Progress and trend of agricultural robots based on WoS bibliometrics and knowledge graph

An agricultural robot system has been ever increasing to develop rapidly in the world, with the progress of the Internet of Things, big data, and artificial intelligence. This study aims to analyze the development of the global agricultural robot system using the domain knowledge map from the Web of Science core data and visualization software. Research findings were as follows: 1) Four stages were roughly divided in the agricultural robot research. 2) The United States, China, Spain, Germany, Japan, Italy, and the United Kingdom presented the most research outputs, and the closest cooperation was found between China and the United States, the United States and Spain, China and Japan. 3) The agricultural robot research in China was about 10 years later than that of the United States, but there was a rapid increase in the most achievements “quantity and quality”, especially in the fruit picking robot. The key technologies, such as stereo vision technology, have been reported almost simultaneously in China and the United States. 4) The development of the agricultural robot system followed the following path: from simple to complex, and gradually to the multi-functional, intelligent autonomous unmanned system. Correspondingly, the development of the agricultural robot system from the birth, shape and growth to a period of rapid development, was great benefit from the big data, artificial intelligence, internet of things, cloud computing, mobile Internet, as well as the new generation of information and communication technology. Now, the agricultural robot has stepped into a period of accelerated development in the new era. The future agricultural robot can be more smart and intelligent, from one single function to the integration of intelligent perception, intelligent decision-making, and intelligent execution of agricultural robot system. The more extensive development of agricultural robots can be extended from the special robots to multi-functional mechanization, automation, and intellectualization suitable for the agricultural production, particularly from the whole mechanization of the same crop production to the comprehensive large-scale intensive mechanization of different varieties of crops development needs. The application of agricultural robots has been developed from a single robot to a group operation system with the intelligent cooperation of multiple robots, such as swarm UAV, harvesting robot group, robot group, and robot team. The application scenarios have been more efficient and competitive in the large-scale cooperative operation of agricultural robots. The unmanned intelligent agricultural robot can be the development trend to cope with the agricultural labor shortage and machine generation. Man-machine cooperation and man-machine integration can also bring the respective strengths of new farmers and agricultural robots to achieve the common growth of man-machine. Consequently, some recommendations were made to strengthen basic research, and break through the restrictions and blockades of algorithms, models, materials, and processes, particularly for the high-level scientific and technological self-reliance in the field of agricultural robots. It is very necessary to accelerate the implementation of the development strategy of agricultural robots during this time. The level of intelligence of agricultural robots needs to be further improved for the stability, high quality, and high efficiency of operating performance suitable for various operating environments. In addition, the decision making on the supportive and guiding policies and the investment can also be critical to strengthen the research and talent team, thereby promoting sustainable and healthy development in the application of agricultural robot technology and equipment.