Project

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

Objective:

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

1. Without using Lookup table.
2. Using Lookup table.

Theory :

• ATV :

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 diving over muddy, rocky, wetlands and dune topologies. in comparison to other utility vehicles(UTVS), ATVs offer excellent off-road capabilities and can carry heavy equipment over long distances an narrow access points. They can also be customized for high performance riding, owing to which they find extensive applications across various industries, including sports entertainment, agriculture, military and defence.

Type	Application	Engine (cc)	Wheels	Drivetrain	Fuel	Capacity
Utility ATV	Sports	Below 400cc	Three Wheels	2WD	Gasoline ATV	One seat
Sport ATV	Entertainment	400- 800cc	Four Wheels	4 WD	Electric ATV	Two or More Seat.
Recreational ATV	Agriculture	Above 800cc	Four Wheels	AWD
OThers	Military & Defence

• CVT:

A continuously variable transmission (CVT) is an automatic transmission that can change seamlessly through a continuous range of gear ratios. This contrasts with other transmissions that provide a limited number of gear ratios in fixed steps. The flexibility of a CVT with suitable control may allow the engine to operate at a constant RPM while the vehicle moves at varying speeds.

CVTs are used in automobiles, tractors, motor scooters, snowmobiles, bicycles and earthmoving equipment.

The most common type of CVT uses two pulleys connected by a belt or chain; however, several other designs have also been used at times. It provides mor usable power , better fuel economy and smooth driving experience than manual gear transmission.

Part 1

• Without Dashboard

A Simulink model for BAJA ATV model is shown below

It consists of following common blocks:

• Signal Builder: The Signal Builder black allows you to create interchangeable groups of piecewise linear signals and use them in a model. You can quickly switch the signal groups into and out of a model to facilitate testing.
• 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 Optional idle speed and red 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 Stall speed, the engine torque is blended to zero. If the engine speed exceeds the maximum speed, the simulation stops and issues an error message.

Connections F and B are mechanical rotational conserving ports associated with the engine crankshaft 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 vector are the assigned parameters.

Engine Sensors:

• Ideal Rotational Motion 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 angle, respectively, of port R relative to port C. The measured angular velocity is positive when the angular velocity at port R is greater than the angular velocity at port C.

• Simple Gear: Represents a fixed-ratio gear or gear box. No inertia or compliance is modeled in this block. You can optionally include gear meshing, backlash, and viscous 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 parameter. Optionally include thermal effects and expose thermal conserving port H by setting Friction model to a temperature-dependent setting.

• CVT Subsystem:

The CVT subsystem consist of following block:

• Inertia: The block represents an ideal mechanical rotational inertia.

The block has one or two mechanical rotational conserving ports. The difference is purely graphical, as the ports are rigidly linked. The block positive direction is from its port to the reference point. This means that the inertia torque is positive if the inertia is accelerated in the positive direction.

• Variable Ratio Transmission:

Represents a variable ratio gearbox such as implemented 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:

Vehicle Body Subsystem contains following blocks:

• 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 a different number of wheels on each axle Optionally include pitch and suspension dynamics or additional variable mass and inertia. The vehicle does not move vertically relative to the ground.

Connection H is the mechanical translational conserving port associated with the horizontal motion of the vehicle body. The resulting traction motion developed by tires should be connected to

this port. Connections 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. f the 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 offsets from vehicle CG to additional load mass CG. M represents the additional mass. If both variable mass and pitch dynamics are included, the physical signal port J accepts the inertia of the additional mass about its own CG.

• Parameters are:
• Mass: 250 kg
• Number of wheels per axle: 2
• Horizontal distance from CG to front axle: 1 m
• Horizontal distance from CG to rear axle: 0.35 m
• CG height above ground: 0.7 m
• Gravitational acceleration: 9.81 m/s^2

• Tire:

Represents the longitudinal behavior of a highway tire characterized by the tire Magic Formula. The block is built from Tire-Road Interaction (Magic Formula) and Simscape Foundation Library Wheel and 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 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 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 coefficient 10
• Magic Formula C coefficient 1.9
• Magic Formula D coefficient 1
• Magic Formula E coefficient 0.97

• Double Shoe Brake:

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 exert a friction torque on a shaft connected to the drum.

Connection S is a conserving rotational terminal associated with the drum shaft. Connection F is a physical 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
• Drum radius: 150 mm
• Actuator location radius: 100 mm
• Pin location radius: 125 mm
• Pin location angle: 15 deg
• Shoe beginning angle: 5 deg
• Shoe span angle: 120 deg

Torque vs Speed Characteristics:

Input 1.1:

Brake and Throttle Input:

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

Throttle input is 0.3 for first 20 sec and then it increase at 1 and constant throughout remaining 60 sec

CVT Ratio:

The CVT gear ratio is 2.3 for start and it drop at 1.8 for time period of around 55 sec

Output 1.1

Velocity

Distance

Throttle

Brake

CVT RPM

Engine

• With Dashboard

A Simulink model for the BAJA ATV Model including the dashboard is shown below. The rest of the parts and subsystems are common in the above part 1.1.

Dashboard: A dashboard (also called dash, instrument panel (1P), 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 = O3

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 2.2:

Velocity:

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:

Lookup Table: A lookup 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 explicitly define the input values, Simulink can estimate an output value 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 value 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 retrieve 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 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_ data.mat

CVT Ratio VS Vehicle Speed:

0 to 5 km/hr , the CVT ratio is constant at 3.5

5 to 35 km/hr , the CVT drops down 0.5

35 onwards , the CVT ratio is constant 0.5

Input 2.1

they are given in steps using the step block

Brake input :

Step time: 35

Initial value :0

Final value 0

Simple time 0

Throttle output :

Step time: 20

Initial value :0.3

Final value 1

Simple time 0

Output 2.1

Velocity:

CVT Shaft Speed:

CVT Ratio:

Engine Speed

2.2 with Dashboard

A Simulink model for the BAJA ATV including the dashboard and Lookup Table is showing 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 and Velocity gauge displays the changes done by the respective knobs

Output 2.2

Engine Speed

CVT Ratio

Velocity

CVT Shaft Speed

CONCLUSION:

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

• Velocity, CVT Shaft Speed and Engine Speed are directly proportional to the Throttle input and inversely proportional to the Brake input
• 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 particular braking resistance