Project
Aim:
To prepare a technical report of Simulation of BAJA All-Terrain Vehicle (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:
An all-terrain vehicle (ATV) is defined as a motorized off-highway vehicle designed to
travel on four low-pressure or non- pneumatic tires, having a seat designed to
be straddled by the operator and handlebars for steering control.
STUDY #1:
CASEl:
SIMULINK MODEL FOR BAJA ATV WITH CVT:
Major components in the model:
Continuously Variable Transmission drive
(CVI):
It is better to have more gears in a transmission, since it can optimize engine
speed in a variety of driving conditions. That means low gears can provide better
acceleration while higher gears can maximize fuel economy. CVTs differ from
traditional automatic transmissions in that they don't have gears that provide "steps"
between low- 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. These form a V-shaped groove in which the
connecting belt rides. One side of the pulley is fixed, and the other side is movable,
actuated by a hydraulic cylinder. The cylinder can increase or decrease the
amount of space between the two sides of the pulley. This allows the belt to ride lower
or higher along the walls of the pulley, depending on driving conditions, thereby
changing the "gear" ratio.
VARIABLE TRANSMISSION RATIO:
Represents a variable ratio gearbox such as implemented by mechanical belt CVT,
electric, or hydraulic transmissions. 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:
Represents a system-level model of spark- ignition and diesel engines suitable for use
at initial stages of modelling when only the basic parameters are available. Optional
idle speed and red line controllers are included. The throttle input signal T lies
between zero and one and 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, respectively. Connections P and FC are
physical signal output ports through which engine power and fuel consumption rate are
reported.
INPUT SIGNAL:
A Signal builder is used to create signals for brake and throttle.
CVT Gear Ratio Input:
Torque vs Engine Speed input:
VEHICLE BODY:
OUTPUT for CASE 1:
VEHICLE SPEED:
It is clear from the graph that the vehicle attains its maximum speed (V = 55km/hr)
at full throttle = 1 after 30 seconds and then remains constant. The brake input value is
zero, hence it has no effect on velocity.
CVT SHAFT RPM:
These graphs shows the variation in angular
velocities of input and output shafts of the
variable gear transmission system. These
values differ with respect to the gear ratio.
STUDY #1:
CASE2:
SIMULINK MODEL FOR BAJA ATV WITH CVT USING DASHBOARD:
BAJA ATV Model
In this model we have a dashboard which contains knobs to control the inputs. In this
case, the inputs- 'Throttle' & 'Brake' are not provided using signal builder. A knob is
provided to control both the parameters in real-time for the user.
OUTPUT for CASE 2:
VEHICLE SPEED:
It can be observed from the graph that the velocity of the vehicle increases drastically
from O to 50kmph when throttle value is 0.5 & brake input is 0. Once the braking value
increases from 0. to 0.5, the velocity of the vehicle decreases to 0 at constant throttle
value. This explains the direct relation of vehicle velocity with respect to throttle and
brake inputs.
CVT SHAFT RPM:
STUDY #2:
CASE 1:
SIMULINK MODEL FOR BAJA ATV WITH CVT
USING LOOKUP TABLE:
CVT BLOCK:
The only Difference between this model and the first model is that in this model, the gear
ratio input to CVT is provided using a lookup table. The vehicle velocity and shaft rpm
outputs are same as before.
CVT GEAR RATIO:
LOOKUP TABLE VISUALISATION:
OUTPUT for CASE 1:
VEHICLE SPEED:
CVT SHAFT RPM:
Both results are same as that of the first
case: - SIMULINK MODEL FOR BAJA ATV
WITH VT since the input parameters are
same.
STUDY #2:
CASE 2:
SIMULINK MODEL FOR BAJA ATV WITH CVT USING LOOKUP TABLE & DASHBOARD:
In this model a dashboard is used to control the inputs- 'Throttle' & 'Brake' with knobs.
OUTPUT for CASE 2:
VEHICLE SPEED:
This graph is similar to that of ct dashboard case. The variation in vehicle velocity can be
observed with change in throttle and brake inputs. With increase in braking value, the
speed of vehicle decreases. On the other hand, increasing the throttle leads to
increased vehicle velocity.
CVT SHAFT RPM:
This graph indicates the variation in rpm of primary and secondary shafts with respect
to input parameters.
CONCLUSION:
Thus we have successfully analysed 4 different models of BAJA ATV WITH VT and
recorded the outputs: - (Vehicle velocity & CVT shaft rpm) with respect to variations in
input throttle and brake.