Project
Aim:
To carry-out the system level simulation of a BAJA ATV
Objectives:
Analyse all components & understand relation & flow between blocks, understand the different types of ways to model this baja ATV.
ATV is a small motor vehicles with low pressure tyres designed for use on various type of terrain. Recreational activities in desrts are usually carried out in ATVs. this project is in refrence to one of the type ATVs used in BAJA SAE competitions.
Components:
Brake & throttle input signals
No brake is provided & constant throttleof0.3 for the first20seconds & full throttle of 1 for the remaining,these two parametrs are fed into the engine
Generic Engine:
1.Engine uses a programmed relationship between speed & torque modulated by the throttle signal. throttle input is fed into & the speed torque data points are extracted from thegraph& fed into the engine through creation of column vectors in matlab.
2.Crankshaft port F connected to an engine sensor which simply senses the angular velocity,angular displacement of crankshaft
3.simple gear between engine & CVT gear box is to slow down the engine rpm(in cas of too high) before it fed to CVT.an appropiate gear ratio needs to be selected so that over or under revving is not issue.
Continuosuly variable transmissions:
1.Two cone shapeed connected by a steel composite belt,whose diameters are continuosusly variable work together to provide infinite gear ratios
2.Optimising engine speed in variety of road conditions according to the speed & torque requirements of the terrrains.
3.Differ from automatic transmissions in the sense that there are not gears the vehicle need to step up/down to for differetn speed/torque requirements similar to automatic transmissions in sense that gears are shiftes automatically
CVT subsystem block:
1.input & output shaft interia represent primary oulley & secondary pulley,variable ratio gear block represent the multiple gears of the CVT with the ratio input given to port-R.
2.Two rotational motion sensors are for tracking the angular velocitites of the two pulleys.
Vehicle Body subsystem block;
1.Vehicle body accounts for body mass aerodynamic drag road incline & weight distribution between axles due to acceleration & road profile.
2.Double shoe brake is to apply brakes to the rear wheels.with this componenet two brakes blocks are applieed at opposite ends of the drum,this prevents an unbalanced force from acting on the shaft & bearing connecting the drum to the wheel which would be the case with single shoe brake.
Vehcile speed output based on throttle brake signals:
there is constant accelration at throttle of0.3 from 0 to20seconds,after 20seconds the car accelerates until peak velocity as throttle hits a max value of1.
CVT shaft speed output based on CVT gear ratio input
CVT gear ratio input is above 1 throughout which is why we see a lower secondary rpm,than primary because the outout shaft will rotates slower to provide more torque to the wheels.