Simulink for Mechanical & Electrical Engineers

Project

Q. Carry out a system-level simulation of an all-terrain vehicle.

Download the model from the given link:

https://www.mathworks.com/matlabcentral/fileexchange/70576-baja-all-terrain-vehicle-atv-model

Prepare a technical report explaining the model properties & comments on the results.

Ans=>

AIM: To carry out a system-level simulation of an all-terrain vehicle using Simulink.

ALL TERRAIN VEHICLE:

An all-terrain vehicle (ATV) is defifined 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.

CVT: A CVT or Continuously Variable Transmission is an automatic, single-speed, and

gearless transmission that can shift through an infinite number of gear ratios.

A continuously variable transmission (CVT) is a transmission that operates on an ingenious

pulley system that automatically varies the transmission ratio, allowing an infinite variability

between highest and lowest gears with no discrete steps or shifts. CVTs provide more

useable power, better fuel economy and smoother driving experience than traditional

transmissions that use gearboxes with fixed numbers of gear sets.

SOLUTION:

Part #1: BAJA ATV Model without Lookup Table

1.1 Without Dashboard

A Simulink model for the BAJA ATV Model is shown below.

The models consist of common blocks as follows:

Signal Builder: The Signal Builder block allows you to create interchangeable groups of piecewise linear signal sources and use them in a model. You can

quickly switch the signal groups into and out of a model to facilitate testing.

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.

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.

Speed vector and Torque vector are the assigned parameters.

Engine Sensor:

Ideal Rotational Motion Sensor: The block represents an ideal

mechanical rotational motion sensor, that is, a device that

converts an across variable measured between two

mechanical rotational nodes into a control signal proportional

to angular velocity or angle. The sensor is ideal since it does

not account for inertia, friction, delays, energy consumption,

and so on.

Connections R and C are mechanical rotational conserving

ports and connections W and A are physical signal output

ports for velocity and angular displacement, respectively.

Simple Gear:

Represents a fixed-ratio gear or gearbox. No inertia or compliance is modeled in this block. You can optionally include gear

meshing and viscous bearing losses.

Connections B (base) and F (follower) are mechanical rotational conserving ports. Specify the relation between base and follower rotation

directions with the Output shaft rotates parameter. Optionally include thermal effects and expose thermal conserving port H by right-clicking on

the block and selecting Simscape block choices to switch between variants.

Follower (F) to base (B) teeth ratio (NF/NB): 4

CVT Subsystem:

The CVT Subsystem consists of the following blocks:

Inertia:

The block represents an ideal mechanical rotational inertia.

The block has one mechanical rotational conserving port. The block positive direction is from its port to the reference point.

This means that the inertia torque is positive if the inertia is accelerated in a positive direction.

Variable Ratio Transmission:

Represents a variable ratio gearbox such as implemented by mechanical belt CVT, electric, or

hydraulic transmissions. The physical signal input r defines the ratio of input to output angular shaft velocities.

Connections B (base) and F (follower) are mechanical rotational conserving ports. Specify the relation between base and

follower rotation directions with the Output shaft rotates parameter.

Vehicle Body Subsystem:

Vehicle Body: Represents 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.

Connection H is the mechanical translational conserving port associated with the horizontal motion of the vehicle body. The resulting traction motion developed

by tires should be connected to this port. Connections V, NF, and NR are physical signal output ports for vehicle velocity and front and rear normal wheel forces,

respectively. Wheel forces are considered positive if acting downwards. Connections W and beta are physical signal input ports corresponding to headwind

speed and road inclination angle, respectively. If the variable mass is modeled, the physical signal input ports CG and M are exposed. CG accepts a two-element

vector representing the x and y distance offsets from vehicle CG to additional load mass CG. M represents the additional mass. If both variable mass and pitch

dynamics are included, the physical signal port J accepts the inertia of the additional mass about its own CG.

Parameters are:

Tire: Represents the longitudinal behavior of a highway tire characterized by the tire Magic Formula. The block is built from Tire-Road Interaction (Magic

Formula) and Simscape Foundation Library Wheel and Axle blocks. Optionally, the effects of tire inertia, stiffness, and damping can be included.

Connection A is the mechanical rotational conserving port for the wheel axle. Connection H is the mechanical translational conserving port for the wheel hub

through which the thrust developed by the tire is applied to the vehicle. Connection N is a physical signal input port that applies the normal force acting on the

tire. The force is considered positive if it acts downwards. Connection S is a physical signal output port that reports the tire slip. Optionally expose physical

signal port M by setting Parameterize by to Physical signal Magic Formula coefficients. Physical signal port M accepts a four-element vector corresponding to

the B, C, D, and E Magic Formula coefficients.

Parameters (common for all tires) are:

Double-Shoe Brake:

Represents a brake arranged as two pivoted rigid shoes symmetrically installed inside or outside a drum and operated by one actuator. The

actuator force causes the shoes to exert a friction torque on a shaft connected to the drum.

Connection S is a conserving rotational terminal associated with the drum shaft. Connection F is a physical signal port representing the force input to the

actuator. Positive force creates friction torque that resists shaft rotation. Optionally include thermal effects and expose thermal conserving port H by setting

Thermal port to Model.

Parameters are:

Torque vs Speed characteristics:

Input #1.1:

Brake and Throttle input:

Brake input is constant i.e. zero throughout the time of 80 sec.

Throttle input is 0.3 for first 20 sec, accelerates to 1 at the same and remains constant throughout the remaining time till 80 sec

CVT Ratio:

The CVT gear ratio 3.5 for the first 4 secs, then drops down to .5 till 35 secs and remains constant thereafter till 80 sec.

Output #1.1:

Velocity:

CVT Shaft Speed:

1.2 With Dashboard

A Simulink model for the BAJA ATV Model including the dashboard is shown below.

The rest of the parts and subsystems are common in the above part #1.1.

Dashboard: A dashboard (also called dash, instrument panel (IP), or fascia) is a control panel usually located directly ahead of a vehicle's driver, displaying

instrumentation and controls for the vehicle's operation.

In this model a dashboard is used to control the inputs- ‘Throttle’ & ‘Brake’ with knobs.

Output #2.2:

Velocity

CVT Shaft Speed:

CONCLUSION:

Hence, the given BAJA ATV Model was simulated successfully and from the above results, we can infer that:

- Velocity, CVT Shaft Speed and Engine Speed are directly proportional to the Throttle input and inversely proportional to the Brake input.

- CVT Primary speed is greater than CVT Secondary speed as they are directly proportional to their shaft diameter.

- The variation in vehicle velocity can be observed with change in throttle and brake inputs.

-With increase in braking value, the speed of vehicle decreases. On the other hand, increasing the throttle leads to increased vehicle velocity.

REFERENCES:

BAJA ATV Model File