SDOF System - Arbitrary Excitation
Procedure
Please read 'Background' related to this experiment. This section explains the procedure related to the experiment.
This experiment models a car as a single degree of freedom system passing over a hump of given shape or falling into a ditch (or from a step) of depth h. You must provide the values of system parameters such as masse of body of the car, M, stiffness of the suspension, K, and coefficient of damping of the suspension, C, and velocity of the car. Also, you need to choose the dimensions and the shape of the hump or the depth of ditch (or step). To view the response of the car, run the simulator and observe the motion of car and plot of displacement of the car versus time after the car passes over hump or the step.
Follow the steps given below:
On clicking the tab 'Simulator', you will be directed to another screen displaying a hyperlink “Click here to open the Simulator”. Click on the hyperlink to open the Simulator.
There are two smaller screens and smaller windows provided to input the values of different parameters. Also given are some notes and massages; read them. Out of the two smaller screens, the one on the left is for viewing the animation of motion of the car – a small clip of motion of an animated car can be viewed in this window. The screen on the right will show a plot of displacement of the car body versus time after the car has passed over the hump or fallen from the step ( or into a ditch).
Input the values of parameters in the smaller windows. See the suggested ranges that appear in the windows and choose any value that lie within the range suggested.
Click on 'Calculate' to get the values of undamped natural frequency, ωn , critical damping coefficient Cc, and the damping factor, ζ. Ensure that the value of ζ is less than 1 - The system is under-damped.
Click on the button 'Run'. The animation on the left screen will begin. The first part exhibits the process of system-modelling wherein we move from a real-life situation to a physical model. In this animation, you will see a car being transformed into a physical model. Near the end of animation, the wheel is seen to fall from a step (or pass over a hump). The shape and size of the hump/step was already selected before starting the simulation.
As soon as the animation is complete, you would see the graph of displacement of the mass, x(t), (representing the body of the car) versus time, t, as the response to excitation provided by hump/step.
Study the graph and observe the maximum values of displacement and time taken to die out the oscillations to a sufficiently low value.
Repeat the experiment trying different set of values of parameters and compare the motion and graphs obtained every time.
Provide feedback on your experiment informing us what your liked and the aspect of experiment needing improvement.