ME2016[1].HW2.F04 - ME 2016 Sections A-B-C-D Fall Semester...

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ME 2016 Sections A-B-C-D Fall Semester 2004 Computing Techniques 3-0-3 Homework Assignment 2 A First Complete Drivetrain Model in Matlab Due: Friday, September 3, 2004, at 5:00PM Description and Outcomes In this assignment, you will create a first model for a complete drivetrain. The model combines the engine model we created last week with an automatic transmission, a differential and the wheels. We will use this model to determine the shift velocities that maximize the power output of a car. In addition to learning about transmissions, you will refresh your Matlab knowledge about functions and control structures. The learning objectives of this assignment are: to learn how to formulate, solve, and interpret an engineering problem to continue developing as an independent learner of Matlab features to learn the basics of Matlab variables functions and control structures to learn how to use Matlab to solve engineering problems Background In this homework assignment, we focus on the drivetrain of a car. The most important component in the drivetrain is the automatic transmission. Transmissions are complex devices in which numerous clutch mechanisms are used to select a particular drive configuration of a planetary gear-set. Modeling such a complex mechanism is a challenging problem. However, a simple model will be sufficient for the simulations we perform in this class. Torque Converter Engine Transmission Differential Tires Car Body The model we will use is a lossless speed reduction with a ratio of n:1 . The gear ratio, n , can take on 5 different values corresponding to 1 st through 5 th gear. (We are not modeling the reverse.) We will assume that shifting between gears takes place instantly, at shift points specified in the transmission controller. Normally, such a controller contains a complex algorithm to determine when to shift up or down depending on throttle position and car velocity. For instance, if you want to accelerate quickly by flooring the accelerator, you need to shift up at higher velocities then when you are just cruising. However, in this assignment, we will assume that the shift points only depend on car velocity. This is an acceptable assumption if our goal is to model a drag race in which we want to use a shift strategy optimized for performance. If the shift points only depend on the velocity of the car, then the entire shift strategy can be specified Page 1
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with 4 shift velocities: [v12, v23, v34, v45] indicating the velocities (in km/h) at which the car shifts from 1 st to 2 nd , 2 nd to 3 rd , 3 rd to 4 th , and 4 th to 5 th . In this assignment, we will model such a transmission as a separate Matlab function, and we will use this model to determine the optimal shift velocities for obtaining maximum power output. We will do so in several steps. First, we will create the model for the entire drivetrain so that we can plot the power of the engine as a function of the car velocity (Note: in the previous assignment, we plotted the power as a function of engine RPM – not car velocity).
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