Challenge

Project

EElango Van15 Jun 2022

AIM:

To study and analyze the BAJA all terrain vehicle (ATV) model using simulink and compare between different models.

OBJECTIVES:

To prepare a technical report explaning the functions of the subsystem & blocks used for preparing the model.
to explain in detail all the five models provided .
to understand and comment on the results.

TYPES OF MODEL STUDIED:

BAJA ATV model without dashboard (cvtmodel)
BAJA ATV model- DATA Extraction(cvtmodel_data)
BAJA ATV model with dashborad(cvtmodel_dashborad)
BAJA ATV model - mapped look up table without dashborad (cvtmodel_mapped)
BAJA ATV model - mapped lookup table with dashborad (cvtmodel_dashboard_mapped)

INTRODUCTION

All Terrain vehicle:

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 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. As the name implies, it is designed to handle a wider variety of terrain than most other vehicles. Although it is a street-legal vehicle in some countries, it is not street-legal within most states, territories and provinces of Australia, the United States or Canada.

By the current ANSI definition, ATVs are intended for use by a single operator, although some companies have developed ATVs intended for use by the operator and one passenger. These ATVs are referred to as tandem ATVs.

BAJA SAE:

Baja SAE is an Collegiate Design Series competition run by the Society of Automotive Engineers International (SAE International). Teams of students from universities all over the world design and build small off-road cars. The cars all have engines of the same specifications. As of 2018 the engine has been an unmodified Briggs & Stratton Model 19 Vanguard engine single-cylinder with a displacement of 305cc and power output of approximately 10 bhp (7.5 kW).

The goal in Baja SAE racing is to design, build and race off-road vehicles that can withstand the harshest elements of rough terrain. The vehicles used in Baja SAE racing are often similar in appearance to dune buggies. Before 2007, the events were called "Mini Baja.

CONTINUOUSLY VARIABLE TRANSMISSION(CVT):

A CVT, or continuously variable transmission, seamlessly changes through an unending range of effective gear ratios while you drive, whereas other kinds of mechanical transmissions offer a fixed number of gear ratios and have hard shifts between each as explained by Certified Transmission Repair. CVT transmission systems are also known as single-speed, shiftless, and stepless transmissions

MAIN AND CRICTICAL BLOCKS USED:

Generic engine block:

The Generic Engine block represents a general internal combustion engine. This block is a suitable generic engine for 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 the engine fuel consumption rate based on the fuel consumption model that you choose. Optional speed and redline controllers prevent engine stall and enable cruise control.

B- engine block
F - engine crank shaft
T - engine throttle level
P - engine power
FC - fuel consumption rate,kg/s

Simple gear:

where there are a number of gears meshing together, the number of teeth on them will form an important ratio: the gear ratio. When several gears are meshing together, they form what's called a gear chain. The ratio is only calculated from the first gear, the driving gear which is attached to the power source, and the last gear in the chain. If you count up the number of teeth on gear one, and on gear X (the last one) and set them in a ratio (1:X), this is the gear ratio. If the number can be reduced, you should reduce it, for example a ratio of 100 teeth:40 teeth reduces to 5:2.

main ports:

B - base,rotational mechanical conserving port associated with the base ,or input ,shaft.

F - follower, rotational mechanical conserving port associated with the follower .

VARIABLE RATIO TRANSMISSION BLOCK:

The Variable Ratio Transmission block represents a gearbox that dynamically transfers motion and torque between the two connected driveshaft axes, the base and the follower.

When you choose to have the block ignore the dynamics of transmission compliance, it constrains the driveshafts to corotate with a variable gear ratio that you control. You can choose whether the follower axis rotates in the same or opposite direction as the base axis. If the follower and base axis rotate in the same direction, ω_F and ω_B have the same sign. If the follower and base axis rotate in opposite directions, ω_F and ω_B have opposite signs.

Transmission compliance introduces internal time delay between the axis motions. Unlike a gear, a variable ratio transmission does not act as a kinematic constraint. You can also control the torque loss caused by transmission and viscous losses.

Main ports:

B - base pulley or drive pulley

F - follower pulley or driven pulley

r - variable transmission ratio(input)

VECHILE BODY BLOCK:

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.

