scholarly journals A new approach to railway track switch actuation: Dynamic simulation and control of a self-adjusting switch

Author(s):  
Saikat Dutta ◽  
Tim Harrison ◽  
Christopher Patrick Ward ◽  
Roger Dixon ◽  
Tara Scott

The track switch is one of the key assets in any railway network. It is essential to allow trains to change route; however, when it fails, significant delays are almost inevitable. A relatively common fault is ‘loss of detection’, which can happen when there is a gradual track movement and the switch machines (actuators) no longer close the gap between the switch rail and stock rail to within safe tolerance levels. Currently, such misalignment is mitigated by a preventative programme of inspection and manual re-adjustment. In contrast to many other industries, the actuators are exclusively operated in open loop, with sensors (often limit switches) mainly being used for detection. Hence, an opportunity exists to investigate the closed loop control concepts for improving the operation of the switch. This paper proposes two advances: first, a novel approach is taken for modelling the dynamic performance of track switch actuators and the moving permanent-way components of the switch. The model is validated against real data from an operational switch. Secondly, the resulting dynamic model is then used to examine the implementation of closed loop feedback control as an integral part of track switch actuation. The proposed controller is found to perform well and offers the potential of ‘self-adjustment’, i.e. re-adjusting itself to close any gap (within a predefined range) between the stock and switch rails, thereby completing the switching operation.

Author(s):  
William J. Emblom

Methods for improving the robustness of panel forming including the introduction of process sensing and feedback and control has resulted in significant gains in the quality of parts and reduced failures. Initial efforts in implementing closed-loop control during panel forming used active tool elements to ensure that the total punch force followed prescribed trajectories. However, more recently local forces within the tooling have been demonstrated to not only follow desired force trajectories but have been shown to increase the operational envelope of the tooling compared to open-loop tests and even closed-loop test where the total punch force had been controlled. However, what has not been examined is the effect of local force, especially during closed-loop control panel forming operations on the total punch force measured during forming. This paper addresses this by comparing the results of both open-loop tests and closed-loop tests and examining the effects on both local and total punch forces. It was found that while open-loop forming with various constant draw bead depths resulted in varying total punch forces, once closed-loop control was implemented the total punch forces followed virtually identical trajectories. The tooling for this project included local force transducers and a total punch force transducer. In addition, active draw beads could be controlled during forming and a flexible blank holder with variable blank holder forces were part of the setup.


Author(s):  
William J. Emblom ◽  
Klaus J. Weinmann ◽  
John E. Beard

An experimental evaluation of the strains in an oval stamp forming die is presented. The die design included a flexible blank holder and active draw beads. The die was instrumented with local punch force and wrinkle sensors and control systems were developed in order to follow local punch force and wrinkle trajectories. Strains were measured after pan forming for both open and closed-loop tests. The relation between blank holder force, draw bead penetration, and strains were explored in the critical strain region of the formed pan. Closed-loop control of the local punch forces at the die ends was established using blank holder forces. The strains for tests with various lubrication conditions and draw bead penetrations were compared. It was observed that there is a tendency for the strains in critical locations to converge or remain constant for the closed-loop control tests while the strains tended to increase with blank holder force for open-loop tests. It was concluded that by controlling local punch forces, strain is indirectly controlled.


2010 ◽  
Vol 63 (3) ◽  
Author(s):  
Denis Sipp ◽  
Olivier Marquet ◽  
Philippe Meliga ◽  
Alexandre Barbagallo

This review article addresses the dynamics and control of low-frequency unsteadiness, as observed in some aerodynamic applications. It presents a coherent and rigorous linearized approach, which enables both to describe the dynamics of commonly encountered open-flows and to design open-loop and closed-loop control strategies, in view of suppressing or delaying instabilities. The approach is global in the sense that both cross-stream and streamwise directions are discretized in the evolution operator. New light will therefore be shed on the streamwise properties of open-flows. In the case of oscillator flows, the unsteadiness is due to the existence of unstable global modes, i.e., unstable eigenfunctions of the linearized Navier–Stokes operator. The influence of nonlinearities on the dynamics is studied by deriving nonlinear amplitude equations, which accurately describe the dynamics of the flow in the vicinity of the bifurcation threshold. These equations also enable us to analyze the mean flow induced by the nonlinearities as well as the stability properties of this flow. The open-loop control of unsteadiness is then studied by a sensitivity analysis of the eigenvalues with respect to base-flow modifications. With this approach, we manage to a priori identify regions of the flow where a small control cylinder suppresses unsteadiness. Then, a closed-loop control approach was implemented for the case of an unstable open-cavity flow. We have combined model reduction techniques and optimal control theory to stabilize the unstable eigenvalues. Various reduced-order-models based on global modes, proper orthogonal decomposition modes, and balanced modes were tested and evaluated according to their ability to reproduce the input-output behavior between the actuator and the sensor. Finally, we consider the case of noise-amplifiers, such as boundary-layer flows and jets, which are stable when viewed in a global framework. The importance of the singular value decomposition of the global resolvent will be highlighted in order to understand the frequency selection process in such flows.


