Project

Aim:

To Carry out a system-level simulation of an All-Terrain Vehicle.

Objective:

To preapere a technical report of BAJA ATV explaining model properties for the following,

• Without using Lookup table.

-without dashboard.

-with dashboard.

• Using lookup table.

-without dashboard.

-with dashboard.

Theory:

ATV:

• An All-terrain vehicle (ATV) is defined as a motorized off-highway vehicle designed to travel on four low-pressure or non-pneumatic tires, having a seat designed to be straddled by the operator and handlebars for steering control. It is also known as a quadricycle type vehicle.
• An All-Terrain motor vehicle could have three, four or even six wheels. Unlike a motorcycle, generally, the ATVs have more than two wheels. This vehicle runs on low-pressure tires.
• ATV offers excellent off-road capabilities and can carry heavy equipment over long distance,They can also be customized for high-performance riding.

CVT:

• The CVT is an automatic transmission that uses two pulleys with a steel belt running between them. To continuously vary its gear ratios, the CVT simultaneously adjusts the diameter of the "drive pulley" that transmits torque from the engine and the "driven pulley" that transfers torque to the wheels.
• 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.

SOLUTION:

Part#1.BAJA ATV Model without Lookup Table:

#1.1 Without Dashboard:

A simulink model for the BAJA ATV model is shown below,

The models consist of common block as follows:

Signal Builder:

• The signal builder block allows you to create interchangeable groups of piecewise linear signal sources.

Generic Engine:

• Represents system-level model of spark-ignition and diesel engine suitable for use at initial stage of modeling.
• 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.
• The torttle input signal T, Connections F and B are mechanical rotational conserving ports associted with engine crankshaft and enjine block, Connections P and FC are physical signal output ports throught which engine power and fuel consumption rate are reported.

Speed vector and Torque vector parameters are shown below,

Engine Sensor:

Ideal Rotational Motion Sensor:

• That is ,a device that converts an across variable measured rotational nodes into a control signal proportional to angular velocity.Teh sensor is ideal since it does not account for inertia,friction,delays,energy consumption,and so on.
• Connectoion R and C are mechanical rotational conserving ports and connections W and A are Physical signal output ports for velocity and angular displacement,respectively.

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

Variable Ratio Transmission:

• Represents a variable ratio gearbox such as implemented by mechanical belt CVT,electrical,or hydrolic transmission.
• the physical signal input 'r' defines the ratio of input to output angular shaft velocities.
• Connections B and F are maechanical rotational conserving ports,Specify the relation between B and F rotation directions with the Output shaft rotates parameter.

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.

Vehicle body subsystem:

The vehical body subsystem consists some blocks there are,inertia,Double shoe break,Tire,vehicle body,Integrator,PS-terminator,PS-Constant.

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. 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 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: 1m
• Horizontal distance from CG to rear axle: 0.35m
• CG height above ground: 0.7m
• 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,

• Tire parameters are parameterize by Constant Magic Formula coefficients,
• Magic Formula B coefficent:10
• Magic Formula C coefficent:1.9
• Magic Formula D coefficent:1
• Magic Formula E coefficent:0.97

Double-shoe Break:

• 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 are,

• 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

PS-Terminator:

Use this block to terminate physical signal outputs. Unconnected physical signal output ports do not generate warnings, but connection to a PS Terminator can be used to indicate that the signal was not inadvertently left unconnected.

Torque vs Speed characteristics:

#1.1 Inputs:

Break and Throttle input:

Break input is constant 0 throughout the time of 80 sec.

Throttle input is 1 for first 20 sec,accelerates to 2.07 at the same and remains constant throught the remaining time till 80 sec.

CVT Ratio:

The CVt gear ratio 3.7 for the first 0.04 sec and then for 0.05 sec CVT ratio is 3.6 and increases CVT ratio 3.7 at 0.1 sec and decreases the CVT ratio 0.7 at 6.173 sec and CVT ratio is constant 0.7 till 10 sec.

Output#1.1:

Velocity:

CVT Shaft Speed:

Engine RPM:

#1.2 With Dashboard:

A simulink model for the BAJA ATV model including the dashboard is shown below,the rest of all the parts and subsystems are commen in the above Part#1.1

Dashboard:

A dashboard is a control pannel usually located directly ahead of a vehicle's driver,displaying instrumentation and controls for the vehicle's operation.

The intial condition are as follows:

Break input:0

Throttle input=0.3

Input#1.2:

It comprises a throttle and break input through a knob which can be varied unlike the builder in the previous model without dashboard.The Engine RPM guage and VElocity guage display the changes done by the respective knobs.

Output#1.2:

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:

• 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,
• Interpolation is a process for estimating value that lie between known data points.
• Extrapolation is a process for estimating value 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.
• As per the 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 value.

In place of CVT ratio input,a lookup table is assigned in the model below,It needs to be loaded in the workspace having the file name as lookuptable_data.mat

CVT Ratio vs Vehicle Speed:

0 to 4 km/hr,the CVT ratio is constant at 3.49

4 to 10 km/hr,the CVT ratio drops down to 1.65

10 to 20 km/hr,the CVT ratio drops down to 0.93

20 to 38 km/hr,the CVT ratio drops down to 0.5

38 to 65 km/h, the CVT ratio is constant at 0.5

Input#2.1:
They are given in steps using the step block,Parameters are,

	Break input	Throttle input
Step Time	35	20
Initial value	0	0.3
Finel value	0	1
Sample Time	0	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 is shown below,the rest of all the parts,lookup table and subsystems are commen in the above Part#1.2

Input#2.2:

It comprises a throttle and break input through a knob which can be varied unlink the signal builder in the previous model without dashboard.The Engine RPM guage and Velocity guage dispalys the changes done by the respective knobs.

Output#2.2:

Velocity:

CVT Shaft Speed:

Engine Speed:

CONCLUSION:

• Hence,the given BAJA ATV model was simulated successfully and from the above results,we can observe that ,
• Velocity,CVT Shaft speed and engine Speed are directly proportional to the Throttle input and inversely proportional to the Break input.
• CVT ratio is directly proportional to Torque and inversely proportional to the Throttle input.
• CVT Primary speed is greater than CVT Secoundary as they are directly proportional to their shaft diameter.
• The speed might get null at a particular break resistance.

REFERENCES:

The model can be refered by BAJA ATV Model File.

https://www.mathworks.com/matlabcentral/fileexchange/70576-baja-all-terrain-vehicle-atv-model