In the following additional tasks, you will be required to criticize the results from your simulations. This is expected of engineers always. You do this by applying engineering dynamics principles in querying whether the results are correct. You can also query the input parameters used in the model. If you suspect they are not right, recommend what correct values they will be and re-run the model showing the updates (hopefully) correct results.
1. Having built up the Car Dynamics Simulator model, three example simulations were studied. Results of such simulations are given in pages 15, 16 & 18. The first task is to interpret what the results mean to you in all three cases.
2. Let us run simulations for varying damping conditions. This is equivalent to running the car on cruise control for varying wind conditions e.g. sunny, no windy day to gale-like conditions. To do this, modify the model parameters such that F=5000N (constant force), coefficient of friction, μ = 0.25 and viscous damping coefficient, c =[0 30 50 70 100 150] Ns/m. After modifying the block diagram, run the simulations and print your results. Hint: Follow similar procedure shown for Simulation 3 above.
3. Using parameters in Table 1, let us run simulations for the dynamics of a hybrid car fixed with a stop-start system. At the instant of interest, the car is travelling with a constant cruise thrust of 5000N when a traffic light turns red and the driver had to press the pedal suddenly. The stop-start system in the car immediately shuts off supply to the engine. This is equivalent to F = 0. Print the resulting displacement, velocity and acceleration graphs; as well as interpreting the graphs. Hint: Replace the thrust constant force in the model window with a Step block (taken from the Sources Library). The parameters of the block can be Step Time = 50s (initial duration of cruise before stop-start mechanism starts); Initial Value = 5000N (cruise force) and Final Value = 0 (cut off point).
4. Using parameters in Table 1, assume that the car is fitted with a vibrating mechanism such that it the engine generates thrust at a sinusoidal fashion. This means that the plot of thrust against time follows the graph of a sine or cosine curve. Run a simulation for such a scenario and show graphs of your displacement, velocity and acceleration plots, as well as interpreting your graphs for the three plots. Reduce the simulation time from 200s to only 20s. Hint: For this simulation, replace any constant thrust force in your model with a Sine Wave block (taken from the Commonly Used Blocks Library). Re-run the simulation this time changing the total time to 200s. Print the new graphs and comment on the form of your acceleration, displacement and velocity plots.
5. Develop a MATLAB-Simulink Model for an airplane just at the point of take-off shown below. On takeoff
roll, the airplane starts from rest and attains accelerates according to: a x kx 2 , where kx 2 is
the acceleration due to aerodynamic drag. Neglect effect of viscous damping. Assume the airplane has the drag constant k varying from k=0.0001 to k = 0.0005 by steps of 0.0001. Print the graphs of displacement, velocity and acceleration for the airplane in the first 200 seconds just before take-off for mass of airplane, m = 10,000kg , μ=0.25, and thrust force, F = 20kN