TECHNICAL AND OPERATIONAL CHARACTERISTICS OF THE YUTONG ELECTRIC BUS RUNNING GEAR

ABSTRACT

This paper investigates the dynamic loading and technical–operational characteristics of the suspension system of YUTONG electric buses, with a focus on the nonlinear behavior of pneumatic suspension components, including the air spring, damper, and bumpstop. Numerical simulations were performed using a multi-body dynamic model developed in the MSC ADAMS/Car environment under static conditions, braking from 50 km/h with a deceleration of 0.3 g, and crossing a 30 mm road obstacle. The results indicate that increasing the air spring pressure from 150 kPa to 500 kPa raises the maximum force from 9–10 kN to 40–42 kN, while the damper generates dynamic resistance forces of up to 3.5–3.8 kN. The bumpstop is activated at a displacement of 20 mm and absorbs loads up to 32–34 kN. These findings provide a scientific basis for optimizing the structural parameters of suspension components in YUTONG electric buses.

АННОТАЦИЯ

В статье исследуются динамические нагрузки и технико-эксплуатационные характеристики подвески электробусов YUTONG с акцентом на нелинейное поведение элементов пневматической подвески, включая пневморессору, амортизатор и ограничитель хода (bumpstop). Численные расчёты выполнены на основе многотельной динамической модели, реализованной в программной среде MSC ADAMS/Car, для режимов статического равновесия, торможения с скорости 50 км/ч при замедлении 0,3 g, а также проезда через дорожную неровность высотой 30 мм. Установлено, что при увеличении давления в пневморессоре с 150 кПа до 500 кПа максимальное усилие возрастает с 9–10 кН до 40–42 кН, тогда как амортизатор развивает динамические сопротивляющие силы до 3,5–3,8 кН. Активация bumpstop происходит при перемещении 20 мм с восприятием нагрузок до 32–34 кН. Полученные результаты создают научную основу для оптимизации конструктивных параметров элементов подвески электробусов YUTONG.

Keywords: electric bus; suspension system; technical–operational characteristics; air spring; damper; bumpstop; dynamic modeling; MSC ADAMS

Ключевые слова: электробус; ходовая часть; технико-эксплуатационные характеристики; пневморессора; амортизатор; bumpstop; динамическое моделирование; MSC ADAMS

Introduction. In recent years, the use of electric buses in urban public transport systems has increased significantly, particularly vehicles manufactured by YUTONG. Due to the use of high-capacity traction batteries with a mass of 2.5–3.5 tons, the total operating mass of electric buses reaches 16–18 tons, resulting in increased static and dynamic loads on the suspension system and other running gear components.

During urban operation, braking, acceleration, and road irregularities generate complex dynamic excitations. Practical data indicate that under braking with a deceleration of 0.3 g or during obstacle crossing, the forces acting on suspension components may exceed static loads by 1.3–1.6 times. In such conditions, the nonlinear characteristics of pneumatic springs, dampers, and bumpstops become the key factors governing the dynamic response of the vehicle.

Since full-scale experimental testing is costly and time-consuming, multi-body dynamic modeling is an effective tool for suspension analysis. In this study, the running gear of a YUTONG electric bus is analyzed using a multi-body dynamic model under static equilibrium, braking from 50 km/h with a deceleration of 0.3 g, and crossing a 30 mm road obstacle to assess the technical–operational characteristics of the suspension system.

Materials and Methods. The dynamic behavior of the YUTONG electric bus running gear was analyzed using a multi-body dynamic model. The total operating mass was assumed to be 16–18 t, including a traction battery mass of 2.5–3.5 t, with major masses distributed along the chassis to accurately represent the center of gravity and suspension loading.

The numerical model was developed in the MSC ADAMS/Car environment and included the front and rear suspension systems, chassis, wheels, braking system, and auxiliary components. Mass and inertia properties were defined based on geometric parameters and material density, while passenger load and auxiliary equipment were represented as distributed masses.

