Keywords: PIC18F452 microcontroller, Stepper motor, Rotary encoder, Visual Basic. Net, MikroC Pro.

Transcription

1 ISSN - Vol.0,Issue.0 May-0, Pages:- PC Based Position Control for Robot Arm NGU WAH, KYAW THIHA Dept of Mechatronic Engineering, Mandalay Technological University, Mandalay, Myanmar, nguwahmc@gmail.com. Dept of Mechatronic Engineering, Mandalay Technological University, Mandalay, Myanmar, kthihacn@gmail.com. Abstract: Nowadays, robots are widely used in many applications such as military, medical application, factories, entertainment, automobile industries and etc. In the world of robotics, robot arm has become popular to help automation in place of human. So, this system is implemented to control the X, Y positions of stepper motors for robot arm. The position control system of robot arm used a peripheral interface controller (PICF), three stepper motors and rotary encoder. The PIC acts as the main controller of the position control system and three stepper motors are used for robot arm rotation. For feedback on motors, the rotary encoder is used to record the changes in position. To control the motors position, the input commands are applied to the motor driver through the PC. This system can control the robot arm during the 0mm X position and 0 mm Y position. This system is implemented by using Visual Basic. Net and MikroC Pro. Keywords: PICF microcontroller, Stepper motor, Rotary encoder, Visual Basic. Net, MikroC Pro. I. INTRODUCTION During the past few decades, industrial robots have become a very important factor in the manufacturing industries. A robot can be describes as a mechanical device programmed to perform a task under automatic control. Robots are used effectively in application where a complicated process is going to be repeated. They are also used effectively in hazardous areas, where a person might be harmed by fumes, high temperature or other harmful factors. Unlike human labors, robots do not need heat, light, coffee breaks, overtime pay and worker s compensation insurance. So, robot is important and useful device for many industries []. As robot is important, the position control for robot arm is also important to correctly perform tasks in industry. This system is designed the real time position control for robot arm that is used to correctly pick and place object. This system contains three axes that are the X direction stepper motor, Y direction stepper motor and Z direction stepper motor. Stepper motors are used to control the motions of the robot. Sketch design of the robot arm is shown in Figure. Three degree of freedom (-DOF) plastic robot arm is proposed in this system. It is the combination of individual joints where the action must be controlled in order to perform tasks on the desired motion cycle. The robot arm motion will be controller with the inverse kinematics solution. In this system, PICF microcontroller is used because it can provide serial communication interface and incorporate all of the peripheral I/O facilities that is needed. Personal computer (PC) is used as graphical user interface (GUI) for monitoring and control of the devices. The implementation of position control system is provided by Visual Basic. Net (VB.Net), and MikroC programming languages. Depending on the control commands on VB.Net window, robot arm will move exactly the required position. 0 cm Z motor 0 cm Figure. Sketch Design of the Robot Arm. Y motor X motor II. SYSTEM BLOCK DIAGRAM The overall block diagram of the system is shown in Figure. In this system, the PICF microcontroller, stepper motors, MAX IC and rotary encoder are used for position control of pick and place robot arm. For picking and placing process, the position of robot arm is important. In this system, three stepper motors are used to design three degree of freedom (DOF) and to control the motions of robot arm such as X motor, Y motor and Z motor. The position of motion for robot arm is controlled by using control commands of VB.Net. After pressing the command buttons on VB.Net window, the required signals send to the RS- serial port with serial communication. RS- also sends the receiving signals from PC to PIC microcontroller via MAX. Depending on the receiving signals, PIC 0 SEMAR GROUPS TECHNICAL SOCIETY. All rights reserved.

