Control of railway wheelsets – A semi-active approach

This paper presents a detailed study of semi-active approach for railway wheelsets. A number of control strategies for active primary suspensions for both solid axle wheelset and independently rotating wheelsets are examined in detail and the key requirements of energy flows on both curved and straight tracks are investigated. A semi-active control scheme is then proposed for the independently rotating wheels and a comprehensive performance evaluation is provided to demonstrate that the proposed semi active control system can be used to continuously and reliably provide the necessary steering control without the need for the energy injection of full active control

Robust control and actuator dynamics compensation for railway vehicles

A robust controller is designed for active steering of a high speed train bogie with solid axle wheel sets to reduce track irregularity effects on the vehicle’s dynamics and improve stability and curving performance. A half-car railway vehicle model with seven degrees of freedom equipped with practical accelerometers and angular velocity sensors is considered for the H∞ control design. The controller is robust against the wheel/rail contact parameter variations. Field measurement data are used as the track irregularities in simulations. The control force is applied to the vehicle model via ball-screw electromechanical actuators. To compensate the actuator dynamics, the time delay is identified online and is used in a second order polynomial extrapolation carried out to predict and modify the control command to the actuator. The performance of the proposed controller and actuator dynamics compensation technique are examined on a one-car railway vehicle model with realistic structural parameters and nonlinear wheel and rail profiles. The results showed that for the case of nonlinear wheel and rail profiles significant improvements in the active control performance can be achieved using the proposed compensation technique

Self-powered active lateral suspension for railway vehicles

This paper presents a design methodology for the development of self-powered active lateral secondary suspensions for rail vehicles. It firstly investigates the energy flows in the active lateral secondary suspensions and analyzes the conditions for self-powered control in detail. The impact of the controller design on both the ride quality and the energy consumption is then used to guide the design/specification of actuators and to define key actuator parameters in order to achieve both expected performance improvement and zero-energy consumption for the actuators. Furthermore, a control strategy for dealing with larger than expected energy consumptions by the active suspensions is proposed to eliminate excessive power requirements, but also to ensure the ride quality improvement in comparison to that of passive suspensions. Computer simulations are used to validate the control strategy for the self-powered active suspension

A novel approach for the measurement of absolute train speed

This paper presents a new approach for the measurement of the absolute travelling speed of rail vehicles. Unlike the conventional techniques where the vehicle speed is obtained from the measurement of rotational speed of wheelset axles, the proposed method derives the speed indirectly from the time shift between motions of any two wheelsets. It will explore vehicle/bogie dynamic responses to track excitations, and extract particular features of motion at the wheelsets from inertial sensors mounted on the bogie frame. The new technique will be able to provide an accurate measurement of the vehicle ground speed, even when the wheel slip/slide occurs under traction/braking. The performance assessment of the proposed measurement method using a conventional bogie vehicle is provided, including the robustness against the parameter variations in the suspensions and the reduced level of track roughness at low travelling speeds

Rotor-position detection in permanent-magnet wheel motor to ensure smooth startup from standstill

In this paper, an innovative rotor-position-detection method for a permanent-magnet wheel motor (PMWM) that operates from standstill to low speed is presented. The neutral voltage, which is sensed through phaseshifted pulse width modulation, overcomes the limitations of the conventional back electromotive force (EMF)-based position-detection method, which is more suitable for high-speed operation. In addition, a technique that ensures a transition between the two position-detection methods is presented to cover the full speed range. Computer simulations are employed to design and assess the neutral-voltage-based and EMF-based position-detection methods. The results of the position detection and angle error are presented starting from standstill to low speed. A step current (iq) corresponding to motor torque demand is applied for the starting process in the two position-detection methods. The experimental studies of the new position-detection method are conducted. The method is successfully applied to drive a 60-kW PMWM that operates from standstill to high speed. This demonstrates the effectiveness and performance of the presented method

Dynamics And Control Assessment Of Rail Vehicles Using Permanent Magnet Wheel Motors

This paper describes a dynamics and control study for rail vehicles using independently-driven wheel motors based upon a novel traction motor where the motor is embedded inside a wheel, and studies the dynamic behaviour of a rail vehicle equipped with such motors. The primary objective of the study is to develop practical control strategies that will use the independently-driven motors, not only to provide adequate traction and dynamic braking control, but also to stabilise the vehicle and to produce the necessary guidance action for the wheels especially on tight curves

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure fl ux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defi ned as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (inmost higher eukaryotes and some protists such as Dictyostelium ) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the fi eld understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation it is imperative to delete or knock down more than one autophagy-related gene. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways so not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

Detection and isolation for actuator failure for actively controlled railway wheelsets

This paper studies a model-based approach for the condition monitoring of an actively controlled railway system, with a focus on actuator failures to detect and isolate failure modes in such a system. It seeks to establish the necessary basis for fault detection to ensure system reliability in the event of an abnormal change in one of the two actuators. Computer simulation is used to demonstrate the effectiveness of the method

Real-time modeling of wheel-rail contact laws with system-on-chip

This paper presents the development and implementation of a multiprocessor system-on-chip solution for fast and real-time simulations of complex and nonlinear wheel-rail contact mechanics. There are two main significances in this paper. First, the wheel-rail contact laws (including Hertz and Fastsim algorithms), which are widely used in the study of railway vehicle dynamics, are restructured for improved suitability that can take advantage of the rapid developing multiprocessor technology. Second, the complex algorithms for the contact laws are successfully implemented on a medium-sized Field-Programmable Gate Array (FPGA) device using six NiosII processors, where the executions of the Hertz and Fastsim parts are pipelined to achieve further enhancement in multiple contacts and the operation scheduling is optimized. In the Fastsim part, the floating point units with buffering mechanism are efficiently shared by five processors connected in a token ring topology. The FPGA design shows good flexibility in utilizing logic element and on-chip memory resource on the device and scalability for a significant speed up on a larger device in future work

Fault tolerant strategy of actuator failure for actively controlled railway wheelsets

This paper presents the development of a fault-tolerant scheme through an analytical redundancy approach for actively controlled railway wheelsets. The main aim of the study is to maintain the basic control of the rail vehicles in the event of actuator malfunction and to ensure the vehicle stability and good curving performance without the need for additional actuators. The presented fault-tolerant strategy mainly consists of a fault detection and isolation (FDI) scheme and re-scheduling of the controllers. The FDI has been developed through the use of a model-based approach to identify actuator and sensor failures and the re-scheduling of the controller has been investigated with the optimization of control gains tuned to deal with different failure modes. Computer simulation has been used to assess the system performance of the proposed fault tolerant strategy