Tractor control system

A control system for a tractor fitted with two or more axles which carry wheels having pneumatic tires and which is set up to pull an implement or trailer,

• the system having a display terminal for displaying to a tractor operator tractor performance parameters and having sensors to determine the current pull force applied to the implement or trailer, the current wheel load and the current tractor ground speed,
• the system also having a processing unit which determines and advises the tractor operator via the display terminal as to the optimum weight of the tractor using a predetermined relationship between pull force and tractor weight and also the required load on each axle to achieve a predetermined optimum axle load ration,
• in which the processing unit calculates a real time value for the current ratio of pull force to tractor weight, and
• in which the real time value of the current ratio of pull force to tractor weight is calculated by measuring a plurality of individual values of pull force over a sample period and calculating in the processing unit the respective ratios therefrom, eliminating extreme, clearly incorrect and unrepresentative individual ratio values, averaging the ratio values in individual ratio zones and plotting these averaged zonal ratio values recorded in the sample period to generate a best fit curve for these plotted values, then selecting as the current real time value either the average ratio value for the ratio zone in which the tractor is operating for the longest time or the ratio on the curve with the highest value of tractive efficiency defined as pull force applied to the implement or trailer divided by performance output at wheel hub.