Control a Winch

This page explains how MAVLink can be used by a ground station or companion computer to control a winch. The user wiki pages for the winch is here.

Control the winch with MAV_CMD_DO_WINCH

The servo’s position can be set by sending a COMMAND_LONG with the command, param1 and param2 fields set as specified for the MAV_CMD_DO_WINCH command.

Command Field	Type	Description
target_system	uint8_t	System ID of flight controller or just 0
target_component	uint8_t	Component ID of flight controller or just 0
command	uint16_t	MAV_CMD_DO_WINCH=42600
confirmation	uint8_t	0
param1	float	Winch instance number
param2	float	Action (0:Relax, 1:Length Control, 2:Rate Control)
param3	float	Length of line to release (negative to wind in)
param4	float	Release rate (negative to wind in)
param5	float	not used
param6	float	not used
param7	float	not used

Example

The example commands below can be copy-pasted into MAVProxy (aka SITL) to test this command. Before running these commands enter:

• setup a winch as described on the Adding Simulated Devices page

• module load message

• module load graph

• graph SERVO_OUTPUT_RAW.servo9_raw

Example MAVProxy/SITL Command	Description
message COMMAND_LONG 0 0 42600 0 0 0 0 0 0 0 0	Relax winch so line can be pulled out manually
message COMMAND_LONG 0 0 42600 0 0 1 5 0 0 0 0	Let out 5m of line
message COMMAND_LONG 0 0 42600 0 0 2 0 0.5 0 0 0	Let out line at 0.5 m/s