Sim2Real by Robotech NITK

• The script initializes the simulation via the Crazyswarm class.
• It retrieves the list of drones (allcfs) and a timing helper (timeHelper).
• Commands are issued to take off (to 1.0 m), hover, and then land (to 0.0 m), with delays ensuring each phase completes.

Stage 2: Trajectory Tracking (Single Drone)

3.1 Objective:

3.2 Boilerplate Code

#!/ usr/bin/env python
"""
Stage 2: Single Drone Trajectory Tracking
This script commands a single drone to take off , move to a new position using a
smooth trajectory ,
and then land .
"""
import time
from crazyswarm import Crazyswarm
def stage2_trajectory_tracking () :
print (" Stage 2: Initializing simulation ...")
swarm = Crazyswarm ()
allcfs = swarm . allcfs
timeHelper = swarm . timeHelper
# Takeoff : Reach 1.0 meter altitude
print (" Taking off ...")
allcfs . takeoff ( targetHeight =1.0 , duration =2.0)
timeHelper . sleep (4.0)
# Trajectory : Move to a new position (e.g. , [1.0 , 1.0 , 1.0])
print (" Executing trajectory ( goTo )...")
goal_position = [1.0 , 1.0 , 1.0]
allcfs . goTo ( goal = goal_position , yaw =0.0 , duration =3.0)
timeHelper . sleep (4.0)
# Hover for 3 seconds at new position
print (" Hovering at new position ...")
timeHelper . sleep (3.0)
# Land
print (" Landing ...")
allcfs . land ( targetHeight =0.0 , duration =2.0)
timeHelper . sleep (3.0)
print (" Stage 2 complete : Trajectory tracking finished .")
if __name__ == " __main__ ":
stage2_trajectory_tracking ()        

3.3 Detailed Explanation

• Takeoff: The drone is commanded to ascend to 1.0 meter in 2 seconds. A delay allows it to stabilize.
• Trajectory Execution: The goTo command calculates a smooth trajectory from the current position to [1.0, 1.0, 1.0].
• Hovering and Landing: After reaching the target, the drone hovers briefly before landing.
• Observation: The simulation window should display the drone taking off, following the trajecetory, hovering, and landing.

Stage 3: Coordinated Flight (Multiple Drones)

4.1 Objective:

4.2 Boilerplate Code

#!/ usr/bin/env python
"""
Stage 3: Coordinated Flight for Multiple Drones
This script commands multiple Crazyflies to take off , fly in a coordinated
formation , and land simultaneously .
"""
import time
from crazyswarm import Crazyswarm
def stage3_coordinated_flight () :
print (" Stage 3: Initializing simulation for multiple drones ...")
swarm = Crazyswarm ()
allcfs = swarm . allcfs
timeHelper = swarm . timeHelper
# Set all drones to the same group (e.g. , group mask = 1)
for cf in allcfs . crazyflies :
cf . setGroupMask (1)
# Synchronized Takeoff
print (" Coordinated takeoff ...")
allcfs . takeoff ( targetHeight =1.0 , duration =2.0)
timeHelper . sleep (4.0)
# Coordinated maneuver : Form a line formation
print (" Forming a line formation ...")
for cf in allcfs . crazyflies :
offset = [0.5 * cf .id , 0 , 0]
current_pos = cf . position ()
goal = [ current_pos [0] + offset [0] , current_pos [1] , current_pos [2]]
cf . goTo ( goal = goal , yaw =0.0 , duration =3.0 , relative = False , groupMask =1)
timeHelper . sleep (5.0)
# Synchronized Landing
print (" Coordinated landing ...")
allcfs . land ( targetHeight =0.0 , duration =2.0)
timeHelper . sleep (3.0)
print (" Stage 3 complete : Coordinated flight achieved .")
if __name__ == " __main__ ":
stage3_coordinated_flight ()        

4.3 Detailed Explanation

• Group Setup: Each drone is assigned a group mask (1) so that broadcast commands affect all drones.
• Synchronized Takeoff and Landing: The entire swarm takes off and lands simultaneously.
• Coordinated Maneuver: The drones are commanded to form a line by moving to positions offset by their IDs.
• Observation: Verify in simulation that all drones take off, form the line, and land simultaneously

Stage 4: Dynamic Trajectory Control

5.1 Objective:

5.2 Boilerplate Code

#!/ usr/bin/env python
"""
Stage 4: Dynamic Trajectory and Re - planning
This script demonstrates advanced control where a single drone follows a circular
trajectory
with continuous re - planning .
"""
import time
import numpy as np
from crazyswarm import Crazyswarm
def stage4_dynamic_trajectory () :
print (" Stage 4: Initializing simulation for dynamic trajectory ...")
swarm = Crazyswarm ()
allcfs = swarm . allcfs
timeHelper = swarm . timeHelper
# Use the first Crazyflie
cf = allcfs . crazyflies [0]
# Takeoff
print (" Taking off ...")
cf . takeoff ( targetHeight =1.0 , duration =2.0)
timeHelper . sleep (4.0)
# Dynamic trajectory : circular motion in the XY plane
print (" Executing dynamic circular trajectory ...")
center = np . array ([1.0 , 1.0])
radius = 0.5
duration = 10.0
steps = 50
dt = duration / steps
6
for i in range ( steps ) :
theta = 2 * np . pi * i / steps
pos_x = center [0] + radius * np . cos ( theta )
pos_y = center [1] + radius * np . sin ( theta )
pos = [ pos_x , pos_y , 1.0]
cf . cmdPosition ( pos , yaw =0.0)
timeHelper . sleep ( dt )
# Hover and then land
print (" Hovering ...")
timeHelper . sleep (2.0)
print (" Landing ...")
cf . land ( targetHeight =0.0 , duration =2.0)
timeHelper . sleep (3.0)
print (" Stage 4 complete : Dynamic trajectory executed .")
if __name__ == " __main__ ":
stage4_dynamic_trajectory ()       

