In some researches of vehicle system dynamics, it’s necessary to optimise various of vehicle parameters to meet the requirements of different objectives. In this paper, an articulated monorail dynamic model together with a genetic algorithm is developed to optimise the curving dynamics of the articulated monorail vehicle. The articulated monorail is modelled as a rigid multi-body dynamic model consisting of six car bodies and seven straddle-type bogies, in which each straddle-type bogie is comprised of two driving wheels, four guide wheels and two stable wheels. The Magic tire model is used to model the nonlinearities in the driving wheels, guide wheels and stable wheels. The validity of the proposed monorail vehicle model is demonstrated through comparing the car body acceleration responses with those obtained in a field test. The genetic algorithm considering 50 individuals and the mutation probability of 0.01 is developed and further combined with the monorail vehicle dynamic model to serve as a multi-parameters and objective optimisation platform. This optimisation platform is employed to optimise the suspension parameters in the monorail vehicle to improve the ride comfort of the vehicle and minimise the wheel unload, overturning coefficients and wear generation in the tire.

This paper introduces a new type of suspended monorail developed in China with the advantages of both German and Japanese monorails. The FE (finite element) model of the bridge is built in Ansys and coupled with the multibody dynamic model of the vehicle in the UM (Universal Machine). software. FIALA formula is used to construct the tire model. Then, the vehicle-bridge coupling system of the new type suspended monorail is set up and simulated with Park method. The result of the modal analysis and vehicle-bridge coupling simulation draw the same conclusion that the span of the stiffeners could result in the resonance of the vehicle system, which is due to the coupling of the frequencies of the natural modes of the car body and bogie with that for vehicle passing through stiffeners. Through the multibody dynamic simulation of the vehicle-bridge coupling system, the modes of the bridge at the frequencies of 5–10, 15–25 and 30–40 Hz are easily excited when the vehicle passes through the bridge. The three constraint modes and free modes of the bridge are similar in these frequency ranges.

This paper introduces two types of articulated monorails. The vehicle model of the traditional monorail is set up first, and a genetic algorithm is used to modify the parameters with the experimental data. Then, the two types of articulated monorail vehicle models are set up with the components and parameters of the model of the traditional monorail. By comparing the dynamic properties of the traditional monorail with the two types of articulated monorails, the advantage of the latter is realized. Finally, it has been concluded that the “non-bolster type” structure will be a better choice for vehicles passing a small radius curve. This analysis can be helpful in selecting the appropriate monorail system for particular conditions.

Wheel out of round, which has a significant influence on the ride comfort of vehicles, is very difficult to detect, especially for vehicles with rubber tires like a monorail. The prominent feature of wheel eccentricity caused by wheel out of round is that there will be a dominant frequency of the vehicle acceleration that varies with the speed of the vehicle, while the wavelengthes are all equal to the wheel circumference. By studying the experimental results of Chongqing straddle monorail, an indirect detection method of the wheel out of round is put forward. Then a simulation model of the monorail vehicle under the influence of the wheel out of round is established. The numerical analysis and experimental results lead to that the main reason for the abnormal vibration of the vehicle is the wheel out of round. Through the analysis of the vertical dynamic equation of the monorail system, all other factors that may affect the dominant frequency of vehicle vibration are analyzed. Finally, it is concluded this abnormal vibration caused by wheel out of round can only be reduced by increasing the vertical stiffness of the air spring and car body mass other than changing wheels.

Analysis of the Chongqing monorail shows that there is no relationship between wheel wear and radial force, which means the radial force cannot be used to evaluate the wheel wear of monorail. Due to the same physical significance of the Schallamach tire wear model for automobiles, the wear index of railway wheels, which represents the creep power of unit wheel–rail contact area, is proved to be effective in evaluating the wheel wear of railway vehicles, automobiles, and vehicles with both properties, namely, monorail. Parameters of Chongqing monorail, modified through genetic algorithm, are used to build the model of the articulated monorail. Through co-simulation of the MATLAB and UM software, the wheel wears of two types of articulated monorail are calculated. For both types of monorails, correlation analysis shows that the variation of driving wheel and guide wheel wear of the inner bogies with the track curvature radius are roughly the same. The variation of the wheel wears in the two end bogies is a little different from that of the inner bogies. Comparison indicates that the wheels of the bolster type monorail wear more than that of the non-bolster type. Regardless of the monorail type, the wheels in the inner bogies wear more.

In order to establish a more accurate model to simulate actual working conditions, a back-calculation method for road excitation of monorail is introduced and dynamic transcendental equations are set up in this paper. By neglecting the subtle influence of the pitching angle on the vertical acceleration of the bogies, this dynamic model (i.e. the dynamic transcendental equations) is greatly simplified. Besides, the calculation result shall be closer to the measured data. Comparison between the back-calculation results of the two vehicles in a monorail proves that this method can be applied to experiments accurately. Through validating the model by comparing the experiment data and the simulated results, it can be noticed that the simulated result of the acceleration under the action of the back-calculated road irregularities is consistent with the experimental data, which indicates the back-calculation process is precise enough. Band pass filtering is applied to the measured acceleration data to get the signals in the frequency range of 0.5–10 Hz as per the standard, which proves that the model is valid only in low frequencies but good enough for researches of vehicle stability.