Project

AIM: To Study and analyze the BAJA All Terrain Vehicle (ATV) model using Simulink.

THEORY:

An All-Terrain Vehicle (ATV), also known as a quad(cycle), Light Utility Vehicle (LUV), 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 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 Caroline. 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.

BLOCKS USED:

• Signal Builder – To input the Brake, Throttle and CVT Ratio.
• Simulink to PS converter – To convert the Simulink signal to 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 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 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 pre-defined gear ratio.
• Step – To increase or decrease an input value for a defined time interval

ENGINE SENSOR:

This block measures angular velocity or angle in a mechanical rotational network. The sensor is ideal since it does not account for inertia, friction, delays, energy consumption, and so on.

The physical signal ports W and A report the angular velocity and angular displacement, respectively, of port R relative to port C. The measurement is positive when the motion at R is greater than the motion at C.

SIMULATION PROCESS:

• The throttle signal is generated by signal builder block and inputted to generic engine.
• The torque and speed vector are inputted from the MATLAB workspaceThe 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.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 reducer will be given to the Variable Ratio Transmission block (CVT).The CVT ratio is provided to the Variable Ratio Transmission (CVT) block through Signal Builder.
• 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 builder and inputted to the vehicle body (Double Shoe Brake) for applying the brake to axle.The power from the CVT is inputted to the axle and the vehicle accelerates according to the speed.The torque and speed are inputted from the MATLAB workspace window to the generic engine block to generate the output RPM accordingly. This plot is common for all the cases because it’s a default input to the engine.Then the Velocity is taken as output from the vehicle body for further analysis.

Here we can see that the engine speed is reduced by the Gear Ratio ‘4’. For verification I calculated the maximum RPM.

Maximum RPM (Before Reducing) = 3833 rpm

Gear Ratio = 1:4

We know that,

Driven = 3833/ 4

Driven = 95625RPM

Thus, the reduced maximum rpm is 958.25rpm which can be verified from the plot.

Note: Driven = Secondary CVT Shaft

Driver = Primary CVT Shaft

The engine reduced speed is controlled by various CVT ratios. For verification I had calculated the maximum RPM.

Maximum RPM (Before Reducing) = 958.25rpm

CVT Ratio = 1:1.8

We know that,

Driven = 3833/ 4

Driven = 95625RPM

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

SPEED vs THROTTLE PLOT:

From the graph we can infer that the brake is not applied during the drive cycle and the Throttle is constant (0.3) till 20 sec and being increased from 0.3 to 1 from 20 sec where it remains constant for the rest of the run. With the increase in throttle, the vehicle speed also increases.

From the above plot, we can infer that the vehicle is accelerated from 0-20kmph and then gradually increases till 30kmph(approx..) and it’s accelerated to 55.74kmph where it remains constant throughout the cycle.

FLOW PROCESS:

The model workflow process is as same as the process of ‘BAJA ATV model without Dashboard’ but the Throttle and Brake inputs are controlled by the user with the Knob. We are also replacing signal builder with two separate constant blocks for Throttle and Brake.

Here the engine speed is generated according to the inputs like throttle, break, torque and speed vectors. The runtime is not defined so that the Throttle and Break are controlled by the user. The step up is throttle and step down are break inputs.

Here we can see that the engine speed is reduced by the Gear Ratio ‘4’. For verification I calculated the constant RPM (42000 – 50000 sec).

Maximum RPM (Before Reducing) = 2759.3 rpm

Gear Ratio = 1:4

We know that,

Driven = 2759.3/4

Driven = 689.825 RPM

The reduced constant rpm is 689.825 rpm which can be verified from the plot.

CVT SPEED REDUCTION PLOT:

The engine reduced speed is controlled by various CVT Ratios. For verification I had calculated the constant RPM (42000 – 50000 sec)

Maximum RPM (Before Reducing) = 689.825 rpm

CVT Ratio = 1:1.8

We know that,

Driven = 689.825/ 1.8

Driven = 383.23 RPM

The reduced maximum rpm is 383.23 rpm which can be verified from the plot.

ACCELERATION PLOT:

From the graph we can infer that the vehicle is accelerated to 46 kmph initially and then the state changes when the user controls the throttle and brake knobs. The step-up and step-down are acceleration and deceleration respectively. The linear one is the constant speed so no changes in throttle or braking.