The front suspension was modeled as an independent pneumatic system with an air spring, nonlinear damper, and bumpstop, whereas the rear suspension was represented by a rigid beam with specified translational and rotational stiffness of the tie rod. Simulations were conducted for static equilibrium, braking from 50 km/h with a deceleration of 0.3 g, and crossing a 30 mm road obstacle at a speed of 15 km/h. During simulations, forces, displacements, and velocities of the suspension components were recorded and analyzed.

Results. The simulation results revealed pronounced nonlinear behavior of the pneumatic suspension components under various operating conditions. As shown in Fig. 1a, increasing the air spring pressure from 150 to 500 kPa led to a rise in the maximum force from 9–10 kN to 40–42 kN at a displacement of +150 mm, indicating a significant increase in suspension stiffness. The damper force–velocity characteristics (Fig. 1b) exhibited nonlinear damping behavior, with resistance forces reaching 3.5–3.8 kN at piston velocities of approximately ±500 mm/s.

a)                                                   b)

Figure 1. Nonlinear elastic and damping characteristics of the suspension

The force–displacement characteristics of the bumpstop are illustrated in Fig. 2. The results indicate that the bumpstop remains inactive at small displacements and is engaged after a threshold of approximately 20 mm.

At a displacement of 25 mm, the bumpstop absorbs loads of up to 32–34 kN, effectively limiting excessive suspension compression. The stiffness characteristics of the rear suspension tie rod are shown in Fig. 3a and Fig. 3b, where translational forces of 48–50 kN at a displacement of 0.6 mm and rotational resistance moments of 450–470 kN·mm at a rotation angle of 10° were obtained.

Figure 2. Nonlinear stiffness characteristics of the bumpstop

Figure 3. Translational and rotational stiffness characteristics of the tie rod

The dynamic response of the front suspension during obstacle crossing is presented in Fig. 4.

During this maneuver, the air spring displacement increased from approximately 0.51 m to 0.54–0.545 m, triggering bumpstop activation. In this phase, the bumpstop experienced short-duration peak forces of 5–6 kN, after which the vibration amplitude rapidly decreased and the suspension returned to a stable state.

Figure 4. Dynamic response of the front suspension bumpstop

These results confirm that the nonlinear interaction of the air spring, damper, and bumpstop governs the dynamic loading and technical–operational characteristics of the electric bus running gear.

Discussion. The results show that the dynamic loading of the YUTONG electric bus running gear is governed by the nonlinear behavior of the pneumatic suspension. As shown in Fig. 1a, increasing the air spring pressure from 150 to 500 kPa raises the force from 9–10 kN to 40–42 kN, confirming a strong dependence of suspension stiffness on operating pressure and vehicle load, while increasing load transmission to the chassis. The nonlinear damper characteristics (Fig. 1b) indicate its key role in vibration attenuation, with resistance forces of 3.5–3.8 kN at piston velocities of ±500 mm/s, highlighting the importance of damper durability under high dynamic loads. The bumpstop engagement (Fig. 2, Fig. 4) limits excessive suspension compression by activating above 20 mm and absorbing loads up to 32–34 kN, with short-duration peak forces of 5–6 kN. Together with the high translational and rotational stiffness of the rear suspension tie rod (Fig. 3a, Fig. 3b), these results emphasize that coordinated tuning of air spring pressure, damping characteristics, and suspension stiffness distribution is essential for improving the technical–operational performance of the electric bus running gear.

Conclusion. This study shows that the technical–operational characteristics of the YUTONG electric bus running gear are determined by the nonlinear behavior of pneumatic suspension components. Increasing the air spring pressure from 150 to 500 kPa raised the maximum force from 9–10 kN to 40–42 kN, indicating a significant increase in suspension stiffness. Under dynamic conditions, the damper developed resistance forces of up to 3.5–3.8 kN, while the bumpstop activated at displacements above 20 mm and absorbed loads up to 32–34 kN, with short-duration peaks of 5–6 kN. The results confirm that coordinated optimization of air spring pressure, damping characteristics, and suspension stiffness is essential to improve durability, ride comfort, and operational reliability of electric buses.

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