Week 7 Challenge

Vehicle Model:

• Here the Vehicle model is  the equation of forces which comes under velocity 
• If when vehicle moves from its rest position for motorized vehicles such as automobiles aircraft and watercraft  vehicle dynamics is the study of vehicle motion.
• For example  how a vehicles forward movement changes in response to driver inputs propulsion system outputs ambient conditions air or surface or water conditions etc.
• We can from below image shows the force acting on a vehicle

• Here

  •  Ftr = Tactive Force
  •  Fa = Aerodymanic drag resistant force
  •  Fg= Gradient Resistance force
  •  Fr = Rolling resistance force
  •  Fi = Inertial resistance force

• Here the Tractive force is the force applied produced by the vehicle powertrain we will now see the quations of three main forces and will implement this by  matlab Fcn block

Aerodynamic drag :

• Here Aerodyamic Drag is a force which the on coming air applies on a moving body.
• Its is the reistance offered by the air to the movement of the body.
• So when a car is moving it displaces the air However it affects the car's speed and performance 
•  It is the aerodynamiv drag or the friction offered by the air to a vehicle

Aerodynamic Drag= 1/2*p*Cd*A*V2

Force of aceelration :

• The acceleration force refers to the vehicle resistance to speed varitaions
• This force holds you back when you increase your speed and also moves you forward when you slow down in other words it means that you consume energy to acclerate up to as certain speed but can recover part of that energy when you decelerate allowing you to drive a certain distance without consuming fuel in equations it is simply written as
• F=m*a m is mass and a  is acceleration

Simulink model :

 

• Here above model shows  the entrie vehicle model
• It consist of driver block vehicle block only
• Here thw Driver block is used to  accleration purpose the  value to overcome the integral windup happeneing while converting tractive force into velocity
• So Hence the  only vehicle block system is consider as major system block in the vehicle modeling

Subsytem of the Driver Block:

 

• In this we created a inputs as  desired velocity and actual velocity 
• And aslo output as Accelerator ,brake , 
• We aslo  used the below steps
  1)Compute the error
  2)Proportional control
  3)Integral control reset when velocity is 0
  4)Derivative controller

Vehicle model subsystem : 

 

In this we used input as traction force and output as velocity

 

Working of the above designed model :

• Initially we loaded the excel file into the siginal builder block as shown in below
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•  
• Here The input  to the vehicle block is tractive force this tractive force is teh force which is applied by the powertrain to the vehicle body
• Here we have given tractive force directly as a input its values are in newton its plot the values as shown in above siginal builder block

Vehicle model subsystem:

 

• This is the major block which lay key role in vehicle modeling
• So to find velocity let us asume that all the forces acting on vehicle  this  force of traction which is given as 
• F_trac = Force of acceleration+ Rolling Resistance Foce+ Gradient Force+ Aerodynamic Force
• The term force of acceleration will help us to find the velcoity we will first seperate the acceleration term and resistive force terms.
• F_trac-Fr-Fg-Fd=Fa
• F_trac-Fr-Fg-Fd= m*a
• F_trac-Fr-Fg-Fd/m=a
• So we now have to acclerate
• Here The forces other than F_trac in model is calculated by  formula implementation using Fcn block 
• So now We have taken grade is zero hence there will be no gradient force acting on vehicle
• Here Fr is independent of velocity value but only acts on vehicle when its moving
• So Hence switch is used to make sure the force is taken into account only when velcoity is of some value
• The Aerodynamic force or drag force is a function of square of velocity
• So the Fcn block is given velocity square as its function
• Here Sum of these forces is then substracted with tractive force.
• Then after this the result of above process  we need to divided by mass to get the acceleration value

Now we have acceleration with us we know that the accleration is the rate of change of velocity 

The derivative of velocity Hence its anti derivation or integration will give us the velocity Which as  been discussed theoritically is acytually implemented in simulink using required blocks

• Here  We have taken the integral windup, the  integral windup particularly occurs as a limitation of physical system.

• When we compared with ideal system due to the ideal output being physically impossible For example  the position of  a valve cannot be any more open than fully open and also cannot be closed any more than fully closed in this case anti windup can actually involve the integrator being turned off for periods of time until the response falls back into an accpetable range as soon as the acc and velocity goes zero the reset button gets active.

• The vehicle paramertes is loaded using mat files.

• The parameters value is shown below

• Parameters                           value

• Vehilce mass                        1200kg

• Gravitation force                   9.81

• RR coefficient                      1.2

• Drag Coff                            2.5

• Grade or angle                    0

Output results:

 

• Here we can see that how the vehicle is operated by using the drive cycle source 
• we created a vehicle model to obtaine the above results 
• Here the vehicle speed can be varied by chaning the acceleration of the driver block 

Conclusion :

We have Loaded  the vehicle parameters. and Completed  the vehicle model by modelling the remaining equations and we Seted the  simulation stop time to 598 sec.