Research Paper Experimental characterisation of front axle suspension systems for narrow-track tractors Michele Mattetti a , Stefano Davoli a , Mirko Maraldi a,*,1 , Francesco Paolini b , Stefano Fiorati b , Giovanni Molari a a Department of Agricultural and Food Sciences (DISTAL), University of Bologna, Viale G. Fanin 50, 40127 Bologna, Italy b CNH Italia, viale delle Nazioni 55, Modena, Italy article info Article history: Published online xxx Keywords: Front axle suspension Comfort Whole-body vibration Narrow-track tractor Over the last few years, stricter comfort and stability standards for agricultural vehicles have generated tough challenges for manufacturers. Front axle suspensions can consid- erably improve tractor comfort. This solution has been typically installed on vehicles over 100 kW but recently, it has also been introduced for narrow-track tractors. These types of tractor require special features in terms of dimensions, manoeuvrability and stability; indeed, the small turning radius and the roll-over performance required present tough constraints. In addition, the lack of space for positioning suspension systems is a concern. A lack of background knowledge has forced companies to search for methods to system- atically validate suspension performance. The aim of this work was to design and validate a test-set that can enable the front axle suspensions of these specialised tractors to be fully characterised. The proposed test-set comprises of two different bumps tests and a braking test which are designed to excite each tractor rigid mode selectively. In tests, a series of sensors was installed to measure accelerations at different tractor positions and other dynamic parameters (tractor speed, pitch rate and roll rate) in real-time. Aggregated data (root mean square and peak-to-peak values) were calculated from the acquired signals which allowed to compare two tractors of the same power class, one equipped with a front axle suspension, and one with a rigid front axle. The collected data could lead to a benchmark definition of the tractor class features, to be compared with newly designed, improved suspension systems. © 2019 IAgrE. Published by Elsevier Ltd. All rights reserved. 1. Introduction The harsh conditions under which tractors operate often leads to poor vibrational comfort, limiting field travelling speed and productivity (Scarlett, Price, Semple, & Stayner, 2005, pp. 1e249). Vibrational discomfort can also affect the perceived quality of vehicles (Bubb & Estermann, 2000) and cause health problems to drivers (Griffin, 1996). It has been * Corresponding author. E-mail address: maraldi.mirko@gmail.com (M. Maraldi). 1 The Cook's distance is a measure that quantifies the changes in the regression model when observation i is removed from the model. Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/issn/15375110 biosystems engineering xxx (xxxx) xxx https://doi.org/10.1016/j.biosystemseng.2019.01.013 1537-5110/© 2019 IAgrE. Published by Elsevier Ltd. All rights reserved. Please cite this article as: Mattetti, M et al., Experimental characterisation of front axle suspension systems for narrow-track tractors, Biosystems Engineering, https://doi.org/10.1016/j.biosystemseng.2019.01.013