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.