Ergonomic and compact armrest of agricultural tractors: Innovative methods to design an ergonomic armrest

Armrest in tractors is like a control dashboard for trains or airplanes; it is fundamental for managing and properly setting the machine. For this reason, there is the need to adjust it for each operator’s size and application. Nowadays, armrests are usually very big and intrusive, because they are full of controls and sometimes they are not really comfortable for each user size and need. Furthermore, agricultural equipment is often used under difficult conditions: steep terrain and extreme weather conditions require products able to guarantee total safety and maximum comfort, minimizing the risk of human error caused by excessive fatigue. The aim of the project is to create an “ergonomic - compact armrest”, focused on the users’ need, with the application of Ergonomics and Human Machine Interface (HMI) principles, shifting the focus from how a machine works to how a task is performed. For designing the “ergonomic - compact armrest” a new system based on the collection of “real” users biomechanical performance within a virtual lab was adopted. In this virtual environment, it was possible to test many different configurations of controls, checking which controls are mostly used, and measure the comfort index and mental work load for each configuration. On this basis, a “digital twin” of the user was created, consisting in a set of scalable virtual manikins that can interact with virtual items, and a comfort index was defined as an objective and reliable measure to evaluate workload during any task execution. Thanks to this new methodology, the “ergonomic - compact armrest” is 30% smaller than the previous one, but at the same time it accommodates in comfort the 95% of the population size, keeping on board only frequent controls positioned in ergonomic way. The results of this study could be used for other tractors controls layout design, so that human comfort can be improved and any task can be felt as natural as possible, encouraging good posture and safe behaviours, and reducing cost of prototypes and time to market.