2 microcontroller controls the required motions. And then, the X-axis stepper motor, Y-axis stepper motor and Z-axis stepper motor can rotate forward or backward to position. PC RS Serial Interface Circuit PIC MICROCONTROLLER Encoders Driver- Driver- Driver- NGU WAH, KYAW THIHA M (X) M (Y) M (Z) A. PIC Pin Assignment of the System The main part of the system is PICF which is used to control the system. PICF has 0 pins and inputoutput (I/O) ports [, ]. The pin connections of microcontroller are important to control the position of robot arm motion. The diagram of pin connection is shown in Figure. X motor vcc MCLR RA0 RA RA RA PICF RC0 RC RC RC RC RC RC RC Encoder MAX Figure. Block Diagram of the Position Control System for Robot Arm. III. SYSTEM HARDWARE COMPONENTS This system consists of several units or modules. These are PICF microcontroller Unipolar stepper motor Stepper motor driver Rotary Encoder Interfacing circuit between PC and PIC Overall circuit diagram of the proposed system is shown in Figure. From PC E E E +V RIN VCC TOUT MAX ROUT TIN 0 VCC OSC/CLK RC0/TOSO/TCKI MCLR/VPP RC/TOS/CCPA RC/CCP RA0/AN0 RC/SCK/SCL RA/AN RC/SDI/SDA RA/AN/VREF- RC/SDO RA/AN/VREF+ RC/TX/CK RA/TOCK RC//RX/DT RA/AN/SS/LVDIN RA/OSC/CLK0 RD0/PSP0 0 RD/PSP RD/PSP RB0/INT0 RB/INT RD/PSP RB/INT RD/PSP RB/CCPB RD/PSP RB RD/PSP RD/PSP 0 RB/PGM RB/PGC 0 RE0/RD/AN RB/PGD RE/WR/AN RE/CS/AN 0 PICF X motor Y motor Y motor RB0 RB RB RA RD0 RD RD RD Figure. Pin Connection of PICF. Z motor In this system, the power supply of this controller is +V DC and connected the pin no.. RA0, RA, RA and RA are used for X-axis stepper motor and bit numbers 0,,, from PORTB are also connected to Y-axis stepper motor. Then, RD0, RD, RD and RD are used for Z-axis stepper motor. Encoder is connected at RC0, RC, RC and RC. And then, MAX IC is connected at RC and RC. B. Unipolar Stepper Motor Stepper motor is an electromechanical device which coverts electrical pulses into discrete mechanical movements. The number and rate of the pulses control the position and speed of the motor shaft. The motor rotation has several direct relationships to this applied input pulses. The sequence of the applied pulses is directly related to the direction of motor shafts rotation. The speed of the motor shaft's rotation is directly related to the frequency of the input pulses and the length of rotation is directly related to the number of input pulses applied. The unipolar stepper motors have the advantage of producing high torque at low speeds [, ]. Z motor Figure. Overall Circuit Diagram of the Proposed System Figure. Unipolar Stepper Motor. Volume.0, IssueNo.0, May-0, Pages: -

