Project

OBJECTIVE :-

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

ATV: 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 II 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. Similarly, riders must also consider the various ATV sizes.

This project is in reference to one of the types of ATVs used in BAJA SAE competitions.

BAJA ATV MODEL :

The BAJA ATV model is given below-

Blocks are used in this model are given below-

(i)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.

Here two 'Signal Builder' block are present. One for giving input of Brake & Throttle signal to Engine and Vehicle body. Another block is giving input of CVT Ratio.

So the signals will look like-

Here Throttle value is constant at 0.5 and Brake value is 0 that means no braking is there. We can change the values as per requirment.

GENERIC ENGINE: Represents a system-level model of spark-ignition and diesel engines suitable for use at initial stages of modelling when only the basic parameters are available. Optional idle speed and red line controllers are included. The throttle input signal T lies between zero and one and specifies the torque demanded from the engine as a fraction of the maximum possible torque. If the engine speed falls below the Stall speed, the engine torque is blended to zero. If the engine speed exceeds the maximum speed, the simulation stops and issues an error message. 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.

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 RPM sensor ports for velocity and angular displacement, respectively.

A 'Ideal Rotational Motion Sensor' used to measure the engine RPM.

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.

Continuously Variable Transmission (CVT):

As per the above animation, two cone-shaped pulleys connected by a steel or composite belt, whose diameters are continuously variable, work together to provide infinite gear ratios. Optimizing engine speed in a variety Of road conditions, according to the speed and torque requirements Of the terrain. Differ from automatic transmissions in the sense that there aren't gears the vehicle needs to step up/down to for different speed/torque requirements. Similar to automatic transmissions in the sense that the gears are shifted automatically.

CVT Subsystem-

Inside CVT subsystem mainly three type of blocks are there. These are i)Ideal Rotational Motion Sensor, ii)Variable Ratio Transmission and iii)Inertia.

i)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.

ii)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 :

So in this subsystem main used blocks are-

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.

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.

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.

CASE 1 (BAJA ATV with CVT only):-

Model-

Model file link-

https://drive.google.com/file/d/1hZOt9wTv0D7leQeGFowR_soccc1p7ocd/view?usp=sharing

INPUTS-

OUTPUT-

REASULT: If there is no braking throughout the simulation time then if throttle increase then velocity will increase slowly and after a certen time velocity will be constant. Also car speed will be same as secondary shaft speed.

CASE 2 (BAJA ATV with dashboard):-

MODEL-

Model fole link-

https://drive.google.com/file/d/1oM8lkVQVdnND_NAZVFMYSAbfpDDXQ-fN/view?usp=sharing

INPUTS-

In this case inpus of throttle and brake willbe given through a 'Knob' block as below-

We can change the value when simulation is runing.

OUTPUT-

CVT secondary RPM-

CVT primary and Velocity-

CASE 3 (BAJA ATV with lookup table):-

Model with lookup table will be-

Model file is given below-

https://drive.google.com/file/d/1Kps1MDq3hZPXa3E82v6RVD-qjX3vcCW7/view?usp=sharing

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 lie 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.

In place of CVT ratio input, a lookup table is assigned in the models below. It needs to be loaded in the workspace having the file name as Lookuptable_ data.mat

With lookup model inside CVT block will look like given below-

INPUTS-

'Step' block will be used to give input.

Parameters	THROTTLE INPUT	BRAKE INPUT
Step time:	20	35
Initial value:	0.3	0
Final value:	1	0
Sample time:	0	0

OUTPUT-

CVT Ratio:

Car speed:

CVT both primary and secondary speed:

CASE 4 (BAJA ATV with lookup table & dashboard):-

Model-

Model file given below-

https://drive.google.com/file/d/1pmhWuITcdtvmElX3NPXioMzS0Tl9CnOh/view?usp=sharing

For this model also, inputs will be given through 'Knob'. And that can be change while simulation is runing.

OUTPUT-

CVT Ratio:

speed:

CVT primary and secondary speed:

Reasult Analysis:

1. Velocity, CVT Shaft Speed and Engine Speed are directly proportional to the Throttle input and inversely proportional to the Brake input.
2. CVT Ratio is directly proportional to Torque and inversely proportional to the Throttle input.
3. CVT Primary speed is greater than CVT Secondary speed as they are directly proportional to their shaft diameter.
4. The speed might get null at a particular braking resistance.

REFERENCES:-

https://atvsafety.org/what-is-an-atv/

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