cmdVel,thrust

[fangjir]

hello ,i want to use a PID to control a crazyflie ,but i am confused about that how to transfer the output(desired value of thrust from PID) to the thrust(0~2^16) of command "cmdVel".could you give me some advise?

[fangjir]

because i have something wrong with hover.launch about the motion capture ,so i just should Subscribe to topics from the miton capture ,and use the PID to control the uav.

[knmcguire]

Hi! I just converterd your question to a discussion, as that is the better place for this.

It would help us if you were a little bit more clear. What would you like to achieve?

• Sending velocity commands to the crazyflie (and let the internal PID controller that already exist handle it)
• Sending roll pitch and yaw commands to the crazyflie based on the output of an offboard pidcontroller?

[fangjir]

i want to choose the second one:
Sending roll pitch and yaw commands to the crazyflie based on the output of an offboard pidcontroller?
in this case ,how to do about the thrust

[fangjir]

@knmcguire hi
Sending velocity commands to the crazyflie (and let the internal PID controller that already exist handle it)
in this case ,Is it run through this command（start_linear_motion(self, velocity_x_m, velocity_y_m, velocity_z_m, rate_yaw=0.0):）

[knmcguire]

Alright... so not sure what you want to achieve but here is info for both:

/cmd_vel_legacy topics is for roll/pitch/yaw/trust are being handled by this callback:

crazyswarm2/crazyflie/scripts/crazyflie_server.py

Lines 825 to 835 in ad90477

	def _cmd_vel_legacy_changed(self, msg, uri=""):
	"""
	Topic update callback to control the attitude and thrust
	of the crazyflie with teleop
	"""
	roll = msg.linear.y
	pitch = -msg.linear.x
	yawrate = msg.angular.z
	thrust = int(min(max(msg.linear.z, 0, 0), 60000))
	self.swarm._cfs[uri].cf.commander.send_setpoint(
	roll, pitch, yawrate, thrust)

/cmd_hover topics is for velx/vely/height are being handled by this callback:

crazyswarm2/crazyflie/scripts/crazyflie_server.py

Lines 837 to 847 in ad90477

	def _cmd_hover_changed(self, msg, uri=""):
	"""
	Topic update callback to control the hover command
	of the crazyflie from the velocity multiplexer (vel_mux)
	"""
	vx = msg.vx
	vy = msg.vy
	z = msg.z_distance
	yawrate = -1.0*degrees(msg.yaw_rate)
	self.swarm._cfs[uri].cf.commander.send_hover_setpoint(vx, vy, yawrate, z)
	self.get_logger().info(f"{uri}: Received hover topic {vx} {vy} {yawrate} {z}")

There is also an example that takes the input of /cmd_vel and transforms it to /cmd_hover. You can find info for that in this tutorial: https://imrclab.github.io/crazyswarm2/tutorials.html#teleoperation-keyboard