Project

AIM: To carry out a system - level simulation of an all - terrain vehicle using Simulink.

OBJECTIVES:

To prepare a technical report on a BAJA ATV explaining model properties for the following:

- Without using Lookup table

- Using Lookup table

THEORY:

ATV - An all-terrain vehicle (ATV) refers to a motorized single-seated tri or quadricycle

bike and buggy that is designed for off-road travel and activities. The vehicle consists of handlebars

and low pressure tires that have deep threaded structures, which assist in driving over muddy ,

rocky, wetlands and dune topologies. In comparison to other utility vehicles(UTVS). ATVs offers

excellent off-road capabilities and can carry heavy equipment over a long distances and narrow

access points. They can also be customized for high performance riding, owing to which they find

extensive applications across various industries, including sports, entertainments, agriculture,

military and defense.

CVT: A CVT or Continuously Variable Transmission in an automatic , single-speed and gearless

transmission that can shift through an infinite number of gear rates.

A continuously variable transmission (CVT) is a transmission that operates on an ingenious

pulley system that automatically varies the transmission ratio, allowing an infinite variability between

highest and lowest gears with no discrete steps or shifts. CVTs provide more useable power, better

fuel economy and smoother driving experiences than traditional transmissions that use gearboxes

with fixed number of gear sets.

SOLUTION:

PART 1 - BAJA ATV Model without Lookup Table.

A simulink model for the BAJA ATV Model is as shown below;

The model consists of common blocks as follows:

Signal Builder - The signal builder block allows to create interchangeable groups of piecewise linear signal,

sources and use them in a model. We can quickly switch the signal groups into and out of a model to

facilitate testing.

Generic Engine: Generic engine represents a 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 idle

speed real line controllers are included.

The throttle input signal T lies between zero and one and specifies the torque demanded from

the engine as a fraction of the maximum possible torque. If the engine speed falls below the

speed the engine torque is blended to zer. If the engine speed exceeds the maximum speed,

the simulation stops and issues an error message.

Connections F and B are machanical rotational conserving ports associated with the engine

crankshafts and engine block, respectively. connections P and FC are physical signal output

ports through which engine power and fuel consumption rate are reported.

Speed vector and Torque vectors are assigned parameters.

Engine Sensor:

Ideal Rotational Motion Sensor: The 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 angles. The sensor is ideal since it does not account for inertia,

frictions, delays, energy consumption and so on.

Connection R and C are mechanical rotational conserving ports and connections W and A are physical

signal output ports for velocity and angular displacement, respectively.

Simple Gear: Simple gear represents a fixed-ratio gear or gearbox. No inertia or compliance is modeled

in this block. We can optionally include gear meshing and various bearing losses.

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 paramater.

Optionally include thermal effect and expose thermal conserving port H by right clicking

on the block and selecting simscape block choices to switch between variants.

Follower(F) to Base (B) teeth ratio (NF/NB):4

CVT Subsystem:

The CVT subsystem consists of following blocks:

Inertia: The block represents an ideal mechanical rotational inertia. The block has one mechanical

rotational conserving port. The block positive direction is from its port to the reference points.

This means that the inertia torque is positive if the inertia is accelerated in positive direction.

Variable Ratio Transmission: It represents a variable ratio gearbox such as imlemented by

mechanical belt CVT, electric, or hydraulic transmissions. The physical signal input r defines the

ratio of input to 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.

Vehicle Body Subsystem:

The vehicle body subsystem consists of the following blocks:

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

block accounts for body mass. Aerodynamic drag, road incline and weight distribution between axles

due to acceleration and road profile. The vehicle can have the same or different number of wheels on each

axle. Optionally include pitch and suspension dynamics or additional variables mass and inertia. The

vehicle does not move vertically relative to ground.

Connection H is the mechanical translational conserving port associated with the horizontal motion

of the vehicle body. The resulting fraction motion developed by tires should be connected to this port.

Connection v, NF and NR are physical signal output ports for vehicle velocity and front and rear normal

wheel forces respectively. Wheel forces are considered positive if acting downwards. Connections W and

beta are physical signal input ports corresponding to headwind speed and road inclination angle, respectively.

If variable mass is modeled the physical signal input ports CG and M are exposed. CG accepts a two-element

vector representing the x and y distance offsetfrom vehicle CG to additional load mass CG. M represents

the additional mass. If both variable mass and pitch dynamics are incuded, the physical signal port

J accepts the inertia of the additional mass about its own CG.

Parmeters are-

Mass-250kg

Number of wheels per axle-2

Horizontal distance from CG to front axle-1m

Horizontal distance from CG to rear axle-0.35m

CG height above ground-0.7m

Gravitational acceleration-9.81m/s^2

Tire: Tire represents the longitudinal behaviour of highway tire charecterized by the tire magic

Formula. The block is built from Tire-Road Interaction (Magic Formula) and Simscape Foundation

Library Wheel nd Axle blocks. Optionally the effects of tire inertia, stiffness and damping can

be included.

