Traditionally, vehicle ride and comfort is evaluated,
subjectively as well as objectively. Based on the outcome of
subjective and objective tests, it is refined by optimizing primary
suspension system, secondary suspension system, seating system,
rubber bushings, frame and BIW for mass, stiffness, damping,
geometry etc. Many a times, the subjective assessment results
stands in contradiction to the objective assessment results;
emphasizing need for having good correlation between subjective and
objective test results. In such cases, it is ambiguous to decide
suitable design refinement action and can lead to no improvement
situation. Hence, it is very much essential to have concurring test
procedures for subjective and objective ride evaluation. This paper
describes a novel methodology to address the above said challenge.
There are defined set of test events and measurement data points to
be used in subjective and objective testing. The subjective
assessment is performed using clearly defined goals for what to
look for and how to look for different ride and comfort attributes
and sub attributes. Similarly for objective test, accelerations,
displacements and loads are measured at defined locations on
vehicle application specific, various types of service roads for
long enough duration, to have no or minimum impact of road inputs
or events having high kurtosis value, on the objective ride
measurement results. Measured data is post processed separately to
arrive at objective ride index value for each of the subjective
attribute i.e. bounce, pitch, roll, head toss, bobbing, choppy ride
etc… For this, set of measured data is processed and analyzed for
interested and relevant frequency ranges instead of limiting it to
ISO 2631. This approach provides direct comparison of subjective
rating number and objective ride index value for each of the
attribute. Measured data also provides insight on transfer function
of different vehicle systems and subsystems and their contribution
in above said ride attributes. This new approach has proven very
useful in refining the vehicle ride and comfort by achieving 85~90%
correlation between subjective and objective test results. Authors:
Hemant Ghanwat, Mithun Chasker, Santosh Gosavi, Vikram Bagal, Rahul
Hagawane Technical Session: Testing & Evaluation Techniques