Px4 control mode summary

Flow chart of attitude control , The outer ring produces an angular rate , The inner ring produces the desired acceleration （ Motor thrust ）.
The outer ring is positioned according to the desired position 、 Speed , Calculate and output the corresponding attitude information .
The attitude information output by the outer loop is used as the input of the inner loop , The inner loop calculates the desired acceleration .

ROS-mavros-PX4 Acceleration control

The original input of the flight control algorithm to be written is roll、pitch And propulsion , because PX4 It is not supported to input specific propulsion force , Use three-way acceleration （ The rotation matrix can be used for transformation ） Control . however PX4 Of setpoint_accel The actual control effect is very poor ,github Some people say it is not available .
Solution ： Refer to the... Of amu laboratory px4_command, Use attitude Output , For personal use cascade pid, To calculate the throttle Convert to attitude, Other methods in the project are basically accel->thurst->throttle->attitude, There are conversion functions for these quantities in the project . I have tried directly to （ Single value ） The propulsion force is converted into the throttle as a function , But it failed , Maybe not PID closed loop , It may also be that you don't understand one-way / Three directions thrust The specific meaning of ？

PX4 Control assignment in

Generally speaking , The control of rotary wing UAV is divided into Position loop control + Attitude loop control Two parts ：

• Position ring input
  • Set quantity ： Desired position 、 Expected speed 、 Expected acceleration, etc
  • State quantity ： The current position 、 Current speed
• Position ring output
  • Desired attitude angle （roll + pitch）、 Desired lift
• Attitude loop input
  • Set quantity ： Desired attitude angle （roll + pitch + yaw）、 Desired lift
  • State quantity ： Current attitude angle 、 Current angular velocity
• Attitude loop output
  • Expected torque （Mx、My、Mz）、 Desired lift （T）

PX4 Open source flight control position control analysis