Passivity-based coupling control for underactuated three-dimensional overhead cranes.

This paper develops a novel Lyapunov function candidate for control of the three-dimensional (3-D) overhead crane, which yields a nonlinear controller to inject active damping. Different from the existing passivity-based controls that employ either the angular displacement or its integral as passive elements, the proposed controller incorporates both of them in a new coupled-dissipation signal, thus significantly enhancing the closed-loop passivity. Owing to the improved passivity, the proposed controller ensures the effective suppression of payload oscillations and robustness. Moreover, the control design is extended with the hyperbolic tangent function to prevent overdriving the trolley. The asymptotic stability is guaranteed by LaSalle's invariance principle. The transit performance of the closed-loop system, including robustness, is validated by numerical simulations.

Design Considerations in the Development of App-Based Oral Anticancer Medication Management Systems: a Qualitative Evaluation of Pharmacists' and Patients' Perspectives.

Smartphone apps can potentially help in enhancing oral anticancer medication (OAM) adherence. Patient adoption and efficacy of such apps depends on inclusion of user-centred and evidence-based features. The objective of this study was to identify important design considerations from the perspectives of patients taking OAMs, caregivers and oncology pharmacists. The study employed a qualitative study design. Data were collected using in-depth interviews with patients (n = 15), caregivers (n = 3) and pharmacists (n = 16). Interviews were audio-recorded, transcribed verbatim and inductive thematic analysis approach was used in data analysis. Monitoring medication-related problems, medication information, replacement of or integration with current systems and accessibility of app content on devices other than smartphones were the key themes identified in the analysis. Flexible input methods for monitored data, glanceability of monitored reports/information, near real-time adherence enhancing and symptom management interventions and customisable reminder options were design considerations identified under the monitoring medication-related problems theme. Participants suggested the provision of focused and easily understandable medication information with a potential for personalisation. Integration of app-based adherence systems with patients' electronic medical records with added mechanisms for alerts in the dispensing system was also suggested as a key design requirement to improve quality of patient care and facilitate adoption by clinicians. Finally, smartphones were the most favoured platform with optional accessibility of app content on other devices. In conclusion, important design considerations were identified through a user-centred design approach. The findings will help developers and clinicians in the design of new app-based systems and evaluation of existing ones.

Dual-axis control of flexure-based motion system for optical fibre transceiver assembly using fixed-order controller.

High-frequency resonant modes appearing in the flexure-based motion systems are the key factors that limit the motion/positioning performance. This paper presents an approach to design the fixed-order (low-order) controller for the flexure-based motion system, which is used for industrial optical fibre transceiver alignment and assembly. The uniqueness of the proposed algorithm is that one single controller can simultaneously stabilize the uncertain high-frequency resonant modes for both x and y-axis motion. Especially, the resulted controller can significantly enhance the tracking and disturbance rejection ability in low frequency. The novelty of the proposed method is mainly twofold. First, the finite-frequency specifications are introduced to robust control of the polytopic systems. As the entire-frequency specifications have the trend to place the dominant poles towards the central polynomial, the finite-frequency specifications largely relax the conservatism for the performance optimization. Second, a new and practical method is proposed to choose the central polynomial by designing a nominal controller, where two different central polynomials are utilized for x and y-axis separately for the practical applications, so that the stability and performance are guaranteed but the conservatism is reduced. Experiments are evaluated on the 2DOF flexure-based motion system, and the results show that the tracking error using designed fixed-order controller has a more than 50% reduction compared with the same-order notch filter based nominal controller, with respect to both the sinusoidal and triangular references.

Classification of Imbalanced Data by Oversampling in Kernel Space of Support Vector Machines.

Historical data sets for fault stage diagnosis in industrial machines are often imbalanced and consist of multiple categories or classes. Learning discriminative models from such data sets is challenging due to the lack of representative data and the bias of traditional classifiers toward the majority class. Sampling methods like synthetic minority oversampling technique (SMOTE) have been traditionally used for such problems to artificially balance the data set before being trained by a classifier. This paper proposes a weighted kernel-based SMOTE (WK-SMOTE) that overcomes the limitation of SMOTE for nonlinear problems by oversampling in the feature space of support vector machine (SVM) classifier. The proposed oversampling algorithm along with a cost-sensitive SVM formulation is shown to improve performance when compared to other baseline methods on multiple benchmark imbalanced data sets. In addition, a hierarchical framework is developed for multiclass imbalanced problems that have a progressive class order. The proposed WK-SMOTE and hierarchical framework are validated on a real-world industrial fault detection problem to identify deterioration in insulation of high-voltage equipments.

Robust vibration control at critical resonant modes using indirect-driven self-sensing actuation in mechatronic systems.

This paper presents an improved indirect-driven self-sensing actuation circuit for robust vibration control of piezoelectrically-actuated flexible structures in mechatronic systems. The circuit acts as a high-pass filter and provides better self-sensing strain signals with wider sensing bandwidth and higher signal-to-noise ratio. An adaptive non-model-based control is used to compensate for the structural vibrations using the strain signals from the circuit. The proposed scheme is implemented in a PZT-actuated suspension of a commercial dual-stage hard disk drive. Experimental results show improvements of 50% and 75% in the vibration suppression at 5.4kHz and 21kHz respectively, compared to the conventional PI control.

Experimental dynamic characterizations and modelling of disk vibrations for HDDs.

Currently, the rotational speed of spindle motors in HDDs (Hard-Disk Drives) are increasing to improve high data throughput and decrease rotational latency for ultra-high data transfer rates. However, the disk platters are excited to vibrate at their natural frequencies due to higher air-flow excitation as well as eccentricities and imbalances in the disk-spindle assembly. These factors contribute directly to TMR (Track Mis-Registration) which limits achievable high recording density essential for future mobile HDDs. In this paper, the natural mode shapes of an annular disk mounted on a spindle motor used in current HDDs are characterized using FEM (Finite Element Methods) analysis and verified with SLDV (Scanning Laser Doppler Vibrometer) measurements. The identified vibration frequencies and amplitudes of the disk ODS (Operating Deflection Shapes) at corresponding disk mode shapes are modelled as repeatable disturbance components for servo compensation in HDDs. Our experimental results show that the SLDV measurements are accurate in capturing static disk mode shapes without the need for intricate air-flow aero-elastic models, and the proposed disk ODS vibration model correlates well with experimental measurements from a LDV.