Project
Aim:To study BAJA all terrain vehicle model and write a report
Objectives:
- download the model from mathworks
- study each block properties and parameters
- simulate the model
- write the report
Baja all terrain vehicle:
baja SAE is an design competition run by the socity of automotive engineers (SAE).All terrain vehicle (ATV) is designed to travel on four low-prssure or non pnematic tires ,having a seat designed to be stratted by the operator and handlebars for steering control.
Model componants study:
Continuously variable transmission drive (CVT):
It is better to have more gears in a transmission,since it can optimize engine speed in varity of driving conditions.That means lower gears can provide good acceleration where higher gears can provide good fuel economy. CVTs differ from traditional automatic transmission in that they donthave gears that provide "steps"between low _and high -speed operations.Instead the mejority of them work via pair of variable -diameter,cone-shaped pullley connected by steel or composite belt. the halves of each pulley are aligned with the pointed ends of cones touching .These form a V-Shaped groove in which the connecting belt rides.One side of pulley is fixed ,and the other side is movable actuated by hydraulic cylinder. The cylinder can increase or decrease the amount of space beetween the two side of the pully . This allows the belt to ride lower or higher along the walls of the pully,depending on driving ccondition ,thereby changing the 'Gear' Ratio.
CVT Block:
Variable transmission ratio:Represents a variable ratio gearbbox such as implemented by mechanical belt CVT,electric ,or hydraulic transmissions.The physical signal input "r" defies the ratio of input too output angular shaft velocities.
Connections B(base) and F(follower) are mechanical rotational conserving ports . Specify the relation between base and follower rotation directions with the output shaft rotates parameter.
Engine:
Represent system level model of spark ignition and diesel engines suitable for use at initial stages of modelling when only the basic parameters are available.Optional modellinng when only the basic parameters are available. Optional idle speed and red line controller are included .The throttle input signal T lies between zero and one and specifies the torque demanded from the engine as a friction of the maximum possible torque.
Connnections F and B are mechanical rotational conserving ports associated with the engine crankshaft and engine ,respectively .Connections P and FC are phisical signal output ports through which engine power and fuel consumption rate are reported.
Input signal :
Signal builder is used to create signals for brake and throttle.
CVT Gear Rratio input:
Torque Vs Engine speed curve:
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Case1:
Output for case 1:
Vehical speed:
Vehical attains maximum speed (V=55km/hr)at full throttle =1 after 30 second and then remainns constant .The brake input value is zero ,hence it has no effect on velocity.
CVT shaft RPM :
These graphs shows the variation in angular velocities of input and output shaft of the variable gear transmission system.These values differ with resoect to gear ratio.
Study 1:case:2
Simulink model for Baja ATV with CVT using dashboard:
In this model we have a dashboard which contains knob to control theinputs.In this case ,the inpuuts "throttle " and "brake"are not provided to control both the parameters in real -time for the user.
Output for case 2 :
vehical speed:
It can be observed from the graph that the velocity of vehicale increases drastically from 0 to 50 kmph when throttle value is 0.5 and brake input is 0 .Once the braking value increases from 0.1 to 0.5 ,the velocity of vehicle decreases to 0 at constant throttle value this explains the direct relation of vehicle velocity with respect to throttle and brake inpputs.
CVT Shaft RPM:
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Study2
Study 2:case 1
Simulink model for BAJA ATV with CVT using LOOKUP table:
CVT Block :
The only difference between this model and the first model is that in this model the gear ratio input to CVT is provided using a lookup table. The vehicle velocity and shaft rpm outputs are same as before
CVT gear ratio:
Lookup table visualization:
Output for Study2:case 1:
Vehicle speed :
CVT shaft RPM:
Both results are the same as that of the first case: Simulink model for BAJA ATV with CVT since the input parameters are same.
STUDY 2:Case 2:
Simulink model for baja ATV with CVT using lookup table and Dashboard:
In this model a dashboard is useed to control the inputs Throttle and Brake with knob.
Output for Case 2:
vehicle speed :
This graph is similar to that of CVT dashboard case.The variation in vehcle velocity can be observed with changed in throttle and brake inputs .With increase in breaking value ,the speed of vehicle decreases .
CVT shaftt RPM
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Cnclusion:
Here we successfully ansalysed 4 diffrent models of BAJA ATV with CVT and recorded the outputs as Vehicale speed and CVT shaft RPM .
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