Final Project: Design of an Electric Vehicle
Answer .
First Let us discuss about the basic idea for electric vehicle modelling in the steps given below-
Battery - Controller - Type Of Required Motor - Vehicle Body and controller will be work as feedback controller for both the vehicle speed and battery power.
Now Let us Understand the block which i have used.
Drive Cycle Source - It will provides us speed vs time data that EV needs to follow. This Data can be taken from the specified Drive cycles or can be given externally to this drive cycle also.
Multiport Swtich - It is a switch which is used to select one input out of multiple inputs by the help of constant block connected to its 1 port. the input which need to be connected is given to as a constant in the block.
Longitudinal Driver - This Block is controlling block which uses PI Control method to track actual speed with reference speed. the output of multiport switch is connected to velocity reference terminal, feedback speed signal from vehicle body is connected to Vehicle feedback port. we can also provides some grading angle to this block for our EV. the output of this block is acceleration signal and deceleration signal.
now if reference speed is > feedback speed deceleration signal is generated
otherwise acceleration signal is generated
Controlled Voltage Source - It is behaved as ideal voltage source which will always produces voltage whatever is the load.
Controlled PWM Voltage - This Block is used to generates the controlled Pulse which will be used as a triggering signal for the switches used in H-Bridge. the pwm frequency and pulse amplitude we can control from here. The +ve Ref port of this switch is connected to the +ve of the terminal of the controlled voltage source while -ve is electrically grounded. PWM pulse is obtained as output from its PWM port.
H-Bridge - It is a power electronics circuit which have four power electronics switches like BJT, MOSFET, IGBT. IGBT is basically considered for nowdays use because of thier higher power and frequency capability. at a time only two switches is on out of four in such a way that our vehicle rotates in one direction than in reverse direction when those two switches are off and remaining switches are on.
for the switches to be on or off it received pulses from pwm voltage controller throught pwm port as input and then reference and reverse is grounded. break signal is received from longitudional driver box to its break port. after that it generates required voltage for the DC Motor operations.
DC Motor - We used permanent magnet type DC Motor here which recieves its terminal voltage from H-Bridge and generates required speed. we connect a current sensor between H-bridge and DC Motor to measure the current flowing through the DC motor and to find out the SOC. Remaining terminals of DC motor is connected to electrical and mechanical references accordingly.
Battery - A Battery block is used to measure State of Charging (SOC) of the battery used according to the vehicles movement following the drive cycle.
Vehicle Body- It has two input terminal, first for feedback speed signal to longitudinal driver block, second is for the motor speed throght gear box mounted inside the vehicle body.
Inside the vehicle body we define tires power either in rear wheels or in front wheels, we can define all the forces like rolling resistance force coefficienct, aerodynamics force coefficient, mass of vehicle, frontal area, its inertia, grading angle and so many other parameters.
After that we have given a solver for the calculations and also powergui block.
Model Parameters -
Duty Cycle-
Controlled PWM Voltage Parameter-
H-Bridge Parameters
DC Motor Parameter-
Vehicle- Body Parameter
Working -
The Model is shown below
1. By the help of switch required speed vs time data is selected.
2. This signal is now given to longitudinal driver block which will compare it with the feedback speed signal so
if Feedback speed > reference speed, deceleration signal is generated and sent to the break port of H-bridge
Feedback speed < reference>
3. Controlled pwm block generates controls pulse accroding to the signal received from longitudinal driver block by voltage source.
4. H- bridge further control the DC Motor's direction of speed and its value by the helps of signals recieved from PWM voltage controllers and from the break port.
5. Now corrosponding speed and torque is generated which is fruther transmitted to vehicle wheels through gear box.
Result-
Speed - We can see our vehicle speed is approaching the driving cycle speed with respect to time.
Current-
According to acceleration and deceleration our current is varying-
SOC-
Battery SOC is down upto 92% and so remaining is only 8% during the drive cycle.
Conclusion- We can design any EV accoring to the requiremnt of the user. we need to calculate the required forces, power, speed, Battery Ah and type of motor, type of battery, type of controller also.
References - https://skill-lync.com/knowledgebase/modeling-of-vehicle-body-and-tires