Pneumatic robots are essential for handling materials in chemical industries where electric or hydraulic robots are unsuitable due to a fire hazard. In this project a 3-axis articulated pneumatic arm (3 degrees of freedom) was designed and assembled together with its control system. The less linear pneumatic bar actuators were used as the main drive system for the robotic arm and were controlled by 5/3-way pneumatic directional proportional control valve. The arm design for this project implements the crank mechanism to convert the linear actuation displacement into angular displacement around the joint. Two control systems were designed for the robotic arm: Programmable Logic Controller (PLC) and the Arduino UNO microcontroller. He employed open loop control with PLC in the first and closed circuit PID control using Arduino UNO in the latter part of the study. The MPU-6050 sensor was used for feedback signals for the Arduino UNO. A point-to-point motion control method was adopted for this robot arm and simple selection and placement applications were performed using a pneumatic clamp as end effector. Mainly, the compressibility of the air and the overall non-linearity of the pneumatic servo system made it very difficult to achieve precise positioning and control with PLC. The PID control of closed circuit with microcontroller and accelerometer and gyroscope allowed a better control with precision of angle of the junta of ± 1 degrees. The force required by the linear pneumatic actuator to move the robot arm over its joint varied non-linearly due to the arm design. In addition, the 5/3 directional control valve proved to be ineffective compared to the proportional valve 5/3 to control the position of the actuators. It was found that the angular displacement of the joint varied approximately linearly with the stroke of the linear actuator and that the pressure required to move the arm without load was around 2.75 bar.
The robotic arm (also known as robotic manipulator) is mainly used to perform highly repetitive tasks, manipulation of materials and precision, such as spot welding, assembly, cutting, palletizing, aerosol painting, etc. In the manufacturing industries. It is a programmable device with attributes similar to those of a human arm and is more suitable for hazardous environments where human intervention is highly undesirable. The main advantages include high quality work, more repeatability, time saving, less material waste and no fatigue. In recent years, the major advances in the field of robotics led to its use in many fields, that is, health care, where it is used for the execution of complex surgical procedures, rehabilitation, prosthesis, etc. Electromechanical robot arms predominate mainly because they exhibit linear characteristics and, control. Despite several advantages, electromechanical robot arms are still restricted to their working cell because of their high rigidity and inability to work safely in a robot-human environment. It also consumes a lot of energy for its operation, has a poor weight-to-weight ratio, voluminous structure and requires high maintenance. This required the robots to implement different drive technologies and, therefore, the pneumatic robot arm emerged.
The system that uses compressed air as its main source of energy is called pneumatic systems. Pneumatic driven systems are less costly than hydraulic and electromechanical systems and perform well in the performance of hard work. The advantages of pneumatically operated systems are mainly a higher level of safety, cleanliness, variable load capacity, simple configuration, minimal contamination, reliability, storage capacity, high resistance / weight ratio, ease of maintenance, high speed and fast transmission. The system is better at work in a hazardous environment where explosions are likely; The industries in which it is very suitable are the mining, chemical, oil and paint industries. It has been used extensively for many years in robotics and factory automation especially for running simple tasks using open loop control. However, they are often avoided because they exhibit high non-linearity and therefore are difficult to control. But the advent of sophisticated control systems and algorithms for the pneumatic servo system in recent years changed the paradigm in pneumatic technologies.
It can be understood in the following video: