A LiDAR-Aided Inertial Positioning Approach for a Longwall Shearer in Underground Coal Mining

The absolute three-dimensional position of a longwall shearer is fundamental to longwall mining automation. The positioning of the longwall shearer is usually realized by the inertial navigation system (INS) and odometer (OD). However, the position accuracy of this positioning approach gradually decreases over time due to the gyro drift. To further increase the positioning accuracy of the shearer, this paper proposes a positioning approach based on the INS and light detection and ranging (LiDAR). A Kalman filter (KF) model based on the observation provided by detecting hydraulic supports which are part of the longwall face, using the LiDAR, is established. The selection scheme of the point features is studied through a set of simulations. In addition, compared with that of the approach based on the INS and OD, the shearer positioning accuracy obtained using the proposed approach is higher. When the shearer moves along a 350 m track for 6 cutting cycles and lasts about 7.1 h, both east and north position errors can be maintained within 0.2 m and the height error within 0.1 m.

Effect of East Gyro Drift and Initial Azimuth Error on the Compass Azimuth Alignment Convergence Time

The effect of gyro constant drift and initial azimuth error on the convergence time of compass azimuth is analyzed in this article. Using our designed compass azimuth alignment system, we obtain the responses of gyro constant drift and initial azimuth error in the frequency domain. The corresponding response function in the time domain is derived using the inverse Laplace transform, and its convergence time is then analyzed. The analysis results demonstrate that the convergence time of compass azimuth alignment is related to the second-order damping oscillation period, the gyro constant drift, and the initial azimuth error. In this study, the error band is set to 0.01° to determine convergence. When the gyro drift is less than 0.05°/h, compass azimuth alignment can converge within 0.9 damping oscillation periods. When the initial azimuth error is less than 5°, compass azimuth alignment can converge within 1.4 damping oscillation periods. When both conditions are met, the initial error plays a major role in convergence, while gyro drift has a smaller effect on convergence time. Finally, the validity of our method is verified using simulations.

Accelerometer-Based Gyroscope Drift Compensation Approach in a Dual-Axial Stabilization Platform

An accelerometer-based gyro drift compensation approach in a dual-axial stabilization platform is introduced in this paper. The stabilization platform consists of platform framework, drive motor, gyro and accelerometer module and contorl board. Gyro is an angular rate detecting element to achieve angular rate and rotation angle of the dynamic platform system. However, the platform system has an unstable factor because of the drift of gyro. The main contribution of this paper is to implement a convenient gyro drift compensation approach by using the accelerometer. In contrast to a kalman filtering method, this approach is simpler and practical due to the high-precision characteristic of the accelerometer. Data filtering algorithm and limit of threshold setting of total acceleration values are applied in this approach. The validity and feasibility of the proposed approach are evaluated by four tests under various conditions.

Angle Detection Using a Continuously Rotating Gyro for Large Scale Profile Evaluation – Reversal Measurement for Eliminating Gyro Drift –

Profile evaluation by detecting tangential angles of the profile is competent for large objects because it inherently requires no reference, which is difficult to define with sufficient accuracy as the object becomes larger. We considered using a gyro for detecting the angles instead of an inclinometer or an autocollimator, which are conventionally used as angle detectors. A gyro can detect angles without angular reference; therefore, profiles can be evaluated without the limitation of a reference. However, angles detected by a gyro generally have considerable fluctuations to ensure accuracy in the μrad range, which is the same level as a highly precise inclinometer. In this work, we adopted a periodic reversal measurement using a rotating mechanism to eliminate fluctuations. Analysis and experimental results show that the angles of the gyro’s rotating axis against the earth’s rotating axis can be derived from the angular signals of two gyros rotating in counter directions, and that this method is effective for reducing the influences of fluctuations.