Robotics is affecting more and more different sectors. In particular automation of agricultural processes could bring several advantages by reducing waste and human effort, that's why several robots to perform a wide range of agricultural tasks are in development. However, the design of a multi-purpose robot for vineyard operations presents still some challenges like its hardware adaptability and compatibility. To tackle some of these challenges, this paper presents the conceptual design of a modular autonomous mobile robot for vineyard operations. The aim of this work is to provide design principles for a modular robot able to perform multiple tasks that are common for vine growers, such as green pruning, winter pruning and spraying. The main advantages of such a robot are multiple. First, it can be considered eco-friendly as it can reduce chemicals consumption, polluting emissions and soil compaction. Second, it can minimize the need for manpower, that means less repetitive tasks to be done and less exposure to chemicals. Finally, its modularity can allow to easily switch tools and to re-design some modules with little changes to other features. For designing this system, we adopted a design thinking approach. Thus, first requirements and concepts were created and evaluated via interviews of vine growers. Second, concepts were classified upon the evaluation. And last, the winning prototype was designed with Solidworks CAD software and evaluated on its mechanical and functional properties via a FEM analysis. By using this method, we have developed an initial design for a multipurpose robot that concentrates on the drive system and the serial hybrid powertrain design, the selection of the structure, the tool design, and their incorporation with the frame, as well as an initial estimation of the mass to conduct a preliminary FEM static analysis of the frame. As a result, we have evaluated the feasibility of the concept and identified the key features of all subsystems. Therefore, this study lays the groundwork for creating a versatile and effective robot that can be used for multiple vineyard operations.