Project

AIM:

To prepare a technical report of Simulation of BAJA All Terrain Vehicle(ATV),model using Simulink and compare between different models.

OBJECTIVES:

• To prepare technical report explaining the functions of the subsystem and blocks used for preparing the model.
• To explain in details all thr differences between all the five models provided.

TYPES OF MODEL:

• BAJA ATV model without dashboard (cvtModel)
• BAJA ATV model with dashboard(cvtModel_dashboard)
• BAJA ATV model-Mapped Lookup Table without Dashboard(cvtModel_mapped)
• BAJA ATV model-Mapped Lookup Table with Dashboard(cvtModel_mapped)

INTODUCTION:

An all-terrain vehicle (ATV), also known as a light utility vehicle (LUV), a quad bike, or simply a quad, 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. As the name implies, it is designed to handle a wider variety of terrain than most other vehicles. Although it is a street-legal vehicle in some countries, it is not street-legal within most states, territories and provinces of Australia, the United States or Canada.

By the current ANSI definition, ATVs are intended for use by a single operator, although some companies have developed ATVs intended for use by the operator and one passenger. These ATVs are referred to as tandem ATVs.

The rider sits on and operates these vehicles like a motorcycle, but the extra wheels give more stability at slower speeds. Although most are equipped with three or four wheels, six-wheel models exists and existed historically for specialized applications. Multiple-user analogues with side-by-side seating are called utility terrain vehicles (UTVs) or side-by-sides to distinguish the classes of vehicle. Both classes tend to have similar powertrain parts. Engine sizes of ATVs currently for sale in the United States (as of 2008 products) range from 49 to 1,000 cc (3.0 to 61 cu in).

CONTINUOUSLY VARIABLE TRANSMISSION [CVT]:

A continuously variable transmission (CVT) is an automatic transmission that can change seamlessly through a continuous range of gear ratios. This contrasts with other transmissions that provide a limited number of gear ratios in fixed steps. The flexibility of a CVT with suitable control may allow the engine to operate at a constant RPM while the vehicle moves at varying speeds.

CVTs are used in automobiles, tractors, motor scooters, snowmobiles, bicycles and earthmoving equipment.

The most common type of CVT uses two pulleys connected by a belt or chain; however, several other designs have also been used at times.

EXPLANATION:

(1.) BAJA ATV MODEL WITHOUT DASHBOARD:

The below figure represents the simulink model for the BAJA ATV using the CTV for power transmission.

Blocks used:-

1. Signal Builder:It is used to display,create and edit group of signal source and quickly switch the groups into and out of a model.We can define any waveform to assign the required input.In this model we have to used two signal builder blocks,one for brake & throttle input and another for CVT Ratio.

a.Brake and Throttle input:

b.CVT Ratio:

2.Generic Engine:The Generic Engine block represent a general internal combustion engine.Engine types include spark-ignition and diesel.Speed- power and speed-torque parameters are provided.

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.

3.CVT:The CVT block is the representation of the actual continuous variable transmission system having subsystems into it.

a.)Inertia block:The block represents an ideal mechanical rotational inertia and has one or two mechanical rotational conserving ports. The difference is purely graphical, as the ports are rigidly linked. 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 the positive direction.There are two inertia one at input and another at output.

b.)Variable ratio gear:It 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.Port B is connected to the PMC(Physical Modelling Connection) signal as input and Port F is output PMC port on the right side of the block with two inertia blocks at entry exit.

c.)Ideal rotational motion 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 angle, respectively, of port R relative to port C. The measured angular velocity is positive when the angular velocity at port R is greater than the angular velocity at port C.

d.)PS terminator and mechanical rotational references connected to the Port A and C of ideal rotational block.

4.)Vehicle body:The vehicle body represents the complete vehicle assembly with all inputs required to operate the engine with the varying parameters.The subsystem of the vehicle is explained below.

a.)Vehicle Body:It 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 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.

b.)Tires:It 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.

c.)Shoe Brake:It 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.

5.)Engine Sensor:This sensor is use to record the output values from the generic engine to the CVT.The Subsystem of this block consists of two PMC port,one ideal rotational sensor and scope to display the change in the values of speed via increasing or decreasing the throttle.Also,mechanical reference and PS Terminator is attached to the connection C and A of the sensor.

