Project
AIM-
To study and analyze the BAJA All Terrain Vechical model (AVT) using simulink and compare different models
OBJECTIVES-
The main objective of this project is,
1) To prepare atechnical report and explaining the function of the simulink block used for preparing the model.
2) To explain all the differences among 'BAJA AVT' model, 'BAJA AVT' model with dashboard and 'BAJA AVT model with mapped dashboard',in detail.
ALL TERRAIN VEHICLES-
An all-terrain vehicle (ATV) is defined as a motorized off-highway vehicle designed to travel as a four low pressure or non-pneumatic tires,having a seat designed to be straddled by the operator and handlebar for steering control. ATVs are subdivided intop two types, as a designed by the manufacturer.type 1 ATVs are intended by the manufacturer for use by a signal operator and no passanger.type 2 AVTs are intended by the manufacturer for use by operator and a passenger,and are equipped with a designated seating position behind the operator.
BAJA SAE-
BAJA SAE is a collegiate design series competition run by the society of automotive engineers (SAE international) Teamsof students from universities all over the world design and build small aff-road cars.The cars all have engines of the same specifications.as of 2018 the engine has been an unmodified briggs and stratton model 19 vanguard engine signle cyclinder with displacement of 305cc and power output of approximately 10bhp(7.5kw)
The goal in BAJA SAE racing is to design,build and race off-road vehicles that can withstand the hardest elements of rough terrain. The vechicls used in BAJA SAE racing are often similar in appearance to dune buggies.before 2007.the events were called 'min Baja'.
CONTINUOUSLY VEARIABLE TENSIMISSION(CVT)-
A continuously variable tansmission (CVT) in an automatic,single speed and gearless transmission that can shift through an infinite number of gear ratio.A continuously variable transmission (CVT) is a trasmission that operates on an ingenious pulley system that automatically varies the transmission ratios,allowing an infinite variability between highest and lowest gears with no discrete steps or shifts CVTs provide more useable poer, better fuel economy and smoother driving experience thet teaditional transmission that use gearboxes eith fixed number of gear sets.
Before entering in to the vechicle models,lets discuss about the main component(blocks) used in the vechicle model.
GENERIC ENGINE-
The generic engine block represents a general internal combustion engine.Engine types include spark ignition and compression ignition.speed power and speed torque parameterizations are provided.A throttel physical signal input specifies the normalized engine torque,opitional dynamic parameters include crankshaft intertia and response lad time.A physical signal port outputs engine fuel consumptionrate based on choice of fuel consumptionmodel,optional speed and redline controllers prevent engine stall and enable cruise control.
Main parts-
* B- Rotational conserving port: representing the engine block(should be connected to rotational motion reference).
* F- Rotational conversing port: Representing the engine crankshaft
* T- physical signal input port: specifyingthe normaluized engine throttle level.
* P- physical signal ouput port: representing the normalized engin e throttle level.
* FC- physical signal output port: representing the fuel consumption rate,in kg/s.
SIMPLE GEAR-
The simple gear block represents a gearbox that constrains the connected driveline axes of the base gear B and the follower gear F to corotate with a fixed ratio that is specificed.
The follower-base gear ratio is,`gFB=frac(rf}{rB}=frac{NF}{NB}`
where,
* NB is the number of teeth in the base gear.
* NBF is the number of teeth in the folloer gear.
MAIN PORTS:
* B- base:Rotational mechanical conversing port associated with the base or input shaft.
* F- follower:Rotational mechanical conversing port associated with the folloer or output shaft.
VARIABLE RATIO TRANSMISSIONBLOCK-
The variable ratio of transmission block represents a gearbox that dynamically transfers motion ad torque between the two connected driveshaft axes and follower.
Ignoring the dynamics of transmission compliance,the driveshafts are constrained to corotate with a variable gear ratio control that you control.you can choose whether the follower axis rotates in the same or opposite direction,wf and wb have opposite signs.
transmission compliance introduces internal time delay between the axis motion.therfore,unlike a gear a variable transmission does not act as a kinematic constraint.you can also control torque loss caused by transmission and viscous losses.
MAIN PORTS:
* B- Base pulley or drive pulley.
* F- follower pulley or Driven pulley.
