**3. Concept**

The concept of the search is separated into two parts: the object or target search and the flight search

### **3.1. Object search**

The task of the object search is to determine the amount and positions of the targets by fusing the results of the object detection with the current position of the quadrocopter (**Figure 7**). It manages the list of found objects and adds new ones if necessary.

**Figure 7.** Object search concept.

Whenever the object detection has a hit, the absolute position of this new target is computed by Formula (1),

Autonomous Quadrocopter for Search, Count and Localization of Objects http://dx.doi.org/10.5772/63568 7

$$\mathbf{P}\_r = \mathbf{P}\_o + \mathbf{P}\_\varrho + \mathbf{C}\_o \tag{1}$$

where *C<sup>O</sup>* is the offset between the camera and the centre of the quadrocopter or its position sensor, *PQ* is the current position of the quadrocopter and *PO* is the relative position of the found object determined by Formula (2)–(5):

$$\mathbf{P}\_o^{\ominus} = \frac{\mathbf{h}}{C\_h} \cdot \left(\mathbf{M} - \mathbf{Z}\right) \cdot \mathbf{C}\_w \tag{2}$$

$$\mathbf{M} = \begin{bmatrix} M\_x & M\_y \\ \frac{R\_x}{R\_x} & \frac{R\_y}{R\_y} \end{bmatrix} \tag{3}$$

$$\mathbf{Z} = \begin{bmatrix} 0.5 & 0.5 \end{bmatrix} \tag{4}$$

$$\mathbf{C}\_{w} = \begin{bmatrix} C\_{x} & \mathbf{0} \\ \mathbf{0} & C\_{y} \end{bmatrix} \tag{5}$$

*Mx* and*M <sup>y</sup>* in Formula (2) are the coordinates of the object's centre point determined by the object detection, *Cx* and *Cy* are the calibration width in *X* and *Y,* respectively, at a height of *Ch* , *h* is the current height and *Z* is a constant. *Cx* and *Cy* are determined by the true FOV of the camera. *Rx* and*Ry* are the resolution of the camera in the *X* ‐ and *Y*‐directions, respectively.

Next, the position *PT* is compared with all positions *<sup>i</sup> PT* with *i* indicating the index of the already accepted position. If the new position *PT* occurs within the masking area of any target *<sup>i</sup> PT*, it is discarded, otherwise it is accepted.

#### **3.2. Flight search**

The masking area (**Figure 6**) determines a square which is set around a found object to avoid multiple detections of the same target. It is determined by a distance named MA. During the search a target might be seen several times from different positions. Because of errors and noise the target is never detected exactly twice at the same position, and therefore would be considered as a new object multiple times. The masking area is subtracted and added to the *X*‐coordinate and the *Y*‐coordinate of every accepted target and it is proved if the newly detected target is located within one of these coordinates. If so, the newly detected target is discarded, otherwise it is accepted. Instead of a circle a square masking area can be chosen for

The concept of the search is separated into two parts: the object or target search and the flight

The task of the object search is to determine the amount and positions of the targets by fusing the results of the object detection with the current position of the quadrocopter (**Figure 7**). It

Whenever the object detection has a hit, the absolute position of this new target is computed

reasons of simplification and the FOV being also a square.

manages the list of found objects and adds new ones if necessary.

**3. Concept**

6 Recent Advances in Robotic Systems

**3.1. Object search**

**Figure 7.** Object search concept.

by Formula (1),

search

The task of the flight search is the waypoint generation. It ensures that the quadrocopter with a determined VFOV covers the whole search area at least once. The VFOV is a static parameter, which represents the FOV. A bigger FOV leads to less waypoints and a shorter flight search, while with a smaller FOV more waypoints and resulting pathways are created. In general, waypoints are not generated next to each other iteratively in small steps because of the bad flight performance of this approach [21], but with maximal distance according to the search strategy.

Then, the flight search is executed statically. That means the waypoint list is generated once at the beginning and it is not changed during the flight. The waypoint list is determined by the search strategy, the search area and the VFOV. **Figures 2**–**5** illustrate the effect of these parameters on the waypoint list.
