Magnetorheological (MR) dampers have significantly advanced automotive suspension systems by providing adaptable damping characteristics in response to varying road conditions and driving dynamics. This review offers a comprehensive analysis of the evolution and integration of MR dampers in semi-active suspension systems. Semi-active systems present an optimal balance by integrating the simplicity inherent in passive systems with the adaptability characteristic of active systems, while mitigating the substantial energy consumption. The fundamental principles of MR technology, the design of MR dampers, and the diverse control strategies employed to optimize suspension performance were examined. The classical, modern, and intelligent control methods, along with the related research, were emphasized. Based on the above-mentioned methods, the benefits of MR semi-active control were highlighted, while the challenges and future research directions in MR damper technology were also addressed. Through a synthesis of recent research findings and practical applications, this paper underscores the advancements in MR-based semi-active suspension systems and their promising prospects in the automotive industry.

The operational speeds of passenger trains have been increasing and now often exceed 300 km/h. Higher speeds can lead to increased vibration and reduced ride comfort for railway passengers. This study investigates the combined effect of speed and track geometry on vibration discomfort in high-speed trains. Railway vehicle dynamic models with various levels of complexity are used, with the measured geometry of a section of a high-speed track as an input. The models have been calibrated with vibration measurements carried out in a train running over this section of the track and then applied to predict the vibration discomfort at increased speeds. To evaluate the vibration discomfort at speeds up to 400 km/h, information on track geometry should include wavelengths up to at least 150 m. Vertical irregularities have the greatest effect at all speeds but lateral irregularities are also important. Both the vertical and lateral irregularities of a high-speed track should be controlled at wavelengths of 50–100 m that excite rigid modes of the car body, corresponding to frequencies of typically 1–2 Hz. Additionally, vertical irregularities with wavelengths of 5–12 m that excite the fundamental flexible mode of the car body, typically around 10–15 Hz, should also be controlled. The effects of cant, the rates of change of cant, and the radius of vertical curves are also evaluated although they only have a small effect on vibration discomfort.

In this paper, modal properties of the seated human body were identified from measured transmissibilities to the head, chest, lumbar spine L3, pelvis, hips and thighs with single-axis translational vibration; how they were affected by vibration direction and magnitude was quantitatively compared for the first time. To this end, eight subjects were exposed to fore-aft, lateral and vertical single-axis vibrations with three magnitudes at 0.4, 0.8 and 1.2 m/s² r.m.s., respectively. Three and five vibration modes were identified with fore-aft vibration and with vertical vibration in the sagittal plane, respectively, while three modes identified with lateral vibration were in the coronal plane. As the vibration magnitude increased from 0.4 to 1.2 m/s² r.m.s., the modal frequencies of the modes at 1.2, 2.2, 2.9 and 6.2 Hz, which contained the pitch, lateral movements, fore-aft movements and vertical movements of the upper body, respectively, were reduced to 1.0, 1.8, 2.3 and 5.8 Hz significantly, and the damping ratios of the modes identified at 0.8, 5.2 and 10.9 Hz were changed. High similarity was observed between the modal shapes identified with different vibration magnitudes.