The block accounts for body mass, aerodynamic drag, road incline, and weight distribution between axles due to acceleration and road profile. Optionally include pitch and suspension dynamics. The vehicle does not move vertically relative to the ground.

The block has an option to include an externally-defined mass and an externally-defined inertia. The mass, inertia, and center of gravity of the vehicle body can vary over the course of simulation in response to system changes.

LIMITATIONS:

The Vehicle Body block lets you model only longitudinal dynamics, parallel to the ground and oriented along the direction of motion. The vehicle is assumed to be in pitch and normal equilibrium. The block does not model pitch or vertical movement. As such, the equations assume that the wheels never lose contact. This constraint can result in negative normal forces.

INPUT PORTS:

BETA - Road incline angle(rad),physical signal input port for road incline angle.

W - Head wind speed (m/s),physical signal input port for road incline angle.

CG - centre of gravity(m),physical signal input port of externally defined mass relative to the cg of vehicle.

m-mass(kg),physical signal input port of the externally defined mass .

J - externally defined moment of inertia(kg*m^2).

OUTPUT PORTS:

NR - Rear axle normal force(N),physical signal input port of the rear axle which is considered positive acting download.

NF - front axle normal force(N),

physical signal input port of the front axle which is considered positive acting download.

V - Longitudinal velocity (m/s),physical signal input port vehicle velocity.

conserving ports:

H - horizontal motion.

Double shoe brake block:

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.

Double-shoe brakes provide high braking torque with small actuator deflections in applications that include motor vehicles and some heavy machinery. The model employs a simple parameterization with readily accessible brake geometry and friction parameters.

You can also enable faulting. When faulting occurs, the belt will exert a user-specified force. Faults can occur at a specified time or due to an external trigger at port T.

Limitations and Assumptions

Contact angles smaller than 45° produce less accurate results.
The brake uses the long-shoe approximation.
The brake geometry does not self-lock.
The model does not account for actuator flow consumption.

inputs:

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

conserving ports:

S -rotational conserving port associated with the rotating drum shaft.

TIRE(MAGIC FORMULA ) BLOCK:

The Tire (Magic Formula) block models a tire with longitudinal behavior given by the Magic Formula , an empirical equation based on four fitting coefficients. The block can model tire dynamics under constant or variable pavement conditions.

The longitudinal direction of the tire is the same as its direction of motion as it rolls on pavement. This block is a structural component based on the Tire-Road Interaction (Magic Formula) block.

To increase the fidelity of the tire model, you can specify properties such as tire compliance, inertia, and rolling resistance. However, these properties increase the complexity of the tire model and can slow down simulation. Consider ignoring tire compliance and inertia if simulating the model in real time or if preparing the model for hardware-in-the-loop (HIL) simulation.

Tire and Wheel Dynamics

The full tire model is equivalent to this Simscape™/Simscape Driveline™ component diagram. It simulates both transient and steady-state behavior and correctly represents starting from, and coming to, a stop. The Translational Spring and Translational Damper are equivalent to the tire stiffness C_Fx and damping b_Fx. The Tire-Road Interaction (Magic Formula) block models the longitudinal force F_x on the tire as a function of F_z and k′ using the Magic Formula, with k′ as the independent slip variable.

The Wheel and Axle radius is the wheel radius r_w. The Mass value is the effective mass, Iwr2w. The tire characteristic function f(k′, F_z) determines the longitudinal force F_x. Together with the driveshaft torque applied to the wheel axis, F_x determines the wheel angular motion and longitudinal motion.

Without tire compliance, the Translational Spring and Translational Damper are omitted, and contact variables revert to wheel variables. In this case, the tire effectively has infinite stiffness, and port P of Wheel and Axle connects directly to port T of Tire-Road Interaction (Magic Formula).

Without tire inertia, the Mass is omitted.

INPUT PORTS:

`N` — Normal force
physical signal

Physical signal input port associated with the normal force acting on the tire. The normal force is positive if it acts downward on the tire, pressing it against the pavement.

`M` — Magic formula coefficients
physical signal | vector | [B, C, D, E]

Physical signal input port associated with the Magic Formula coefficients. Provide the Magic Formula coefficients as a four-element vector, specified in the order [B, C, D, E].

