# Development of an Insect-like Flapping-Wing Micro Air Vehicle with Parallel Control Mechanism
## 4 Experimental Results
### Force and Torque Measurement  
Some previous research has examined the force/torque (F/T) measurement system for FMAV [32, 34]. Drawing on these designs, an F/T measurement system based on 6-axis sensors (model Nano17, ATI Industrial Automation, Apex, NC, USA) was built to detect  
Figure 14: The wing rotation and flapping angle in one flapping cycle. Three curves indicate the angles at different positions of the leading edge. Figure 13: The decoupler used in attitude control. the control torque at different control inputs. Figure 15 shows the F/T system for the lift and control torque measurements. Figure 15a shows the connection between the sensor and the prototype. The test plate of the sensor was fixed to the FMAV and the fixing plate was fixed to the base. The base was padded away from the ground and the prototype was inverted to reduce the ground effects. Figure 15b shows the connection of the peripherals. A two-channel DC supply powered the prototype. One channel provided the required voltage for the motor of the flapping-wing mechanism and another channel provided 3.7 V voltage for the servos of the control mechanism. A microcontroller outputted the PWM signal needed to control the servos. The initial data obtained by the sensor were sent to the interface devices to solve, and the solved F/T data were acquired by DAQ. Figure 16 shows the setup for control torque generated by the trailing edge movement using the F/T measurement system. Figure 16a shows that the flapping wing mechanism was fixed to the fixture with an adjustment board. The adjustment plate had a set of holes to fit the trailing edge rod that allowed the trailing edge to be placed in the expected position. Figure 16b shows the correspondence between the trailing edge movement directions and the control torque. Figure 16c shows how to adjust the position of the trailing edge during the test and defined the commands of three torques. Three control commands corresponded to three sets of experiments and each set contained five experiments. The circles indicate the corresponding position of the trailing edge and the numbers indicate the order. We set the minimum and maximum control commands for the first and last experiment of each group. The trailing edge moved 1.5 mm per experiment. Figure 15: F/T measurement system for lift and total control torque. (**a**) The connection of prototype and sensor. (**b**) The components of the F/T measurement system. Figure 17 shows the relationship between lift produced by the flapping-wing mechanism and input voltage. A max lift of 34 gf was detected at 4 V and this figure shows the strong linearity of voltage and lift. The result indicates that the designed flapping wing mechanism can provide sufficient lift for the flight of FMAVs. Figure 16: F/T measurement system for control torque produced by trailing edge movement. (**a**) The connection of flapping wing mechanism and sensor. (**b**) The correspondence between the trailing edge movement and control command. (**c**) The position of the trailing edge under different control commands. Figure 17: Lift–voltage relationship of flapping wing mechanism. Figure 18 shows **M\({}_{\textbf{t}}\)**, the control torque produced by the trailing edge movement. As the roll command increases, the roll torque increases while the pitch and yaw torque changed little and showed no tendency. Roll and yaw followed the same pattern as pitch. The maximum and minimum roll torque were about 1.6 Nmm and \(-\)1.6 Nmm, respectively. The maximum and minimum pitch torque were about 1.3 Nmm and \(-\)2 Nmm, respectively. The maximum and minimum yaw torque were about 0.6 Nmm and \(-\)0.6 Nmm, respectively. The result verifies the relationship between **M\({}_{\textbf{t}}\)** and trailing edge movement as represented in Equation (12). **M\({}_{\textbf{t}}\)** and input **U** were linearly related and the coupling between the individual control inputs was low.