Aerial Rock-and-Walk

This directory contains code for the aerial experiments, including:

• rnw_ros and rnw_msgs are specific to rock-and-walk.
• uwb_mocap_broadcast for transmitting mocap information.
• djiros and n3ctrl for the underlying quadrotor control

Hardware Requirements

• DJI N3 Flight Controller
• DJI Manifold 2-G Onboard Computer
• OptiTrack Motion Capture System
• 2 x Nooploop UWB Transmitter
• Logitech F710 Wireless Gamepad
• Custom end-effector for aerial rock-and-walk

Run as hardware-in-the-loop (HIL) simulation

1. Connect DJI N3 Autopilot to a PC/Mac with DJI Assistant installed
2. Enter simulation in DJI Assistant
3. roslaunch rnw_ros sim.launch

UWB Config Channel #9 is Drone #1 Channel #4 is Drone #2

Run real experiments

1. Open OptiTrack
2. roslaunch rnw_ros ground_station.launch on ground station i.e. your laptop
3. SSH into the aircraft and roslaunch rnw_ros real.launch

Pre-Flight Checklist

Make sure UAV odometry is correct

• Fly it using real.launch, hover and moving around

Make sure ConeState is correct

• Calibrate the center point and tip point using roslaunch rnw_ros mocap_calib.launch
• Calibrate ground_z by placing a marker on the ground
• Run roslaunch rnw_ros check_cone_state.launch, check the cone state visually
• Check the estimated radius and the true radius, make sure they mactch.

Make sure GripState is correct

• Calibrate flu_T_tcp using roslaunch rnw_ros mocap_calib.launch
• Run roslaunch rnw_ros check_grip_state.launch, see does it make sense intuitively.
• Move the quadrotor along cone's shaft, see is the estimated grip_depth correct, adjust flu_T_tcp to make grip_depth match reality.

Make sure rock-and-walk planning is correct

• make sure ConeState and GripState are correct following the instructions above
• run roslaunch rnw_ros check_rnw_planning.launch

Documentation

Control Flow

1. rnw_controller_node sends trajectory to rnw_traj_server_node

2. rnw_traj_server_node transform the trajectory into position command, send to n3ctrl_node

3. n3ctrl_node performs position control, sends attitude and trust commands to djiros_node

State Flow

1. OptiTrack sends out mocap for the aircraft and object through Ethernet.

2. ground_station.launch receives mocap from Ethernet and sends odometry to the onboard computer through UWB.

3. uart_odom receives odometry from the ground station, then publish to ROS

4. pub_cone_state_node reads odometry and configuration files, calculate cone_state, then publish to ROS

5. rnw_controller_node read cone_state, and performs rock-and-walk.

Playback

rosbag record -a is called by default, the .bag files can be retrieved after flight.

Inspect them using:

• playback.launch will replay the experiments in RViz.
• PlotJuggler
• MATLAB

Swarm Ground Station

Topics

/drone1

• /drone1/odom
• /drone1/traj
• /drone1/position_cmd
• /drone1/state

/drone2

• /drone2/odom
• /drone2/traj
• /drone2/position_cmd
• /drone2/state

/cone

• /cone/odom
• /cone/state

/rnw

• /rnw/start
• /rnw/state

Nodes

swarm_planner_node takes all /droneX/odom, and sets all /droneX/traj

traj_server_node takes /drone1/traj and sets /drone1/position_cmd

uwb_transceiver takes /drone1/odom and /done1/position_cmd and send it to the drone

Swarm Drone

Topics

/odom/uav

/position_cmd

/djiros/rc

Nodes

uwb_transceiver sets /odom/uav and /position_cmd

n3ctrl executes /position_cmd while monitoring /uav/odom and /djiros/rc

Configuration

In motion capture volumn, the max height drones can safely fly is $1.9$-$2.0$ meters.

placement

cone tip points out

left: drone1

right: drone2

Planner

step_direction value range: $\pm1$ , the tilting will be a rotation along $(0,0,\pm1)$ at $G$

take $+ 1$ step when $\phi < 0$, $\psi$ increasess

heavy object tip over at 25

steel object gain 60

exp9 for 45 120 exp8 for 45 90