Comfort optimization of a combine harvester cab

In the past several years, there has been increased market place awareness of noise, vibration, and harshness performance in vehicles. We can refer to the NVH, Noise Vibration Harshness, as the study and modification of the noise and vibration characteristics of vehicles. Nowadays manufacturers give a lot of importance to NVH in order to achieve higher level of satisfaction with respect to competitors since quality and reliability standards are set by the market. For example, all-terrain vehicle industry invests resources on development of new materials and damping techniques in order to upgrade comfort and driving performances. Carpeting treatments, the addition of rubber to vehicle panels, gap sealant, and the injection of expandable foam into body panels are some of the methods used to reduce noise and vibrations. The aim of this study is to analyse the actual catalogue of combine harvesters’ cabins provided by AGCO Corporation, exploring the one that can guarantee better performances in terms of visibility and series production layout and then improving the comfort parameters. This study evaluates the noise and vibration levels of the actual models in order to correlate physical parameters to subjective sensations, so referring to the field known as psychoacoustics. NVH sometimes fails to correlate precisely subjective sensations with objective quantifications, so engineers are asked to tune comfort parameters to obtain positive results. Amplifying or reducing particular frequencies rather than introducing or smoothing harmonics permit to achieve a desired arrangement. ?? The main parameters that a potential buyer evaluates during the purchasing of a combine harvester are visibility and ergonomics at driving position. The machine works using front attachments, named headers, which are various in widths and shapes, so a total control on them is a key factor during design. The cab fits the driver, so the layout of devices and systems should be coordinated with capacities and requirements of the worker. High comfort requirements are achieved isolating the vibration source from the cab platform by means of shock absorbers or dampers. Depending on the level of isolation you want to accomplish, different types of installations can be used. In automotive application, where ride quality and vehicle handling affect whole performances, mechanical and hydraulic shock absorbers are part of suspensions, while traditional cab suspension systems must typically compromise between ride comfort and stability. In the most sophisticated solutions, these conflicting goals are achieved designing dampers, control units and sensor systems that permits to adjust instantaneously the damping force to the optimum level. Obviously, this kind of solution is not feasible for every range of agricultural machines: if it is a benefit for tractor application, combine harvesters’ list price cannot deal with this added cost. Therefore, in this application, rubber shock absorbers hold a role of primary importance toward vibrations and noise insulation. Nevertheless, their design is not simple since so many parameters as loads, stiffness, temperature and relative movements affect their behaviour. ?? The target of the final part is to introduce modifications of the actual design and validate the results obtained in order to observe legislation protocols and fulfil customers’ satisfaction.