Research Article MICROCONTROLLER BASED CONTROL OF …

1 Journal of Engineering Research and Studies E-ISSN0976-7916 JERS/Vol. II/ Issue IV/October-December, 2011/ Research Article MICROCONTROLLER BASED CONTROL OF three PHASE BLDC MOTOR P. Devendra1*, 2 Madhavi TVVS*, 3K Alice Mary, 4Ch. Saibabu Address for Correspondence 1 Associate Professor, EEE dept, GMR Institute of Technology, Rajam, Andhrapradesh, India 2PG Student, EEE dept, GMR Institute of Technology, Rajam, Andhrapradesh, India 3 Professor & Head, Electrical and Electronics Engineering Department, Vignan s Institute of Information Technology, Vishakhapatnam, India 4 Professor, Electrical and Electronics Engineering Department, Jawaharlal Nehru Technological University, Kakinada, India ABSTRACT This paper introduces a novel method which is intended to assist in the design and CONTROL of cost effective, efficient brushless direct current (BLDC) motors with additional features like auto restart and auto power down while maintaining constant speed.

2 Speed CONTROL of BLDC motor using 8051 micro controller requires more hardware, and with the availability of PIC microcontrollers with versatile features motivated to develop a cost effective and reliable CONTROL with variable speed range. In the present paper, an algorithm which uses the Hall sensor signals acquired from the motor is developed and the program has been written using MPLABIDE v This program generates the firing pulses required to drive the MOSFETs of three phase fully controlled bridge converter driven by IR2101 FET drivers. Later the program has been dumped on the PIC16F series device and tested on the 24V, 80 W, 1500 rpm BLDC motor which can make the motor run at constant speed ranging from 6 to 1500 rpm. The proposed hardware and the program are found to be efficient and the results are promising. KEYWORDS brushless direct current motor, PIC16 Fseries, MPLABIDE, Hall sensor, IR2101 FET driver.

3 I. INTRODUCTION PERMANENT magnet brushless dc (BLDC) motors have used wide application due to their power density and ease of CONTROL . Moreover, the machines have high efficiency over a wide speed range. The highly efficient conventional DC motors are suitable for various applications because of their characteristics. They require commutator and brushes, for conversion of dc to ac which are subject to wear and require maintenance. This only drawback of conventional DC motors makes us to shift to BLDC motors which are electronically commutated by using solid state .Recent legislation imposing efficiency standards in appliances, has forced appliance manufacturers to migrate to BLDC motors in their applications. In view of these enormous applications, researchers started developing methods for efficient use of these motors in diversified fields.

4 To mention a few: Jianwen Shao Nolan [1] has developed a novel MICROCONTROLLER - BASED Sensorless brushless DC (BLDC) motor drive for automotive fuel pumps in 2003. Also, they have developed an Improved MICROCONTROLLER - BASED Sensorless brushless DC (BLDC) Motor Drive for Automotive Applications, in 2006[2]. Nikolay Samoylenko [3] studied the Dynamic performance of brushless DC motors with unbalanced Hall sensors. To the extent the authors have surveyed not much work has been reported on micro controller driven sensor BASED BLDC motors. Hence in this paper, an algorithm for sensor BASED micro controller driven BLDC motors with additional features like auto restart and auto power down is presented and effectiveness of the work is shown through hardware realization. II. REVIEW OF BLDC MOTOR CONTROL SCHEMES The CONTROL schemes of BLDC motor are mainly classified in following two ways Sensor BASED CONTROL Sensor less CONTROL In sensor BASED CONTROL , a Hall sensor is used which detects the position of the rotor magnet and gives a signal which is used to give appropriate excitation to the stator winding.

5 Hall sensor works on Hall effect which states that when a current carrying conductor is placed in magnetic field, it exerts a transverse force on the conductor. The sensor BASED CONTROL scheme is shown in Sensor BASED CONTROL Micro controller BASED CONTROL using Hall sensors gives effective CONTROL on BLDC motors. The sensor less drive principle is BASED on the detection of the rotor position using various techniques one of which is the EMF detection. There are various methods for position and velocity estimation BASED on the induced Back EMF Journal of Engineering Research and Studies E-ISSN0976-7916 JERS/Vol. II/ Issue IV/October-December, 2011/ detection. Various micro controllers and DSP controllers are available for sensor less CONTROL .

