## 6 Experiment and Analyses  
For the purpose of this project, the details of the physical mechanism were omitted. To verify the accuracy of the string drive mechanism simulation, high-speed photography was used to capture the flapping trajectory of the physical mechanism, which was then compared with the simulation results. Since the validation target of this part was the accuracy of the drive mechanism simulation and to eliminate the influence of inertia under high-speed flapping conditions, the drive mechanism was set to operate at a lower voltage. This was captured under high-speed photography (5000 fps) at a voltage of 1.5 V. As shown in the schematic diagram of the testing environment (Figure 20), two high-speed photography captures of the flapping trajectory from different angles were conducted, where the blue dots represent the marker points that were marked on the carbon fiber rods used for installing wings with a white oil-based ink. This was performed to  
Figure 19: (**a**) Complete comparison between the smoothed cam trajectory and the circular trajectory. (**b**) Practical design of cam mechanism using the parameters detailed above from Solidwork. Figure 18: (**a**) Comparison between the simulated cam mechanism trajectory with the circular trajectory. (**b**) Comparison between the smoothed cam mechanism trajectory and the circular trajectory after using an adaptive design. facilitate a spatial position calibration, which was achieved with three-dimensional video processing software. Through high-speed photography captures of the actual mechanism, as well as a reproduction of the three-dimensional space position, the motion trajectory of the marker points in three-dimensional space could be obtained. Figure 21 shows the three-dimensional spatial motion trajectory of the four marker points on the two carbon fibers. When compared with the string-based mechanism simulation trajectory with the same design parameters, it can be seen from Figure 22 that, under the condition of low flapping speed and minimal inertia influence, the actual flapping trajectory of the cam mechanism was approximate to the simulation flapping trajectory, which proves the simulation accuracy of the string drive flapping mechanism; thus, it can be used as a guide for physical design. Figure 21: The actual flapping trajectory obtained by processing video, captured by high-speed photography, is presented in three dimensions. Point 1–2 is on the left carbon fiber rod, and Point 3–4 is on the right carbon fiber rod. Figure 20: Environment for the experiment. Also, a phase difference between the left and right flapping was observed. The reason for this was because the string was trying to keep an equal phase, specifically due to the elongation error of the string and the error of manual installation. In the subsequent design, a device for adjusting the tightness of the string was added to keep the tension of the string, which will thus decrease the error in the manual installation. To verify the superiority of the circle roller over the cam roller, we designed an experiment to compare the energy consumption difference between the different roller mechanisms. We added the same load (8 cm long and a 0.75 mm radius carbon fiber rod) to the circular roller and the cam roller, as well as drove them with the same DC motor at the same driving voltage (which were 2 V and 2.5 V). The current of motor was tested using a hall-effect high-sensitivity current probe, and the force torque fluctuations of the mechanism could be analyzed by comparing the currents of the DC motor to drive the circular roller and cam mechanism. The reason for this was due to the fact that the output power of a DC motor is positively correlated with the current at the same voltage.