Connection A is the mechanical rotational conserving port for the wheel axle. Connection H

is the mechanical translational conserving port for the wheel hub through which the thrust

which the thrust developed by the tire is applied to the vehicle. Connection N is a physical

signal input port that applies the normal force acting on the tire . The force is considered

positive if it acts downwards. Connection S is a physical signal output port that reports the

tire slip. Optionally expose the physical signal port M by setting parameterize by to physical

signal magic formula coefficients. Physical signal port M accepts a four element vector corresponding

to the B, C, D and E magic formula coefficients.

Parameters (common for all tires) are:

Parameterize by: Constant Magic Formula Coefficients

Magic Formula B coefficients:10

Magic Formula C coefficients:1.9

Magic Formula D coefficients:1

Magic Formula E coefficients:0.97

Double-Shoe Brake: It represents a brake arranged as two pivoted rigid shoes

symmetrically installed inside or outside a drum and operated by one actuator. The

actuator force causes the shoes to exerts a friction torque on a shaft connected to a drum.

Connections S is a conserving rotational terminal associated with the drum shaft. Connected

F is a physicaln signal port representing the force input to the actuator. Positive force

creates friction torque that resists shaft rotation. Optionally include thermal effects and

expose thermal conserving port H by setting thermal port to model.

Parameters are:

Drum radius-150mm

Actuator location radius-100mm

Pin location radius-125mm

Pin location angles-15deg

Shoe begining angles-5deg

Shoe span angles-120 deg

Torque vs Speed charecteristics:

Input #1.1:

Brake and Throttle input-

Brake input is constant i.e. zero throughout the time of 80 sec.

Throttle input is 0.3 for first 20 sec; accelerates to 1 at the same and remains constant throughout

the remaining time till 80 sec.

cvtModel/Signal Builder:Brake and Throttle Input

CVT Ratio:

The CVT gear ratio 2.3 for the first 4 secs, then drops down to 1.8 till 35 secs and remains constant

thereafter till 80 sec.

cvtModel/CVT Ratio: CVT Ratio

Output #1.1:

Velocity:

CVT Shaft speed:

Engine speed:

1.2 With Dashboard:

A simulink model for the BAJA ATV model including the dashboard is shown below. The rest of the ports

and subsystem are common in above part #1.

Dashboard: A dashboard (also called dash, instrument panel(IP), or fascia) is a control panel usually

located directly ahead of a vehicle's driver, displaying instrumentation and controls for the vehicle's

operation .

The initial conditions are as follows:

Brake input = 0

Throttle input = 0.3

Input #1.2:

It comprises a throttle and brake input through a knob which can be varied unlike the signal builder

in the previous model without dashboard . The Engine RPM gauge and velocity gauge displays the

changes done by the respective knobs.

Output#1.2:

CVT Shaft speed:

Engine speed:

Part #2: BAJA CVT using LOOKUP Table

2.1 Without Dashboard

A simulink model for the BAJA ATV Model including the lookup table is shown below.

Lookup Table: A lokup table is an array of data that maps input values to output values, thereby

approximating a mathematical function. Given a set of input values, a lookup operation retrieves

the corresponding output values from the table. If the lookup table does not explicitily defines the

input values, simulink can estimate an output values using interpolation, extrapolation or rounding

where;

-interpolation is a process for estimating values that lie between known data points.

-extrapolation is a process for estimating values that lie beyond the range of known data

points.

-rounding is a process for approximating a values by altering its digits according to a known rule.

A lookup table block uses an array of data to map input values to output values, approximating

a mathematical function. given input values, simulink performs a 'lookup' operation to retrieves

the corresponding output values from the table . If the lookup table does not define the input

values, the block estimates the output values based on nearby table values.

In a place of CVT ratio input, a lookup table is assigned in the models below. It needs to be

loaded in the workspace having the file name as Lookuptable_datamat

Input #2.1:

They are given in steps using the step block. parameters area;

Brake input -

step time-35

initial value-0

final value-0

sample time-0

Throttle input-

step time-20

initial value-0.3

final value-1

sample time-0

Output #2.1:

CVT Ratio:

Velocity:

CVT shaft speed:

Engine speed:

2.2 with Dashboard:

A simulink model for the BAJA ATV model including the dashboard and the lookup table is shown below.

Input #2.2:

It comprises a throttle and brake input through a knob which can be varied unlike the signal

builder in the previous model without dashboard. The engine RPM gauge nd Velocity gauge

displays the changes done by respective knobs.

Output #2.2:

Velocity

CVT shaft speed:

Engine speed:

conclusions:

Hence the given BAJA ATV Model was simulated successfully and from the above result, we can infer that:

-CVT Ratio is directly proportional to torque and inversely proportional to the throttle input.

-CVT primary speed is greater than CVT secondary speed as they are directly proportional to their

shaft diameter.

-The speed might get null at a perticular braking resistance.

-velocity, CVT shaft speed and Engine speed are directly proportional to the throttle input and

inversely proportional to the brake input.