Project
AIM:
To study and analyze the BAJA All Terrain Vehicle (ATV) model using Simulink andcompare between different models.
OBJECTIVES:
1 To Prepare a technical report explaining the functions of the subsystems & blocksused for preparing the model
2. To Explain in detail all the differences between all the five models provided
3. To undertand and comment on the results
TYPES OF MODEL studied:
1 BAJA ATV model without Dashboard (cvtModel)
2. BAJA ATV model-Data Extraction(avtModel_data)
3. BAJA ATV model with Dashboard(cvtModel_dashboard)
4. BAJA ATV model-Mapped Lookup Table without Dashboard(cvtModel_mapped) 5. BAJA ATV model-Mapped Lookup Table with
Dashboard(evtModel_dashboard_mapped)
Introduction:
All Terrain Vehicle:
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. ATVS are subdivided into two types as designated by the manufacturer. Type I ATVs are intended by the manufacturer for use by a single operator and no passenger. Type il ATVs are intended. by the manufacturer for use by an operator and a passenger, and are equipped with a designated seating position behind the operator.
BAJA SAE:
Baja SAE is an collegiate design series competition run by the Society of automotive engineers (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 and 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 continuously variable transmission (CVT) is anautomatic 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.
fig=cvt
Main and critical blocks used: Generic Engine block:
fig-generic engine block
The Generic Engine block represents a general internal combustion engine. Engine types include 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 engine fuel consumption rate based on choice of fuel consumption model. Optional speed and redline controllers prevent engine stall and enable cruise control.
Main ports:
1.B-Rotational Conserving Port representing the Engine Block(should be
connected to rotational motion reference)
2. F-Rotational Conserving Port representing the Engine Crankshaft
3 T-Physical signal input port specifying the normalized engine throttle level 4 P-Physical signal output port: reporting the instantaneous engine power, in W 5. FC Physical signal output port: reporting the fuel consumption rate, in kg/s
The Simple Gear block represents a gearbox that constrains the connected driveline axes of the base gear, & and the follower gear, F, to corotate with a fixed ratio that is specified.
The Simple Gear block represents a gearbox that constrains the connected driveline
axes of the base gear, B, and the follower gear, F, to corotate with a fixed ratio that is
specified
fig=simple gear
The follower-base gear ratio is
where:
• Nis the number of teeth in the base gear Nais the number of teeth in the follower gear
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, or
output, shaft
Variable Ratio Transmission block:
fig=Variable Ratio Transmission block
The Variable Ratio Transmission block represents a gearbox that dynamically transfers motion and torque between the two connected driveshaft axes, base and follower
Ignoring the dynamics of transmission compliance, the driveshafts are constrained to corotate with a variable Gear Ratio control that you control. You can choose whether the follower axis rotates in the same or opposite direction as the base axis. If they rotate in the same direction, wy and we have the same sign. If they rotate in opposite directions, we and we have opposite signs.
Transmission compliance introduces internal time delay between the axis motions. Therefore, unlike a gear, a variable transmission does not act as a kinematic constraint You can also control torque loss caused by transmission and viscous losses.
Main ports:
18-Base Pulley or Drive Pulley
2 F-Follower Pulley or Driven Pulley
3.r-Variable Transmission Ratio (input)
Vehicle 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.
fig=Vehicle Body block:
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:
1. Beta-Road incline Angle (rad):physical signal input port for road incline angle 2. W-Head Wind Speed (m/s) physical signal input port for road incline angle
3. CG-center of gravity(m):physical signal input port of externally defined mass
relative to the cg of vehicle(only available with externally defined additional mass
is set to on) LM-mass(kg) physical signal input port for mass of the externally defined
mass(only available with externally defined additional mass is set to on)
LJ-Externally defined moment of inertia(in kg*m^2) physical signal input port of the externally defined mass
Output ports:
1. NR-Rear Axle Normal Force (N): physical signal output port for the rear axle which is considered positive acting downward
2. NF-Front Axle Normal Force (N) physical signal output port for the front ande which is considered positive acting downward 3. V-Longitudinal Velocity (m/s):physical output signal of vehicle velocity
Conserving ports:
H-Horizontal Motion conserving port related to the horizontal motion of vehicle
body(tyres should be connected to this port)
Double shoe brake Block:
S
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 couse 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
Limitations:
• 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.
Input ports:
F-Physical signal input port associated with the applied actuating force
Conserving ports:
S-Rotational conserving port associated with the rotating drum shaft
1:BAJA MODEL WITHOUT DASHBOARD
FIG=BAJA MODEL WITHOUT DASHBOARD
Steps:
The throttle signal is generated by signal builder block and inputted to generic engine.
iv.The same output speed will be given to a simple gear mechanism to reduce the speed where the Gear Ratio is 4.
Transmission block (CVT). vi.The CVT ratio is provided to the Variable Ratio Transmission (CVT) block through
ii. 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. v.Then the output speed from the gear reducer will be given to the Variable Ratio Signal Builder. ix. The power from the CVT is inputted to the axle and the vehicle accelerates according to the speed.
vil. The speed is controlled by the variable CVT ratios and the controlled output speed is inputted to the vehicle axle.
viii. The brake signal is generated by the signal builder and inputted to the vehicle body (Double Shoe Brake) for applying the brake to axle.
x.Then the Velocity is taken as output from the vehicle body for further analysis.
INPUT DATA
RESULS PLOT
FIG=RESULT PLOT
CVT RESULT PLOT
FIG=CVT PLOT
THROTTLE INPUT AND BRAKE SPEED SIGNAL
FIG=THROTTLE INPUT
SPEED TORQUE PLOTS
VEHICLE SPEED
2: BAJA MODEL MAPED WITH LOOKUP TABLE
fig=BAJA MODEL MAPED
Steps
The model workflow process is same as the process of 'BAJA ATV model without Dashboard except that it used instead of Signal Builder Blocks for Brake and Throttle Input Step input blocks are used. At 35 sec the brake input will take a step of value "0" and at 20 sec throttle input will increases from 0.3-1 then remains constant throughout.
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 lle 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.
At last the vehicle speed output is given as a feedback to the 2-D Lookup Table so that
we can verify that the velocity of the vehicle is changing perfectly when the CVT Ratio
changes. The vehicle speed is converted to m/s from Kmph.
3:BAJA MODEL-DATA EXTRACTION
FIG=DATA EXTRACTION MODEL
CVT RESULTS OF GIVEN DATA
4:BAJA MODEL WITH DASHBOARD
FIG=BAJA MODEL WITH DASHBOARD
DASHBOARD
RESULTS
Steps:
The model workflow process is same as the process of 'BAJA ATV model-mapped lookup table without Dashboard' but the Throttle and Brake inputs are controlled by the user with the knob followed by the vehicle speed is given as feedback to the CVT Ratio lookup table.
In this BAJA ATV Model, the Engine is pre-set 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 pre-defined as 2.3 and 18 respectively. When the simulation is started the initial throttle value 0.3 is achieved so that the CVT Ratio is nearby to 1.85. When the throttle is being increased the CVT Ratio move towards 1.8 where the state is maximum engine speed. Simultaneously 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 achieve the nearest state of 23 (Minimum Engine Speed). When braking is reduced the
FIG=RESULT OF CVT