Cable shovel digging optimization for energy efficiency

Operator practices have long been suspected to contribute towards the inefficient use of cable shovels. The objective of this work is to find the optimal crowd arm and hoist rope speeds for given initial conditions, material properties and uncertain bulk densities. The excavation process has been modeled using shovel kinematics and dynamics and includes dynamic shovel payload and material cutting resistance models using geometric simulation and passive soil pressure techniques. The models have been used to simulate the energy per unit loading rate of the P&H 2100BL shovel. Extended simulations were carried out for crowd arm and hoist rope speeds ranging from 0.25 to 0.5 m s−1 and 0.5 to 0.7 m s−1, respectively. From the results, the optimal crowd arm and hoist rope speeds were found to be 0.25 and 0.7 m s−1, respectively. The objective function value was 0.2111 kJ s/kg with a standard deviation of 0.0161 kJ s/kg. At 95% confidence, the energy per unit loading rate lies within 0.1795 and 0.2428 kJ s/kg. The study also shows that the optimal operating conditions yield an average of 2.5 million tonnes/annum more than the non-optimal conventional operation.