Project

AIM :

To Prepare a Technical report for BAJA All Terrain Vehicle ATV Model Without Using Look Up Table and Using Look Up Table.

OBJECTIVE :

Carry out the System level Simulation of an BAJA All terrain vehicle and prepare the technical report explaining the model properties of Without Using Look Up Table and Using Look Up Table and Comments the results.

EXPLANATION :

BAJA ALL TERRAIN VEHICLE (ATV) MODEL :

All Terrain Vehicles(ATV) are among the most useful land vehicles ever invented.Designed to combat the hazards of different kinds of terrain, they can be used in almost every worksite there is. Not only do they make traveling easier for drivers, they are also safe to use when transporting loads or cargo.Suspension and chasis play a vital role in the structural performance of an off-road vehicle.

Fig: BAJA ATV

MAJOR COMPONENTS USED IN THIS SIMULATION:

GENERIC ENGINE:

The Generic Engine block represents a general Internal Combustion (IC) Engine, which is a type of Spark Ignition (SI-Petrol) or Compression Ignition (CI-Diesel). The speed torque and speed power parameters are provided

Ports:

• B – Rotational Conserving Port representing the Engine Block
• F – Rotational Conserving Port representing the Engine Crankshaft
• T – Physical signal input port specifying the normalized engine throttle level
• P – Physical signal output port reporting the instantaneous engine power, in Watts (W)
• FC – Physical signal input port reporting the fuel consumption rate, in kg/s

SIMPLE GEAR:

The simple gear is a combination of a driver and driven gear where the speed is reduced by the gear ratio. The gear ratio is defined as,

Ports:

• B – Base Gear or Driver Gear
• F – Follower Gear or Driver Gear

CVT TRANSMISSION:

In CVT (Continuous Variable Transmission), the variable diameter pulley plays a vital role in transmission. Variable – diameter pulleys must always come in pairs. One of the pulleys, known as the drive pulley (or driving pulley), is connected to the crankshaft of the engine. The driving pulley is also called the input pulley because it’s where the energy from the engine enters the transmission. The second pulley is called the driven pulley because the first pulley is turning it. As an output pulley, the driven pulley transfers energy to the driveshaft.

The distance between the center of the pulleys to where the belt makes contact in the groove is known as the pitch radius. When the pulleys are close together, the belt rides higher and the pitch radius increases. The ratio of the pitch radius on the driving pulley to the pitch radius on the driven pulley determines the gear when the pitch radius is small on the driving pulley and large on the driven pulley, then the rotational speed of the driven pulley decreases, resulting in a lower “gear”. When the pitch radius is large on the driving pulley and small on the driven pulley, then the rotational speed of the driven pulley increases, resulting in a higher “gear”. Thus, in theory, a CVT has an infinite number of “gears” that it can run through at any time, at any engine or vehicle speed.

Ports:

• B – Base pulley ore Drive Pulley
• F – Follower Pulley or Driven Pulley
• r – Variable Transmission Ratio (Input)

VEHICLE BODY:

Two – axle vehicle with longitudinal dynamics and motion and adjustable mass, geometry, and drag properties. The vehicle can have the same or a different number of wheels on each axle. For example, two wheels on the front axle and one wheel on the rear axle. The vehicle wheels are assumed identical in size. The vehicle can also have a center of gravity (CG) that is at or below the plane of travel.

Ports,

• NR – Rear Axle Normal Force (N)
• NF – Front Axle Normal Force (N)
• Beta – Road Incline Angle 9rad)
• V – Longitudinal Velocity (m/s)
• W – Head Wind Speed (m/s)
• H – Horizontal Motion

DOUBLE SHOE BRAKE:

The Double-Shoe Brake block represents a frictional brake with two pivoted rigid shoes that press against a rotating drum to produce a braking action. The rigid shoes sit inside or outside the rotating drum in a diametrically opposed configuration. A positive actuating force causes the rigid shoes to press against the rotating drum. Viscous and contact friction between the drum and the rigid shoe surfaces cause the rotating drum to decelerate.

Ports:

• S – Rotational conserving port associated with the rotating drum shaft
• F – Physical signal input port associated with the applied actuating force

TIRE:

The vehicle body is connected to 4 tires each per axle to move the vehicle according to the power input to the axle.

Ports:

• N – Normal Force
• S – Tire Slip
• A – Axle
• H – Mechanical translational port associated with the wheel hub that transmits the thrust generated by the tire to the remainder of the vehicle.

BLOCKS USED:

• Signal Builder – To input the Brake, Throttle and CVT Ratio.
• Simulink to PS converter – To convert the Simulink signal to Simscape environment.
• Solver Configuration – To specify the solver parameters before starting the simulation.
• Mechanical Reference – To make sure all the components are clamped to the ground.
• Generic Engine – To run the engine with speed and torque values as input.
• PS to Simulink Converter – To convert Simscape signal to Simulink environment.
• Scope – To view the graph of the parameters for better understanding.
• Display – To view the calculated engine power.
• Inertia – To represent the solid inertia.
• Rotational Motion Sensor – To sense the rotational motion from the engine and give output as RPM.
• Variable Gear Ratio – To vary the speed according to the gear ratios.
• PS Terminator – Terminator for unconnected physical signal outputs.
• Double Shoe Brake – To apply brake to the vehicle when needed.
• PS Constant – Generate constant physical signal.
• Tire – For transportation of the vehicle.
• Rotational Free End – For mechanical component (Tire)
• Vehicle Body – To represent the BAJA ATV model body.
• Custom Measure Gauge – To measure the brake and throttle input.
• Knob – To increase, decrease and vice-versa of throttle and brake inputs.
• Lookup Table – To insert the CVT values from the workspace.
• Simple Gear – To reduce the speed of the engine with pre-defined gear ratio.
• Step – To increase or decrease an input value for a defined time interval.

