Project

AIM: To do a detailed case study on Continous Variable Transmission (CVT) using BAJA ATV vehicle and write a report.

THEORY:

An all-terrain vehicle (ATV), also known as a light utility vehicle (LUV), a quad bike, or simply a quad, as defined by the (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.

BAJA ATV (SAE):

The BAJA SAE Series is an event for the 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 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 manoeuvrability characteristics and finally its ability to endure that back breaking durability test.

Static events, such as written reports, presentations and design evaluations are provided by participating teams. This is when the teams are judged on ergonomics, functionality, and producibility of their cars; ensuring that the final placement of the team does not rest solely on the vehicle's performance but rather on a combination of static and dynamic events. Required reports detail the engineering and design process that was used in developing each system of the team's vehicle, supported with sound engineering principles.

Continous Variable Transmission(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, 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.

Blocks:

Generic Engine:

Represents a system-level model of spark-ignition and diesel engines suitable for use at initial stages of modeling when only the basic parameters are available. Optional idle speed and red line controllers are included.

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.

In the main tab of matlab the values of torque vector and speed vecor are reported in the form array data set.

Simple Gear:

Engine is Connecting to CVT with Simple Gear ratio for Speed Reduction.

The main components are

1. Primary pulley
2. Secondary pulley
3. Belt
4. Varitor

• If primary pulley goes inward and secondary pulley goes outward which leads to overdrive.
• If primary pulley goes outward and secondary pulley goes inward which leads to speed reduction

Signal Builder:

Signal Builder is used to give input values of Brake Input and Throttle input and it is connected with Generic Engine Block.

Where,

Throttle Input = 0.3 for first 20 sec, after 20 sec throttle input will be 1.

Brake Input = 0,

CVT Ratio:(Signal Builder)

CVT Ratio Block is connected with CVT by giving random values to get the velocity for those random CVT ratio.

Vehicle Body:

It is 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.

Remaining Small Blocks

• 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.
• Solver Configuration – To specify the solver parameters before starting the simulation
• Mechanical Reference – To make sure all the components are clamped to the ground
• Simulink to PS Converter – To convert the Simulink signal to Simscape environment
• PS to Simulink Converter – To convert Simscape signal to Simulink environment
• Rotational Motion Sensor – To sense the rotational motion from the engine and give output as rpm
• PS Terminator - Terminator for unconnected physical signal outputs
• PS Constant - Generate constant physical signal
• Variable Gear Ratio – To vary the speed according to the gear ratios
• Step – To increase or decrease an input value for a defined time interval
• Knob – To increase, decrease and vice-versa of throttle and brake inputs
• Lookup Table – To insert the CVT values from the workspace

Case study:

CASE 1: BAJA ATV With CVT

Block diagram:

Output:

Graph 1: Engine torque vs Speed curve

Graph 2: CVT Shaft speed plot

In Continously Variable Transmission (CVT) Variator of Primary Pulley goes inward and Secondary Pulley goes Outward it will leads to Overdrive. Primary Pulley radius increases and Secondary Pulley radius decreases. So Speed of Primary pulley is greater than Secondary Pulley.

Graph 3: Vehicle Speed plot

In the above plot, Throttle input 0.30 for 20 sec and Brake input is 0, By increasing the Throttle input value to 1 velocity will reach to 20.

Graph 4: Engine speed.

Initially engine speed is decreased because of increasing gear ratio that increases the torque. By increasing the throttle value it reaches maximum speed.

CASE 2: ATV With CVT Using DASHBOARD

Block Diagram:

• To see the variation in speed and velocity Dashboard is connected to the BAJA All terrain Vechicle i.e., above case.The variation of speed and velocity is diplayed while running the simulation
• RPM gauge refers the Speed of the Primary & Secondary Pulley and Velocity gauge refers the Speed of the vehicle.

Output:

Graph 1: Block diagram

Initially the rpm and velocity is Zero in the dashboard, By giving the time value as 'inf' and change the brake input abnd throttle input we can see claearly variation of speed and velocity.

Graph 2: Velocity speed plot

From the above plot, By increasing the brake input value velocity will increase and by increasing throttle input value speed will be increased.

Graph 3: CVT Shaft Speed Plot

By increasing the throttle input value,it will increase the RPM of the Primary & Secondary Pulley and by increasing the brake input value it will decrease the RPM of the Primary & Secondary Pulley.

Graph 4:Engine speed

By increasing the throttle input value,it will increase the Engine Speed and by increasing the brake input value it will decrease the Engine Speed.

CASE 3 ATV With CVT:( By using LOOK UP Table)

Block Diagram:

Here we are giving lookup table data as input instead of CVT ratio.

Code for Look Up table:

Output:

Graph 1: Look up Table

Graph 2: Velocity Speed plot

In the above plot, Throttle input 0.30 for 20 sec and Brake input is 0, By increasing the Throttle input value to 1 velocity will reach to 20.

Graph 3: CVT Ratio Plot: (Look Up Table Data)

If Throttle value increases CVT ratio decreases. If Throttle value decreases CVT Ratio increases.

Graph 4: CVT Shaft Speed Plot

In Continously Variable Transmission (CVT) Variator of Primary Pulley goes inward and Secondary Pulley goes Outward it will leads to Overdrive. Primary Pulley radius increases and Secondary Pulley radius decreases. So Speed of Primary pulley is greater than Secondary Pulley.

Graph 5: Engine speed

Initially engine speed is decreased because of increasing gear ratio that increases the torque. By increasing the throttle value it reaches maximum speed.

CASE 4: ATV With CVT With DASHBOARD:( By using LOOK UP Table)

Block Diagram:

• To see the variation in speed and velocity Dashboard is connected to the BAJA All terrain Vechicle i.e., above case.The variation of speed and velocity is diplayed while running the simulation
• RPM gauge refers the Speed of the Primary & Secondary Pulley and Velocity gauge refers the Speed of the vehicle.

Output:

Graph 1: Velocity Speed plot

From the above plot, By increasing the brake input value velocity will increase and by increasing throttle input value speed will be increased.

Graph 2: CVT Ratio Plot: (Look Up Table Data)

If Throttle value increases CVT ratio decreases. If Throttle value decreases CVT Ratio increases.

Graph 3: CVT Shaft Speed Plot:

In Continously Variable Transmission (CVT) Variator of Primary Pulley goes inward and Secondary Pulley goes Outward it will leads to Overdrive. Primary Pulley radius increases and Secondary Pulley radius decreases. So Speed of Primary pulley is greater than Secondary Pulley.

Graph 5: Engine speed

By increasing the throttle input value,it will increase the Engine Speed and by increasing the brake input value it will decrease the Engine Speed.

CONCLUSION:

• Simulation of an BAJA ALL TERRAIN vehicle is done and results are plotted.
• Simulation of an BAJA ALL TERRAIN vehicle is done by using 'Look Up table and results are plotted.