Project
BAJA ALL TERRAIN VEHICLE (ATV) ANALYSIS USING SIMULINK:-
AIM :-
To study and analyze the BAJA All-Terrain Vehicle (ATV) model using Simulink.
PLATFORM USED:-
- Software – Simulink (MATLAB)
- Version – R2020a
SYSTEM SPECIFICATIONS:-
- Manufacturer - DELL
- Model – Vostro 3478
- Operating System - Windows 10
- Processor - Intel(R) Core(TM) i5-8250U CPU @ 1.60GHz 1.80GHz
- RAM – 8 GB
OBJECTIVES:-
- To prepare a technical report of the BAJA ATV model with and without Lookup Table.
THEORY:-
ALL-TERRAIN VEHICLE:-
An all-terrain vehicle (ATV), also known as a quad (cycle), three-wheeler, four-track, four-wheeler, or quadricycle, 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. It is designed to handle a wider variety of terrain than most other vehicles.
BAJA ATV (SAE) :-
The BAJA SAE Series is an event for undergraduate engineering students, organized globally by the Society of Automotive Engineers, USA. The event originated in the name of Mini - BAJA, in the year 1976 at the University of Carolina. Since then, the event has spanned across six countries – USA, Mexico, South Africa, Korea, Brazil, and India. The BAJA SAE tasks the students to design, fabricate and validate a single-seater four-wheeled off-road vehicle to take part in series of events spread over a course of 3 days that test the vehicle for the sound engineering practices that have gone into it, the agility of the vehicle in terms of gradeability, speed, acceleration and maneuverability characteristics and finally its ability to endure that back-breaking durability test.
MAJOR COMPONENTS USED IN THIS SIMULATION:-
GENERIC ENGINE:-
The Generic Engine block represents a general Internal Combustion (IC) Engine which is a type of Spark Ignition (SI-Petrol) or Compression Ignition (CI-Diesel). The speed torque and speed power parameters are provided.
PORTS,
- B – Rotational Conserving Port representing the Engine Block
- F – Rotational Conserving Port representing the Engine Crankshaft
- T - Physical signal input port specifying the normalized engine throttle level
- P - Physical signal output port reporting the instantaneous engine power, in W
- FC - Physical signal output port reporting the fuel consumption rate, in kg/s
SIMPLE GEAR:-
The simple gear is a combination of a driver and driven gear where the speed is reduced by the gear ratio. The gear ratio is defined as,
GearRatio=Follower.Gear.SpeedBase.Gear.SpeedGearRatio=Follower.Gear.SpeedBase.Gear.Speed
PORTS,
- B – Base Gear or Driver Gear
- F – Follower Gear or Driven Gear
CVT TRANSMISSION:-
In CVT (Continuous Variable Transmission) the variable diameter pulley plays a vital role in transmission. Variable-diameter pulleys must always come in pairs. One of the pulleys, known as the drive pulley (or driving pulley), is connected to the crankshaft of the engine. The driving pulley is also called the input pulley because it's where the energy from the engine enters the transmission. The second pulley is called the driven pulley because the first pulley is turning it. As an output pulley, the driven pulley transfers energy to the driveshaft.
The distance between the center of the pulleys to where the belt makes contact in the groove is known as the pitch radius. When the pulleys are far apart, the belt rides lower and the pitch radius decreases. When the pulleys are close together, the belt rides higher, and the pitch radius increases. The ratio of the pitch radius on the driving pulley to the pitch radius on the driven pulley determines the gear. when the pitch radius is small on the driving pulley and large on the driven pulley, then the rotational speed of the driven pulley decreases, resulting in a lower “gear.” When the pitch radius is large on the driving pulley and small on the driven pulley, then the rotational speed of the driven pulley increases, resulting in a higher “gear.” Thus, in theory, a CVT has an infinite number of "gears" that it can run through at any time, at any engine or vehicle speed.
PORTS,
- B – Base Pulley or Drive Pulley
- F – Follower Pulley or Driven Pulley
- r – Variable Transmission Ratio (Input)
VEHICLE BODY:-
A two-axle vehicle with longitudinal dynamics and motion and adjustable mass, geometry, and drag properties. 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.
PORTS,
- NR – Rear Axle Normal Force (N)
- NF – Front Axle Normal Force (N)
- Beta – Road Incline Angle (rad)
- V – Longitudinal Velocity (m/s)
- W – Head Wind Speed (m/s)
- H – Horizontal Motion
DOUBLE SHOE BRAKE:-
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 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.
PORTS:
- S - Rotational conserving port associated with the rotating drum shaft
- F - Physical signal input port associated with the applied actuating force
TIRE:-
The vehicle body is connected to 4 tires each per axle to move the vehicle according to the power input to the axle.
PORTS,
- N – Normal Force
- S – Tire Slip
- A – Axle
- H – Mechanical translational port associated with the wheel hub that transmits the thrust generated by the tire to the remainder of the vehicle.
