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Design and Mechanism of Controlling a Robotic Arm
Introduction:
Definition:
A robotic arm is a type of mechanical arm, usually programmable, with similar functions to a human arm; the arm may be the sum total of the mechanism or may be part of a more complex robot. The links of such a manipulator are connected by joints allowing either rotational motion (such as in an articulated robot) or translational (linear) displacement.[1] [2] The links of the manipulator can be considered to form a kinematic chain. The terminus of the kinematic chain of the manipulator is called the end effector and it is analogous to the human hand.
A Robot is a virtually intelligent agent capable of carrying out tasks robotically with the help of some supervision. Practically, a robot is basically an electro-mechanical machine that is guided by means of computer and electronic programming. Robots can be classified as autonomous, semiautonomous and remotely controlled. Robots are widely used for variety of tasks such as service stations, cleaning drains, and in tasks that are considered too dangerous to be performed by humans. A robotic arm is a robotic manipulator, usually programmable, with similar functions to a human arm. This Robotic arm is programmable in nature and it can be manipulated. The robotic arm is also sometimes referred to as anthropomorphic as it is very similar to that of a human hand. Humans today do all the tasks involved in the manufacturing industry by themselves. However, a Robotic arm can be used for various tasks such as welding, drilling, spraying and many more. A self-sufficient robotic arm is fabricated by using components like micro-controllers and motors. This increases their speed of operation and reduces the complexity. It also brings about an increase in productivity which makes it easy to shift to hazardous materials. This specific micro controller is used in various types of embedded applications. Robotics involves elements of mechanical and electrical engineering, as well as control theory, computing and now artificial intelligence.
Design of the Robotic Arm:
The Robotic Arm is designed using the Microcontroller Micro-controller using Arduino programming. This process works on the principle of interfacing servos and Joystick. This task is achieved by using Arduino board. Joystick play an important role The remote is fitted with joystick and the servos are attached to the body of the robotic arm. The joystick converts the mechanical motion into electrical motion. Hence, on the motion of the remote the potentiometers produce the electrical pulses, which are in route for the Arduino board. The board then processes the signals received from the joysticks and finally, converts them into requisite digital pulses that are then sent to the servomotors. This servo will respond with regards to the pulses which results in the moment of the arm.
Degree of Freedom:
Robot arms are described by their degrees of freedom. This number typically refers to the number of single-axis rotational joints in the arm, where higher number indicates an increased flexibility in positioning a tool. This is a practical metric, in contrast to the abstract definition of degrees of freedom which measures the aggregate positioning capability of a system.
So It has four degree of freedom.The figure of a robot is shown below.
Practical Portion:
Servo Motors:
Servo refers to an error sensing feedback control which is used to correct the performance of a system. Servo or RC Servo Motors are DC motors equipped with a servo mechanism for precise control of angular position. The RC servo motors usually have a rotation limit from 90° to 180°. But servos do not rotate continually. Their rotation is restricted in between the fixed angles. The Servos are used for precision positioning. They are used in robotic arms and legs, sensor scanners and in RC toys like RC helicopter, airplanes and cars. The specifications for Servomotor used are as follows: Dimension: 22.2 x 11.8 x 31 mm approx. Stall torque: 1.8 kgf·cm • Operating speed: 0.1 s/60 degree Operating voltage: 4.8 V (~5V) Dead band width: 10 µs Temperature range: 0 ºC – 55 ºC
· Weight 9g
The figure is given below.
Joystick:
A joystick is an input device consisting of a stick that pivots on a base and reports its angle or direction to the device it is controlling. A joystick, also known as the control column, is the principal control device in the cockpit of many civilian and military aircraft, either as a center stick or side-stick. It often has supplementary switches to control various aspects of the aircraft's flight.
Joysticks are often used to control video games, and usually have one or more push-buttons whose state can also be read by the computer. A popular variation of the joystick used on modern video game consoles is the analog stick. Joysticks are also used for controlling machines such as cranes, trucks, underwater unmanned vehicles, wheelchairs, surveillance cameras, and zero turning radius lawn mowers. Miniature finger-operated joysticks have been adopted as input devices for smaller electronic equipment such as mobile phones.
The Diagram for this robot is given as.
End-Effector Selection: The end effector is probably one of the most important and most complex parts of the system. The end effector varies mainly according to the application and the task that the robot arm accomplishes for; it can be pneumatic, electric or hydraulic.
Since our robot arm is based on an electric system, we may choose electric basis of end effector. Besides, And end effector is controlled by servo. the main application of our system is handling, accordingly, the recommended type of our end effector is a gripper, as shown in Figurer 5.22 and Figurer 5.23. Please note that the end effector is controlled by a servo motor .
Arduino: Arduino Uno is a microcontroller board based on the ATmega328P . It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz quartz crystal, a USB connection, a power jack and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started.. You can tinker with your UNO without worrying too much about doing something wrong, worst case scenario you can replace the chip for a few dollars and start over again.
"Uno" means one in Italian and was chosen to mark the release of Arduino Software (IDE) 1.0. The Uno board and version 1.0 of Arduino Software (IDE) were the reference versions of Arduino, now evolved to newer releases. The Uno board is the first in a series of USB Arduino boards, and the reference model for the Arduino platform; for an extensive list of current, past or outdated boards see the Arduino index of boards.
Programming: The Arduino Uno can be programmed with the (Arduino Software (IDE)).The ATmega328 on the Arduino Uno comes preprogrammed with a bootloader that allows you to upload new code to it without the use of an external hardware programmer. It communicates using the original STK500 protocol.
Power: The Arduino Uno board can be powered via the USB connection or with an external power supply. The power source is selected automatically. External (non-USB) power can come either from an AC-to-DC adapter (wallwart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. Leads from a battery can be inserted in the GND and Vin pin headers of the POWER connector
Arduino Development “IDE”:
The Arduino integrated development environment (IDE) is a cross-platform application written in Java, and is derived from the IDE for the Processing programming language and the Wiring projects. It is designed to introduce programming to artists and other newcomers unfamiliar with software development. It includes a code editor with features such as syntax highlighting, brace matching, and automatic indentation, and is also capable of compiling and uploading programs to the board with a single click. There is typically no need to edit make files or run programs on a command-line interface.
Here in this window we put in our code, compile it and upload it to the controller.
Simple copy and paste the program in the software and click on the arrow on the left side of the software window for compilation.
After compilation it will upload the code inti controller.
Circuit Diagram of Robotic Arm:
Working Procedure of Robot Arm:
Positive and negative aspects of robotic arm The Positive: Increase productivity Use equipment effectively Reduce working costs Flexibility at work Get the job done in the shortest time Provide good returns on investment Better accuracy in performance Ability to work in risky ways and make it more safe.