Project
AIM:- BAJA-All-Terrain-Vehicle
OBJECTIVES-
- Prepare a technical report explaining the model properties & comments on the results
Vehicle body:-
is most expensive part of a car. Vehicle body could be the main supporting structure or its particular element. The Vehicle Body of modern car consist of: engine section, saloon, trunk.
Vehicle body is the main supporting structure of a vehicle, to which all other components are attached. Truck uses a separate frame as chassisThe basic form of the modem automobile body is older horse driver carriage. They have a single seat type body construction which provides less safety to the passenger from weather. Larger and more stylish bodies were developed and manufactured with passage of time to provide increased space, safety or protection to the passengers.
The vehicle body should fulfill the following requirements.
1. It must be strong enough to withstand all types of forces acting on the vehicle.The forces are including the weight of the car, inertia, luggage, braking and cornering forces.
2. Stresses induced in the body should be distributed evenly to all portions.
3. Weight of the body should be as minimum as possible.
4. It should be able to cope with impact loads of reasonable magnitude.
5. It should have reasonable fatigue life.
6. It must provide adequate space for both passengers and the luggage.
7. It should have minimum number of components.
8. It must have sufficient torsional stiffness i.e., ability to resist the twisting stresses produced by irregular road surface.
9. It should have good access to the engine and suspension elements.
10. It must ensure a quite ride, easy entry and exit.
11. It should create minimum vibration during running.
12. The shape of the body should be minimum drag.
13. It is easy to manufacture as well as cheap in cost.
14. It should be designed in such a way that passengers and luggage are protected from bad weather.
15. It should give appeal finish in shape and colour.
- Generic Engine:-The Generic Engine block represents a general internal combustion engine. This block is a suitable generic engine for spark-ignition and diesel. Speed-power and speed-torque parameterizations are provided. A throttle physical signal input specifies the normalized engine torque. Optional dynamic parameters include crankshaft inertia and response time lag. A physical signal port outputs the engine fuel consumption rate based on the fuel consumption model that you choose. Optional speed and redline controllers prevent engine stall and enable cruise control
The engine power is nonzero when the speed is limited to the operating range, Ωmin ≤ Ω ≤ Ωmax. The absolute maximum engine power Pmax defines Ω0 such that Pmax = g(Ω0). Define w ≡ Ω/Ω0 and g(Ω) ≡ Pmax·p(w). Then p(1) = 1 and dp(1)/dw = 0. The torque function is:
τ = (Pmax/Ω0)·[p(w)/w].
You can derive forms for p(w) from engine data and models. The Generic Engine block uses a third-order polynomial form
p(w) = p1·w + p2·w2 – p3·w3
that satisfies
p1 + p2 – p3 = 1, p1 + 2p2 – 3p3 = 0.
In typical engines, the pi are positive. This polynomial has three zeros, one at w = 0, and a conjugate pair. One of the pair is positive and physical; the other is negative and unphysical:
w±=12(−p2±√p22+4p1p3).
For the engine power polynomial, there are restrictions on the polynomial coefficients pi to achieve a valid power-speed curve. If you use tabulated power or torque data, the corresponding restrictions on P(Ω) apply.
Typical Engine Power Demand Curve
Determine the speed and power, w = Ω/Ω0 and p = P(Ω)/P0, and define the boundaries as wmin = Ωmin/Ω0 and wmax = Ωmax/Ω0. Then:
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The block restricts the engine speed to a positive range above the minimum speed and below the maximum speed: 0 ≤ wmin ≤ w ≤ wmax.
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The engine power at minimum speed must be nonnegative: p(wmin) ≥ 0. If you use the polynomial form, this condition is a restriction on the pi:
p(wmin) = p1·wmin + p2·w2min – p3·wmin3 ≥ 0.
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The engine power at maximum speed must be nonnegative: p(wmax) ≥ 0. If you use the polynomial form, this condition is a restriction on wmax: wmax ≤ w+.