3 Unipolar stepper motor is shown in Figure. In this system, three unipolar stepper motors are used as X-axis, Y-axis and Z-axis motors. The properties of this motor are as follows: Unipolar stepper with 0." spaced -pin cable connector steps per revolution / geared down reduction V-V DC suggested operation Weight: g. Dimensions: mm diameter, 0mm tall not including mm shaft with mm diameter " / cm long cable Holding VDC: 0 gram-force*cm, N*mm/. oz-force*in Shaft: mm diameter flattened C. Stepper Motor Driver In this system, Darlington transistor is used as the stepper motor driver. It is designed for general-purpose amplifier and low speed switching applications. Features of Darlington transistor are as follows: High DC Current Gain, Collector-emitter sustaining voltage is 00V, Collector-emitter saturation voltage is V, Monolithic construction with built-in base emitter shunt resistors, Pb-Free Packages are available [0]. PC Based Position Control for Robot Arm processed elsewhere into information such as speed, distance, and position. In robot applications, the feedback device (encoder) plays a vital role in ensuring that the equipment operates properly. By using the rotary encoder, the microcontroller can't afford to miss any pulses or the resolution of movement that is going to suffer. E. Interfacing Circuit between PC and PIC Interfacing circuit is required to control the input and output conditions of the process, and to use as serial port. MAX IC is used for signal/ level translation. MAX IC provides RS serial communication with PC easily. This IC is used to perform necessary adjustment. This circuit is powered with a single V voltage. It is used to convert a serial signal from TTL to RS standard and vice versa by means of a built-in voltage generator []. MAX board is connected to a PC via a standard serial cable provided with a pair of female connectors DB. The female connector DB enables connection with devices that use RS standard, whereas the connector enables connection with the microcontroller pins intended for serial communication (USART) []. Interfacing circuit between PC and PIC is shown in Figure. PICF microcontroller RC/RX/DT RC/TX/CK Figure. Darlington Transistors. VCC Darlington transistor is shown in Figure. In the design of the Darlington transistor, Pin is Base, Pin is Collector, Pin is Emitter and Pin is Collector. D. Rotary Encoder Rotary encoders are used in many applications that require precise shaft unlimited rotation including industrial controls, robotics, special purpose photographic lenses, computer input devices, controlled stress rheometers, and rotating radar platforms []. Rotary encoder is shown in Figure. Figure. Rotary Encoder. Rotary encoder provides information about the motion of the motor shaft on DC motor, which is typically further Volume.0, IssueNo.0, May-0, Pages: - From PC +V RIN TOUT ROUT TIN Figure. Interfacing Circuit between PC and PIC. µf III. SOFTWARE IMPLEMENTATION OF THE SYSTEM Overall flowchart of the robot arm position control system is shown in Figure. This system is implemented as the PC based position control system for robot arm. In this system, robot arm needs to reach the required grid locations which is located in the x matrixes between X=0mm and Y=0mm. So, the robot motion will be control with the inverse kinematic solution. PC based position control system for robot arm allows the user to control the designated position during working area. 0 µf µf µf

4 Start Define Required Grid Locations as Inputs in PC Program (VB) Calculate X, Y and Z degree with Inverse Kinematics in PC program Calculate X, Y and Z degree to Step Values in PC Program Send X, Y and Z Step Values to PIC by UART Drive X, Y and Z Step Values by PIC Check X, Y and Z Encoder Values by PIC To detect current Grid NGU WAH, KYAW THIHA desired location []. For the DOF planner robot arm, these inverse kinematics equations can be simplified as follows: x y cos () l l sin cos k cos k sin atan(y,x) atan(k,k ) atan(sin,cos ) 0 atan(y,x) In the above equations, θ 0 is the angle of base rotation, θ and θ are the angles of first link joint and second link joint. k and k are constants. l and l are the lengths of first link and second link. x and y are the lengths of target positions. TABLE I: RESULT OF SAMPLE JOINT DEGREES () () () () () () Send back X, Y and Z Encoder Values by PIC To PC (VB Program) Check X, Y and Z Encoder Values by VB Program to verify current location Is current location correct? YES NO Adjust X, Y and Z Degree/ Step by Program to correct current location End Figure. Overall Flowchart of the Robot Arm Position Control System. In this system, PICF microcontroller is used for the heart of process. MikroC Pro programming is used to control the whole process. Three stepper motors are driven with stepper motor drivers ( Darlington transistor). When the operation is started, the robot will be in its home position. Required grid locations are defined as input in PC via VB.Net. And then, X, Y and Z degree are calculated by using inverse kinematics method. After calculating, X, Y and Z step values are sent to PIC by using MAX IC. And then, PIC drive X, Y and Z step values. To detect current grid, X, Y and Z encoder Values are checked by PIC. Then, PIC sends back X, Y and Z encoder values to PC. To verify current location, X, Y and Z encoder values are checked by VB.Net. A. Inverse Kinematics for Robot Arm In this system, when the desired location for the tip of the robotic arm is given, the inverse kinematics method calculates the angles of the joints to locate the tip of the arm at the IV. SIMULATION AND TEST RESULTS The proposed robot arm position control system used the personal computer (PC) to control the system by using the serial port. This system is implemented by using Visual Basic. Net (VB.Net), and MikroC Pro programming languages. In the VB.Net form, the proposed system allows the user to choose either the manual mode or the auto mode. At manual mode, X position and Y position are firstly entered in the message box. And then, the RUN button must be clicked. After clicking, the correct θ, θ and θ 0 will be showed at Command. Manual position control for robot arm is shown in Figure 0. At auto mode, required target positions are chosen by clicking the check box. After Volume.0, IssueNo.0, May-0, Pages: -