6.)Simple Gear:It represents a fixed-ratio gear or gear box. No inertia or compliance is modeled in this block. You can optionally include gear meshing, backlash, 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 setting Friction model to a temperature-dependent setting.

7.)Solver Configuration:It defines solver settings to use for simulation.

8.)Mechanical Reference:This block represents a mechanical rotational reference point, that is, a frame or a ground. Use it to connect mechanical rotational ports that are rigidly affixed to the frame (ground).

9.)Goto & From Blocks:Goto blocks are used to send signals to From blocks that have the specified tag and From blocks are used to receive signals from the Goto block with the specified tag if tag is 'scoped', then a Goto Tag Visibility block must be used to define the visibility of the tag.

10.)Scope:It displays the signals generated during simulation.

PROCEDURE:

1.)A signal builder block is used to provide the brake and throttle input to the system.The output from the throttle is connected to the generic engine block and output of the CVT ratio to CVT block.

2.)An Engine sensor is attached to output from the generic block and the output of the engine sensorcis attached to the CVT block.

3.)The CVT block takes the input from the CVT ratio and to transfer the CVT power to the wheels,the simple gear block is attached between them.

4.)The power ouput from the simple gear block is attached to the input of vehicle body where we cancheck the values of throttling and braking effect displayed on the scope for the particular effect.

5.)Goto and From block attached to the output of vehicle body block and scope respectively to display the performance curve when we applied brake or throttle the vehicle.

(2.)ATV Model with a dashboard:

The below figure represents the Simulink model for the BAJA ATV using the CTV for power transmission using a dashboard.

a.) The process is the same as above,the only change is that instead of the signal builder block we are using circular gauge block which acts as a speedometer where values can be displayed from the inputs knob.

b.)The knob is used to provide the input values to Brake and Throttle where we can set the knob placement as per the required conditions.

RESULT:

The output graphs from default values of brake=0 and throttle=0.5

fig(a)Torque-Speed Graph

fig(b)CVT Shaft Speed graph

fig(c)Vehicle Speed Graph

OBSERVATION:

1. The torque is high at start as it is required for pickup,but as speed is increased the torque is reduced.
2. The Vehicle speed increases gradually and becomes constant at a certain level as we can see in the velocity speed graph.
3. The value is '0' ata the start for the driving gear which is represented by CVT primary RPM and then a sudden increase in the rpm with less time.

PART 2:Simulink model of ATV with a lookup table

(1.)ATV Model without a dashboard:-

The below figure represents the Simulink model for the BAJA ATV using the CTV for power transmission using a lookup table.

1.)Lookup Table:

A lookup table is an array of data that maps input vlause to output values,thereby resembling a mathemathical function.If there are given a set of input values, a lookup operation retrieves the output values from the table.

In this we are using the output signal from the vehicle body as the input to the CVT as the CVT Gear Ratio.It needs to be loaded in the workspace.

The procedure and the working is as the above,the only difference is the lookup table.

(2.)ATV Model with a dashboard:-

The below figure represents the simulink model for the BAJA ATV using the CTV for power transmission using a dashboard along with the lookup table.

• The process is the same as above,the only change is that instead of step input,we are using a circular gauge block which acts as a speedometer where values can be displayed from the inputs knob.
• The knob is used to provide the input values for brake and throttle where we can set the knob placement as per the required conditions.

RESULTED GRAPH:

The output graphs from default values of brake and throttle.

Fig.(a)-Vehicle Speed Graph

Fig.(b)-CVT Shaft Speed Graph

OBSERVATION:

1. Using the lookup table,the vehicle speed increases gradually and takes longer time to become constant at a certain level as we can see int he vehicle speed graph as compared to the previous model.
2. There is a gradual increase in the speed at the seocmdary gear of the cvt as the intila speed is picked by the driving gear i.e the primary CVT.
3. The lookup table graph shows the CVT ratio w.r.t the output power at the wheel.

CONCLUSION:

1. Successfully studied and carry out a system-level simulation of an all terrain vehicle of SAE BAJA.
2. In this we have observed the vehcile speed,CVT shaft speed and Torque Speed curve when changing the vlaued of throttle and brake at the input.
3. The speed becomes constant after certain rpm and decreases when the brakes are applied at different time.