Search

Unmanned driving technology has enormous advantages in improving efficiency, saving costs and reducing safety hazards. In the current implementation of localization and navigation solutions in underground environments, there are problems of implementation difficulties, high costs, and time-consuming construction of maps. In order to solve the above problems, a localization and navigation method for underground mine autonomous driving based on local geometric topology map is proposed. A local geometric topology map has been designed. The main structure of the underground environment road network is represented by a topology map. The map defines roadways (sides) and intersections (nodes), and stores a local geometric map built around the node in each node to achieve precise positioning at the node. A localization method based on local geometric topology map is proposed, which uses a LiDAR-based intersection detection algorithm and intersection localization algorithm for global vehicle localization. A trajectory-following algorithm based on adaptive model predictive control (MPC) has been designed to ensure the path-tracking precision of vehicles turning at high curvature intersections. A simulation environment and vehicle simulation model for underground mines are constructed by using a 3D physical simulation platform. The simulation results show that this method can achieve underground mine autonomous driving localization and navigation functions. The positioning errors are within 0.2 m at various types of intersections, meeting the positioning localization precision requirements of autonomous driving. Throughout the entire driving process, the vehicle maintains a relatively stable driving state and a small tracking error. Compared with the current localization and navigation methods that rely on technologies such as 5G and UWB, this method only relies on two types of vehicle sensors: LiDAR and inertial measurement unit. It has great advantages in controlling equipment costs.

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The lateral flow in hard disk drives is greatly disturbed because of the arm swinging rapidly during track seeking, which can greatly affect off-track residual vibrations during track following of the head-gimbal assembly (HGA), as well as the slider. Until now, no simulation studies have been performed to investigate off-track residual vibrations of the HGA that consider lateral flow effects. In this paper, the effect of track-seeking on off-track residual vibrations of the HGA is investigated for air and helium environments using the so-called “fluid dynamic mesh” and the “fluid-structure interaction” methods for the first time. Three different angular acceleration profiles (a square wave, a triangular wave, and a sinusoidal wave) are investigated as a function of seek time (10 and 5 ms). Results show that the smoothening of sharp transitions in the seek profile improves the performance of off-track residual vibrations and shortens the track-following time of the head positioning servo system. In addition, the effect of lateral flow (windage) on off-track residual vibrations must be considered for a square-wave angular acceleration profile. Simulation results show that helium improves the track-following accuracy compared to air because of the lower windage forces acting on the HGA. We observe that the sinusoidal-wave angular acceleration performs best for the three angular acceleration profiles investigated. Furthermore, seek time is found to have only a small effect on off-track residual vibrations during track following. [ABSTRACT FROM PUBLISHER]

The authors proposed a new actuator for track following on a spin-stand that evaluated magnetic heads and media for high density magnetic recording with high speed. The new actuator was named “Nano-Motion Actuator (NMA)” by the authors. At the present time, effect of azimuth angle which causes between a center line of a head slider and a tangential direction of the track is increasingly actualized as a track pitch of the head becomes narrow. Therefore, if a discrete track media (DTM) will be put to practical use, the effect of the azimuth angle will be actualized more clearly. Because, DTM will have large RRO (Repeatable Run-Out) that is caused by eccentricity error between a medium and a hub of an air-spindle. Furthermore, NRRO (Non-Repeatable Run-Out) which is caused by mechanical vibration of the air-spindle, flutter of the medium, turbulence around a HGA (Head gimbals Assembly) and so on is overlapped with the RRO. Especially in case of the large NRRO, since the azimuth angle will rapidly change, compensations of the azimuth angle should be absolutely necessary. Therefore, precision positioning actuator with high speed on an X-Y plane which is coplanar will be required the evaluation of the high density magnetic recording. We proposed a new actuator which was consisted of a NMA mechanism and a translation mechanism. The translation mechanism was composed of a stacked piezoelectric that was supported by two elastic springs. The new actuator that was called “2D Nano-Motion Actuator (2D NMA)” could move within 10 square micrometer and be positioned by nanometer resolution with high speed.

