**3.2 Fusion of sensors**

The sensors attached to the robo-mower shown in **Figure 3** are listed in **Table 1**. The robo-mower has originally been equipped with built-in sensors. The 9-axis

**Figure 3.**

time (t), and then, estimation results *cst* ð Þ ð Þ are obtained using AI algorithms. The control parameter set at time ð Þ *t* þ Δ*t* for motors is given to the real robo-mower. This

This section describes the work vehicle used in the following discussions and experiments. A commercial robo-mower [8] is used as the experimental hardware for evaluating the proposed algorithms with the available fusion of sensors.

The exterior and the backside of the robo-mower are shown in **Figure 2(a)**. The system configuration is shown in **Figure 2(b)**. It has two kinds of motor controllers,

loop is repeated during the operation of the robo-mower.

**3. Work vehicles**

*Hybrid twin within work vehicles.*

*Robotics Software Design and Engineering*

**Figure 1.**

**Figure 2.**

**124**

*Robotic Lawn mower and target system configuration.*

**3.1 Robotic Lawn mower**

*Robotic Lawn mower with sensors and devices for development.*


**Table 1.** *Fusion of sensors.* inertial measurement units (IMUs), MPU-9250 [16], are attached inside and to the surface of the robo-mower to measure acceleration and angular acceleration. Six built-in sensors are available for measuring the corresponding parameters as shown in **Table 1**. Here the noise of sensors is negligibly small; however, outliers are excluded in the Digital Twin. The adequate fusion of these sensors is determined in each of the proposed algorithms, and this is verified in the experiments.

## **3.3 Estimation problem of Lawn grass lengths**

The estimation problem of lawn grass lengths and ground conditions is defined below. The problem is to estimate lawn grass lengths in real time using sensor fusion data. The objective function is to increase the accuracy of estimation.

The Estimation Problem.

**Input:** set of available sensors, robo-mower's specifications, set of areas labeled. long lawn grass, short lawn grass, and without lawn. grasses, some of which are specified as test areas.

**Output:** fusion of sensors necessary for estimation and estimation results for test areas.

**Objective Function:** maximization of estimation accuracy.
