¶
The ARK Flow MR is connected to the CAN bus using a Pixhawk standard 4 pin JST GH cable.
Multiple sensors can be connected by plugging additional sensors into the ARK Flow’s second CAN connector.
The recommended mounting orientation is with the connectors on the board pointing towards back of vehicle, as shown in the following picture.
Connect the sensor to the autopilots’ CAN port
Set FLOW_TYPE = 6 (DroneCAN)
Set CAN_P1_DRIVER = 1 to enable DroneCAN
Set CAN_D1_PROTOCOL = 1 (DroneCAN)
To use the onboard lidar:
Set RNGFND1_TYPE = 24 (DroneCAN)
Set RNGFND1_MAX = 50 to set range finder’s maximum range to 50m
Additional Notes¶
FlowHold does not require the use of a rangefinder but normally does not perform as well as Loiter which does require a rangefinder
Performance can be improved by setting the sensors position parameters. For example if the sensor is mounted 2cm forward and 5cm below the frame’s center of rotation set FLOW_POS_X to 0.02 and FLOW_POS_Z to 0.05.