5.3 Detailed Explanation

• Takeoff: The drone ascends to 1.0 meter and stabilizes.
• Circular Trajectory: A loop computes a circular path using numpy. The drone’s position is updated continuously using cmdPosition to follow the circle.
• Hover and Land: After completing the circle, the drone hovers briefly before landing.
• Observation: In simulation, the drone should follow a smooth circular trajectory.

Stage 5:Advanced Swarm Behavior with Collision Avoidance.

6.1 Objective:

6.2 Boilerplate Code

#!/ usr/bin/env python
"""
Stage 5: Advanced Swarm Behavior with Collision Avoidance
This script demonstrates advanced behavior where multiple Crazyflies execute a
coordinated maneuver
and dynamically adjust trajectories to avoid simulated collisions .
"""
import time
import numpy as np
from crazyswarm import Crazyswarm
7
def compute_avoidance_offset ( current_pos , desired_pos , other_positions ,
min_distance =0.3) :
"""
Computes a simple repulsive offset to maintain a minimum distance from other
drones .
For each drone closer than min_distance , a repulsive force is applied
proportional to the difference .
"""
avoidance = np . array ([0.0 , 0.0 , 0.0])
for pos in other_positions :
vec = np . array ( desired_pos ) - np . array ( pos )
distance = np . linalg . norm ( vec )
if distance < min_distance and distance > 0:
avoidance += ( vec / distance ) * ( min_distance - distance )
return avoidance
def stage5_advanced_swarm () :
print (" Stage 5: Initializing simulation for advanced swarm behavior ...")
swarm = Crazyswarm ()
allcfs = swarm . allcfs
timeHelper = swarm . timeHelper
# Set group mask for coordinated control
for cf in allcfs . crazyflies :
cf . setGroupMask (1)
# Synchronized takeoff : All drones ascend to 1.0 meter .
print (" Coordinated takeoff for swarm ...")
allcfs . takeoff ( targetHeight =1.0 , duration =2.0)
timeHelper . sleep (4.0)
# Define target formation ( example formation )
target_formation = [
[1.0 , 1.0 , 1.0] ,
[1.2 , 1.0 , 1.0] ,
[1.0 , 1.2 , 1.0] ,
[0.8 , 1.0 , 1.0] ,
[1.0 , 0.8 , 1.0]
]
steps = 30
dt = 0.5
# Dynamic formation and collision avoidance loop
for step in range ( steps ) :
for i , cf in enumerate ( allcfs . crazyflies ) :
target = target_formation [ i % len ( target_formation ) ]
current_pos = np . array ( cf . position () )
desired = np . array ( target )
error = desired - current_pos
other_positions = [ np . array ( other_cf . position () ) for j , other_cf in
enumerate ( allcfs . crazyflies ) if j != i ]
avoidance = compute_avoidance_offset ( current_pos , target ,
other_positions )
new_setpoint = current_pos + 0.1 * error + avoidance
cf . cmdPosition ( new_setpoint . tolist () , yaw =0.0)
timeHelper . sleep ( dt )
# Hover in formation for 2 seconds
print (" Hovering in formation ...")
8
timeHelper . sleep (2.0)
# Synchronized landing : All drones descend to 0.0 meters .
print (" Coordinated landing ...")
allcfs . land ( targetHeight =0.0 , duration =2.0)
timeHelper . sleep (3.0)
print (" Stage 5 complete : Advanced swarm behavior executed .")
if __name__ == " __main__ ":
stage5_advanced_swarm ()

6.3 Detailed Explanation

• Takeoff: The drone ascends to 1.0 meter and stabilizes.
• Group Coordination: All drones are assigned a group mask (1) to ensure they receive synchronized takeoff and landing commands.
• Synchronized Takeoff: The swarm takes off simultaneously to 1.0 meter.
• Dynamic Re-planning Loop: For each time step:
  • Each drone calculates its error relative to a predefined target formation.
  • A collision avoidance offset is computed based on the positions of neighboring drones.
  • These factors are combined to update the drone’s setpoint using cmdPosition, ensuring smooth and safe re-planning.
• Synchronized Landing: The swarm lands in unison after the maneuver.
• Observation: The simulation should display all drones taking off, dynamically adjusting their positions to form the target formation while avoiding collisions, and landing simultaneously

Submission Guidelines

• A public Git repository with source code.
• A README with setup instructions and execution steps.
• A 5-minute video demonstrating the simulation results.
Submit here

References

• Crazyswarm Documentation
• Python API Reference
• Crazyflie Firmware and CRTP Protocol