Project
Question:
Carry out a system-level simulation of an all-terrain vehicle.
Download the model from the given link:
https://www.mathworks.com/matlabcentral/fileexchange/70576-baja-all-terrain-vehicle-atv-model
Prepare a technical report explaining the model properties & comments on the results.
Aim:
-Study the components of a BAJA ATV
-To study the system level simulation of an all terrain vehicle.
-Defining the gear ratio and Effect of parameter variation
-study the baja the ATV model with and without Dashboard.
-Incorporating CVT data into the model.
Introduction:
A typical car transmission is comprised of between five and six gear sets and a series of gear trains (essentially belts or chains that run along the outside of two or more gears) – that allows a driver to control how much power is delivered to the car without changing how fast the engine runs. There are four types
-Manual transmission
-Continous Variable Transmission
-Semi-Automatic Transmission
-Automatic Transmission
CVT stands for continuously variable transmission, and this type of automatic transmission uses pulleys and a steel band instead of traditional fixed gears. It's always automatically adjusting to your driving, and it provides smooth, stepless gear changes. Depending on the vehicle and the driver, a CVT can provide a smoother driving experience when comparing it to a traditional automatic. According to Carfax, one of the most significant advantages to having a CVT is that they are often more fuel-efficient than a regular automatic. They have the following advantage over standard automatic transmission.
- Improved fuel efficiency.
- Desired responsive Power At all Times.
- Smooth Rides over Long Distance.
- Better Torque Ratio.
- Lighter unit and fewer parts to mend.
But how ever they also have some disadavantages as below.
- Expensive to Repair.
- High maintenance costs.
- Peculiar Acceleration tone.
*Study 1:
By using simulink model of CTV consist of sognal builder, generic engine , motion sensors, vehicle transmissionn vehicle body , tyres and solver configuration etc. as shown below. The CTV subsystem is mainly made up of input and output shaft, transmission block and motion sensor. The initial speed of the engine is given as 2100 rpm. mechanical rotation for driven pulley and driver pully is given as 0.8 and 0.7. Mass of vehicle is 250kg and vehicle is of 4 wheel.
Signals:
The signal builder is used as inout for brake, throttle and gear ratio. Brake is set in as 0 for overall simulation. The throttle input is given as 0.3 for 20 sec and increases to 1 for overall simulation. below is the plot of the egine throttle.
-The gear ratio of the CVT is given as shown below in the signal builder
Simulation:
Below is the simulation of the vehicle as it accelerates with a higher VTC gear ratio and later slows down as the gear ratio drops although the acceleration climbs.
Study 2: BAJA model with Dashboard
The above figure shows the BAJA ATV Dashboard which consist of a speedometer and a distance calculating guage then a throttle for input speed variation and a brake input. The rest of the system is the same as above just for the fact that acceleration and braking will be done manualy during simulation. The main aim here is to study the instantanious effects of the change in throttle or brake input on the output values such as velocity and distance covered. Beloe is and image which shows as velocity and distance changes when brake and throttle are changed.
Study 3 BAJA model using lookup chart:
The simulink model is the BAJA ATV All terrain vehicle. It is the same for the above simulation. In this case a lookup table is an array of data that maps the input value to output values, thereby approximating a mathematical function, Given a set of input values, a lookup operation retrieves the corresponding output values from the table. If the lookup table does not explicitly define the input values, simulink can estimate an output values using interpolation, extrapolation or rounding where.
-An interpolation is a process for estimating values that lie between known data point.
-An extrapolation is a process for estimating values that lie beyond the range of known data point.
-A rounding is a process for approximating a value by altering its degits according to a known rule.
Study 4 : BAJA ATV with Dashboard using lookup table:
The below figure shows the BAJA ATV with dashboard and a lookup table with throttle meter and brake input to manual give in input simulation if not the entire system is as shown above in the previous simulation. The main reason of using the dashboard is to have an actual effect on the effect of varying throttle and brakes input using thier various inputs. The lookup table gives the Gear ratio, Simulink gets the input values from the lookup table. While we increase the brake input value, the speed reduces and the gear racio reduces. When throttle input increases ,the speed and velocityincreases, leading to and increase in gear racio. When gear racio increases or decreases this is due to a change in the transmission or change in rotation of primary and secondary shaft. The gear racio is also directional to torgue hence torgue also changes each time gear ratio changes.
Observation:
-In the above image the brakes (in blue) is kept constant at 0. while the throttle is at 0.3 for 20 sec then to 1. We observe a velocity change in the first image.
-Similar to the below image where at a certin time there is some brakes applyed at a constant throttle input. we notice that the velocity responds to the brakes input by gradualy slowing down.
-During throttling and braking something very significant happends on the primary and secondry shaft of the CVT. There is a indrease and decrease in the gap of the pully creating an increase in decrease in the rpm of the various shafts to adjust vehicle speed smoothly.
Conclution:
With help of the four differnet analysis on the BAJA ATV with CVT we could see the effects or observe the functioning of the Continous Varrying Transmission due to speed change due to altherying the throttle input and brakes input.