5 PC Based Position Control for Robot Arm choosing, the Connect button must be clicked to display the correct θ, θ, θ 0, X, Y, Z motor directions and steps at Command, and OK at Received Data. Auto mode can be run one or more target points in x matrixes. Auto position control for robot arm is shown in Figure. Figure0. Manual Position Control for Robot Arm. Figure. Simulation Result of the System. Photo of complete circuit is shown in Figure. Figure. Photo of Complete Circuit. Photo result of DOF robot arm is shown in Figure. Figure. Auto Position Control for Robot Arm. To open the virtual terminal, the RUN button must be clicked. And then, the data enter in the virtual terminal. According to the entered data, the required motors will be operated with the exact motor step. As an example, if X,, 0000# is entered in virtual terminal, steps will be rotated due to the clockwise of X motor direction. If Y, 0, 0000# is entered in virtual terminal, steps will be rotated due to the counter clockwise of Y motor direction. If Z,, 0000# is entered in virtual terminal, steps will be rotated due to the clockwise of Z motor direction. The simulation result of the system is shown in Figure. Figure. Photo Result of DOF Robot Arm. Volume.0, IssueNo.0, May-0, Pages: -

6 V. CONCLUSION The PC based position control system for robot arm is designed to get optimum performance with available components at the local market. In this system, both auto and manual modes can be used to control the position of the robot arm. The robot arm is intended for simple pick and place operation. By using this robot arm position control system, many benefits can be obtained including the reduction of unpleasant tasks, improved quality of pick and place process, and reduced time consuming. This system can be extended by changing the motors and microcontroller for future work. VI. ACKNOWLEDGMENT The author is very thankful to Dr. Myint Thein, Rector of Mandalay Technological University, for his encouragement, invaluable permission and his kind support in carrying out this paper work. The author is deeply grateful to Dr. Wutyi Win, Associate Professor and Head, Department of Mechatronic Engineering, Mandalay Technological University for supplying all necessary things. The author also wishes to thank to supervisor Dr. Kyaw Thiha, Associate Professor, Department of Mechatronic Engineering, Mandalay Technological University, accomplished guidance, his willingness to share his ideas and, helpful suggestions and for his patience, continuous supervision and encouragement during a long period of this paper. The author especially appreciates and thanks all her teachers for paper support, and guidance during theoretical study and paper preparation durations. VII. REFERENCES []Naoki Asakawa and Yoshimi Takeuchi. Techingless Spray-Painting of Sculptured Surface by amn Industrial Robot, Department of mechanical and Control Engineering, University of Electro-Communications, Chofu, Tokyo, Japan,. [] Microchip PICFXX Microcontroller Data Sheet, Microchip Technology Inc., 00. [] Ken Toe, PICF, University of Cambridge, UK. [] DC Motor Driver Fundamentals, Semiconductor Components Industry, March, 0. [] Moududur Shamim, Stepper Motor Interfacing with Microcontroller, March, 0. [] MAX Board, MikroElektronika, Software and Hardware Solutions for Embedded World. [] MECH : Introduction to Robotics, Inverse Manipulator Kinematics by M.O Malley. [] en.wikipedia.org/wsiki/max. [] en.wikipedia.org/wiki/rotary_encoder. [0] NGU WAH, KYAW THIHA Volume.0, IssueNo.0, May-0, Pages: -