Project

Aim:- The sole aim of this project is to carry out the system level simulation of an all-terrain vehicle.The model includes BAJA ATV model with Continuously Variable Transmission(CVT).The agendas behind the simulation are:-

1. To study about the components of BAJA ATV.
2. Vehicle modelling which includes:

• Defining gear ratio.
• Effect of parameter variation

3. Incorporating CVT data into the model.

Description:-

The components of BAJA ATV are namely- Vehicle Body, Suspension, Tyre, Engine, CVT.

VEHICLE BODY:- This block contains the settings through which the real time vehicle data can be logged into the simulation model to get the real time results.It enables the alteration of the accessories as per the user requirements.The input to the vehicle body block is brake and initially it is set to zero while the output consisits of velocity and distance plots as shown in the file "Project1_output1"b. Initially, the speed is at the maximum value of 60km/hr corresponing to the throttle input of 1. After sometime (at t=5*10^5 secs), the throttle input is reduced to 0.5 and consecutively the speed reduces to a new steady state value of 50km/hr.

CVT block:- This block is responsible for the actual Continous variable transmission mechanism governing the gear ratio and hence the speeds of the primary and secondary pulleys. The input and output shaft inertia correspond to the primary and secondary pulleys respectively.The rotational motion sensors enable the controlling of engine rpm based on the speed of the vehicle. The suitable gear ratio may be chosen as per the terrain type and the speed requirement.The current model has been simulated for gear ratio=10.

Engine:- This block uses the generic engine parameters as per our requirement. Here we can adjust the engine Torque and speed vector. The engine sensor block forms an interface between the CVT block and the generic engine and modulates the engine rpm as per the requirement of the pulley.The input Torque-speed characteristics can be fed to the engine generic engine by utilising the data points in the Torque and speed vector tables.

VEHICLE MODELLING:-

Vehicle modelling majorly includes- assigning the gear ratio & setting up of different vehicle parameters like, mass, cvt ratio,, tyre types, etc. The gear ratio can be altered by changing the it from the simple gear block in the cvt subsystem. The current model is designed for the gear ratio=10. If the model is simulated for gear ratio less than 10 like 2,4,6 or 8 the vehicle engine cannot develop enough Torque to get started and vehicle speed reduces to zero after certain duration.

Similarly, when the cvt ratio is more than 1 (t<=4sec), the secondary rpm is more than primary rpm and after t=4sec, the primary rpm dominates the secondary rpm as displayed in the file cvt rpm_200sec.

If we plot the variation of velocity with time for vehicles of different masses, the lightest vehicle would attain the highest velocity at the transient stage. Secondly, at the steady state(after few seconds)all the vehicles attain the same velocity.

Once the open loop model is simulated, the next step is to incorporate the cvt data into the model. For doing this, we bring feedback from the vehicle speed output and connect it to the primary input of the cvt. The variation of speed with the throttle input now shows a different behaviour as displayed in the file throttle input_speed_CL.The simulink model for the closed loop simulation is named as "cvtModel_dashboard_mapped".The closed loop simulation is governed by the lookup table provided in the model which converts the speed signal into equivalent cvt ratio which is the more realistic case.The lookup table governing the close loop system is displayed in "CVT ATV LOOKUP TABLE".