BLOCKS USED:-
- Signal Builder – To input the Brake, Throttle, and CVT Ratio
- Simulink to PS Converter – To convert the Simulink signal to a Simscape environment
- Solver Configuration – To specify the solver parameters before starting the simulation
- Mechanical Reference – To make sure all the components are clamped to the ground
- Generic Engine – To run the engine with speed and torque values as input
- PS to Simulink Converter – To convert Simscape signal to Simulink environment
- Scope – To view the graph of the parameters for a better understanding
- Display – To view the calculated engine power
- Inertia – To represent the solid inertia
- Rotational Motion Sensor – To sense the rotational motion from the engine and give output as rpm
- Variable Gear Ratio – To vary the speed according to the gear ratios
- PS Terminator - Terminator for unconnected physical signal outputs
- Double Shoe Brake – To apply the brake to the vehicle when needed
- PS Constant - Generate constant physical signal
- Tire – For transportation of the vehicle
- Rotational Free End – For mechanical component (Tire)
- Vehicle Body – To represent the BAJA ATV model body
- Custom Measure Gauge – To measure the brake and throttle input
- Knob – To increase, decrease, and vice-versa of throttle and brake inputs
- Lookup Table – To insert the CVT values from the workspace
- Simple Gear – To reduce the speed of the engine with a pre-defined gear ratio
- Step – To increase or decrease an input value for a defined time interval
TYPES OF MODEL:-
- BAJA ATV model without Dashboard
- BAJA ATV model with Dashboard
- BAJA ATV model - Lookup Table Data Extraction
- BAJA ATV model – Mapped Lookup Table without Dashboard
- BAJA ATV model – Mapped Lookup Table with Dashboard Model 1. (A) : cvtModel
- In this model, the Brake and Throttle inputs are given with the help of a Signal Builder block. Here, the brake input value is kept 0 throughout, and just the throttle input is given rise, at t=20 sec, to study the variation of the vehicle speed.
- The input CVT Ratio is also given with the help of another Signal Builder block. Its value remains constant at 2.3 for the first 4 sec, then is reduced linearly to 1.8 at t=35 sec.
Result/Output :
- These are the angular velocities before and after the Variable Gear Ratio coming into play in the CVT subsystem.
- The 2 signal builder plots are nothing but the Brake and Throttle inputs given to the model.
- Vehicle speed varies as shown in the plot. Due to the initial throttle of 0.3 units, the vehicle shows a sudden rise in the velocity at the start. For the next 20 sec of the constant throttle, the vehicle speed gradually increases up until the point where the throttle is given a complete push. The vehicle accelerates at a higher rate until it reaches the top speed.
Model 1. (B) : cvtModel_Dashboard
- The only difference between this and the previous model simulation is - instead of giving a signal builder inputs of Brake and Throttle, these are provided by connecting Knobs.
- This enables us to run the model as per Real-time simulation, wherein the input can be varied while the simulation is running.
- Accordingly, the stop time is set to infinite.
Result/Output :
- While the simulation is being run, the Brake was applied at around t=4 sec, while keeping the throttle input constant, the velocity of the vehicle quickly falls down to 0 i.e it comes to rest.
The next three models are based upon taking the input values for the CVT subsystem from a Lookup Table which is itself created in one of the models.
Model 2. (A) : cvtModel_data
- This is the same as model 1. (A) discussed above.
- Here, the Lookup Table is created by taking the values from the CVT Ratio block and the final velocities of the vehicle corresponding to the CVT Ratio values. The To Workspace blocks are used for this purpose.
- By running the model, the values of the Lookup table are stored in the Base Workspace.
Lookup table visualization -
Model 2. (B) : cvtModel_mapped
- This model takes input for the CVT subsystem from the Lookup Table created in the previous model, instead of the Signal Builder block used earlier.
- GoTo and From blocks are used in order to visualize the values of the CVT Ratio in the output.
Result/Output :
- Since the values of the Lookup table are already taken from the initial models, the final result velocity plot is in turn, similar to the earlier one.
Model 2. (B) : cvtModel_dashboard_mapped
- This model, as the name suggests, is similar to model 1. (B), wherein the Brake and the Throttle inputs are given from Knobs. (Real-time simulation)
- Also, the model uses the Lookup table for the CVT Ratio values.
Result/Output :
- The simulation is run while keeping the Throttle input constant. Brake is applied at t=2.5 sec, accordingly, the vehicle comes to rest quickly.
CONCLUSION:
1. As the throttle increases, the velocity also increases which inturn the power in the engine also increases.
Figure - 20
In the above figure, at the beginning the speed reducing because of gear ratio and torque output. When the gear ratio increases, the torque increases.
2. As the brake input increases, the velocity decreases and engine power also decreases. At a certain brake input value the engine may shut down and there is no power output. The engine power is inversely proportional to the brake input.
Figure - 21
3. As the gear ratio increases, torque increases which inturn the velocity decreases.
Figure - 22
In the above figure, the torque is increasing by an increase in engine speed. At a particular point, the torque is decreasing when the gear ratio increases in order to achieve maximum velocity.
Figure - 23
In the above figure, the velocity is varying wrt the gear ratio. For the high gear ratio, the torque is more which decreases the velocity. By changing to high gear, the gear ratio becomes less parallelly the torque also less which can get high velocity.
4. With help of a lookup table, we can vary any input value and also get the output value by using the interpolation and extrapolation method which the Simulink can solve.
A system-level simulation was performed on the ATV model and the models along with the simulation results were studied successfully
SIMULINK MODEL:-
REFERENCES:-
- https://www.pathwayz.org/Tree/Plain/FORCES+-+NAMES+AND+DIAGRAMS
- https://in.mathworks.com/help/physmod/sdl/ref/tiremagicformula.html
- https://in.mathworks.com/help/physmod/sdl/ref/doubleshoebrake.html#:~:text=Double%2Dshoe%20brakes%20provide%20high,brake%20geometry%20and%20friction%20parameters.
- https://in.mathworks.com/help/physmod/sdl/ref/vehiclebody.html
- https://in.mathworks.com/help/physmod/sdl/ref/genericengine.html#:~:text=Description,specifies%20the%20normalized%20engine%20torque.
- https://bajasaeindia.org/downloads.html
- In this model, the Brake and Throttle inputs are given with the help of a Signal Builder block. Here, the brake input value is kept 0 throughout, and just the throttle input is given rise, at t=20 sec, to study the variation of the vehicle speed.