Optimised PID control for tilting trains

Nulling-type tilt control in tilting railway vehicles, i.e. Single-Input-Single-Output (SISO) control using non-precedent sensor information for lateral acceleration and tilt angle, suffers from performance limitations due to the system's non-minimum phase characteristics [Zolotas, A. C., & Goodall, R. M. (2000). Advanced control strategies for tilting railway vehicles. UKACC international conference on control, University of Cambridge, Cambridge, UK. 6p., ISBN: 0-85296-240-1.]. From an engineering point of view, this is due to the suspension's dynamic interactions and the sensor information used for feedback control. This paper revisits SISO PID-based nulling-type tilt control design (hereby referred to as 'economical tilt control') and rigorously studies its design via optimization to improve system performance. The strong coupling between the roll and lateral dynamic modes of the vehicle body is shown and the performance limitations using conventional control highlighted. PID controllers are designed to illustrate different levels of tilt performance regarding the deterministic (curving acceleration response) and stochastic (ride quality) with the latter being a bounded constraint. With novel contribution to use of PID control in the tilt control application with rational transfer functions, particular emphasis is placed on the practical aspects of the tilt dynamics within the design framework via detailed simulation results.