## 3 Dynamic Model and Control
### Actual Motion Process Experiments (Including Bionic Adsorption)  
The main working state transitions of the robot (LAWCDR) are air-wall transformation and land-air transformation. The air-wall transformation process includes the flight adsorption process and the inverse process. The robot takes off from the ground, hovers at a height of 1 m, flies to the front of the wall, and performs flight adsorption. Firstly, the robot adjusts the servos to the preparation state to reduce the reaction time of performing the adsorption action. Secondly, the robot adjusts its heading to face the wall. Thirdly, the robot flies toward the wall at a slow, desired speed. When the wheels contact the wall, the shock absorbers are compressed to further adjust the robot's heading. Fourthly, the flight control detects the contact. The servos horizontally stretch out the suction cup to contact the wall and the robot finally completes the flight adsorption process. The robot performs a fast contact detection through the IMU. Once the acceleration of the \(x\)-axis that exceeds a threshold momentarily is detected, the robot controls the servos to start moving from the preparation position and stretches out the suction cup to contact the wall. As shown in Figure 18, after 138 s, the robot contacts the wall, and the actual position of the robot reaches 2 m without further change (as shown in the red line). The \(x\)-axis acceleration (as shown in the yellow line) steps from 0 to 20 m/s/s, exceeding the threshold value (8 m/s/s). The robot imitates a gecko for adsorption as shown in Figure 19, where (a) the robot is hovering in the air and the suction cup moves to the preparation state for adsorption. (b) The robot starts to fly toward the wall. (c) The front wheels start to contact the wall (the contact point between the right wheel and the wall is the blue point). The shock absorbers start to work, adjusting the robot's heading. (d) The suction cup driven by the servos moves towards the painted wall. As shown in Figure 19e,f, the suction cup contacts the wall (the contact point between the suction cup and the wall is the red point) and a negative pressure environment is established. As shown in Figure 20, the robot adjusts the desired attitude angle from 0 degrees to \(-25\) degrees after contact is detected at 138 s. The desired and actual roll angles remain at about 0 degrees. The actual pitch angle changes from 0 to \(-25\) degrees, and a horizontal component force is applied to the wall. This assures that the wheels are attached to the wall before the suction cup contacts the wall. During the roost state, the desired pitch angle is 0 and the rotors stop working. The actual pitch angle of the robot is kept at \(-10\) degrees due to gravity. Figure 18: Process of the IMU-detecting robot contacting the wall. The angle curves of servo 1 and servo 2 during the adsorption process are shown in Figure 21. When the contact is detected, the angle of servo 1 changes from 0 degrees to 24.5 degrees. The angle of servo 2 changed from 93 degrees to 41 degrees. Therefore, the servos keep horizontally stretching out the suction cup to contact the wall. Figure 19: Robot flight adsorption step diagram (the red point is the contact point between the suction cup and the wall, and the blue point is the contact point between the right wheel and the wall). Figure 20: Attitude curve of the robot. (The different working states are divided by the yellow dotted line). The trajectory of the land and air transformation process of the robot is shown in Figure 22. The experiment to verify the land-air motion movement capability of the robot was carried out. The robot follows a planned trajectory of ground motion, air flight, takeoff, and landing. The robot moves from point A to point B, takes off at point B and moves to air point C, then flies through points D and E to point F, lands at point G, and then moves to points H and I on the ground. The entire movement process is completely autonomous. Figure 21: Servo angle curve of the robot.