Project - BAJA ATV

(Word File Attached - Project1 Baja ATV)

Project – BAJA ATV

Aim : To prepare a technical report of Simulation of BAJA All Terrain Vehicle (ATV) under different conditions.

Objectives : Carry a system level simulation of an all terrain vehicle and prepare a technical reportexplaining the model properties & comments on the results.

All Terrain Vahicle (ATV) : A small motor vehicle with three or four wheels that is designed for use on various types of terrain

— called also 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.

Study 1 : BAJA ATV Model

Simulink Model For Baja ATV with CVT :

Components used in the Model :

• Continuously Variable Transmission (CVT)

A continuously variable transmission system is a type of automatic transmission in which an arrangement of pulleys and belts made it possible for a drive to achieve n-number of continuous gear ratios within a range (depends on the design).

A continuously variable transmission in a vehicle senses the accelerator input with engine load and get shifted to the desired speed or torque gear ratio automatically, in other words we can say that a cvt transmission is one of the simplest types of automatic transmission that provides continuous uninterrupted power within a specified range of speed and torque ratios.

How CVT Works : The engine shaft rotates according to the accelerator input which in turn rotates the input shaft.

With the input shaft rotation, input pulleys mounted over it also rotates which in turn rotates the belt wrapped around them.

This belt transfers power from input shaft to the output pulley as it is also wrapped around the output pulleys.

Output pulleys rotate the output shaft and final output is obtained.

CVT Module Block :

Variable Transmission Ratio :

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.

Engine :

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.

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.

Input Signal :

A signal builder is used to create signals for brake and throttle (accelerator).

CVT Gear Ratio Input :

Torque Vs Engine Speed Input :

Vehicle Body Simulink Module :

Study 2 : Simulink Model For Baja ATV with CVT :

In this Model we have a dashboard which contains knobs to control the inputs. The separate control of Throttle & Brake is not provided using signal builder. A knob is provided to control both the parameters in real time for the user.

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 dashboard as shown in figures. The main concept of using of using dashboard is study the result by varying the input of brake and throttle, which shows that the velocity and speed of the engine. The gear ratio is maingtained as 2.3 for 5 secs and linearly decreases to 1.8 and maintained constant for overall simulation as shown in figure. As the brake input varies 0-0.5 the velocity and speed decreases accordingly. By increasing the throttle, the velocity and speed of the engine & shaft increases.

Study 3 : BAJA ATV Model Using Lookup Chart

By using Simulink model pf CVT consists of step time, generic engine, motion sensors, vehicle transmission, vehicle body, tyres and solver configuration blocks etc. as shown in fig. The CVT system includes look up table, transmission block, input and output shaft inertia and motion sensors as shown in fig. The vehicle body subsystem includes vehicle body block, double drum brake and tyre as shown in fig. The inertial engine speed is given as 2100rpm, 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 values using interpolation, extrapolation, or rounding, where :

• An interpolation is a process of 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 step time, which depends on the run time and varies accordingly. 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. The gear ratio varies from 2.3 to 1.8 as taken as input and output in terms of velocity. The maximum velocity reached as 57kmph approximately.

Study 4 : BAJA ATV Model 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 dashboard and indicated as constant block. Rest of the blocks and subsystems are common in the Baja ATV Model without dashboard as shown in figures. The main concept of using dashboard 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 from the lookup table and obtain the result according to the lookup table. As the brake input varies from 0-0.5, 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 and secondary pulley, in which the radius of primary pulley increases 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. As the max torque, the speed and velocity is decreases.

Study 1 : Variation of velocity and shaft speed

In the above figure, the brake is maintained as constant and increase in throttle which shows increase in velocity. The flow of fuel is increase when the throttle increases from 0.3 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 and velocity can achieve maximum.

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

Study 2 : Variation of velocity and shaft speed

In the above figure, the velocity of the vehicle of the vehicle is maintained as constant for constant throttle value as 0.3 and varying by increasing the value of throttle which increases the velocity of Vehicle. By increasing the brake input, the velocity of the vehicle decreasing accordingly which shown in the fig. above.

In the fig. above The primary shaft speed increases by increasing throttle and decreasing by increasing brake input value, which defines that the throttle can flow more amount of fuel which increases the power power of the engine and similar to the secondary shaft. The radius of the primary shaft as more than the secondary 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 : Variation of velocity and shaft speed

In the figure, The brake is maintained as constant and increase on throttle which shows increase in velocity. The flow of fuel is increases when the throttle increases from 0.3 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.

In the fig above, The primary shaft speed increases by increasing throttle and decreasing by increasing brake input value, which defines that the throttle can flow more amount of fuel which increases the power of the engine and similar to the secondary shaft, the speed is directly proportional to the radius of the shaft. As the radius increases the speed of the shaft also increases.

Study 4 : Variation of velocity & shaft speed

In the above fig. the velocity of the vehicle is maintained as constant for constant throttle value as 0.3 and varying by increasing the value of throttle which increases the velocity of vehicle. By increasing the break input, the velocity of the vehicle decreasing according which shown in fig. By using lookup table, it works as closed loop by recording the velocity value and we can get any particular value of gear ratio which is beyond the range or any random value within the range by using extrapolation and interpolation by lookup table.

In the above fig. The primary shaft speed increases by increasing throttle and decreasing by increasing brake input value, which defines that the throttle can flow more amount of fuel which increases the power of the engine and similar to the secondary shaft. The radius of the primary shaft as more than the secondary shaft, the speed is directly proportional to the radius of the shaft. As the radius increases the speed of the shaft also increases. The throttle value and brake input value can be varying in dashboard, so we can get any particular value for input.

Conclusion :

1. As the throttle increases, the velocity also increases which inturn the power in the engine also increases at the begining the speed reducing because of gear ratio and torque output. When the gear ratio increases, the torque increases.
2. As the brake input increases, the velocity decreases and engine power also decreases. At a certain brake input value the engine may shut down and there is no power output. The engine power is inversly proportional to the brake input.
3. As the gear ratio increases, torque increases which in turn the velocity decreases. the torque is increasing by increase in engine speed. At a particular point the the torque is decreasing when the gear ratio increases in order to achieve maximum velocity. 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 parallelly the torque also less which can get high velocity.
4. 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.