# Winged Aerial Manipulation Robot with Dual Arm and Tail
## 2 Design of Winged Aerial Robot with Dual Arm and Tail
### Design of Winged Aerial Manipulation Robot  
The study of the anatomy of birds presented in [23] reveals that the structure of the wings can be assimilated to a manipulator with three links: upper arm (humerus), forearm (radius and ulna), and hand (carpometacarpus and digits). This makes possible the application of some design concepts and methodologies derived from the development of lightweight dual arms for aerial manipulation [5]. The winged aerial manipulator developed here follows a modular and bioinspired design approach, building the dual arm and tail with the micro-servo actuators described previously and with a simple frame structure manufactured in aluminum and with 3D printed PLA (polylactic acid) parts. The different structures of the arms can be seen in Figure 3, and their masses are indicated in Table 3.  
Figure 2: Customized micro-servo actuator based on Poloula micro-motor.  
The dual arm manipulator implements the kinematic configuration considered in [22], with three joints for end effector positioning (shoulder yaw, shoulder pitch, and elbow pitch), reducing the scale by half with regard to the human arm (250 mm reach), as motivated in [7]. Note that in this model, unlike our previous prototype, the joints are stiff in order to simplify the mechanics and reduce the weight (0.4 kg in total).  
The fuselage link consists of a hollow aluminum tube, 400 mm in length and 6 mm in \(\mathcal{O}\), attached to the shoulder structure, which supports the tail servo on the other end. The tail mechanism is built with a pair of V-shaped aluminum rods that can be rotated in the pitch angle, allowing the control of the orientation of the WAMR at this angle during the gliding maneuvers, whereas the rotation of the shoulder joints is used to generate lateral aerodynamic wrenches, as will be seen in Section 5.4.  
The batteries (2 x 1S, 320 mAh) and control electronics of the aerial robot are located in the fuselage frame. This includes the STM32F0 Nucleo microcontroller board, a BNO055 9-DOF IMU (inertial measurement unit), and an XBee module used as a wireless link with the GCS (ground control station) laptop. The hardware architecture is represented in Figure 4, while in Figure 5, the components are shown. It is interesting to compare this prototype to the compliant dual arm developed in [7], by which the reduction in the wiring due to the modular design approach of the micro-servos is noticeable. The arms provide around 0.15 kg lift load at the elbow joint, with a nominal operation time of around 15 min with the batteries.  
The whole body of the winged aerial robot is covered by a light nylon cloth attached to the forearm and upper arm links, the fuselage tube, and the tail rods to create the aerodynamic surfaces identified in Section 4. The total area is around 0.2 (m\({}^{2}\)). The cloth is arranged in such a way that it is stretched when the arms adopt the gliding configuration, but it can be folded without affecting the rotation of the joints during the manipulation phases. Since the nylon cloth lacks elasticity, it is necessary to introduce small folds close to the joints to facilitate its accommodation to the adopted pose when acting as a morphing wing.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Structure** & **Mass** & \(\mathbf{I_{xx}}\) & \(\mathbf{I_{yy}}\) & \(\mathbf{I_{zz}}\) & \(\mathbf{I_{yy}}\) & \(\mathbf{I_{zz}}\) & \(\mathbf{I_{yz}}\) \\ \hline Shoulder & 73 & 3240 & 133 & 3270 & 0 & 0 & 0 \\ Sh. pitch & 36 (\(\times\)2) & 50 & 44 & 47 & 0 & 0 & \(-\)3 \\ Upper arm & 37 (\(\times\)2) & 728 & 713 & 30 & 0 & \(-\)2 & 6 \\ Forearm & 12 (\(\times\)2) & 277 & 278 & 3 & 0 & 0 & \(-\)1 \\ Fuselage & 17 & 2603 & 2603 & 1 & 0 & 0 & 0 \\ Tail & 19 & 910 & 479 & 1387 & 0 & 0 & 0 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Mass (in (g)) and moment of inertia (in (g-cm\({}^{2}\)), relative to the center of mass) of the different structures of the winged aerial manipulation robot.  
Figure 3: Rendered view of the structure of the dual arm.