Project

Aim: To study a system - level simulation of an All-terrain vehical and prepare a technical report of All- terrain vehicle under different condition.

Objectives:

• Study the baja ATV model without dashboard.

• Study the baja ATV model with dashboard.

• Study the baja ATV model using lookup table without dashboard.

• Study the baja ATV model using lookup table with dashboard.

Introduction:

An all-terrain vehicle(ATV), is also known as a quad, quad bike or four wheeler, is defined by the American National Standards Institute (ANSI) as a vehicle that travels on low pressure tires, with a seat that is straddled by the operator, along with handle bars for steering controls. As the name implies, it is designed to handle a wide variety of terrain than most other vehicles.

Transmission, which transmits the power from engine to the wheels through the shafts. It has a significant impact on their efficiency. The transmission allows the variation of torque between the engine and gearbox. It consists of 4 types mainly,

• Manual transmission
• Continous variable transmission
• Semi-automatic transmission
• Automatic transmission

A continuously variable transmission, or CVT, is a type of automatic transmission that provides more useable power, better fuel economy and a smoother driving experience than a traditional automatic transmission. The CVT is a system that makes it possible to vary stepless the transmission ratio without interruption of the torque flow. Therefore an infinite number of ratios (between a minimum and maximum value) are possible. It is an automatic, single speed, and gearless transmission that can shift through an infinite number of gear ratios. This ability to seamlessly shift through these different gears provides a number of benefits including extremely smooth shifts and exceptional fuel economy. A CVT draws top engine power from a small engine, which gives drivers quicker acceleration than standard automatic transmissions. Because of their greater ability to control the engine speed range, CVTs produce fewer emissions. CVTs are also lighter weight than traditional automatic transmissions.

Study 1:

SIMULINK MODEL FOR BAJA ATV WITH CVT:

figure:1

CVT Subsystem block:

figure:2

Vehicle body subsystem bolck:

figure:3

By using simulink model of CVT consists of Signal builder, generic engine, motion sensors, vehicle transmission, vehicle body,tyres and solver configuration blocks etc., as shown in figure-1. The CVT subsystem includes Transmission block, input and output shaft inertia and motion sensors as shown in figure-2. The vehicle body subsystem includes vehicle body block, double drum brake and tyres as shown in figure-3. The initial engine speed is given as 2100 rpm, mechanical rotation for driven pulley and driver pulley as 0.8 & 0.7 respectively. The mass of the vehicle as 250kg and 2 axles which connects 4 wheel accordingly.

Inputs:

figure:4

figure:5

The signal builder is used as input for brake, throttle and gear ratio. Brake input is maintained as 0 for overall simulation. The throttle input is given as 0.5 for 15 secs and increases to 1 for overall simulatuion. The throttle valve is mainly to control the flow or amount of fuel into the engine, if the throttle value increases the flow of fuel increases to the IC engine which inturn increases the power of the engine. The gear ratio is initially 3.7 and then exponentially decreases for overall simulation as shown in the above figure (4 - 5).

Outputs:

Output of Variation of Velocity, Distance, Throtle, Break and shaft speed in rpm as shown below in graph:

In the above figure, the brake is maintained as constant to 0 and increase in throttle which shows increase in velocity. The flow of fuel is increses when the throttle increases from 0.5 to 1, thus the power in the engine increases. The gear ratio is directly proportional to the torque. By this gear ratio, the speed & velocity can achieve maximum.

In the above figure, the secondary shaft reaches high speed and primary shaft as low rotational speed because the radius of the secondary shaft as more than the primary shaft, the speed is directly proportional to the radius of the shaft. As the radius increases the speed of the shaft also increases.

Study 2:

SIMULINK MODEL FOR BAJA ATV WITH CVT USING DASHBOARD:

The above figure shows 'Baja ATV with dashboard' model which consists throttle meter and brake input in the dashboard instead of giving input through signal builder. Rest of the blocks and subsystems are common in the above baja ATV model without dash board as shown in figure 2 & figure 3.

Inputs for the Model:

The following are the variables inputs to the model.

• The variable m1, m2 stands for the mass input for the inertial at input shaft and output shaft at CVT Transmission system.
• The variables ‘speedVector’ & ‘torqueVector’ are the engine parameters for the Generic Engine, which provides us the relation between torque and rpm of the engine.
• Using Signal Builder block we have given the CVT ratio is changed with time.

