AIM: to prepare a technical report of simulation of BAJA all terrain vehicle(ATV) under different condition.
OBJECTIVES: carry out a sysytem level simulation of an all terrain vehicle and prepare a technical report expalining the model properties and coments on the results.
ALL TERRAIN VEHICLE: An all terrain vehicle(ATV) is defined as the 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.
MAJOR COMPONENTS IN THE MODEL:
continuously variable transmission drive(CVT)
it is better to have more gear in a transmission ,since it can optimize engine speed in a variety of driving condition . that means low gears can provide better acceleration whilw higher gears can maximize fuel economy.CVT's differ from traditional automatic transmission in that they don't have gears that tey provide 'steps' between low and high speed operations. instead, the majority of them work via 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 cone touching. these form a V shaped groove in which connecting belt rides. one side of the pulley is fixed , and the other side is movable ,actuated by a hydraulic cylinder. the cylinder can increases or decreases the amount of space between the two sides of the pulley . this allow the belt to ride lower or higher along the walls of the pulley, depending on driving conditions thereby, changing the gear ratio.
VARIABLE TRANSMISSION RATIO:
Represents a variable ratio gearbox such as implemented by mechanical belt CVT, electric or hydraulic transmission. the physical signal input r defines the ratio of input to output angular shaft velocities.
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 signals T lies between zero and one and specifies the torque demanded from the engine as a fraction of the maximum possible torque.
Connections F & B are mechanical rotational conserving ports associated with the engine crankshaft and engine block, respectively.connections P & FC are physical signal output ports through which engine power and fuel consumption rate are reported.
VEHICLE SPEED:
It is clear from the graph that the vehicle attains its maximum speed at full throttle after 30sec and then remains constant. the brake input value is zero, hence it has no effect no velocity.
CVT SHAFT RPM:
these graph shows the variation in angular velocities of input and output shafts of the variable gear transmission system. these values differ with respect to gear ratio.
CASE 2
SIMULINK MODEL AOR BAJA ATV WITH CVT USING DASHBOARD:
In this model we have a dashboard which contains knob to control the inputs. in this case, the inputs, 'THROTTLE & BRAKE' are not provided using signal builder . A knob is provided to control the parameters in real time for the users.
VEHICLE SPEED:
It can be observed from the graph that the velocity of the vehicle increases drastically from 0to50kmph when throttle value is 0.5 brake input is 0. once the braking value increases from 0.1to 0.5 the velocity of vehicle decreases to 0 at constant throttle value. this explain the direct relation of vehicle velocity with respect to throttle and brake inputs.
CONCLUSION:
thus, we have analysed 4 different models of BAJA ATV WITH CVT and recorded the outputs with respect to variations in input throttle and brake.