Technologies for safety and ergonomics in the cab
Technological innovation has made it possible to develop numerous solutions to increase safety on tractors and improve the ergonomics of the controls in the driver's seat. Many of these innovations have been introduced thanks to the extraordinary progress made in the field of electronics
Talking about safety and accident prevention in relation to the driving position of a tractor means dealing with two distinct issues: firstly, the risk that a manoeuvring error or an unintentional movement may cause injury to oneself or others, and secondly, the threat of occupational illnesses, to which the concept of ergonomics is inextricably linked, since traumatic events are not the only health problems associated with the use of agricultural machinery. Equally important, although mentioned less frequently, are all those illnesses that are wholly or partially dependent on being on board a tractor or work machine for several hours a day.
The dominance of electronics. Forty years ago everything we are about to talk about simply did not exist. It is indeed thanks to the digitisation of functions and the adoption of electro-hydraulic or electronic controls that it has been possible to include - on the controls themselves - safety systems that make the occurrence of an accident due to unintentional actuation truly unlikely. On the other hand, the adoption of these preventive measures has become necessary both because of the concentration of numerous controls in a small space - think of the multifunctional armrest, which we will discuss later - and because of the emergence of new functions, such as differentiated steering response, four-wheel steering and forward motion at the touch of a lever or button. Three examples of applications that are possible today, although not present on every machine, and which, if activated unintentionally, can cause serious injury to the operator or those moving around the vehicle. Let us start with the ignition, which today requires a precise sequence of actions, varying according to the manufacturer and the level of safety it has decided to apply to the controls. The minimum one requires that the engine does not start unless the clutch is depressed or the shuttle lever is in neutral or parking position (depending on the type of lever). It is also often necessary for the parking brake - even the classic, mechanical lever - to be activated. Some manufacturers - and not for all markets - go so far as to offer ignition systems linked to a breathalyser: only if the driver's blood alcohol level is below a preset value (which can also be zero) does the tractor start. Another safety measure that is now ubiquitous is the pressure-sensor seat: when the driver is not seated at the wheel, the tractor locks up and interrupts basic functions, from the movement of the power lift to the operation of the PTO and the auxiliary hydraulic services. The principle is almost identical, although applied differently, for the operation of the most sensitive controls. The lever that controls the transmission, for example, is usually equipped with one or more consent buttons: to perform certain operations, such as changing direction, switching to a higher gear range or starting a gear, it is necessary to press a consent or safety button, usually located behind or to the side of the lever. This ensures that the operator really wants to carry out that manoeuvre and prevents an unintentional movement that could, for example, move the tractor or disengage the transmission ranges, an operation that usually puts the machine in neutral and creates a hazard, especially on a slope. The systems that interrupt certain applications when travelling on the road respond to the same logic: PTO and hydraulic spool valves cannot operate above a certain speed and the linkage must be locked in the high position with a special transport button. The controls can be manual or engage automatically, depending on the models and their complexity.
