How to mimic the batbot’s flying mechanism?

 To monitor the batbot’s flying mechanism, we used the IR sensors. Flight behavior was monitored with two high-speed IR-sensitive video cameras mounted in corners of the room (Figure 1). Moreover, by using sensor and camera, it is possible to reconstruct three-dimensional wing and body kinematics (Figure 2). The top of figure 2 shows frames extracted from high speed video of landing bat. Shown on the bottom are the corresponding frames of the reconstructed 3D wing and body kinematics. From These data, we can calculate the inertia of body and wing, and the kinematics of wing. From now on, we consider the Batbot as two parts. First is kinematics of Batbot and second one is Inertia of Batbot.

Figure 1. IR sensors and Cameras for detecting the bat's flying motion

Figure 2. Reconstruction of bat's flying motion

1)     Kinematics

The frames of Batbot is derived from the structure of skeleton of bat (figure3). Moreover, by observing the bat’s flying, it is possible to determine DH(Denavit-Harthenberg) parameters(Table 1). With this data, the position velocity vector of Batbot’s wing can be determined by using forward kinematics.

 This equation is about how to calculate the basic rotation matrix(r) and the position vector (p). Therefore, we can calculate the wing trajectories and maneuvers. In addition, by calculating, it is possible to analyze the forward flight and turning flight.

Figure 3 (a). The frames of Batbot

Figure 3 (b). Whole structure of Batbot

Table 1. DH-parameters

a.     Forward flight

The wingbeat cycle of bat is consists of up-stroke and down-stroke. Moreover, when wings going upward, bats contract wings, and when wings going downward, bats extend its wings. Therefore, q3 movement is very important because batbot contracts and extends the wings to reduce the drag force. In addition, observing the trajectory of bat’s wing, we can determine the wing’s motions as function of time.

b.     Turning flight

To turn, bats roll around its cranio-caudal axis and rolling makes bats move its center of mass itself. To achieve rolling motion, one wing should contract and extend less proportion compared to the other.

 2) Inertia

 To calculate inertia of batbot, Equations of Motion(EOM) are formulated by Newton-Euler formalism using spatial operator. Spatial operators leads to 6-D physical quantities that consists of angular and linear aspects of rigid body and forces. Using these variables, we can get the information of position, velocity, acceleration, and force at each joint and inertia of whole body. Table 2 shows the algorithm of calculation.

Table 2. Algorithm for computing the inertia model

References:

1. J.D.Colorado, 2012, BaTboT: a biologically inspired flapping and morphing bat robot actuated by SMA-based artificial muscles, Universidad Politecnica de Madrid

2. TIAN X, MIDDLETON K, GALVAO R, ISRAELI E, ROMERE ASULLIVAN A, SONG A, and SWARTZ S, 2006, Direct measurements of the kinematics and dynamics of bat flight

3. S.STERBING-DAngelo M, CHADHA C, CHIU B, FALK B, XIAN J, BARCELO J.M, ZOOK and C.F. MOSS, 2011, Bat wing sensors support flight control