This week I worked with Jerry, Likai and Carol to test Crazyflie's thrust force. We used the method from  to measure the thrust force created by one motor and one propeller on crazyflie with different PWM signal. From the measurement, we conclude the system needs more than one motor to provide enough lift force. Therefore to creat a flyable single motor system, propoller, motor and battery on Crazyflie needs to be modified to increase thrust and reduce system weight.
I also compared the control loop introduced in Crazyflie 2.0 technical report  and paper , . Crazyflie used a cascade control loop to control the system. The outer loop of crazyflie controller controls the position of the system and the inner loop controls the attitude. Both loops in the controller are PID controllers. The control states were readed from sensors. Paper  proposed a method to control a quadrocopter losing one, two and three propellers. The control strategy controls the quadrocopter spinning about an fixed axis with respect to the vehicle,and the axis is tilted for translational control. Although successfully implement the control algorithm on quadrocopter losing one and two propellers, losing three propellers case cannot provide enough thrust to lift the quadrocopter. Therefore this case was not tested on real quadcopters but only validated using simulation. The control states were readed from positioning system. Using similar control algorithm as , paper  proposed a controllable flying vehicle with a single moving part. This system used a cascade control loop, with a outer PID controller controlling the position and an inner LQR controller controlling reduced attitude.
-  https://wiki.bitcraze.io/misc:investigations:thrust
-  Carlos Luis, Jérôme Le Ny. (2016) Design of a Trajectory Tracking Controller for a Nanoquadcopter.
-  Mueller, M. W., & Dandrea, R. (2014). Stability and control of a quadrocopter despite the complete loss of one, two, or three propellers. 2014 IEEE International Conference on Robotics and Automation (ICRA).
-  Zhang, W., Mueller, M. W., & Dandrea, R. (2016). A controllable flying vehicle with a single moving part. 2016 IEEE International Conference on Robotics and Automation (ICRA).