Transient acceleration in belt conveyor speed control

In bulk material handling applications, belt conveyors generally run at a constant speed. The belt can be only partially filled when the loaded material flow at the tail of the conveyor is smaller than the nominal conveying capacity of the system. Literature including DIN 22101 indicates that reducing the belt speed, and thereby maximizing the belt loading degree, always results in a reduction of the required drive power. To maximize the loading degree in operations, belt conveyor speed control has been proven to effectively achieve energy savings in dry bulk material transport. Current studies of speed control mainly focus on establishing models to predict the energy savings and on developing methods for variable conveyor speeds in conveyor startup operations. There is little research that focuses on the effect of belt conveyor acceleration in transient operations associating belt conveyor dynamics. If the acceleration is too high and the regulation of speed is too frequent, speed control may potentially damage the system or reduce the technical lifetime of the entire system. This paper presents an approach to determine the admissible acceleration and the applicable acceleration frequency under transient operations. Taking into account the risks of belt over-tension, slippage between drive pulley and belt and drive motor overheating, the maximally allowed acceleration is estimated. Further the estimation is evaluated by finite element method to optimize the acceleration towards a proper speed control process with respect to conveyor dynamics. A case study shows the implementation of the approach.