2015 International Conference on Communication, Control and Intelligent Systems (CCIS) 978-1-4673-7541-2/15/$31.00 © 2015 IEEE Implementation of Closed Loop based Scan Mechanism Leo Louis Saffrony Institute of Technology, Department of Electronics and Communication, Gujarat Technological University, Ahmedabad, India E-mail Id: leo.louis@yahoo.com Ashok Kumar Scientist Engineer, SFED, SEG, SEDA, Space Applications Centre, (SAC), Indian Space Research Organization, (ISRO), Ahmedabad, India E-mail Id: ashokkumar@sac.isro.gov.in Abstract—This paper presents a closed loop scan mechanism using a stepper motor based Gimbal Technique. For its control, Arduino microcontroller based drive electronics is developed. This paper proposes a flexible structure for usefulness in various applications like tracking, satellite imaging etc. This paper analyzes the programming and hardware structure for an easy implementation using the Arduino microcontroller. For a bipolar stepper motor drive, the full H-bridge driver based electronics is developed. Motor shaft position is sensed by incremental optical encoder. The proposed module has high accuracy (.06% in scan rate). Keywords: Scan Mechanism, Stepper Motor, Motor Driver, Arduino Mega, Rotary Encoder I. INTRODUCTION The sensors used in the INSAT series of satellites have a point area of scan or a pencil beam of light that are used to scan a wider area. As scan mechanisms are an essential part in the field of Remote Sensing, Inertial Navigation and Photography, the sensors used for scanning should be able to cover a wider area. Scanning a larger plus a wider area can now be possible using electrical or electromechanical devices as actuators which have now become easier with the improvement in technology. For a point sensor having a point area of scan or a sensor having a pencil beam of light can only be able to scan larger and wider area with the help of some actuators which can make the sensors have a movement of-x° → +x°. For this type of rotations here we are using a Gimbal as an actuator for the front end of the sensor. These gimbals can be made up of stepper motors, dc motors or even solenoids. To improve the system accuracy it is operated in a closed loop. The existing scan mechanisms were developed using analog mechanisms, which always had accuracy issues making them not as reliable as this proposed digital system. The sensors that are being used for sensing should be perfectly facing the desired direction and angle, with a high accuracy. This can only be possible, if the sensor is placed or mounted, on such a device, which can have similar movements. For this type of mechanism we use the concept of a “Gimbal”[9]. With the help of this proposed module, the sensor being used would face correct direction accurately. For this, a closed loop mechanism is used, for continuous monitoring of the acquired encoder data. The sensors are mounted on the Gimbal, which works with the help of a Stepper Motor, which is connected to a microcontroller with the help of a motor controller / motor driver [9]. This proposed module also checks whether the Gimbal is working in the desired way; if there is any error in its functioning, the program stored in the microcontroller automatically rectifies it by sending the appropriate signal pulse to the motor. Here we are using a commercially available Arduino Microcontroller which is an open source user friendly electronic platform with high accuracy and simple features. This platform has been selected due to its low cost and its usage in various automation projects for similar systems. With this project, we will explore how it accurately helps out in the scan mechanism. Results are also discussed. II. METHODOLOGY For successfully accomplishing and designing this project it is divided into five sub tasks; each specifically focusing on the detailed and easy implementation of the project. First we analyzed the different types of motors to select an appropriate motor which has a precise stepping and also a high accuracy for the Gimbal [9]. The second task was to study each hardware precisely, it’s working behavior with each other, and to study the steps by which we could proceed with this project. The third task was to design and develop a suitable motor driver for the stepper motor that is capable of micro stepping the motor in the Gimbal for maintaining the accuracy in the directions. The fourth task was to develop the code in the Arduino IDE. Finally, the fifth task was to implement the project by assembling it with all the studied conditions and maintaining its parameters for an easy implementation. III. DETAILED DESCRIPTION The Fig. 1 shows the functional block diagram of this system and all its sub-blocks representing the overall flow of program control from the microcontroller to the various