2.1 Design and Assembly of Multi-Sensor Fusion UGVs for Greenhouse

The design of the UGV aims to create a robust and efficient system specifically tailored for greenhouse environments (Xiong et al., 2020). The UGV integrates a multi-sensor system, a computational unit, and a motion system. Fig. 1 presents a comprehensive depiction of the UGV’s structural arrangement along with its hardware components.
The fusion of information from multiple sensors contributes to a more comprehensive and precise understanding of the environment, which is particularly advantageous in complex scenarios like greenhouses. The cornerstone of the sensor suite is a 16-channel LiDAR. It can accurately capture environmental data up to 100 meters away, with its performance less affected by changes in illumination compared to other sensors. An ICM-42605 IMU is incorporated into the UGV to provide accurate orientation and acceleration data. Additionally, the system incorporates a customized 400-line optical encoder, offering precision that is 36.36 times higher than conventional 11-line photoelectric encoders. Both the IMU and the optical encoder are centrally located on the UGV, optimizing data acquisition accuracy and minimizing potential errors in orientation and position estimation. This significant enhancement in precision improves the reliability of odometry computations. Moreover, accurate pose estimation significantly enhances the quality of map construction.
The incorporation of multiple sensors increases computational requirements. Consequently, an Intel NUC is installed as the primary processing unit for the ROS, tasked with managing the sensor data and executing the autonomous navigation algorithms. Moreover, an ESP32 is equipped to generate a Wi-Fi signal, enabling external computers to receive real-time information from the UGV. Additionally, a STM32 microcontroller is utilized as the motion controller for the robot.
A motion system has been engineered to address the complex ground features of greenhouse environments. It is a custom-designed LAUGV platform, as depicted in Fig. 1. The MiniUGV20C suspension of it delivers superior shock absorption on bumpy terrains, while the large size of wheels provides stronger traction on uneven terrains. Additionally, a 10000mAh battery with a current output of 20A is incorporated, ensuring sufficient power for long-duration operations. In practical tests, this UGV demonstrated an ability to work continuously for up to 7 hours in greenhouse conditions, extending working hours without the need for frequent recharging.