A new traction theory capable of predicting the tractive performance of track-type tractors is developed using Wismer-Luth (1974) theory for wheeled tractors as a basis. The new model employs an iterative procedure to account for the firming action of the soil and its associated cone index along the length of the track. Calibration of the model to tractive data with four field conditions is achieved using a genetic algorithm technique. Within a search space containing one trillion possible combinations of the nine model parameters, a set is found which allows the equations to accurately model field results. For the new model, a total of three parameters, including the soil cone index, vary with field conditions. The resulting working model is used to illustrate design optimization in the tractive performance of crawler tractors.
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