TYPES OF MODEL:

• BAJA ATV model without Dashboard
• BAJA ATV model with Dashboard
• BAJA ATV model – Mapped Lookup Table with Dashboard

BAJA ATV MODEL WITHOUT DASHBOARD

MAIN MODEL:

ENGINE SENSOR:

This block measures angular velocity or angle in a mechanical rotational network. The sensor is ideal since it does not account for inertia, friction, delays, energy consumption, and so on.

The physical signal ports W and A report the angular velocity and angular displacement, respectively, of port R relative to port C. The measurement is positive when the motion at R is greater than the motion at C.

CVT SYSTEM:

VEHICLE BODY:

SIGNAL BUILDER BLOCK INPUT:

• The signal builder is used as input for brake, throttle and gear ratio. Brake input is maintained as 0 for overall simulation. The throttle input is given as 0.3 for 20 secs and increases to 1 for overall simulatuion. The throttle valve is mainly to control the flow or amount of fuel into the engine, if the throttle value increases the flow of fuel increases to the IC engine which inturn increases the power of the engine. The gear ratio is maintained as 2.3 for 5 secs and linearly decreases to 1.8 and maintained constant for overall simulation.

CVT GEAR RATION BLOCK INPUT:

ENGINE TORQUE-SPEED CURVE :

The torque and speed are inputted from the MATLAB workspace window to the generic engine block to generate the output RPM accordingly. This plot is common for all the cases because it’s a default input to the engine.

OUTPUT FOR CASE 1 :

VEHICLE SPEED PLOT :

• It is clear from the graph that the vehicle attains its maximum speed (V = 55km/hr) at full throttle = 1 after 30 seconds and then remains constant. The brake input value is zero, hence it has no effect on velocity.

CVT SHAFT SPEED PLOT :

• These graphs shows the variation in angular velocities of input and output shafts of the variable gear transmission system. These values differ with respect to the gear ratio.

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BAJA ATV MODEL WITH DASHBOARD

MAIN MODEL:

SIMSCAPE MODEL FOR BAJA ATV WITH CVT USING DASHBOARD :

• In this model we have a dashboard which contains knobs to control the inputs. In this case, the inputs- ‘Throttle’ & ‘Brake’ are not provided using signal builder. A knob is provided to control both the parameters in real-time for the user.

OUTPUT FOR CASE 2 :

VEHICLE SPEED PLOT :

• It can be observed from the graph that the velocity of the vehicle increases drastically from 0 to 50kmph when throttle value is 0.5 & brake input is 0. Once the braking value increases from 0.1 to 0.5, the velocity of the vehicle decreases to 0 at constant throttle value. This explains the direct relation of vehicle velocity with respect to throttle and brake inputs.

CVT SHAFT SPEED PLOT :

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STUDY #2 :

CASE 1 :

SIMSCAPE MODEL FOR BAJA ATV WITH CVT USING LOOKUP TABLE :

CVT SUBSYSYTRM :

• 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.

VEHICLE BODY SUBSYSYTRM :

CVT GEAR RATION BLOCK INPUT:

LOOKUP TABLE VISUALISATION :

OUTPUT FOR CASE 1 :

VEHICLE SPEED PLOT :

CVT SHAFT SPEED PLOT :

• Both results are same as that of the first case : - SIMSCAPE MODEL FOR BAJA ATV WITH CVT since the input parameters are
  same.

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STUDY #2 :

CASE 2 :

SIMSCAPE MODEL FOR BAJA ATV WITH CVT USING LOOKUP TABLE & DASHBOARD :

• In this model a dashboard is used to control the inputs- ‘Throttle’ & ‘Brake’ with knobs.

OUTPUT FOR CASE 2 :

VEHICLE SPEED PLOT :

• This graph is similar to that of cvt dashboard case. The variation in vehicle velocity can be observed with change in throttle and brake inputs. With increase in braking value, the speed of vehicle decreases. On the other hand, increasing the throttle leads to increased vehicle velocity.

CVT SHAFT SPEED PLOT :

• This graph indicates the variation in rpm of primary and secondary shafts with respect to input parameters.

Fig: Primary & Secondary CVT output

It is clear that the speed of secondary CVT is higher than the primary CVT. As a result, the output speed is higher than the input. It stays the same throughout. As the throttle input decreases both the speed goes down to zero suggesting that the CVT is not working.

Fig: Torque v/s Engine Speed

The above graph shows the Engine Speed against the Torque. Even though the engine speed was high, the torque came down.

Fig: CVT Ratio v/s Vehicle Speed

The graph is a testament to the fact that at high speed, the CVT ratio decreases

CONCLUSION :
Thus we have successfully analysed 4 different models of BAJA ATV WITH CVT and recorded the outputs :- (Vehicle velocity & CVT shaft rpm) with respect to variations in input throttle and brake.