A Method for Suppressing Pantograph Bounce of Trolley-Assisted Mining Dump Trucks

A method for suppressing pantograph bounce of trolley-assisted mining dump trucks is proposed and verified. Pantograph bounce is a phenomenon in which a pantograph loses contact with an overhead trolley line. Electrical components installed in the dump truck may be damaged by arcing when pantograph bounce occurs. In conventional countermeasures, road roughness is reduced by maintenance of the road surface and pantograph contact pressure is increased by additional actuators; however, pantograph bounce recurs when road and dump-truck conditions change. It is therefore important to prevent pantograph bounce even in the cases of no road maintenance and no pantograph modification. The proposed suppression method consists of two key functions: predicting pantograph bounce and preventing the front end of vehicle from sinking on the basis of the predicted pantograph bounce. The pantograph-bounceprediction function uses principal vehicle-vibration frequency to calculate the extent that pantograph installed in the front end of the vehicle sinks. The function outputs some information related pantograph-bounce if the calculated extent that the pantograph sinks is below a threshold value. The function to prevent sinking of the front end of the vehicle controls torque of a traction-motor installed in the dump truck. When pantograph bounce is predicted, the function increases the rear-tractionmotor torque in order to raise the front end of the vehicle. According to experimental confirmation of effectiveness of the technique, the proposed method can suppress pantograph bounce of less than 5 cm. The proposed method can thus achieve stable trolley-assisted driving at mining sites.