Dependencies

Port M is exposed only if the Main > Parameterize by parameter is set to Physical signal Magic Formula coefficients. For more information, see Main Parameter Dependencies.

Output

collapse all

`S` — Slip
physical signal

Physical signal output port associated with the relative slip between the tire and road.

Conserving

collapse all

`A` — Axle
mechanical rotational

Mechanical rotational port associated with the axle that the tire sits on.

`H` — Hub
mechanical translational

Mechanical translational port associated with the wheel hub that transmits the thrust generated by the tire to the remainder of the vehicle.

OTHER BLOCKS USED:

solver configureation - to specify the solver parameters before starting the simulation.
signal bulider - to input the brake ,throttle,cvt ratio.
simulink to ps converter
ps to simulink converter.
mechanical reference - to make sure all the components are clamped to the ground.
rotational free end
scope -to display different graphs.
display - to viwe the calculated engine power.
inertia - to represented the solid inertia.
rotational motion sensor - to sence the rotational motion from the and give outputs.
ps terminator - terminator for unconnected physical signal output.
ps constant - generate constant physical signal
rotational free end - for mechanical component.
custom measure gauge - to measure the brake and throttle input
knob - to increase ,decrease and vice versa of throttle and brake inputs.
look up table - to insert the cvt values from the workspace.
step - to increse or decresae an input value for a defined time interval.

BAJA ATV MODEL WITHOUT DASHBOARD (cvt model):

MAIN MODEL:

STEPS:

The throttle signal is generated by signal bulider block and inputted to generic engine.
the torque and speed vector are inputted from the matlab worspace.
The engine will generate the output rpm which can be taken from the crankshaft output.this speed will be given to the ideal ratational motion sensor to sence 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 reduser will be given to the variable ratio transmission block(cvt).
The cvt ratio is provided to the variable ratio transmission block through signal bulider.
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 bulider and inputted to the vehicle body 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 vehiclr body for further analysis.

INPUT SIGNALS:

Throttle input signal:

Throttle starts at 0.3 and then it steps to 1 at the 20th second

BRAKE INPUT SIGNAL:

THE brake input remains zero through the whole simulation.

Torque and speed matlab workspace input:

Cvt ratio input:

Cvt ratio starts at 2.3,then 5sec it gradually reduces until it reaches 1.8 at 35 th sec and it remains so till the end of the simulation.

ENGINE SENSOR SUB-BLOCK:

This subblock measure engine rotational speed as it takes the output of the engine as its input and outputs engine rpm.

CVT SUB-BLOCK:

The cvt subblock provides the input and the output shaft of the cvt with inertia,and measures the input shaft rpm and the output shaft rpm.

VEHICLE BODY SUB-BLOCK:

RESULTS:

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 behavior is generic to all ICE.

Engine speed plot:

the engine rpm generated according to the throttle ,speed and torque inputs.its clearly evident hoe the setp increase in throttle at 20th second resulted inan increase in the engine revolutions from 2250 t0 3800 rpm.

Engine speed vs gear reduction speed plot:

Here we can see that the engine speeed is reduced by the gear ratio 4.

Maximum rpm = 3833 rpm was redused to 958.25. rpm which can be verified by dividing the 3833 by the gear reduction ratio 4.

cvt speed reduction plot:

the engine redused speed is controlled by various cvt ratios.for verfication the maximum rpm is calculated at 1.8 gear ratio which is applicale from the 35th second.

maximum rpm = 958.25 rpm.

The reduced maximum rpm is 532.36 rpm which can be verified from the plot.

speed vs throttle plot:

From the graph we can inform that the brake is not applied during the drive cycle and the throttle is constant till 20 sec and being increment from 0.3 to 1 from 20 sec where it remains constant throughout.with increase in throttle the vehicle speed incresed from 30 to 55kmph.

BAJA ATV MODEL- DATA EXTRACTION(CVTMODEL_DATA);

Main model:

steps:

The model workflow process is same as the process of 'BAJA ATV model without dashboard'.the small addition is here the cvt ratio and vechicle speed data are extracted using 'TO WORKSPACE' block.

Results:

The results are same as 'BAJA ATV model with out dashboard , but an additional output is the cvt ratio and vehicle velocity to the workspace.

