Research Papers

Longwall Shearer Cutting Force Estimation

[+] Author and Article Information
A. W. Reid

Senior Research Fellow
School of Mechanical and Mining Engineering,
The University of Queensland,
St. Lucia, Queensland 4072, Australia
e-mail: anthony.reid@uq.edu.au

P. R. McAree

School of Mechanical and Mining Engineering,
The University of Queensland,
St. Lucia, Queensland 4072, Australia
e-mail: p.mcaree@uq.edu.au

P. A. Meehan

Associate Professor
School of Mechanical and Mining Engineering,
The University of Queensland,
St. Lucia, Queensland 4072, Australia
e-mail: meehan@uq.edu.au

H. Gurgenci

School of Mechanical and Mining Engineering,
The University of Queensland,
St. Lucia, Queensland 4072, Australia
e-mail: h.gurgenci@uq.edu.au

This highlights a need to accurately model the plant dynamics.

The pick lacing is repeated twice on the cutter head, resulting in a fundamental frequency of the forcing harmonics that is twice the cutter head angular speed.

Determined by verifying that the observability matrix is full-rank, see [5].

1Corresponding author.

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received November 21, 2012; final manuscript received December 15, 2013; published online February 19, 2014. Assoc. Editor: Srinivasa M. Salapaka.

J. Dyn. Sys., Meas., Control 136(3), 031008 (Feb 19, 2014) (9 pages) Paper No: DS-12-1384; doi: 10.1115/1.4026326 History: Received November 21, 2012; Revised December 15, 2013

Longwall mining is an underground coal mining method that is widely used. A shearer traverses the coal panel to cut coal that falls to a conveyor. Operation of the longwall can benefit from knowledge of the cutting forces at the coal/shearer interface, particularly in detecting pick failures and to determine when the shearer may be cutting outside of the coal seam. It is not possible to reliably measure the cutting forces directly. This paper develops a method to estimate the cutting forces from indirect measurements that are practical to make. The structure of the estimator is an extended Kalman filter with augmented states whose associated dynamics encode the character of the cutting forces. The methodology is demonstrated using a simulation of a longwall shearer and the results suggest this is a viable approach for estimating the cutting forces. The contributions of the paper are a formulation of the problem that includes: the development of a dynamic model of the longwall shearer that is suitable for forcing input estimation, the identification of practicable measurements that could be made for implementation and, by numerical simulation, verification of the efficacy of the approach. Inter alia, the paper illustrates the importance of considering the internal model principle of control theory when designing an augmented-state Kalman filter for input estimation.

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Fig. 1

A dual ranging arm shearer. Two cutter heads (laced with picks) shear coal from the seam and load a conveyor as the shearer moves laterally across the face.

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Fig. 2

Planar model of longwall shearer. Five rigid bodies are described by seven degrees of freedom. Generalized coordinates, dimensions and frames of references are shown with thin arrows and external and inertial forces are shown with thick arrows. Model parameters are described in Table 1.

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Fig. 3

Kalman filter estimating the state of an augmented system. Note that Gm/Gf and Jm/Jf represent partitions of Gp and Jp, respectively, relating to the known and estimated inputs. The Kalman gain is similarly partitioned.

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Fig. 4

The structure of the shearer simulation software

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Fig. 5

Horizontal cutting forces (Fxl, Fxr) and chassis support forces (Fnl, Fnr) predicted from the shearer plain coal simulation showing the progression of forces from stationary shearer, with cutter heads disengaged from the seam, to steady-state fully-engaged cutting operation. Refer to Fig. 2 for force definition.

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Fig. 6

Spectral density of the unknown shearer inputs. Each of the inputs has a series of harmonics at integer multiples of a base frequency of 9.3 rad/s, twice the angular speed of the cutter head. Beyond the seventh harmonic, the density peaks are less than 5% of their maximum values.

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Fig. 7

Shaping filter design combining a step, a sinusoidal input at the fundamental frequency and the second harmonic at twice the fundamental frequency. Additional harmonics (not shown) can be included in the same manner at the summing junction. Uncertainty on the individual shaping filters is represented by independent, Gaussian white noise processes wf,step, wf,fund, and wf,harm as described in Sec. 4 for application within a Kalman filter framework.

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Fig. 8

Acceleration measurements made with sensors mounted in the shearer chassis (symmetrically located Sa from the CM) and ranging arms (at the cutter axis)

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Fig. 9

Steady-state estimates of right side cutting loads versus drum orientation using the offset harmonic 7 filter. Refer to Fig. 2 for force definition. The fiducial forces are indiscernible from the noisy estimates, i.e., the estimates track the fiducial forces well over all drum angles.

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Fig. 10

Steady-state estimates of right side cutting torque versus drum orientation using the offset sine filter. Arrows indicate lagging estimates of Tcr due to an incomplete model of the estimated cutting forces and torques.



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