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Byline: Yuping He, John McPhee A method is presented for determining the critical speed of rail vehicles. Dynamic Mode Tracking (DMT) is used to identify the dynamic modes for a given speed and a Sequential Quadratic Programming (SQP) algorithm determines the critical speed at which the least-damped mode has zero damping. It is shown that the SQP algorithm without DMT often fails to find the critical speed. In comparison, the combined SQP-DMT algorithm provides a reliable identification of the critical speed. This integrated algorithm can be applied to rotor dynamics, wind turbine dynamics, aeronautics, and road vehicle dynamics for automatically identifying the critical speed corresponding to a linear stability analysis.

Byline: Yuping He, John McPhee A systematic method is proposed for automating the design synthesis of ground vehicle suspensions. This method combines optimisation algorithms and numerical multibody dynamics software and considers ISO 2631 standard requirements on ride quality. The proposed method is tested and evaluated by optimising three ground vehicle models. It is recommended that stochastic global search algorithms be used with numerical multibody dynamics software in the initial design optimisation, whereas gradient-based algorithms should be used in the fine stage of fine-tuning the parameters. Results show that compared with suspension stiffness and damping coefficients or inertial property parameters, geometric parameters have a more significant effect on the ride quality.