Project

Aim: To prepare a technical report of simulation of BAJA All-terrain vehicle (AVT) under different conditions.

Objectives: Carry out a system level simulation of an all-terrain vehicle and prepare a technical report explaining the model properties and comments on the result.

All Terrain Vehicle:

An all-terrain vehicle 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:

Case 1:

Simulink model for BAJA ATV with CVT:

Major components in the model:

Continuously Variable Transmission drive (CVT)

It is better to have more gears in a transmission, since it can optimize engine speed in a variety of driving conditions. That means low gears can provide better acceleration while higher gears can maximize fuel economy. CVTs differ from traditional automatic transmissions in that they don’t have gears that provide “steps” between low-and high-speed operations. Instead, the majority of them work via a pair of variable-diameter, cone-shaped pulleys connected by a steel or composite belt. The halves of each pulley are aligned with the pointed ends of the cones touching. These form a V-shaped groove in which the connecting belt rides. One side of the pulley is fixed, and the other side is movable, actuated by a hydraulic cylinder. The cylinder can increase or decrease the amount of space between the two sides of the pulley. This allows the belt to ride lower or higher along the walls of the pulley, depending on driving conditions, thereby changing the “gear” ratio.

CVT 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:

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 specifies the torque demanded from the engines 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.

Torque vs Engine speed input:

Vehicle Body:

Vehicle speed:

It is clear from the graph that the vehicle attains its maximum speed (V=55km/hr) at full throttle=1 after 30 seconds and then remains constant. The brake input is zero, hence it has no effect on velocity.

CVT SHAFT RPM:

These graphs shows the variation in angular velocities of input and output shafts of the variable gear transmission system. These values differ with respect to the gear ratio.

STUDY 1:

CASE2:

SIMULINK MODEL FOR BAJA ATV WITH CVT USING DASHBOARD:

In this model we have a dashboard which contains knobs to control the inputs. In this case, the inputs- ‘Throttle’ & ‘Brake’ are not provided using signal builder. A knob is provided to control both the parameters in real-time for the user.

OUTPUT for case2:

VEHICLE SPEED:

It can be observed from the graph that the velocity of the vehicle increases drastically from 0 to 50 kmph when throttle value is 0.5 & brake input is 0. Once the braking value increases from 0.1 to 0.5, the velocity of the vehicle decreases to 0 at constant throttle value. This explain the direct relation of vehicle velocity with respect to throttle and brake inputs.

CVT BLOCK:

The only difference between this model and the first model is that in this model, the gear ratio input to CVT is provided using a lookup table. The vehicle velocity and shaft rpm outputs are same as before.

OUTPUT for case2:

VEHICLE SPEED:

This graph is similar to that of cvt dashboard case. 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.

CVT SHAFT RPM:

This graph indicates the variation in rpm of primary and secondary shafts with respect to input parameters.

Conclusion:

Thus we have successfully analysed 4 different models of BAJA ATV WITH CVT and recorded the outputs:(Vehicle velocity & CVT shaft rpm) with respect to variations in input throttle and brake.