Project
AIM:
To prepare a technical report of Simulation of BAJA - ATV under different conditions.
OBJECTIVES:
Carry out a system-level simulation of an all-terrain vehicle and prepare a technical report explaining the model properties & comments on the results.
ALL TERRAIN VEHICLE [ATV]:
An All-Terrain Vehicle (ATV) is also called as a motorized off-highway vehicle. This vehicle runs on low-pressure tires. However, it has handlebars instead of wheel for controlling the steering. As the name indicates, an ATV is designed to handle a broader variety of terrain than regular vehicles. In some countries it is a street-legal motor vehicle and licensed for use on public roads. On an ATV, the operator is seated in a straddle position. ATVs are normally built for just one rider, some are made to carry the operator and one passenger. When operated safely and correctly, ATVs offer a quick and nimble means of transportation over a variety of terrain.
Fig.(a) All-Terrain Vehicle.
SECTION-A
CASE-1: SIMULINK MODEL FOR BAJA-ATV WITH CVT
Fig.(b) Simulink Model for BAJA-ATV with CVT.
Components Used in the Model:
Continuously Variable Transmission Drive (CVT):
A CVT is an automatic transmission that can change seamlessly through a continuous range of gear ratios. This contrasts with other transmissions that provide a limited number of gear ratios in fixed steps. The flexibility of a CVT with suitable control may allow the engine to operate at a constant RPM, while the vehicle moves at varying speeds. As more no. of gears in transmission system, which optimizes engine speed in different driving conditions. So, low gears provides better acceleration and high gears can maximizes fuel economy. CVT is different from traditional automatic transmissions, in which instead of gear system, steps are provided between low-speed and high-speed operations. Instead, the majority of them work via a 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 cones touching, which forms V-shaped groove in which connecting belt rides. Pulley's one end is fixed and other end is movable and actuated with the help of hydraulic cylinder. The cylinder is can varies the amout of spaces between both sides of the pulley, which allows the belt to ride lower or higher along the walls of the pulley, depending on driving conditions, thereby changing the gear ratio.
Fig.(c) CVT Construction.
CVT Block:
Fig.(d) CVT Block.
Variable Transmission Ratio:
It represents a variable ratio gearbox which is implemented by mechanical belt, CVT, electric, or hydraulic transmissions. This gearbox that dynamically transfers motion and torque between the two connected driveshaft axes, the base and the follower.
The physical signal input 'r' defines the ratio of input to output angular shaft velocities. Connections B (base) and F (follower) are mechanical rotational conserving ports. Specify the relation between base and follower rotation directions with the Output shaft rotates parameter.
Engine:
The Generic Engine block represents a general IC engine. It is a system-level model of spark-ignition and diesel engines which is used at initial level of modelling by using some basic parameters. Optional idle speed and red line are included.
The throttle input signal 'T' lies between zero and one, which specifies the torque demanded from the engine as a fraction of the maximum possible torque.
Connections 'F' and 'B' are mechanical rotational conserving ports associated with the engine crankshaft and engine block.
Connections 'P' and 'FC' are physical signal output ports through which engine power and fuel consumption rates are calculated.
Input Signal:
A signal builder is used as input to building the signal for brake and throttle.
Fig.(e) Signal Builder block.
CVT Gear Ratio:
Fig.(f) CVT gear Ratio.
Torque Vs Speed Curve:
Fig.(g) Torque vs Speed curve.
VEHICLE BODY:
Fig.(h) Vehicle body.
RESULT FOR CASE-1:
Vehicle Speed:
From the above plot we can conclude that, if vehicle attains its maximum speed (V=65km/hr) at full throttle 1 after 140 seconds and then remain constant. The brake input value is 'zero', hence it has no effect on velocity.
CVT SHAFT RPM:
This plot shows that variation in the input and output shafts of variable transmission system and this value differs with respect to the gear ratio.
SECTION-A
CASE-2: SIMULINK MODEL FOR BAJA ATV WITH CVT USING DASHBOARD
Fig.(i) Simulink Model for BAJA ATV with CVT using Dashboard.
In this BAJA ATV model, a dashboard is given which contains knobs to controls the inputs. By using these knobs can control the inputs of brake and throttle. So, instead of using signal builder block, knobs are used. With the help of knobs, the input parametrs are controlled in real time mode for the user.
RESULT FOR CASE-2:
Vehicle Speed:
From the vehicle speed plot we can observe that, Initialy velocity of vehicle increases rapidly from 0 kmph to 55 kmph at throttle value is 0.5 and brake input value is zero. If we vary throttle value till 1 then vehicle attains its maximum velocity 60kmph. After that when we increase brake input value from 0 to 0.5, which effects on velocity of vehicle decreases from 60 kmph to 30 kmph. So, from that we conclude that their is direct relation between the vehicle velocity with respect to the throttle and brake inputs.
CVT SHAFT SPEED:
SECTION-B
CASE-1: SIMULINK MODEL FOR BAJA ATV WITH CVT USING LOOKUP TABLE
Fig.(j) Simulink Model for BAJA ATV with CVT using Lookup Table.
In this model of BAJA ATV with CVT uses lookup table to feed input parameters.
CVT BLOCK:
Fig.(k) CVT Block.
In this model gear ratio input to CVT is provided with the help of lookup table and the vehicle velocity & its RPM is similar as the previous model.
CVT Gear Ratio:
Fig.(l) CVT Gear Ratio.
LOOKUP TABLE VISUALIZATION:
Fig.(m) Lookup Table Visualization.
Input data is entered in the lookup table and these point connected each other which forms a plot of CVT Ratio and vehicle speed.
RESULT FOR CASE-1:
Vehicle Speed:
CVT Shaft Speed:
Results in both the cases are same as the input parameters are same.
SECTION-B
CASE-2: SIMULINK MODEL FOR BAJA ATV WITH CVT USING LOOKUP TABLE AND DASHBOARD
Fig.(n) Simulink Model for BAJA ATV CVT using lookuptable and dashboard.
Given simulink model is same as previous simulink model of BAJA ATV using lookup table, except one in this model dashboard is provided to control the inputs of throttle and brake using variable knobs.
RESULT FOR CASE-2:
Vehicle Speed:
This plot of speed of vehicle is similar to CVT dashborad, as we increase brake input value the velocity of vehicle decreases and in other case when we increase value of throttle input which results in velocity of vehicle also increases.
CVT Shaft Speed:
This plot shows that, when input parameters changes,the variation occurs in RPM of primary and secondary shafts of CVT.
CONCLUSION:
Thus, we studied BAJA All-Terrain Vehicle and its four various operating models. we simulated these models using simulink and taken the output results, vehicle velocity and CVT shaft RPM with respect to variations in throttle and brake input.