New insights from fractional order skyhook damping control for railway vehicles

Active suspensions for railway vehicles have been a topic of research for a number of decades and while their applications in service operation are limited it seems clear that they will in due course see widespread adoption. Railway suspension design is a problem of compromise on the non-trivial trade-off of ride quality vs track following (guidance), and the skyhook damping control approach has been paramount in illustrating the potential benefits. Since skyhook damping control, various advanced control studies appeared contributing to redefine the boundaries of the aforementioned trade-off. Yet there is no study on the impact of fractional order methods in the context of skyhook railway active suspensions, and in particular related to skyhook damping control. This is the area to which this paper strongly contributes. We present findings from a current project on fractional order controllers for railway vehicles active suspensions, in particular work on the effect of fractional order methods in basic skyhook damping control schemes, i.e. pure and intuitively-based skyhook. Firstly we present a brief review of conventional skyhook damping control and then proceed to a rigorous investigation of the impact of fractional order on the ride quality / track following trade-off. The relevant benefits from fractional order methods are appraised and new insights highlighted

Modelling and control of railway vehicle suspensions

This chapter uses a railway vehicle as an example of a mechanical dynamic system to which control can be applied in a manner that yields significant benefits from an engineering and operational viewpoint. The first part describes the fundamentals of railway vehicles and their dynamics: the normal configuration, the suspension requirements, how they are modelled and an overview of the types of control concept that are currently applied or under consideration. The second part provides a case study of controller design issues

Optimized Ziegler-Nichols based PID control design for tilt suspensions

PID control design using optimized modified Ziegler-Nichols tuning is for active suspensions of tilting nature is presented. The study of this refers to non-precedent tilt active suspensions for railway vehicles which comprises a cumbersome design trade-off. No study exists on detailed Ziegler-Nichols PID tuning for Single-Input-Single-Output type non-precedent tilt control. We therefore investigate such an approach, referred to here as simple3 tilt, emphasizing control performance that can be achieved in such type of tilting suspension problem. The aim is to provide a baseline design tool for control practicioners, in active suspensions of that nature, who may be more familiar with traditional PID tuning rules. Without loss of generality the suggestions in this paper can be considered in other applications of tilting suspension nature

H∞ voltage control of a direct high-frequency converter

Providing a secure power network is a demanding task but as network complexity is expected to grow with the connection of large amounts of distributed generation so the problem of integration, not just connection, of each additional generator becomes more protracted. A fundamental change to contemporary network architectures may eventually become necessary and this will provide new opportunities for power electronic converters to deliver advanced management and new power flow control features. Direct resonant converters (Dang 2005), could be used in novel devices such as the Active Transformers (Garlick 2008). The key to the successful exploitation of these devices will be their versatility, controllability and cost efficiency

Active suspensions: a reduced-order H∞ control design study

This paper studies order reduction issues for a vehicle active suspension system throughout its modelling, H-infinity controller design and controller refinement. Computer simulations demonstrate that an H-infinity controller for a full active suspension can be significantly reduced to nearly one third of its full order, while the active suspension performance is only slightly degraded. As a by-product, this paper also provides an explicit algorithm for reduced H-infinity control for singular and non-singular continuous-time systems

Optimised sensor configurations for a Maglev suspension

This paper discusses a systematic approach for selecting the minimum number of sensors for an Electromagnetic levitation system that satisfies both deterministic and stochastic performance objectives. The controller tuning is based upon the utilisation of a recently developed genetic algorithm, namely NSGAII. Two controller structures are discussed, an inner loop classical solution for illustrating the efficacy of the NSGAII tuning and a Linear quadratic gaussian structure particularly on sensor optimization

LQG control for the integrated tilt and active lateral secondary suspension in high speed railway vehicles

The paper deals with the tilt control performance of high speed railway vehicles. In particular it discusses the integration of active tilt control with an active lateral secondary suspension solution using LQG control design. The tuning of the weighting matrices of the LQG controller, for the aforementioned dual-actuator system, is accomplished using Genetic Algorithms based upon minimizing given tilting performance metrics. Issues of vehicle modeling and practical tilting performance are also included. The solution is validated via appropriate simulations and comparison with a conventional (tilt-only) precedence controller which provides a performance benchmark for the local control strategie

Optimised sensor configurations for a MAGLEV suspension system

This paper discusses a systematic approach for selecting the minimum number of sensors for an Electromagnetic suspension system that satisfies both optimised deterministic and stochastic performance objectives. The performance is optimised by tuning the controller using evolutionary algorithms. Two controller strategies are discussed, an inner loop classical solution for illustrating the efficacy of the evolutionary algorithm and a Linear Quadratic Gaussian (LQG) structure particularly on sensor optimisation

Integrated tilt and active lateral secondary suspension control

This paper describes a theoretical study on the integration of tilt and active lateral secondary suspension control issues relate to the system performance requirements, controller assessment approaches, modelling process and dynamics interaction analysis. Two dual-actuator control system configurations with classical decentralized controllers are presented. The work aims to improve the performance of a tilt controller based only upon local vehicle measurements by integrating the lateral active secondary suspension with the roll (tilt actuator). The effectiveness of the integrated control is illustrated via simulations and comparisons with previous modified nulling tilting control as well as the commercial precedence equivalent

Wing tilt scheduling in tandem-wing VTOL configurations

The effect of scheduling wing tilt angle in tandem tilt-wing vertical take-off and landing (VTOL) aircraft is investigated with respect to both the static and dynamic longitudinal stability; a first-principles three degree of freedom model of longitudinal motion is derived and simulated with aerodynamic coefficients from a conventional subsonic aerofoil profile. Model trimming through readily available optimisation software is used to determine the values of thrusts and tilts needed for trimmed flight; at airspeeds that correspond to hover and cruise flight modes. The resulting equilibria are discussed qualitatively and compared to equilibria resulting from a model that accounts for the interaction between propeller slipstream and wing aerofoils. Through simulations, it is shown that propeller slipstream influences the dynamic longitudinal modes of the aircraft, under the parametric assumptions of this paper