# Assessment of Active Wheelset Steering System Using Computer Simulations and Roller Rig Tests
## 1 Introduction  
Force interaction in between rails and railway wheels is one of the most important issues in the development of the new rolling stock. The forces in the wheel-rail contact, and their mutual relationship, must meet the safety against derailment criteria first specified by [PERSON] [1] which are still the subject of a number of obligatory standards [2, 3]. However, todays' effort to build an economic and environmentally friendly railroad brings a general and sustained demand to reduce wheel-rail contact forces below legislative limits as much as possible. Particular attention is paid to the lateral component of wheel-rail contact forces during passing a curved track, also called guiding forces. Conventional methods of reduction in guiding forces are based on the optimization of suspension characteristics [4], or on mechanic or hydraulic linkages between the various components of the running gear. As the capabilities of conventional methods are increasingly encountering their limits, ideas of the utilization of active controlled elements in the wheelset guidance and railway vehicle suspension occur. A number of theoretical studies describing various strategies for controlling active elements in railway running gears and proving by means of computer simulations [5, 6, 7] or experimental results [8] their possible benefits for reductionin guiding forces have been published. One of the first practical utilization of such systems are active yaw dampers developed by Liebner and offered as an option for Siemens Vectron locomotives [9] (Figure 1).  
Nevertheless, these systems are still rare on vehicles in ordinary railway traffic and the utilization of modern approaches for the reduction in guiding forces is a topical issue addressed by many railway vehicle manufacturers and university research teams.  
This article describes the results of the introductory part of the project, the aim of which is to develop a system of active wheelset steering for an electric locomotive to reduce the magnitude of guiding forces in track curves. Section 2 asses the contribution of existing systems for the reduction in guiding forces and compares them with active wheelset steering. The main goal of this comparison is to gain arguments for the development of the active wheelset steering system. The control algorithm for steering wheelsets is not addressed in the article. However, it is assumed that the necessary input of the controller will be information about the actual curvature of the track. Section 3 deals with methods of track curvature detection and proposes a method for estimating track curvature which is based on the measurement of the rotation of bogies towards the car body. It is assumed that a scaled roller rig will be used to verify and demonstrate the results of mathematical simulations and to assess different wheelset steering algorithms in the following stages. Therefore, the Czech Technical University roller rig has been significantly innovated recently. Section 4 presents the results of initial experiments on this device, which were aimed at verifying the new functions of the roller rig and the experimental bogie that are necessary to perform experiments with active steering of wheelsets and to assess its impact on the magnitude of forces in wheel-rail contact.