Design of a Scaled Roller-Rig Test Bench for Anti-Slip Control Development for Railway Traction

Anti-slip control is a prominent part of modern railway traction control systems due both to performance and safety concerns. This paper explains the development of a scaled roller-rig test bench which emulates the rail and the wheel of a train. The final purpose of the developed roller-rig test bench is twofold: to study the theory/behaviour of existing anti-slip strategies and to test new designs, before their implementation in the real system. Estimation of adhesion coefficient using a disturbance observer method is explained and tested under various conditions. Anti-slip control is implemented in wheel drive using a direct method by adding a slip speed controller. The tests are conducted using both fixed roller speed and variable roller speed, i.e. dynamic roller. In this second case, train inertia emulation will be key. Two methods are proposed to emulate train inertia, being this the main contribution of this paper. Both methods are verified in simulation first, and further confirmed experimentally in the test bench.

I. Introduction

Railway vehicles often require large tractive effort. Due to the design of wheel and rail, combined with the large elastic coefficient of steel, transfer of forces between the wheel and the rail occur through a small steel-to-steel contact area. While this is advantageous regarding frictional losses, it will curb the maximum force transfer. The maximum transferable force between the wheel and rail will not only be a function of design parameters such as wheel and rail shapes and materials, vehicle weight, etc. but also will be strongly affected by the surface conditions of rail [1]. Exceeding the maximum tractive force can produce an uncontrolled wheel slip, which can result in a number of unwanted effects, including reduced acceleration/deceleration performance [1], and also the risk of triggering torsional vibration phenomena [2]. This creates an interest and necessity to study slip phenomena and to develop anti-slip control methods.