Project

Project week 4

Aim: to understand the CVT Simulink model and make conclusion regarding the output files from the model.

1. Open loop model

Blocks used:

Signal builder

Engine block

Engine subsystem

Cvt subsystem

Mechanical gear ratio

Vehicle body subsystem

Goto blocks

From block

Scope block

Working:

The brake and throttle input is made using a signal builder. The brake is initially given 0 signal or 0 magnitude while the throttle is given a signal of around 0.3 to 1.

The throttle signal is fed onto the engine block which generates the rpm. An engine sensor subsystem is used to sense the speed (rpm) generated by the engine.

A signal generator block is used to generate the variable cvt gear ratio from 4 to somewhere around 0.5.

This cvt ratio signal along with the engine rpm signal is fed onto the cvt subsystem block.

Inside the CVT subsystem block a variable gear ratio block is used to generate the cvt primary and secondary rpm. They are then measured using a motion sensor and their data are given to a goto block.

The secondary shaft signal is given to a mechanical gear ratio block with pre determined gear ratio (here 10) to get a speed (rpm) signal. This signal is then passed onto the vehicle body block.

The goto signal from the brake which was generated using the signal generator is also given to the vehicle subsystem as input.

Inside the Vehicle subsystem, a vehicle body block is used which gives the vehicle velocity, the mechanical translational port which is connected to the 4 wheels and finally the normal force connected to the two front and rear wheels.

The vehicle body block also accepts inputs for inclination and wind speed which were not used here to keep the model simple.

A double shoe brake block is connected to the rear wheels. Its input signal is obtained from the brake signal created by a signal generator with a gain of 1000.

 

Conclusion from the output:

From the data inspector it can be seen cvt reatio is decreased from around 3.3 to 0.3 as the throttle is increased from 0.5 to 1.

Initially the primary rpm is greater than the secondary rpm however after a certain time secondary rpm becomes greater and continues to increase and flattens.

Velocity of the body increases non linearly from 0 to 65 after which it flattens.

Rpm of the engine increases non linearly from around 1600 rpm to 3840 rpm.

2. Closed loop model.

In the closed loop model the velocity of the vehicle body is used to determine the cvt ratio from a look up table and a loop is made which feeds onto the veraible gear ratio block.

This model is more realistic compared to the open loop model.