Modelling performance and retarder chart of off-highway trucks by cubic splines for cycle time estimation

Cycle time is a crucial parameter for determining the number of trucks in the transportation system of an open pit mine. During the development of surface mining projects, the haulage roads are planned and the road conditions are predicted. Accordingly, the time that the trucks may spend on that haulage road is estimated. The performance and retarder charts installed within the cabs of the trucks are widely used to calculate the speeds and the time spent for particular road conditions. In this study, a computer-aided system is developed to estimate the truck speed, cycle time and truck number. Speed data for different resistances are read from truck performance and retarder charts and used to build a database. The database with total resistance and speed pairs is modelled by the cubic spline interpolation method. After modelling, the developed system could estimate the speed for any given total resistance. As the road distance is known, the time that any truck would spend travelling on this haul road may be calculated. The approach is coded in C++ and applied to a real overburden stripping mine panel. The results obtained show that the system is convenient for chart modelling and cycle time calculation. Also, the developed system can be used as a part of truck dispatching and simulation system.