580 California St., Suite 400
San Francisco, CA, 94104
Key research themes
1. How can the torque transmission and drag reduction in magnetorheological clutches be optimized through fluid dynamics and geometric design?
This theme focuses on understanding and modeling the torque generation mechanisms and drag torque in magnetorheological (MR) clutches, especially those involving fluid-immersed plate systems. It highlights the role of lubrication flow dynamics, plate geometries such as grooving, and fluid shear characteristics determined by MR fluids. Optimizing these aspects is critical for enhancing clutch efficiency by maximizing transmissible torque while minimizing energy losses through drag and viscous effects.
Key finding: Developed an asymptotic lubrication model based on Navier-Stokes equations tailored for the thin fluid gap between clutch plates, which accurately predicts drag torque due to viscous shear in disengaged wet clutches.... Read more
Key finding: Combined experimental and simulation analyses demonstrated that applying magnetic fields modulates shear stresses of MR fluids inside hydrodynamic clutches, effectively controlling pressure drops and flow resistances. The... Read more
Key finding: Developed semi-analytical and CFD approaches to study the coupled fluid-solid mechanics in wet multi-plate clutches, focusing on pressure and velocity fields of the lubricating fluid film that affect torque build-up during... Read more
Key finding: Presented a multi-layered disc MR clutch design employing micro-scale (1 micron) fluid gaps to reduce magnetic resistance, thus lowering power consumption and device size. Detailed modeling of the rapid viscosity transition... Read more
Key finding: Introduced a wedge-shaped drum MR clutch where inclined sliders create a converging film producing pressure via magnetorheological grease, increasing yield stress-related torque over conventional drum designs. Theoretical... Read more
2. What mechanisms and designs enable energy-efficient, self-energizing clutch actuation with precise torque control for automotive systems?
This theme examines clutch actuator systems, particularly electromechanical designs employing self-energizing mechanisms that amplify engagement force with low energy input. It emphasizes the integration of novel mechanisms (such as rack and pinion wedges) and control strategies for achieving proportional torque control without instability. These actuator technologies aim to improve fuel efficiency and transmission performance by reducing energy consumption and enabling fast, smooth clutch engagement, essential for automated and dual-clutch transmissions.
Key finding: Proposed a novel electromechanical clutch actuator featuring a rack-and-pinion wedge mechanism providing self-energizing torque amplification without slip instabilities typical of ball-ramp mechanisms. The mechanical modeling... Read more
Key finding: Analyzed and proposed design strategies for dry dual-clutch transmissions (DCT) focusing on reducing control energy consumption while maintaining reliable torque transmission and safety. The study underscores the importance... Read more
3. How do thermo-mechanical behavior and thermal management impact the design and durability of multi-plate clutches under transient operating conditions?
This research area addresses the modeling and analysis of temperature distributions, thermal stresses, and related damage mechanisms in multi-plate clutches during engagement and frictional transient states. Understanding the thermo-mechanical response is crucial for preventing thermal degradation, ensuring safety-critical functionality, and extending service life. Finite element methods (FEM) are predominantly used to simulate temperature and stress fields, guiding material selection and geometric optimization to maintain uniform pressure distribution and mitigate hot spots.
Key finding: Developed a parameterizable 2D finite element model capturing transient temperature and stress fields in multi-plate clutches, validated against experimental data. The study revealed peak temperatures occurring near the outer... Read more
Key finding: Using integrated analytical-field design and thermal simulation (AGROS2D), this study compared MR clutch variants with differing disc counts under steady continuous duty. It quantified coil copper losses (Joule heating) and... Read more