Project
TECHNICAL REPORT
OBJECTIVE:
simulation and technical report on baja avt explaining model properties for with and without dashboard-using lookup table-without using lookup table
THEORY:
AVT- an all terrain vehicle (avt) is defined as a motorized off highway vehicle designed to travel on four low pressure or non-pnematic tires, having a seat designed to be straddled by the operator and handlebars for steering control. avts offer excellent off road capabilities and can carry heavy equipment over long distances and narrow access points. it has application across various industries including sports entertainment agriculture military and defense.
CVT: a continusly variable transmission is an automatic transmission that can change seamlessly through a continuous range of gear ratios. this contrasts with other transmission 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.
cvts are used in automobiles, tractors, motor scooters, snowmobiles,and earthmoving equipment.
PROCEDURE:
BAJA AVT Model without dashboard
brake and throttel input:
brake inpute is constant ,example zero throughout the time of 80 sec, throttle input is 0.3 for first 20sec , accelerates to 1 at the same and remains constant throughout the remaining time till 80 sec .
signal builder:
the signal builder block allows you to create linear signal sources and to use them in a model. you can quickly switch the signal groups into and out of a model to faciliate testing.
the cvt gear ratio 2.3 for the first 4 secs, then drops down to 1.8 till 35 sec and remains constant therafter till 80 sec.
Generic engine:
it represent a model of spark ignition and diesel engines suitable for use at initial stages of modeling when only the basic parameters are avaliable. the throttel input signal t lies between zero and one and specifies the torque demanded from the engine as a fraction of the maximum speed , the simulation stops and issues an error message.
connections Fand B are mechanical rotational conserving ports associted with the engine crankshaft and engine block respectively.
connection p and fc are physical signal output ports through which engine power and fuel consumption rate are reported
Engine sensor:
ideal rotational motion sensor the block repersents an ideal mechanical rotational motion sensor,that is a device that converts an across variable measured between two mechanical rotational nodes into a control signal proportional to angular velocity or angle . connections r nad c are mechanical rottional conserving ports and connections Wand A are physical signal output ports for velocity and angular displacement , respectively.
CVT Subsystem:
Inertia: the block represents an ideal mechanical rotational inertia. the block has one mechanical rotational conserving port.
the block has one mechanical rotaion conserving ports. the block positive direction is from its port to the reference point. this means that the inertia torque is positive if the inertia is accelerated in a positive direction.
Variable Ratio Transmission:
represents a variable ratio gearbox such as implemented by mechanical belt cvt, electric or hydraulic transmission . the physical signal input definse the ratio of input to out put angular shaft velocities.connections b based and f follower are mechanical rotational conserving ports .
specify the relation between base and follower rotation direction with the outputs shaft rotates parameter.
Simple Gear:
Represents a fixed ratio gear or gearbox. no inertia or compliance is modeled in this block. you can optionally include gera meshing and viscous bearing losses . connections b anfd f are mechanical rotation conserving ports. speciy the relation between base and folower rotation direction with the output shaft rotates parameter . optionally include thermal effects and expose thermal conserving port H by right clicking on the block and selecting simscape block choices to switch between variants.
follower (f) to base (b) teeth ratio (nf/nb):4
Vehicle body subsystem:
Vehicle Body:
represents a two axle vechicle body in longitudinal motion. the block accounts for body mass,areodynamic drag,rod incline and weight distribution between axles due to acceleration and road profile. the vechicle can have the same or a different number of wheels on each axle. optionally include pitch and suspension dynamics or additional variable mass and inertia . the vechicle does not move vertically relative to the ground.
connections h is the mechanical translational conserving port associated with the horizontal motion of the vehicle body. the resulting tranction motion developed by tires should be connected to this port. connections V,NF,and NR are physical signal output ports for vechicle velocity and front and rear normal wheeel forces respectively. wheel forces are considered positive if acting downwardes.connectins w and beta are physical signal input ports corresponding to headwind speed and road inclinatilon angle, respectively if the variable mass is modeled the physical signal input ports cg and m are exposed. CG accepts a two element vector respecting the x and y distance offsets from vechicle cg to additional load mass cg. m represents the attotional mass. if both variables mass and pitch dynamics are the physical signal port j accepts the inertia of the additional mass about its own cg.
parameters are:
number of wheels per axle:
horizontal distance from cg to front axle:
cg height above ground:
gravitational acceleration:
TIRE: Repressent the longitudinal behavior of a highway tire characterized by the tire magic formula. the block is build from tire road interaction and simscape foundation library wneel and axle blocks. optionaly the efficiency of tire inertia stiffnes and damping can be included.
connection a is mechanical rotation conserving port as a wheel axle.connection h is the mechanical translation conserving port for the wheel hub through which the thrust developed by the tire is appelied to the vehical. connection n is a physical signal output port that report the tire slip optinally expose physical signal port m by setting magic formula coefficengt. physical signal port m accepts a foue element vector correcpondin to the b,c,d, and e magic formula coefficents.
magic formula b coefficent:
magic formula c coefficent:
magic formula d coefficent:
magic formula e coefficent:
DOUBLE SHOE BRAKES :
Repersent a brake arranged as two pivoted rigid shoes symmetrically installed inside or outside a drum and operated by one actuator the actuator force causes the shoes to exert a friction torque on a shaft connected to the drum.
connection s is a conserving rotational terminal associate with the drum shaft. connection s is a conserving rotational terminal associates with the drum shaft. connection f is a physical signal port repercinding the force input to the actuater. positive force creates friction torque that ressist shaft rotation. optionally include terminal conserving port h by setting thermal port to model.
parameter are:
drum radius:
actuvator location radius:
pin location radius:
shoe location radius:
shoe pan angle:
BAJA ATV MODEL WITH DASHBOARD
a dashbord (also called dash,instrument panel(ip),or fascia)is a control panel usually located directiy ahead of a vechical driver , displaying instrument and controls for the vehical driver , displaying instrumentation and controls for the vehicle operation.
the initial conditions are as folliws
brake input =
throttle input =
it comprises a throttle and brake input through a knob which can be varied unlike the signal builder in the previous model without dashbord . the engine RPM gauge and velocity gauge displays the changes done by the respective knobs.
WITHOUT DASHBOARD
LOOKUP TABLE:
A look up table is an array of data that maps input values to output values therby 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 value using interpolation extrapolation or rounding where:
intropalation is a process for estimating values that lie between known data points .
extrapolation is a process for estimating values that lie beyond the range of known data points.
rounding is a process for approximating a value by altering its digits according to a known rule.
CONCLUSION:
Hence the given baja avt model was simulated successfully
velocity cvt shaft speed and engine speed are directly proportional to the throttle input and inversely proportional to the brake input.
cvt ratio is directly proportional to torque and inversely proportional to the throttle input.
CVT primary speed is greater than cvt secondary speed as they are directly proportional to their shaft diameter.
the speed might get null at a particular beaking resistance.