Design and Fabrication of PUMA Robot Manipulator
Assoc. Prof. Dr. Eng. Amir R. Ali
Emad Maximos, B.Sc. (2017)
Brief description for the project:
Industrial robot manipulators are multi-purpose machines used for industrial automation, which is one of the most crucial resources for development, in order to increase productivity, flexibility, and quality and help eliminate the human error in heavy and health-hazardous work by relying less on humans. Utilization of industrial manipulators in the field of automation has also proven to be very useful when it comes to manufacturing sophisticated equipment used on daily basis by everyone from medical equipment like: x-ray machines and MRIs, etc. to refrigerators and automobiles. Robot motion control is a key expertise for robot manufacturers, and the current development focuses on improving the robot's performance, reducing its cost, insuring safety, and introducing new capabilities. Therefore, there is a continuous need to develop new models and control methods in order to fulfil all contradicting requirements, such as increased performance for a robot with lower weight. One main reason for this development of the robot mechanical structure is surely cost-reduction, but additional advantages are lower power consumption, improved agility, safety issues, and low environmental impact. A robotic arm can be compared to a human arm where it can contain free revolute joints (for rotational movements) and/or prismatic sliding joints (for translational movements) giving it quite similar mobility and freedom of motion as the typical human arm. These arm movements can be driven by electric actuators (motors) or even by pneumatic and hydraulic actuators (pistons). The actuators are usually controlled by a microcontroller (CPU), programmable and made to perform a set of specific sequential tasks. Majority of robotic arms are designed to be used in industrial purposes for fast and reliable performance, helping for mass productions. This thesis is a project-based thesis discussing the process of design, fabrication and motion control of a light-weight, educational purposed six-axis robot arm fabricated entirely out of a plastic-based material called: "Polylactic Acid (PLA)" using the 3D-printing technology. The robot arm presented in this thesis though being a relatively small educational one compared to the industrial robot manipulators mentioned above. It is greatly inspired in design by these manipulators including different design considerations like: the robot's weight issue and selection of suitable actuators (motors) required for driving it.
Challenges of the project:
The PUMA robot arm is now ready in terms of hardware with the whole robot printed and assembled and all the motors have been tried out and tested separately with the codes. In my opinion, it is ready as a solid platform to work on and apply appropriate motion control on it whether simple PD control or non-linear control but the dynamic equations of motion will have to be revisited first to ensure that the modeling of the manipulator is done right which is the basis of any control problem. An end effector or gripper will be designed for the robot to be able to hold and handle objects with it. Some aspects of the designs might be altered if we wish to replace the DC motors already used with better, more powerful motors having higher torque capacity. Also, we can work on the task of "Base Excitation" where the end-effector of the robot can be held fixed in a certain configuration while the large base on which the robot arm is mounted, which is the cart moving on four wheels, can move in a planned path for instance: a circle or an ellipse; through controlling the motors that will be used to move the wheels of the base. Moreover, for the purpose of getting a better and more accurate feedback from the six motors actuating each joint of the robot arm, we can use optical sensors instead of the usual electric sensors and analyze the positon or velocity feedback readings from the motors using the optical setup in the ARAtronics lab. Finally, we will work on the task of "Computer vision" by mounting one or more camera on the base where the robot is mounted and using the following setup to learn more about image processing.