Simple Gear-The Simple Gear block represents a gearbox that constrains the connected driveline axes of the base gear, B, and the follower gear, F, to corotate with a fixed ratio that you specify. You choose whether the follower axis rotates in the same or opposite direction as the base axis. If they rotate in the same direction, the angular velocity of the follower, ωF, and the angular velocity of the base, ωB, have the same sign. If they rotate in opposite directions, ωF and ωB have opposite signs. You can easily add and remove backlash, faults, and thermal effects.
This example shows a simple gear coupling two inertias (shafts). The gear ratio between the follower (F) and base (B) is 2:1. Thus the angular velocity of the follower shaft is half the angular velocity of the base shaft. The follower shaft torque is twice the base shaft torque.
An alternative to adding sensors to your model is to use Simscape™ data logging. This example has data logging enabled, passing results to the workspace variable 'simlog_sdl_gear'. For example, entering 'plot(simlog_sdl_gear.Gear.B.w)' at the command line plots the angular velocity at port B of the Gear block. See the Data Logging Example in the Simscape User Guide for further details.
Tires and breaks- In order to have a detailed insight of a vehicle dynamics and performance of a car and its influencing parameters, it is common to use simulation programs to get this job done. The purpose of this work is to model the longitudinal dynamics of a Formula SAE prototype in Matlab/Simulink® environment, focusing on the braking dynamics and on the incorporation of collected data from the brake lining materials. The model was designed to receive data from a Formula SAE prototype, which are used in the interaction of subsystems, such as, brakes, sprung mass, aerodynamics and tires. The implementation of the three degrees of freedom for the sprung mass and the non-linear model used for the tires assure a better precision in the model. The brake bench tests were made in a machine that simulates the braking process and was defined as a Krauss testing procedure, which could be used to evaluate the coefficient of friction variation versus temperature. This data was implemented in the model, and through it the reliability and the precision could be improved. Besides the implementation of the real data from the parts and the interaction between the systems, it is crucial the validation of such tool compared to the real behavior of the car. The validation of the model results was made comparing the real test data of the ES09 prototype from the Formula Cefast Team in a straight-line braking carried out in the competition of this category. The data compared between the model and the test validation were the rear wheel speed, the longitudinal acceleration, the prototype speed, the braking distance and the the braking time. The results could represent the car braking behavior precisely, with low values of errors and little discrepancies, such as the percentage error of longitudinal acceleration as 4,8%, the braking distance percentage error as 2,5% and the braking time percentage error as 8%.
- Major and crucial components- cvs the meaning abbreviation cvt is continuosly Variable transmission type of single speed automatic gearbox the cvt gearbox.
A Cvt is automatic single speed and gearless transmission compact size and simplicity of constration means it more cost effect to use in a small car than a conventional.
RPM SENSOR-
The Rotational Power Sensor block measures the rotational power change between ports R and C. The physical signal output can be an instantaneous or averaged value depending on what you select for the Measurement type parameter.
When you set:
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Measurement type to
Instantaneous power, the instantaneous power is the product of the current angular velocity and torque. Use this setting to analyze peak power transmission and identify heavily loaded components. -
Measurement type to
Average power over a specified period, the time-averaged power is the integral of the instantaneous power over one sample period, divided by that period. For simulation times smaller than the sample period, the average power is zero. The power output is constant for each sample period. -
Measurement type to
Average power over a vibration, the average vibration power is the integral of the power over one vibration period, divided by that period. The vibration period is the time between two consecutive crossings from negative to positive velocity values. If the vibration has a variable frequency, the averaging period can change. For simulation times smaller than the vibration period, the average power is zero. The power output is constant for each vibration period. -
Measurement type to
Average power over a revolution, the average revolution power is the integral of the instantaneous power over one revolution period, divided by that period. The revolution period is defined as the time between two consecutive crossings of zero angular position. If the revolution has a variable frequency, the averaging period can change. For simulation times smaller than the revolution period, the average power is zero. The power output is constant for each revolution period.
