Threading multiple crazyflies (not using swarm class), erratic flying. How to fix?

[john-amadora]

I coded in control of 3 synchronous drones via the python wrapper for the crazyflie and using only the motion commander class for movement. I did this instead of the swarm class because each drone will be having its own command and the swarm class is limited to sending setpoints, synchronous movement, and sequential movement.

I implemented my system using threading in python. That is, the crazyflie and the motion commander is initialized in a function and the thread is enabled three times in main all with its own URI.

When one drone is enabled, hovering is steady, but when 3 drones are enabled, the drones tend to drift by a lot.

How can I fix this? I am thinking that perhaps they are sharing state estimates. Any ideas?

Here's what the function looks like. This is called 3 times in main to thread together. For more context, I want to control each drone based on command submitted by an external controller (handled by another thread). May not be the smartest implementation, I am not a compsci major after all. I just develop as needed.

with SyncCrazyflie(URI, cf) as scf:
        scf.cf.param.add_update_callback(group='deck', name='bcFlow2',
                                         cb=param_deck_flow)
        logconf = LogConfig(name=drone, period_in_ms=500)
        logconf.add_variable('stateEstimate.x', 'float')
        logconf.add_variable('stateEstimate.y', 'float')
        logconf.add_variable('stateEstimate.z', 'float')
        logconf.add_variable('pm.vbat', 'float')
        scf.cf.log.add_config(logconf)
        logconf.data_received_cb.add_callback(log_pos_callback)
        if not deck_attached_event.wait(timeout=3):
            print(f"{drone}:No flow deck detected!")
            enable = False
        mc = MotionCommander(scf, default_height = DEFAULT_HEIGHT)
        mc._reset_position_estimator()
        logconf.start()
        with Multiranger(scf) as mr:
            print(f"{drone}: Ready to Fly!")
            while not enable:
                #Checks every 0.2 second
                enable = flight_enable
                time.sleep(0.2)
            if enable == True:  
                print(f"{drone}: Flying Started!")
                mc.take_off(height = 0.5, velocity = 0.5)
            mc.stop()
                # Drone 1 Logic
                if drone == "Drone 1" and (drone1 or groupDrone) and control_enable:
                    local_movement = movement
                    drone1_command = movement
                    printDroneMovementWhenChanged(movement_prev, local_movement, drone)
                    if local_movement == 'up':
                        mc.up(cmd_dist)
                        mc.stop()
                    elif local_movement == 'down':
                        mc.down(cmd_dist)
                        mc.stop()
                    elif local_movement == 'left':
                        mc.left(cmd_dist)
                        mc.stop()
                    elif local_movement == 'right':
                        mc.right(cmd_dist)
                        mc.stop()
                    elif local_movement == 'fward':
                        mc.forward(cmd_dist)
                        mc.stop()
                    elif local_movement == 'bward':
                        mc.back(cmd_dist)
                        mc.stop()
                    movement_prev = local_movement
                elif drone == "Drone 1":
                    drone1_command = 'hover'
                    
            print(f"{drone}: Stopping")
            mc.land()
        
        print(f"{drone}: Stopped")
        time.sleep(2)
        logconf.stop()