# Research Progress on Synergistic Technologies of Agricultural Multi-Robots
## 4 Discussion  
In general, in the past 10 years, the synergistic technologies of agricultural multi-robots have achieved some research results, and multi-robot collaborative operations have been realized in specific agricultural scenarios. But with the increasing demand for agricultural operations, the following challenges in the application of multi-robots in agriculture still exist to be solved:  
* Flexible agricultural multi-robot system architecture  
Multi-robot architecture is the basis for collaborative operations of multi-robot systems. In the last decade, agricultural multi-robot systems have mainly focused on centralized or distributed architectures to accomplish collaborative operations under pre-defined conditions. Both architectures have their advantages and disadvantages, but as the number of robots increases (such as multiple aerial robots cooperating with multiple ground robots) and new agricultural operational needs increase (such as sampling in marine environments [131], cargo handling in hilly mountainous areas, pest control in orchards, etc. ), it is clear that the scalability and flexibility of multi-robot systems relying on only one architecture are limited. The advantages of centralized and distributed architectures are combined to form a hybrid architecture, or the application architecture is dynamically selected according to the task attributes, which can overcome the low performance caused by the self-centeredness in the distributed architecture and reduce the lack of control flexibility in the centralized architecture. * Fast and precise environmental perception  
In environmental awareness, positioning and sensor fusion answer the question of \"where am I\" and building a map answers the question of \"what's around me\", and the answers to these two questions are the prerequisites for robots to start their operations. The positioning and sensor fusion technologies of agricultural multi-robot are mostly used in large fields with unobstructed outdoor signals, where the communication between robots is normal and the robots can get accurate positioning, heading, speed, obstacles, and other information based on their sensors. However, considering the severe compaction of soil by large agricultural machines, the compression of application costs, and the promotion of this concept of refined agriculture, light, and small agricultural robots will be the trend of future development, which will make multi-robot positioning unable to continue to rely on the high-precision positioning of a particular robot or a particular sensor (e.g., GPS). Especially in case of robot failure or communication failure, how to ensure the accurate positioning of the remaining individuals and make the multi-robot system with good robustness is a problem that needs to be solved urgently. Mapping not only can accurately learn the information of detailed agricultural information, static obstacles, and the location of other robots but also can assign tasks and plan paths for multiple robots. The more accurate the agricultural information, the more accurate the operation objects will be, but this contradicts agricultural tasks that urgently need a fast response, which means that the time spent on the subsequent processing of information data reduces the real-time and flexibility of multi-robot operations. How to obtain dynamic agricultural information quickly and accurately and match it with the precise location of the operation object is another urgent problem in environment sensing. * Reasonable task assignment in real-time  
The task assignment is related to the multi-robot coordination and collaboration mechanism, and the simple zoning assignment of robots cannot adapt to the dynamically changing operational tasks. Also, the number of robots, operating time, and cost of robot operations need to be dynamically adjusted to the operating task. Even for the same type of robots, items such as fuel or electricity, fertilizers, herbicides, and pharmaceuticals can change differently depending on the target of the operation.