2011 ◽  
Vol 22 (12) ◽  
pp. 1393-1407 ◽  
Author(s):  
HONGYUE DU

This paper investigates the modified function projective synchronization (MFPS) in drive-response dynamical networks (DRDNs) with different nodes, which means that systems in nodes are strictly different. An adaptive open-plus-closed-loop (AOPCL) control method is proposed, which is a practically realizable method and can overcome the model mismatched to achieve synchronization. It is well known that each of the close-loop and open-loop control method possesses some advantages and disadvantages. By combining their advantages, the open-plus-closed-loop (OPCL) control method was proposed by Jackson and Grosu. For arbitrary nonlinear dynamic systems, dx/dt = F(x,t), Jackson and Grosu proved that there exists solutions, x(t), in the neighborhood of any arbitrary goal dynamics g(t) that are entrained to g(t), through the use of an additive controlling action, K(g,x,t) = H(dg/dt,g) + C(g,t)(g(t) - x), which is the sum of the open-loop action, H(dg/dt,g), and a suitable linear closed-loop (feedback) action C(g,t). This method is a practically realizable method and robust to limited accuracy of data and effects of noise. The AOPCL control method preserve the merits of OPCL control method and its closed loop control part can be automatically adapted to suitable constants. Considering time-delays are always unavoidably in the practical situations, MFPS in DRDNs with time-varying coupling delayed is further investigated by the proposed method. Corresponding numerical simulations are performed to verify and illustrate the analytical results.


2011 ◽  
Vol 467-469 ◽  
pp. 978-983
Author(s):  
Zhi Peng Ma ◽  
Xing Yu Zhao ◽  
Fu Jun Wang ◽  
Da Wei Zhang

To study the dynamic performance and control strategy of a kind of high speed precision positioning XY table with a new kind of decoupling mechanism, the electromechanical co-simulation model with three closed-loop control system using proportional–integral–derivative controller (PID controller) is constructed. By use of finite element analysis (FEA) and co-simulation method, the preloaded spring as the key component in the decoupling mechanism is optimized. The matching law of the spring stiffness and preload is presented. The decoupling mechanism influence on the dynamic performance of the XY table during the movement is fully discussed. Based on the electromechanical model, a three closed-loop control scheme with disturbance observer and feed-forward controller is proposed. Co-simulation results demonstrate the validity of the control strategy.


Author(s):  
Christopher Pelzmann ◽  
Laxman Saggere

This paper presents a novel approach to manipulation and assembly of micro-scale objects using a chip-scale multi-fingered micromanipulator, in which multiple, independently controlled compliant fingers coordinate with each other to grasp and manipulate multiple objects simultaneously on-chip. The structural and functional advantages of this multi-fingered micromanipulator in achieving high dexterity in a compact form as compared to other state-of-the-art manipulation tools are discussed. A formulation of the kinematics of the manipulator’s compliant fingers along with two different control strategies including an operator-driven closed-loop control and a semi-autonomous open-loop control for coordinated manipulation and on-chip assembly of micro-scale objects are introduced. Finally, the details of implementation of both control strategies and successful experimental demonstration of manipulations and assembly of two interlocking micro-scale parts with sub-micron mating clearance using the multifingered manipulator are presented.


