Performance Improvement of a Vineyard Robot through its Mechanical Design

Abstract. The VineRobot project ended in May 2017 with the field evaluation of its ultimate version, which contains all the lessons learned along the project since 2014. Experience showed that agricultural robots cannot overlook traction and mechanics in favor of electronics and computing; rather, the synergism of coupling an efficient drive chain with an intelligent core of reduced complexity may yield remarkable results. The mechanical improvements incorporated to the final prototype comprised a new body frame with a redesigned suspension system, and a larger reduction ratio in the electrical motors powering the wheels, which now grant much better traction at the expense of limiting the top speed of the robot. The electric supply has been enhanced by two solar panels, which additionally provide a visual battery control to avoid dangerous power drops when operating in automatic mode. A faster computer processing images at higher rates resulted in greater agility under autonomous navigation. In terms of functionality, user controls have been simplified, with only two speeds and an automatic detection of the row spacing to better adjust navigation parameters. All these new features resulted in lower vertical accelerations on the robot body, and a more stable behavior of autonomous navigation along the rows where key parameters will be measured. This paper focuses on the improvements carried out on the suspension and steering systems, in particular the implementation of springs with a lower elastic constant and a new geometry to absorb terrain-induced shocks, and an optimized steering mechanism that provides wheel turns up to 29º, granted by a positive camber angle plus a caster angle of approximately 5º.