Project

AIM : To study and analyze the BAJA All-Terrain Vehicle (ATV) model using simulink.

OBJECTIVE : To prepare technical report of BAJA ATV model with and without lookup table.

THEORY :

An all-terrain vehicle (ATV), also known as a light utility vehicle (LUV)^, a quad bike, or simply a quad, as defined by the American National Standard Institute (ANSI); is a vehicle that travels on low-pressure tires, with a seat that is straddled by the operator, along with handlebars for steering control. As the name implies, it is designed to handle a wider variety of terrain than most other vehicles.

BAJA ATV (SAE) :

The Baja ATV SAE series is an event for undergraduate engineering students, organized globally by the society of Automotive engineers, USA. The event originated in the name of mini-BAJA, in the year 1976 at University of caroline. Since then, the event spanned across six countries - USA, MEXICO, SOUTH AFRICA, KOREA, BRAZIL and INDIA. The BAJA SAE tasks students to design, fabricate and validate a single seater four-wheeled off road vehicle to take part in series of event spread over a course of 3 days that test the vehicle for the sound engineering practices that have gone into it, the agility of the vehicle in terms of gradeability , speed, acceleration and finally its ability to endure that back breaking durability test.

MAJOR COMPONENTS USED IN THE SIMULATION :

1. GENRIC ENGINE :

The Generic Engine block represents a general internal combustion engine. Engine types include 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 engine fuel consumption rate based on choice of fuel consumption model. Optional speed and redline controllers prevent engine stall and enable cruise control.

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 W
• FC - Physical signal output port reporting the fuel consumption rate, in kg/s

2. 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 i.e input, shaft

F- Follower i.e output, shaft

3. CONTINUOUS VARIABLE TRANSMISSION :

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

PORTS :

B - Base pulley or drive pulley

F - Follower pulley or driven pulley

r - Variable transmission ratio (input)

4. VEHICLE BODY :

The Vehicle Body block represents a two-axle vehicle body in longitudinal motion. 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.

5. 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 rotating drum shaft

F - Physical signal input port associated with the applied actuating force.

6. TIRES :

The Tire (Simple) block represents a simple, no-slip model of a tire that you parameterize by tire radius.You can optionally add inertia, stiffness, or damping. These dynamics require additional computation that tends to make models less suitable for real-time simulation.

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 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 referance - To make sure all the components are clamped to the ground.
• Genric Engine - To run 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 view 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 gear ratio's.
• PS Termintor : Terminator for unconnected physical signal outputs.
• Double Shoe Brake : To apply brake to the vehicle when needed.
• PS constant : Generate constant physical signal.
• Tires: For transportation of the vehicle.
• Rotational Free End : For mechanical component (tire)
• Vehicle Body : To represent BAJA ATV model body.
• Custom Measure Gauge : To measure the brake and throttle input.
• Knob : To increase, Decrease or vice-versa of throttle and brake inputs.
• Look-up 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 Look-up table with dashboard.

BAJA ATV MODEL WITHOUT DASHBOARD

MAIN MODEL:

ENGINE 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.

CVT SYSTEM :

VEHICLE BODY :

SIMULATION PROCESS :

• The throttle signal is generated by signal builder block and inputed to genric engine.
• The torque and speed vector are inputted from the matlab workspace.

• The engine will generate the ouput rpm which can be taken from the crankshaft output. This speed will be given to the ideal rotational motion sensor to sense the output rpm.
• The same output speed will be given to a simple gear mechanism to reduce the speed where the gear ratio is '4'.
• Then the output speed from the gear will be given to the variable transmission block (CVT).
• CVT ratio is provided to the Continuously Variable Transmission block through signal builder block.

• The speed is controlled by the CVT ratios and the controlled output speed is inputted to the vehicl axle.
• The brake signal is generated by the signal builder and inputted to vehicle body (double shoe brake ) for applying the brake to axle.

• The power from the CVT is inputted to the axle and the vehicle accelerates according to the speed.
• Then the velocity is taken as output from the vehicle body for further analysis.

OUTPUT :

TORQUE-SPEED PLOT :

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

BAJA ATV MODEL WITH DASHBOARD

MAIN BODY:

DASHBOARD (SIMULATION OFF) :

DASHBOARD (SIMULATION ON) :

FLOW PROCESS :

The model workflow process is same as 'BAJA ATV Model without dashboard' but Throttle and brake inputs are controlled by the user with the help of knob. We are also replacing signal builder with two seperate constant blocks Throttle and Brake.

OUTPUT :

ENGINE SPEED :

Here the engine speed is generated according to inputs like throttle, brake, torque and speed vectors. The runtime is not defined so that the Throttle and Brake are controlled by the user. The step up is Throttle and step down is brake inputs. As you can see, at first throttle input increses speed of the engine and as the brake input implemented it shows sudden decrease in engine speed.

CVT SPEED REDUCTION PLOT:

VELOCITY VS THROTTLE PLOT :

From the graph we can infer that the vehicle is accelerating while throttle is applied (step-up) and decelerated while brake is applied (step-down).

ACCELERATED PLOT:

From the graph we can infer that the vehicle is acceletated to 54 KMPH intially and the state is changes when the user controls the throttle and brake input konbs. The step-up and step-down are acceleration and decleration respectively.

BAJA ATV MODEL- MAPPED LOOK UP TABLE WITH DASHBOARD

MAIN BODY :

DASHBOARD :

FLOW PROCESS :

The model workflow process is same as the process of 'BAJA ATV MODEL with Dashboard'. The small addition is here that CVT ratio and vehicle speed extracted using 'To workspace' block.

Instead of a signal builder block for CVT ratio, the 2-D look-up table is used. The interpolation and extrapolation methods set to linear.

LOOKUP TABLE VISUALIZATION :

OUTPUT :

ENGINE SPEED PLOT :

Here the engine speed generated according to the inputs like Throttle, break, torque and speed vectors. The runtime is not decided so that the throtte and brake are controlled by the user. The step up is throttle and step down is brake inputs.

CVT SPEED REDUCTION PLOT :

VELOCITY VS THROTTLE PLOT:

From the graph we can infer that, the vehicle is accelerating while throttle is applied (step up) and decelerated while brake is applied (step down).