Validation of an Articulated Vehicle Simulation

Tests were performed on a typical UK articulated vehicle to measure dynamic tyre forces and sprung mass accelerations. The measured road profile data and vehicle response data are used to determine some of the important characteristics of articulated vehicle vibration behaviour. In particular, roll motions and their effect on dynamic tyre forces are examined. The measured data are used to validate two and three-dimensional computer models of the vehicle. Attention is given to modelling the tandem leaf-spring trailer suspension. The conditions under which a two-dimensional model can accurately simulate vehicle behaviour are examined.     

Active Roll Control of Articulated Vehicles

This paper describes an investigation into active roll control of articulated vehicles. The objective is to minimise lateral load transfer using anti-roll bars incorporating low bandwidth hydraulic actuators. Results from handling tests performed on an articulated vehicle are used to validate a nonlinear yaw/roll model of the vehicle. The methodology used to design lateral acceleration controllers for vehicles equipped with active anti-roll bars is developed using a simplified linear articulated vehicle model. The hardware limitations and power consumption requirements of the active elements are studied. The controller is then implemented in the validated articulated vehicle model to evaluate the performance of an articulated lorry with active anti-roll bars. The simulation results demonstrate the possibility of a significant improvement in transient roll performance of the vehicle, using a relatively low power system (10 kW), with low bandwidth actuators (5 Hz).     

Modelling high frequency force behaviour of hydraulic automotive dampers

Little information on automotive damper performance above 30 Hz is found in the published literature. Design of vehicles for low levels of noise, vibration and harshness requires attention to higher frequencies. This paper describes research into modelling damper behaviour at frequencies up to 500 Hz. The performance of a monotube damper was measured and the empirical data were used to evaluate a recently published parametric model. Methods of assessing prediction accuracy using transfer and coherence functions, and a wavelet-based transfer function were introduced. Modifications to the model were then developed to improve the prediction of high-frequency behaviour.     

Force Control of a Semi-Active Damper

Two strategies are investigated for controlling a semi-active damper to track a prescribed force demand signal: (i) 'open loop' control, using a model of the damping force versus velocity characteristics; and (ii) force feedback (closed loop) control.

The damping characteristics and switching transients of a prototype damper were measured, and used to develop a mathematical model of the dynamics of the damper. The two control strategies were investigated using an idealised (constant velocity) test. Their performance was also simulated and measured under realistic operating conditions using the Hardware-in-the-Loop testing method.

Open loop damper control was generally found to give superior performance to force feedback control, due to its smaller phase lag at high frequencies.     

Simplified and advanced modelling of traction control systems of heavy-haul locomotives

Improving tractive effort is a very complex task in locomotive design. It requires the development of not only mechanical systems but also power systems, traction machines and traction algorithms. At the initial design stage, traction algorithms can be verified by means of a simulation approach. A simple single wheelset simulation approach is not sufficient because all locomotive dynamics are not fully taken into consideration. Given that many traction control strategies exist, the best solution is to use more advanced approaches for such studies. This paper describes the modelling of a locomotive with a bogie traction control strategy based on a co-simulation approach in order to deliver more accurate results. The simplified and advanced modelling approaches of a locomotive electric power system are compared in this paper in order to answer a fundamental question. What level of modelling complexity is necessary for the investigation of the dynamic behaviours of a heavy-haul locomotive running under traction? The simulation results obtained provide some recommendations on simulation processes and the further implementation of advanced and simplified modelling approaches.     

An Experimental Investigation of Preview Control

There is mounting theoretical evidence to suggest that preview control can be of substantial benefit to a semi-active suspension for random road inputs. In this paper, the benefits of wheel-base preview control are measured experimentally, using a prototype semi-active damper in a half-car 'Hardware-in-the-loop' (HiL) rig with a planar two-axle heavy vehicle model. The benefits of preview control using the prototype semi-active damper are found to be less than theoretically possible, due to the phase lag between the demanded and achieved damping force. It is shown that the performance of the prototype damper can be improved significantly by having a theoretical simulation running ahead of the HiL vehicle. The theoretical simulation is used to predict the demanded damper force for the HiL vehicle, and thereby compensate for the phase lag in the prototype damper.