New functions. Let us now move on to additional functions, typical of more recently designed machines. One of the first to be introduced, and a direct consequence of modern hydraulic or electric steering, is the differentiated response of the steering wheel: extremely light at low speed, it gradually increases its resistance. The aim is to facilitate manoeuvring but at the same time prevent too loose a response from leading to incorrect steering when travelling on the road. For the same reason, beyond a certain limit - 15-20 km/h - the differentiated steering is also disengaged, thanks to which, when manoeuvring, it is possible to switch from one full turn to the other with less than three turns of the steering wheel. On the other hand, during road transfers the relationship between steering wheel and wheel movement returns to more car-like proportions. The steering is obviously a crucial element in driver protection and is therefore involved in several safety systems. For example, simply moving the steering wheel is enough to deactivate automatic steering, which is increasingly used today by contractors and farmers. By intervening on the steering wheel, but also on the brakes for example, the driver can then easily regain control of the vehicle in the event of unexpected obstacles or other problems. Since we have opened it by switching the tractor on, we close it by switching it off. When getting out of the vehicle, the courtesy lights, located on the roof and on the ladder, remain on for an interval decided by the owner: another small trick in order to avoid, after a day spent in safety, getting hurt getting out of a vehicle that is now at rest. Occupational diseases and ergonomics. If we move from traumatic risk to medical risk, we need to introduce the concept of occupational disease, i.e. all those pathologies directly related to activities, postures and situations that occur during work. In the sector we are interested in, i.e. driving agricultural machinery, these are mainly affecting the spinal column, bones and joints, but also the hearing and respiratory system. Finally, possible tendon and nerve problems are not to be overlooked, due essentially to unnatural arm or hand positions and the continuous use of knobs requiring repeated finger pressure. Starting with the spinal column, we should remember that the discs are subjected to a pressure of 2.5 bar when the subject is seated, which rises to 10 if the vehicle encounters a pothole or a bump. It is therefore quite clear that the shock-absorbing systems are essential. Suspension on the front axle, in the cab but above all in the seat can reduce jolting for the driver almost to zero. The latest generation of seats, in particular, are equipped with a variable response adaptable to the weight of the operator, as well as to the magnitude of the impact. They also have functions that are useful for comfort - ventilation and seat climate control, for example - but also for health. Lumbar cushions that adapt the shape of the backrest to that of the occupant's spinal column, inflatable side supports and, lately, even a massage system for the back and buttocks are devices that reduce fatigue, facilitate the change of position and limit the risk of inflammation, sciatica and various myalgias. Finally, the importance of armrests should not be overlooked: by using them, the operator reduces the load on the spinal column by more than a third. From this clinical data, as well as from the desire to simplify work, comes the decision to adopt the multifunctional armrests that everyone is now familiar with.
A science that comes from afar. When discussing multifunctional armrests, it is essential to introduce the concept of ergonomics. Conceived in 1949 in the United Kingdom, it has roots dating back to the 1700s, when the first treatise was written relating certain pathologies to the work performed by those affected. The aim of what we can consider a true science, somewhere between physiology, anatomy, industrial design and with hints of physics and psychology, is to adapt work objects to the shape and natural limitations of man. Returning to the example of the armrest, it is ergonomics that defines its shape, size, length and even function. Position and orientation of the transmission lever, for example, are crucial in preventing hand or wrist ailments, and the same applies to the main controls. An important choice, which all designers must make, is how many and which controls to place on the main stick and what kind of response they should give to human action. If it is too weak, there is a risk of operating it by mistake, but if it is too strong, there could be inflammation of the fingers or tendons in the hand. Think, for example, how many times you use the lift lowering or reverse direction buttons and how much your thumb might suffer if they are too hard to activate. Let us close this quick overview with a structural element: insulation from the outside. This does not only concern noise - a possible cause of occupational diseases as well as certain discomfort - but also air quality. Think, for example, of the vehicles used for weeding and pesticide treatments. The adoption of active carbon filters, in so-called Category IV protection cabins, is a concrete element in preventing potentially very serious problems.
The autonomous tractor and safety
After having described at length the systems for preventing accidents mainly at the expense of the operator, we cast a glance into a future that is no longer so distant, with a peek at autonomous driving and the complex safety problems it introduces. By autonomous driving we do not mean classic self-driving, which allows the tractor to follow a virtual line, but a real transfer of control from man to machine, whereby it is left to the on-board electronic system not only to drive, but also to activate and deactivate implements and stop work. To choose, above all, how to avoid an unexpected obstacle. In a word, autonomous driving turns the tractor into a true automaton. In terms of safety, this step introduces enormous problems. Firstly on civil and criminal liability in the event of an accident with injuries or fatalities, but preventive countermeasures are also extremely complex. How should an autonomous tractor behave in the presence of an obstacle? Go around it? Stop? Wait for it to move? And how should the tractor, which reads the environment via cameras, recognise a real obstacle from the shadow of a tree, for example? These are issues that involve the principle of artificial intelligence and its so-called training. A delicate task that it has so far limited the introduction of autonomous operation, which from a technological point of view would have been possible long ago.