Scope-
The Scope block displays its input with respect to simulation time. The Scope block can have multiple axes (one per port); all axes have a common time range with independent y-axes. The Scope allows you to adjust the amount of time and the range of input values displayed. You can move and resize the Scope window and you can modify the Scope's parameter values during the simulation.
When you start a simulation, Simulink does not open Scope windows, although it does write data to connected Scopes. As a result, if you open a Scope after a simulation, the Scope's input signal or signals will be displayed.
If the signal is continuous, the Scope produces a point-to-point plot. If the signal is discrete, the Scope produces a stair-step plot.
The Scope provides toolbar buttons that enable you to zoom in on displayed data, display all the data input to the Scope, preserve axis settings from one simulation to the next, limit data displayed, and save data to the workspace. The toolbar buttons are labeled in this figure, which shows the Scope window as it appears when you open a Scope block.
PS Terminator-
Use the PS Terminator block to cap physical signal output ports that do not connect to other blocks.
Unlike conserving ports in physical modeling, or Simulink output ports, unconnected physical signal output ports do not generate warnings. However, you can use a PS Terminator block for clarity, to indicate that the signal was not inadvertently left unconnected.
The block icon size allows you to connect the PS Terminator block to an open port without rerouting the adjacent lines
Mechanical Rotational Elements-The Mechanical Rotational Reference block represents a reference point, or frame, for all mechanical rotational ports. All rotational ports that are rigidly clamped to the frame (ground) must be connected to a Mechanical Rotational Reference block.
Ideal Rotational motion sensor-
The Ideal Rotational Motion Sensor block represents an ideal mechanical rotational motion sensor, that is, a device that converts an across variable measured between two mechanical rotational nodes into a control signal proportional to angular velocity or angle. You can specify the initial angular position (offset) as a block parameter.
The sensor is ideal since it does not account for inertia, friction, delays, energy consumption, and so on.
Connections R and C are mechanical rotational conserving ports that connect the block to the nodes whose motion is being monitored. Connections W and A are physical signal output ports for velocity and angular displacement, respectively.
The block positive direction is from port R to port C. This means that the velocity is measured as ω = ωR – ωC, where ωR, ωC are the absolute angular velocities at ports R and C, respectively.
The Wrap angle to [0, 2*pi] parameter lets you control the angular displacement output range. When set to On, it keeps angular displacement within the range from 0 to 2π radians (360 degrees), regardless of the number of revolutions performed by the object and the direction of rotation. When set to Off, the output range is unrestricted.
The figure demonstrates the difference between the two options.
In this example, the object is moving at 6 rad/s in the positive direction for the first 5 seconds, and then switches to the negative direction at the same speed. The default angular displacement output (line 1) shows that the object turned forward by 30 rad and then turned back in the negative direction, continuing until –20 rad. If you set Wrap angle to [0, 2*pi] to On, the output (line 2) stays in the range from 0 to 2π rad.
Setting the Wrap angle to [0, 2*pi] parameter to On simplifies development of models with complex relationship between model parameters and rotation angle, such as pumps and motors.
The Variable Ratio Transmission block represents a gearbox that dynamically transfers motion and torque between the two connected driveshaft axes, the base and the follower.
When you choose to have the block ignore the dynamics of transmission compliance, it constrains the driveshafts to corotate with a variable gear ratio that you control. You can choose whether the follower axis rotates in the same or opposite direction as the base axis. If the follower and base axis rotate in the same direction, ωF and ωB have the same sign. If the follower and base axis rotate in opposite directions, ωF and ωB have opposite signs.
Transmission compliance introduces internal time delay between the axis motions. Unlike a gear, a variable ratio transmission does not act as a kinematic constraint. You can also control the torque loss caused by transmission and viscous losses.
Reference -matlab help/google/wikipidea/tms.engin.umich.edu/CTMS/index.php?aux=Extras_Blocklib etc..
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