BEFORE AND AFTER WORSPACE BLOCK:

BAJA ATV MODEL WITH DASHBOARD(cvtmodel_dashboard):

main model:

dashboard:

steps:

The model workflow process of 'BAJA ATV model without dashboard ' but the throttle and brake input are controlled by the user with knobs.

results:

Engine speed plot:

Here the engine speed is generated according to the inputs like throttle ,breake,torqe 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 input.

Engine speed vs gear reduction speed plot:

The engine speed is redused by a factor of 4 at any moment in the drive cycle as it is evident by the curve.

CVT speed reduction plot:

The Cvt gear reduction plot shows that at constant the reduction ratio of 1.8 is applicable at these large time frame and it can be verified by taking 689 constant RPM and dividing it by 1.8 = 383 RPM which verfies the plot

speed vs throttle input:

From the graph we can infer that the vehocle is accelerating while throttle is applied and deaccelerating while brake is applied .the constant speed areas represent no changes in throttle or braking.

BAJA ATV model - mapped lookup table without dashboard(cvtmodel_mapped);

main model:

steps:

The model workflow process is same as the process of 'BAJA ATV model without dashboard except that it used instead of signal bulider blocks for brake and throttle input step input blocks are used.at 35sec the brake input will take a step of value '0' and at 20 sec throttle input will increase from 0.3 -1 then remains constant throught.

The cvt subblock is the same as the previous model ''BAJA ATV MODEL without dashboard" but instead of signal bulider block for cvt ratio the 2 -D look up table is used

LOOK UP 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:

An interpolation is a process for estimating values that lie between known data points.
An extrapolation is a process for estimating values that lie beyond the range of known data points.
A 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.

results:

CVT ratio plot:

When we compare the above plot , the ratio varies from 2.3 -1.8 with in timespan of 80 sec which is same as the previous BAJA ATV models.and from 32 sec it 's constant ratio of '1.8' compared to 35 sec in the first model.also the reduction from 2.3 ratio to 1.8 is not perfectly linaer as in the first model.

CVT ratio vs vehicle velocity:

0 to 20 km/hr ,the CVT ratio is constant at 2.3

20 to 30 km/hr, the cvt ratio drops down to 2.03

30 to 50 km/hr, the cvt ratio drops down to 1.8

50 km/hr onwards,the cvt ratio is constant at 1.8

Hence ,we can conclude that the vehicle accelerates and remains constant when the cvt ratio is being varied.

engine speed:

The same graph is shown in the first model.

CVT shaft speed:

The output shaft speed follows the cvt ratio discussed before.

speed vs throttle plot:

it shown same results as the first model.

BAJA ATV model - mapped lookup table with dashboard(cvtmodel_dasgboard_mapped):

Dashboard (simulation off)

steps:

The model workflow process is same as the process of "BAJA ATV model mapped lookup table with out dashboard" but the throttle and brake inputs are controlled by the user with the knob folowed by the vehicle speed is given as feedback to the CVT ratio look up table.

results:

CVT ratio plot:

IN this baja atv model ,the engine is preset to run at 3300 rpm with the throttle value of '0.3' .And the velocity at 45 kmph.the cvt ratio for minimum and maximum speed of the engine was predefined as 2.3 and 1.8 respectviy.when thw simulation is strated the initial throttle value 0.3 is achived so that the cvt ratio is near by to 1.85.when the throttle is being increased the cvt ratio move towards 1.8 where the state is maximum engine speed.

simutaneously when the throttle is being decreased the cvt ratio will move towards 1.85.while the braking is applied the cvt ratio increases so that it can achive the nearest state of 2.3.

engine speed plot:

From the graph we can infer that the vehicle was first running at minimum rpm of 3300 rpm and then throttle is applied then braking then brake is relesed so that engine rpm is increased then braking is applied.

cvt speed reduction plot:

From the above plot we can unterstanding that throttle is applied and then kept constant then braking is applied then brake is released so that the engine speed is increased with increase in throttle input.

speed vs throttle plot:

From the plot we can infer that when throttle is applied the vehicle speed increase and when brake is applied vehicle speed decrease simultanously.

reference:

math works.

Project