* R- variable transmission ratio(input)
VECHICLE BODY BLOCK-
The variable body block representss a two axle vechicle body in longitudinal mption.The vechicle can have the same or a different nuber of wwheel on each axle
The block account for body mass, aerodynamic drag,road incline(grade),and weight distribution between axles due to acceleration and road profile.optionally include pitch and suspension dynamics.the vechical does not move vertically relative to the ground the block has an option to include an externally defined mass and an externally define inertia.the mass,inertia,and center of gravity of the vechicle body can vechicle body can vary over the course of simulation in response to system changes.
input ports:
* Beta - road incline angle(rad):physical signal input port for road incline angle.
* W - Head wind speed (m/s):physical signal input port for road incline angle.
*CG-center of gravity(m):physical signal input port of externally defined mass relative to the CG of vechicle{only available with externally defined additinal mass is set to on).
M-Mass(kg):physical signal input port for mass of the extrnally defined mass(only available with externally defined additional ,massis set to on)
*J- Externally defined moment of inertia(kg*m^2):physical signal input port of the externally defined mass.
output ports-
* NR-Rear axle normal force(N):phiysical signal output port for the rear axle which is considered positive acting downward.
* NF-Front axle normal force(N):physical signal output port for the front axle which is considered positive acting downward
* V-Logitudinal velocity(m/s):physical output signal of vechicle velocity.
conserving ports-
* H-Horizontal motion:conserving port to the horizontal motion of vehicle body(tires should be connected to this port)
DOUBLE SHOE BRAKE-
the double shoe brake represents a frictional brake with two pivoted rigid shoes that press against a rotating drum to produce a ranking action.The rigid shoes sot inside or outside the rotating drum in a diametrically opposed configuration.A positive actuating force causes the rigid shoes to press against the rotating drum.viscous and contact friction between the drum the rigid shoe surfaces cause the rotating drum to decelerate.
Double shoe brakes oprovide high braking torque with small actuator deflections in applications that include motor vehicles and some heavy machinery.The model employs a simple parameterization with readily accessiable brake geometry and frictiion parameters.
input ports-
F- physical signgal input port associated with the applied actuating force.
conserving ports-
S-rotational conserving port associated with the rotating drum shaft.
TIRE(MAGIC FORMULA)BLOCK-
The tire (magic formula)block models a tire models a tire with longitudinal behavior given by the magic formula.an empirical equation based on four fitting coefficients.the block can model tire dynamics under constant or variable pavement conditions.
the longitudinal direction of the tire is the same as its direction of motion as it rolls on paverment.This block is a structual component based on thetire road interaction block.To increase the fidelity of the tire model,we can specify properties such as tire compliance,inertia and rolling resistance however,these properties increase the complexity of the tire model and can slow down simulink.consider ignoring tire compliance and inertia if simulating the model in real time or if preparing the model for hardware in loop simulation
OTHER BLOCKS USED-
* solver configuration-To specify the solver parameters before starting the simulation.
* rotational free end-for mechanical components(tire).
*custom measure gauge-to measure the brake and throttle input.
*signal builder- to input the brake,throttle and cvt ratio.
*simulink to ps convertor- To convert the simulink signal to simscape environment.
*mechanical reference- To make sure all the components are clamped to the ground.
* knob-To increase,decrease and vic versa from the workspace.
* lookup table-To insrt the cvt valus from the workspace.
* step-To increase or decrease n input vALUES FOR A DEFINED TIME INTERVAL.
* rotational motion sensor- To sensor the rotational motion from the engione and give output as RPM.
*ps terminator- Terminator for unconnected physical signal outputs.
*inertia- To represemt the solid inertia.
* ps constant - generate constant physical signal.
* rotational free end- The rotational free end block represents a mechanical rotational poty that rotates freely,without torque
*scope- to display the output graphs.
*display- To represent the solid inertia.
BAJA AVT model without dashboard(cvt model)-
The above model is a basic model,so no need to change the input values of brake,throttle and CVT ratios.because the CVT ratio is already generated in signal builder.the generic engine takes the inputs from the workspace(speed and torque)and it generates the follower speed and inputted to the engine sensor,the engine sensor genetrates the base signal.those signals are transfered to the CVT block(subsystem),the output from the CVT block is conneted to simple gear to reduce the speed according to the gear ratio(gear ration is 10).in CVT ration reduces the engine speed according to the CVT ratio that we have given from the signal bulider.The output from the simple gear block is connected to the vehicle body,the vehicle body moves with the velocity.The vechicle body output is connected to the velocity and distance output block to visualize the vechicle velocity and distance.The velocity and distance is conneted to scope block to visualize the results.
