In the development of heavy-duty vehicles, the design of hydro-pneumatic suspension (HPS) is important for improving various aspects of vehicle performance, such as comfort and stability. An HPS with gas–oil emulsion is advantageous with respect to cost and design compared to that with a separated chamber, because it shares a chamber with gas and oil. This paper presents an optimisation procedure for obtaining the optimal design of HPS with gas–oil emulsion for heavy-duty vehicles. The HPS model is developed from a mathematical analysis of the gas–oil emulsion, and a parameter study is performed to confirm the design sensitivity of the spring and damping characteristics. A full vehicle model with HPS is constructed to analyse the vehicle performance. The necessity of this vehicle model is shown by comparing its results with those of a simplified vehicle model. To alleviate the problem of excessive computational effort caused using the full vehicle model, surrogate models with respect to performance are developed for the design optimisation of HPS. By performing a multi-objective optimisation of the HPS design, a Pareto front considering the contradiction between the comfort and stability of the performances is obtained.

To be used as a robotic actuator, a surface-mounted permanent magnet synchronous motor (SPMSM) requires a low cogging torque characteristic. The aim of this study is to analyze and reduce the cogging torque's variation due to the assembly imperfection of the segmented stator that is widely used in the SPMSM. Considering the interconnection of the stator segments, an equivalent modeling method of the segmented stator with assembly imperfection is introduced. In addition, the variation in the cogging torque caused by the assembly imperfection is mathematically evaluated. Then, a robust design process that incorporates a sensitivity analysis and a robust design optimization is proposed. By using the proposed design, a robust optimum design model was built and its validity was verified through Monte Carlo simulation and tests.

Hybrid electric vehicles have different performance depending on power distribution and energy management. For heavy-duty vehicles, in particular, these differences will be more pronounced. This paper presents a hybrid powertrain design framework for a heavy-duty multi-purpose vehicle assuming driving conditions. A diesel-powered conventional vehicle was adopted for the hybridization target, and a series hybrid system was suggested as a suitable hybridization topology with an in-wheel motor (IWM) system. The introduced framework supplied the adequate power distribution and the IWM specification based on the speculated drive cycle and a simple energy management strategy. In particular, the reduction ratio of IWM was determined to minimize the gross mass of the motor and reduction gear. The hybridization reduced the vehicle weight by 213 kg while increasing the peak power by 53 kW. Finally, the vehicle simulation was performed using the advanced vehicle simulator for the design result from the proposed framework. The acceleration performance and gradeability limits were improved by 18 % and 10 %p, respectively, compared to the conventional vehicle. In addition, the gasoline equivalent fuel economy of the series hybrid powertrain was 53 % higher than conventional diesel powertrain for the target drive cycle.