Author(s):  
Donald L. Simon ◽  
Aidan W. Rinehart ◽  
Scott M. Jones

Aircraft flying in regions of high ice crystal concentrations are susceptible to the buildup of ice within the compression system of their gas turbine engines. This ice buildup can restrict engine airflow and cause an uncommanded loss of thrust, also known as engine rollback, which poses a potential safety hazard. The aviation community is conducting research to understand this phenomena, and to identify avoidance and mitigation strategies to address the concern. To support this research, a dynamic turbofan engine model has been created to enable the development and evaluation of engine icing detection and control-based mitigation strategies. This model captures the dynamic engine response due to high ice water ingestion and the buildup of ice blockage in the engine’s low pressure compressor. It includes a fuel control system allowing engine closed-loop control effects during engine icing events to be emulated. The model also includes bleed air valve and horsepower extraction actuators that, when modulated, change overall engine operating performance. This system-level model has been developed and compared against test data acquired from an aircraft turbofan engine undergoing engine icing studies in an altitude test facility and also against outputs from the manufacturer’s customer deck. This paper will describe the model and show results of its dynamic response under open-loop and closed-loop control operating scenarios in the presence of ice blockage buildup compared against engine test cell data. Planned follow-on use of the model for the development and evaluation of icing detection and control-based mitigation strategies will also be discussed. The intent is to combine the model and control mitigation logic with an engine icing risk calculation tool capable of predicting the risk of engine icing based on current operating conditions. Upon detection of an operating region of risk for engine icing events, the control mitigation logic will seek to change the engine’s operating point to a region of lower risk through the modulation of available control actuators while maintaining the desired engine thrust output. Follow-on work will assess the feasibility and effectiveness of such control-based mitigation strategies.


2021 ◽  
Author(s):  
Liang Liao

In this thesis, a new approach is presented for the modelling and control of an automated polishing/deburring process that utilizes a dual-purpose complaint toolhead mounted on a parallel tripod robot. This toolhead has a pneumatic spindle that can be extended and retracted by three pneumatic actuators to provide tool compliance. By integrating a pressure sensor and a linear encoder, this toolhead can be used for polishing and deburring. For the polishing open-loop control, the desired tool pressure is pre-planned based on the given part geometry. To improve control performance, a closed-loop controller is applied for pressure tracking through pressure sensing. For the deburring control, another closed-loop controller is applied to regulate the tool length through tool extension sensing. The two control methods have been tested and implemented on a polishing/deburring robot, and the experiment results demonstrate the effectiveness of the presented methods. To future improve the control performance, an adaptive controller is developed to deal with the uncertainties in the compliant tool. This control method combines the adaptive control theory with the constant stress theory of the contact model. A recursive last squares (RLS) estimator is developed to estimate the pneumatic plant model, and then a minimum-degree pole placement (MDPP) is applied to design a self-tuning controller. Afterwards, the simulation and experiment results of the proposed controller are presented and discussed. Finally, a nonlinear model of the pneumatic plant is developed. The nonlinear controller developed by using feedback linearization method is applied on the nonlinear pneumatic system of the compliant toolhead. The simulation is carried out to test the effectiveness of the pressure tracking for the polishing process.


2015 ◽  
Vol 18 (01) ◽  
pp. 69-83 ◽  
Author(s):  
F.A.. A. Dilib ◽  
M.D.. D. Jackson ◽  
A. Mojaddam Zadeh ◽  
R.. Aasheim ◽  
K.. Årland ◽  
...  

Summary Important challenges remain in the development of optimized control strategies for intelligent wells, particularly with respect to incorporating the impact of reservoir uncertainty. Most optimization methods are model-based and are effective only if the model or ensemble of models used in the optimization captures all possible reservoir behaviors at the individual-well and -completion level. This is rarely the case. Moreover, reservoir models are rarely predictive at the spatial and temporal scales required to identify control actions. We evaluate the benefit of the use of closed-loop control strategies, on the basis of direct feedback between reservoir monitoring and inflow-valve settings, within a geologically heterogeneous, thin oil-rim reservoir. This approach does not omit model predictions completely; rather, model predictions are used to optimize a number of adjustable parameters within a general direct feedback relationship between measured data and inflow-control settings. A high-resolution sector model is used to capture reservoir heterogeneity, which incorporates a locally refined horizontal grid in the oil zone, to accurately represent the horizontal-well geometry and fluid contacts, and capture water and gas flow. Two inflow-control strategies are tested. The first is an open-loop approach, using fixed inflow-control devices to balance the pressure drawdown along the well, sized before installation. The second is a closed-loop, feedback-control strategy, using variable inflow-control valves that can be controlled from the surface in response to multiphase-flow data obtained downhole. The closed-loop strategy is optimized with a base-case model, and then tested against unexpected reservoir behavior by adjusting a number of uncertain parameters in the model but not reoptimizing. We find that closed-loop feedback control yields positive gains in net-present value (NPV) for the majority of reservoir behaviors investigated, and higher gains than the open-loop strategy. Closed-loop control also can yield positive gains in NPV even when the reservoir does not behave as expected, and in tested scenarios returned a near optimal NPV. However, inflow control can be risky, because unpredicted reservoir behavior also leads to negative returns. Moreover, assessing the benefits of inflow control over an arbitrarily fixed well life can be misleading, because observed gains depend on when the calculation is made.


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