Numerical Studies of the Dynamics of the Roadheader Equipped with an Automatic Control System during Cutting of Rocks with Different Mechanical Properties

Piotr Cheluszka

doi:10.3390/en14217353

Abstract

The process of cutting rocks with a boom-type roadheader results in extreme dynamic loads and vibrations. Mining, especially in the case of hard rocks, is associated with large energy consumption, which, when combined with low process efficiency, can lead to low drilling performance. These phenomena are undesirable because excessive dynamic load leads to low machine durability, as well as deterioration of work conditions and safety. Low mining efficiency affects the economics of mining works conducted using roadheaders. However, these adverse effects can be minimized by optimizing the cutting process, thanks to the automatic control of the roadheader. The present article discusses the concept of automatic control of a boom-type roadheader’s cutting heads movement. Based on previously conducted computer investigations, it was assumed that reducing the energy consumption of the cutting process and improving the dynamic state of the roadheader (objective functions) are possible only by controlling three of the four parameters characterizing the cutting process: angular speed of the cutting heads, boom swinging speed, and cut height. The web of cut and workability of the rock can be treated as variables of a stochastic nature. This paper presents selected results of computer tests during simulated cutting of rocks with different uniaxial compressive strengths (UCS) in automatic and manual mode. In addition, the tests studied the behavior of the roadheader during the cutting of rocks with variable workability, which is typical of drilling excavations in a layered rock mass. The results of simulated cutting in automatic and manual mode were compared to assess the effectiveness of the adopted automatic control strategy. It was found that the algorithm developed for automatic control of the cutting heads’ movement allows reducing the consumption of cutting energy by up to half compared to the consumption during cutting in manual mode. Furthermore, it was found to improve the dynamic state of the machine.

Highlights

A prerequisite for the robotization of roadheaders is the automation of cutting, which is their primary working process
Thanks to the skillful selection of the frequency of the supply voltage and the cut height as the movement speed of the cutting heads increased, the excessive dynamic load of the roadheader’s drives, which occurs in the range of medium boom swinging speed, was avoided
The peak torque values on the motor shaft Tmax in the cutting system were higher during the simulated mining of hard rock compared to the peak values of dynamic load noted for other types of rocks, in the entire range of boom swinging speed (Figure 4b)