Achieving multi-Terabyte capacity in tape cartridges requires a substantially higher track density than that available in present systems, and hence a significantly higher positioning accuracy is required of the track-following servo in tape drives. In this paper, advanced concepts are considered for several elements of a tape system that enhance the track-following servo performance to reach nanometer positioning accuracy. We introduce a novel method for optimizing the geometry of servo patterns in a timing-based servo system. The design criterion aims to minimize the measurement error in the position-error signal (PES) yielded by a digital synchronous servo channel. A flangeless tape path is adopted to mitigate high-frequency components of the lateral tape motion. The track-following servo controller, which is designed based on the H\infty approach, takes into account the measured plant transfer function, the disturbance characteristics of the tape path, and the properties of servo channel. These elements are combined to investigate the track-following performance achievable with a new high-SNR magnetic tape based on perpendicularly-oriented BaFe particles. With this setup, a record closed-loop track-following performance of less than 14 nm PES standard deviation is demonstrated. [ABSTRACT FROM PUBLISHER]

A time optimal-based discrete-time sliding mode control (DSMC) scheme with application to hard disk drives (HDDs) is developed in this study. In this approach, an approximate time optimal switching curve is adopted for the time-varying sliding mode design and the controller, which consists of an equivalent part and a discontinuous one, is designed such that the trajectory from any initial point is driven into a sliding region in the vicinity of the switching surface without chattering and thereafter remains inside it. By using the time-varying switching surface, one unified framework for both track seeking and following control is provided and smooth transition from seeking control to track following control is achieved as well. Simulation and experimental studies on the design of controller in HDDs were conducted to illustrate its feasibility and effectiveness. The simulation/experimental results demonstrate that the proposed scheme provides better performance during track seeking than the commonly used discrete-time proximate time-optimal servo-mechanism (PTOS) and sliding mode proximate time optimal servomechanism (SMPTOS). Moreover, the unified controller achieves better disturbance suppression in track-following than the proportional-integral-differential (PID) control. [ABSTRACT FROM AUTHOR]

This paper considers the design of an iterative learning controller for the reduction of repeatable runout (RRO) in disk drives. The advocated controller is an add-on controller that does not require modification to the existing track following controller. A design methodology is provided for the selection of the parameters of the update law to ensure convergent learning. It is shown that the update law to ensure convergent learning is equivalent to stabilization of a multi-input multi-output system using static output feedback. Experimental results using a 3.5-in Western Digital drive show that a 50% reduction in the sigma of the RRO is achieved in ten iterations when the levels of repetitive and nonrepeatable runout in the position error signal are comparable. [ABSTRACT FROM AUTHOR]

Abstract: To develop high-density magnetic recording systems, a simple feedback system without servo writing was applied to a quasi-static read/write tester in which a medium reciprocates against a stand-still head. The head position signal in cross–track direction during the scanning is fed back to the high-precision piezoelectric actuator of the media stage. The stage is controlled so as to make the head/medium alignment error zero. A contact head slider assembled on a parallel–link suspension was used to evaluate the feedback system. The tester shows an accuracy of 1.5nm in cross–track direction which is preferable for the read/write tests at future high recording densities. [Copyright &y& Elsevier]

Improving the position control of the disk drive read/write heads is an important step in increasing the storage capacity of a drive, especially in the presence of internal and external disturbances. To address this problem, the typical feedback loop of a disk drive servo system was augmented with a disturbance observer. The disturbance observer uses the position error signal and a nominal model of the plant to create an estimate of the disturbance. This estimate is then used to compensate for the disturbance effects. No additional sensors are required, which is particularly relevant in products such as disk drives where cost is a major concern. The effectiveness of the disturbance observer in rejecting shock and vibration disturbances is demonstrated in simulation and shake table experiments. The vibration experiments showed a decrease in the position error of 61%-96% at frequencies below 100 Hz. The maximum position error due to an experimental shock disturbance was decreased by 59%. The effects of noise in the position error signal are also discussed [ABSTRACT FROM PUBLISHER]

A two-degree-of freedom (2 DOF) control structure is proposed for read/write head servo systems of hard disk drives (HDDs). This structure is applied to both track seeking and track following, and makes mode switches found in conventional HDD servo systems unnecessary. Two innovative features introduced in the paper are: 1) a new method for generating the reference signal for track seeking and 2) two robust feedback control schemes for rejection of disturbances; one scheme uses a disturbance observer (DOB), and the other uses adaptive robust control (ARC). Simulation results show that the 2 DOF structure with ARC provides better performance than either the conventional servo system with mode switches or the 2 DOF structure with DOB. Experimental results show the advantage of the new reference generation method and the use of the DOB-based robust controller [ABSTRACT FROM PUBLISHER]