solve 2 quiz 2 link of book httpwwwirccynecnantesfrmartinet

solve 2, quiz 2

link of book ; http://www.irccyn.ec-nantes.fr/~martinet/Mobrob/FundamentalsofVehicleDynamics.pdf

A Home Times Layout 122% Document Elements Tables charts Smart Art Review Styles Paragraph AaBbCcDdEle Normal No spacing Heading 1 Heading 2 Problem 2 Show how the science of vibrations is applied in vehicle dynamics for determining the perception of ride. [relare natural frequency, damping to ride properties] Print Layout View Sec 1 Pages: 1 of 1 rds: 2 of 26 AaBbc Tit Search in Document Aa Text Box Shape Picture Themes 122%

Solution

SCIENCE OF VIBRATION APPLIED IN VEHICLE DYNAMICS AFFECTS THE PERCEPTION OF RIDE

Ride is normally associated with the level of comfort experienced when travelling in a vehicle.The ride quality normally associated with vehicle\'s response to bumps is a factor of relatively low frequency bounce and rebound movements of suspension system.

Ride is perceived as most comfortable when natural frequency is in the range of 60 to 90 cycles per minute (CPM) or about 1 to 1.5Hz. A high performance sports car can have a stiffer suspension with natural frequency of 120 to 150 CPM or about 2 to 2.5Hz.The amplitude affects human sensitivity to frequency.For Ex:-a frequency range of 30 to 50 CPM will produce motion sickness.The head and neck region are especially sensitive to vibrations of 18 to 20 Hz which emanate from tires or axle hop.

The perception of ride quality is degraded by virtually any disturbance experienced by the occupant .To produce a comfortable ride,high frequency vibrations of wind and drivetrain noise must be minimised and properly isolated.The suspension system must be set in appropriate rubber mountings to isolate high frequency roadway induced vibrations.However ,the natural frequency of a suspension system is still considered the cornerstone of comfortable ride.For Ex:-Natural frequency of a suspension is determined by

f_n=188/(deflection)^1/2

where f_n is natural frequency in CPM,static deflection in inches is the distance the sprung mass moves downwards in response to weight.

Moreover,the selection of damping ratio is a sensitive issue when a too small damping may compromise vehicle dynamic performance and a too high damping leads to increase in system damping rigidity.Tires too also play a significant role in ride quality.The forces generated by roadway irregularities must be overcome by springs in order to keep the tires in contact with the road.When the tires are firmly in contact with the road,best ride is attained i.e. a high sprung to unsprung ratio can attain such property in low mass vehicles.