roject work presentation

Transcription

1 roject work presentation roject Title: roject Index: 122 Microcontroller based power controller for an Electric Vehicle. y: Eric Bulimo Ubaga F17/1451/2011 upervisor: xaminer: Mr. C. Ombura. Dr. Dharma.

2 ntroduction An electric vehicle (EV) is a vehicle that is powered, at least in part, by electricity This project, therefore, seeks to design such a controller system that is microprocessor based to monitor the power flow of the EV i.e. monitoring the battery conditions and controlling the flow of power from the battery to the traction motor. Key issues addressed in the project include: 1. What is an Electric Vehicle (EV)? 2. Why an EV? 3. Possible implementation.

3 pecifications the power controller was to be designed meeting the following conditions: 1. Drive a 600W motor. 350W motor was however used in implementation. 2. Must be microprocessor based. 3. Drive an EV while minimizing the cost of production. 4. Determine the state of charge (SOC) of the battery and indicate its capacity.

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5 lectric Vehicle and Applications The controller take power and delivers it to the motor. The accelerator pedal hooks to a pair of potentiometers that provide the signal that tells the controller how much power it is supposed to deliver. Has mainly three components: i. The drive system ii. iii. The control system The battery pack system Electric traction has been in application though mainly in forklifts. Over the years, electric traction study and research has been intensified and its application be used in many different ways such as electric vehicle, electric train, electric motorcycles, electric scooter and electric traction elevators

6 esign Divided into Circuitry and program. The motor picked on was a dc motor, 350 Watts A. Circuitry he skeleton of the designed circuit was the h-bridge H- Bridge. An H-Bridge or full bridge converter is a switching configuration composed of four switches in this case MOSFETs in an arrangement that resembles an H. H- bridge enables voltage to be applied across a load in either direction.

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10 esign. Circuitry. hile designing this circuit, a choice had to be made between the IGBT and power OSFET. ower MOSFETS have a much higher switching frequency capability than do GBTs. They do not have as much capability for high voltage and high current pplications, and tend to be used at voltages lower than 250V and less than 500W. Since this project is about design of a 24V, DC motor control to be used in electric ehicle MOSFET is the ideal choice. Also MOSFET being a voltage controlled evice, it can be driven directly from CMOS or TTL logic and the same gate signal an be applied to diagonally opposite switches since the gate drive current required is ery low.

11 esign. PWM. Pulse Width Modulation (PWM) ulse-width modulation uses a square wave whose pulse width is modulated resulting n the variation of the average value of the waveform. he average of voltage that supply to DC motor is given by, Where = / in Vave = average voltage supply to DC motor ton = time ON of switches T = period of PWM ton /T = DC, duty cycle n PWM method, operating power to the motors is turned on and off to modulate the urrent to the motor. The duty cycle determines the speed the motor he Pulse Width Modulation (PWM) in microcontroller is used to control duty cycle of C motor drive.

12 esign. PWM Example: = = = = = = The PWM is effected through the optocoupler that is put on the ground side of the H-Bridge circuit.

13 esign.. Software. e microcontroller was programmed in the Arduino language that is based on C programming guage. e flow chart showing the working algorithm inside the microcontroller is shown below. ogram begins by initializing the microcontroller pins and the display unit. crocontroller constantly checks for the battery capacity allowing for movement only when the ttery has a percentage capacity greater than 0. This translates to input greater than 30V.

14 esign. Flow chart start INITIALIZE THE MICROCONTROLLER INITIALIZE THE VARIABLES INITIALIZE THE LCD DISPLAY UNIT CHECK BATTERY SOC. ENOUGH CHARGE? NO YES DISPLAY DRIVING MODE DISPLAY STATE OF BATTERY CHARGE ENGAGE DRIVING GEAR A CHECK IF THE ACCELERATOR IS PRESSED NO C

15 esign. Flowchart. A B C D YES PRINT SPEED SET THE INPUT PINS TO ZERO GOOD CHECK BATTERY CAPACITY LESS DON T RUN THE MOTOR

16 esults.. he constructed controller was tested and found to drive a 350W DC motor. Some of the esults are shown below. On the time of testing, the speed module had not yet been ompleted. hen driving the motor in reverse, the yellow LED lights as shown below.

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20 esults waveforms. The forward and reverse waveforms are similar and were

21 losing Microcontroller gives out a perfect square wave that is varied by the variable resistor acting as acceleration pedal. The controller is able to run the motor. The output of the H-Bridge was not a perfect square wave. In overall the main objectives of the project were obtained. The greatest limitation was time.