The brake and throttle inputs:
The CVT ratio inputs:
THe CVT ratio starts at above 3.5 and then it gradually decreases to less 1.and the value will remain same for whole simulation.
speed vector and torque vector:
The engine sensor:
This sub-block measure engine rotational speed as it takes the output of the engine as its inputs and output engine RPM
CVT SUBSYSTEM:
The CVT subsystem provides the input and output shaft of the CVT with inertia and measures the input shaft rpm and the output shaft RPM
vechicle body subsystem:
The model shows that the vechicle is rear wheel drive,as the output from the gear box is inpuutted to the rear axle,then an inertia is added to simulate axle inertia then the shoe brake conserving port is connected to the axle the same axle is connected to the rare wheels,while the front wheels are free to rotational free end.All the tires H hub port is connected together and then connected to the vechicle H port,also the rear wheel N port is connected together and connected to the vechicle body Nr output ports,while the front wheels are connected to the Nf vechicle body output ports the vechicle body takes the road inclination and wind velocity from physical constants.
Torque speed plot:
The torque and speed are inputted from the matlab workspace to the generic engine bkock to generatethe output RPM accordindgly.This plot behaviour is generic to all Ic engines.
output graph for velocity,distance,throttle and brake:
output CVT shaft speed:
The engine reduced speed is controlled by various CVT ratios.for verification the maximum RPM is calculated by using below formula,
gear ratio = driven/driver
driven=driver/gear ratio
BAJA AVT model with dashboard (CVT model)-
BAJA AVT model with dashboard CVT model has a dashboard to see the velocity ,RPM,Throttle input values and brake input values.In this model we need to change the throttle input 1 to 0.5 and start the simulation.According to the throttle input the engine RPM and velocity will increase up to certain level,now change the brake and throttle inputs gradually we can observe the velocity and RPM changes in the dashbord.
keep the brake input 0 and increase the throttle input,we can observe the velocity and RPM increase according to the throttle input,if we increase the brake input and keep the throttle value at 0.5 the velocity and RPM will decreases,because we are applying the brake load on the wheel so the engine velocity and RPM decrease ,here also the ctv ratio is inputted with the help of signal builder,for the cvt ratio signal builder also no need to change any inputs,because the cvt ratio is already given in the signal builder.
If we observe the scope block,we can understand what hapeens,while increasing and decreasing the throttle & brake input and the cvt shaft speed graphs also.
The below scope block visualizes the velocity,distance,throttle and brake graphs:
The below scope block visualizes the CVT shaft speed for both promary and secondary:
According to the below engine torqe and speed plot the engine torque ad speed will be given as an input to the generic engin block.
BAJA AVT MODEL-MAPPED LOOKUP TABLE WITH DASHBOARD(CVT MODEL-DASHBOARD-MAPPED):
The BAJA AVT mapped lookup table with dashboard(CVT Model-Dashboard-Mapped) model has a dashboard to visulize the velocity,engin RPM,brake input and throttle input.The initial condition of throttle input must be 0.3 and break input will be 0. We can give the throttle and break input from the skimscape model and from the dashboard also by moving the pointer in the dashboard knob.Hear in this model we don't use any signal builder block to give CVT ratio to the CVT block,we used a loop to give CVT ratio instead of using signl builder block.The vechile body block output velocity loop is connected CVT input port,with respective to the velocity the speed will be controlled in the CVT subsystem.In the CVT subsystem 'lookup' table is used to give the CVT ratio data from the MATALAB workspace.
A lookup table block uses an array of data to map input values tonthe output values,approximating mathematical function.Given input values,simulink performs a "lookup" operation to retrive the corresponding output values from the table.Likewise, the lookup table output 27 in response to an input of 3.Here the lookup table is used to give the input of 'CVTR' data from the MATALAB workspace.According to that data the CVT block will controll the speed of the vechicle.
The Engine Torque and Speed Curve:
The above engine speed an torque plot shows the input of engine speed and torque data.
Lookup Table Visualization:
The above figure (plot) visulizes the CVT ratio or 'CVRT' data from the workspace.According to the above plot the datav will be inputted to the lookup table.
Graph for velocity,throttle input and break input:
Graphs for both CVT primary and secondary RPM:
The above plot visulizes the CVT shaft speed for both primary and secondary shafts.For this CVT shaft speed is get controlled with resect to the throttle and break inputs.