Dynamic Modelling and Parameter Optimisation of Friction-Induced Panhead Pitching and Dual-Strip Load Redistribution in a Metro Pantograph–Rigid Overhead Contact Line System

Unequal load sharing between collector strips causes local contact deterioration in metro rigid overhead contact line (ROCL) systems, whereas conventional equivalent-strip models cannot resolve independent strip contact or friction-induced panhead pitching. This study develops a coupled pantograph–ROCL model with independent vertical degrees of freedom for the two strips and a panhead pitch degree of freedom. The ROCL is represented by planar Euler–Bernoulli beam elements with Hermite interpolation and coupled to the pantograph through two moving unilateral contacts. The baseline model is validated against measured contact-force statistics from a Guangzhou Metro line. A representative low-temperature, low-humidity, snow-free scenario is then introduced through test-informed friction variation, modified support stiffness and small support-height deviations. The scenario has little effect on mean contact force but increases force fluctuation, impact peaks, panhead pitching and local poor-contact risk. Sensitivity-guided derivative-free optimisation of local panhead parameters reduces the maximum pitch angle, total-contact-force standard deviation and dual-strip load-imbalance index by 38.24%, 23.09% and 44.43%, respectively. The model provides a mechanical framework for evaluating friction-induced pitch vibration and improving dual-strip load sharing in rigid current-collection systems.