6 III. MICROCONTROLLER BASED CONTROL SCHEME The proposed CONTROL for BLDC motor CONTROL using PIC microcontrollers of MICROCHIP with device name PIC16F690 is shown in the figure (3). Micro Controller BASED CONTROL The base drive to the MOSFETS in the Inverter circuit is given by the PIC16F690 micro-controller. The Hall signals from the motor are fed as inputs to the PIC16 Fseries device and BASED on the Hall position and the direction of rotation of the motor specified by the manufacturer the corresponding gate drive is made active by the MICROCONTROLLER and fed to the stator of the BLDC motor. The commutation sequence for rotating the motor in clock wise direction when viewed from the non driving end is given in the Table (1). Table (1): Sequence for rotating motor in clockwise direction BASED on the Hall sensor input to the MICROCONTROLLER , the corresponding transistors are made active and current flows through two windings and the other winding is inactive and hence commutation is done electronically with the use of a MICROCONTROLLER .

7 The commutation sequence for rotating the motor in counter clock wise direction when viewed from the non driving end is given in the Table (2). Thus by properly exciting the corresponding winding BASED on the hall signal, the motor is commutated and is made to run at the desired speed. Initially irrespective of the rotor position, the windings are excited in the given sequence and once the motor starts rotating, rotor position is sensed by the Hall sensor and then the motor is excited BASED on the Hall signal and according to the direction of rotation of the motor. The speed can be controlled in a closed loop by measuring the actual speed of the motor. If the speed is greater than the desired rated speed, then all the transistors are turned off for a short duration and then again excited BASED on the Hall position and accordingly speed can be adjusted to get constant speed.

8 The ADC of the MICROCONTROLLER is used to convert the analog signal corresponding to the speed of the motor to a digital value and comparison is done with the calculated digital value which is proportional to the rated speed A. PIC16 Fseries Micro controller PIC16 Fseires MICROCONTROLLER which is used for this project is a 40-pin device, 8 bit CMOS MICROCONTROLLER which belongs to the MICROCHIP family of microcontrollers . It has 10-bit Analog to Digital converter (ADC) and we have used only 8 bits for our CONTROL so that the speed can be controlled in 255 steps ranging from 6 to 1500 rpm. The various features of this device make this device to be selected for the proposed CONTROL . Timer1 is operated in external oscillator mode with an external crystal oscillator of 20 MHz connected to the micro controller device. An external Potentiometer is connected to the ADC pin which provides the required speed range.

9 B. Algorithm for Assembly language code written using MPLAB IDE MPLAB IDE of MICROCHIP has been used to write the code in assembly language using PIC16F690 data sheets provided by MICROCHIP. The algorithm to run and maintain constant speed of a BLDC motor is Set PORTE as digital hall input. Set PORTC as Outputs to transistors. Generate interrupt on timer1 over flow and also on completion of ADC conversion by setting the appropriate registers. Enable Global interrupt. Give excitation to the motor windings irrespective of the Hall signal according to the direction of rotation of the motor (clock wise or counter clock wise). Start TIMER1 which is operated with external crystal oscillator at 20 MHz frequency Generate LOOK-UP Table for clock wise rotation of the motor irrespective of the Hall signal. At the timer overflow interrupt service routing (ISR), generate LOOK-UP Table Journal of Engineering Research and Studies E-ISSN0976-7916 JERS/Vol.

10 II/ Issue IV/October-December, 2011/ for clock wise rotation of the motor BASED on Hall signal. Set the motor speed using external potentiometer connected to the ADC pin. Enable ADC to convert the analog voltage into digital. Compare this digital value with the counter value equivalent to the motor speed (rated). If motor speed is higher than the rated speed then turn off all the transistors for short duration in ADC conversion complete ISR and return back from the ISR. Then repeat the excitation process BASED on Hall signal. This program drives the BLDC motor at constant speed and by varying the external potentiometer value we can change the motor speed and according make the motor run at that constant speed. This algorithm is used to write a program in MPLAB IDE and is dumped on to the PIC16F690 device and tested on the 24 V, 80 W, and 1500 rpm BLDC motor shown in the figure (4).