The University of Toledo University Transportation Center : UTUTC-AE-2: Reducing Noise and Vibration of Hydraulic Hybrid and Plug-In Hybrid Electric Vehicles-Phase II

Focus Area: Alternate Energy

Principle Investigator:

Mohammad Elahinia
Assistant Professor
Industrial and Manufacturing Engineering Department
The University of Toledo
419.530.8224
Mohammad.elahinia@utoledo.edu

Project Dates: 08/01/2008 – 07/31/2009

UT-UTC Designation: UTUTC-AE-2

Abstract:

The University of Toledo University Transportation Center (UT-UTC) has identified
hybrid vehicles as one of the three areas of the research. The activities proposed in this
research proposal are directed towards the noise, vibration, and harshness (NVH)
solutions for hybrid vehicles. The soaring fuel prices require imperious steps in
developing alternate propulsion technologies. The design and development of hybrid
vehicles is a critical issue for an economy dependent on an efficient, fast, and secure
transportation system. To date, better fuel economy has been mainly achieved by
combining two propulsion sources (hybridization) and/or by developing better managing
algorithms for the internal combustion engines. Examples for the hybridization are the
plug-in hybrid electric and the hydraulic-hybrid vehicles. An example of managing
internal combustion engines is the cylinder on demand as a solution that Honda has
recently introduced. One common problem with these solutions is excessive noise and
vibration that is caused by switching between the propulsion sources and propulsion
modes. To mitigate this problem there is a need to develop vibration isolation devices
that can provide isolation over a wide range of frequencies. This proposal seeks to study
the NVH problem of the hybrid vehicles and to introduce isolation mounts to overcome
these issues.
 
Hydraulic and elastomeric mounts are generally used to dynamically isolating engines
and power trains form the chassis, while statically holding these elements together.
Hydraulic mounts overcome some of the drawback of the elastomeric mounts. The
stiffness and damping of the hydraulic mounts vary with frequency and amplitude of
vibration. It is possible to design a hydraulic mount that has a significantly larger static
stiffness, compared to an elastomeric mount, and has a much smaller dynamic stiffness at
a specific frequency. To achieve low vibration transmissibility, the mount can be tuned to
the primary frequency of the vibration source. On the other hand, to isolate the high
frequency vibration of the engine the mount should have low stiffness and low damping,
which is not possible to achieve.
 
This proposal proposes to continue the development of a semi-active mount, which will
be realized by improving the existing hydraulic mounts through adding a
magnetorheological (MR) fluid element. In response to magnetic fields, MR fluids
change their viscosity, which can be harnessed in a variable stiffness and damping mount.
The resulting mount will provide shock and vibration isolation over a wide range of
frequencies. This extended isolation frequency range will be achieved through the
variable dynamic stiffness of the MR portion of the mount. This solution will make it
possible to improve the noise and vibration characteristic of hybrid vehicles with
alternative propulsion systems.