Output: After the simulation, the outputs of the models

• Variation of velocity & Shaft speed

In the above figure, the velocity of the vehicle is maintained as constant for constant throttle value as 1. By increasing the brake input, the velocity of the vehicle decreasing accordingly.

In the above figure, The radius of the secondary shaft as more than the primary shaft, the speed is directly proportional to the radius of the shaft. As the radius increases the speed of the shaft also increases.

STUDY 3:

Simulink model for BAJA ATV with CVT using lookup table:

CVT Subsystem:

Vehicle Body Subsystem:

By using simulink model of CVT consists of signal builder, generic engine, motion sensors, lookup table, vehicle transmission, vehicle body,tyres and solver configuration blocks etc., as shown above. The CVT subsystem includes Transmission block, input and output shaft inertia and motion sensors as shown above. The vehicle body subsystem includes vehicle body block, double drum brake and tyres as shown above. The initial engine speed is given as 1750 rpm, mechanical rotation for driven pulley and driver pulley as 0.8 & 0.7 respectively. The mass of the vehicle as 250kg and 2 axles which connects 4 wheel accordingly.

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:

• An interpolation is a process for estimating values that lie between known data points.
• An extrapolation is a process for estimating values that lie beyond the range of known data points.
• A rounding is a process for approximating a value by altering its digits according to a known rule.

The brake input and throttle input is given by signal builder. By using Lookup table for gear ratio which takes as input to the CVT and works according to the input gear ratio and obtained the output. This method is very effective which can avoid the unusual torque at the certain speed and very easy to achieve greater velocity & engine speed. It works as closed loop when the input is given by lookup table. The simulink get the input value from lookup table and obtain the result according to the input values of gear ratio.

Break input and Throttle input in signal builder:

Output:

Variation of velocity & Shaft speed

In the above figure, the brake is maintained as constant to 0 and increase in throttle which shows increase in velocity. The flow of fuel is increses when the throttle increases from 0.6 to 1, thus the power in the engine increases. The torque reaches approximately 7N-m at 1.8 gear ratio, which defines that gear ratio is directly proportional to the torque. By this gear ratio, the speed & velocity can achieve maximum. The gear ratio is assigned in lookup table and given as input to the simulink which reads every input value and obtain the result according to the input.

See the graph of speed of CVT primary and secondary RPM in the above figure.

Variation of Engine Torque-speed curve:

In the above figure, the torque is increasing by increase in engine speed. At a particular point the the torque is decreasing when the gear ratio increases inorder to achieve maximum velocity.

Study 4:

Simulink model for BAJA ATV with dashboard using lookup table:

The above figure shows 'Baja ATV with dashboard' model using lookup table which consists throttle meter and brake input in the dash board and indicated as constant block. Rest of the blocks and subsystems are common in the above baja ATV model without dash board as shown in figure 8 & figure 9. The main concept of using dash board is study the result by varying the input of brake and throttle, which shows that the variation of velocity and speed of the engine. The gear ratio is given by lookup table, simulink get the input value from the lookup table and obtain the result according to the lookup table. As the brake input 0 and increases, the velocity and speed decreases accordingly which inturn the gear ratio also decreasing. By increasing the throttle, the velocity and speed of the engine & shaft increases. The transmission as primary pulley and secondary pulley, in which the radius of primary pulley increses by compacting and the radius of secondary pulley decreases. As the gear ratio varies, the torque also varies. Gear ratio is directly proportional to the torque, which increases by increasing the gear ratio. At the max torque, the speed and velocity is decreases.

In the above figure, see we define each variable of the model in the workspace.

Output:

Variation of velocity & Shaft speed

In the above figure, see the graph of velocity which is constant due to break is 0 and also see the speed of CVT primary RPM and Secondary RPM.

In the above figure, the torque is increasing by increase in engine speed. At a particular point the the torque is decreasing when the gear ratio increases inorder to achieve maximum velocity.

In the above figure, the velocity is varying wrt the gear ratio. For the high gear ratio, the torque is more which decrease the velocity. By changing to high gear, the gear ratio become less paralelly the torque also less which can get high velocity.

With help of lookup table, we can vary any input value and also get the output value by using interpolation and extrapolation method which the simulink can solve.