Challenge

Project

RRahul Jadhav1 Jan 2022

AIM: To Study and analyze the BAJA All Terrain Vehicle (ATV) model using Simulink.

OBJECTIVES:

To prepare a technical report of Baja ATV model with and without Lookup Table.

THEORY:

ALL TERRAIN VEHICLE:

An All-Terrain Vehicle (ATV), also known as a quad(cycle), Light Utility Vehicle (LUV), as defined by the American National Standards 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. It is designed to handle a wider variety of terrain than most other vehicles.

BAJA ATV(SAE):

The BAJA SAE series is an event for the 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 has spanned across six countries – USA, Mexico, South Africa, Korea, Brazil and India. The BAJA SAE tasks the students to design, fabricate and validate a single seater four – wheeled off road vehicle to take part in series of events 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 maneuverability characteristics and finally its ability to endure that back breaking durability test.

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 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.

SIMULATION PROCESS:

The throttle signal is generated by signal builder block and inputted to generic engine.
The torque and speed vector are inputted from the MATLAB workspace.
The engine will generate the output 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 reducer will be given to the Variable Ratio Transmission block (CVT).
The CVT ratio is provided to the Variable Ratio Transmission (CVT) block through Signal Builder.
The speed is controlled by the variable CVT ratios and the controlled output speed is inputted to the vehicle axle.
The brake signal is generated by the signal builder and inputted to the 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 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.

SIMULINK MODEL : BAJA All-Terrain Vehicle (ATV) Model - File Exchange - MATLAB Central (mathworks.com)

REFERENCES:

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Ship work like this
in your own course.