The Design of a Polishing Robotics System - Essay Example

The Design of a Polishing Robotics System Introduction Robots are primarily automated machines which are instructed by some set of instructions to do a particular job. Essentially, a robot manipulator is a sophisticated system which is composed of actuators, sensors, structural properties, nature of materials, dynamic attributes, control procedures (Boulet, et al. 1993) only to state a few components. Robots are designed for specific purposes and normally their uses vary from one robot to another. Therefore, manipulator is a system which operates similarly like the human hand. Robots are applicable in almost every field of manufacturing and other industries worldwide. They are efficient and effective in terms of time management. Abstract The project entails the design of a robotic system manipulator. It highlights some of the construction methods of a manipulator with some key consideration factors. Some of the advantages is that the performance of the actuator will improve at the same time reducing the complexity of the system. Normally, two kinds of robotic controllers are employed in the system; regular and adaptive. Some of the fundamental and essential configurations of a robot include; the polar, cylindrical, jointed-arm and Cartesian coordinate configurations. All of these are required for a system to be called a robot or there will be no robot. They are the key components for the operation of a robot. Structural Design overview The structural requirements of the robotic system are the piston actuators because it has many benefits over the rotary vane actuators. Piston actuators are very durable and strong, have higher levels of efficiency and are easy to maintain. The chief parts include the central stem, actuator cradles, double actuator forks, output flange, and ground link and double Hooke joints. The principal structural parts are listed by order of decreasing design difficulty. This is followed by examining the type of loads and magnitudes in each bearing. Most of the polishing systems construction are made of steel to enhance and improve the strength while aluminium is used for a few parts in the system. The use of such measures is to minimize the collision of the moving parts of the robotic system. Lists of variables 1. VSC-Variable structure control: This reduces the vibrations and sliding mode of the machine. 2. PID-for stability investigation of a robot. List requirements 1. Actuators, 2. Sensors, 3. Structural properties, 4. Materials preferably aluminum and steel, 5. Dynamic attributes, 6. Control procedures or codes, 7. Cower supply Design description In the design of a robot, there are specific and key factors that should be considered. Foremost, the robot must be in a state of isolation that is stand-alone feature like. It should be able to support itself without any assistance from any object. Secondly, the robot must accept the programming codes in order to accept the outlined instruction to give desirable objective. The machine should be easy and simple to operate and understand in order to accommodate for the unskilled technicians. There robot motions are categorized into two; arm and body motions and motions associated with wrist. In the design overview of a manipulator, joints and links must be the first factors to be considered. Mainly, joints features are the ones to provide the motion while on the other hand links are firm affiliates between the joints. The joints can either be linear or rotary and every joint provides degree of freedom, most of the robots have about five to six degrees of freedom (Inoue, et al, 1986). The robot has two arms that is the arm and motion and the motion associated with wrist. Principally, body and arm motion is responsible for the positioning and location of objects while the wrist is for item orientation or alignment. Design concept and operating principles As detailed earlier, the robot system consists the basic components which include the manipulator, the end effect, the power supply and finally the controller. Essentially, the manipulator is the arm of the robot and is composed of segments which are jointed together with axes which is basically capable of moving from one direction to another. The gripper tool which normally performs the work is attached to the robots arm. The robot is connected to power to supply the required energy which is then converted motion by the actuator. Conclusively, the controller starts, ends and coordinates the motion series of a robot. Moreover, the controller accepts the necessary key inputs to the robot and gives the yield interface with the outside arena. Once, the arm of the manipulator comes in contact with the object, the force is coordinated and controlled by the wrist force feedback which can be adjusted through the grip force. The wrist force is send back to the joystick (controller). These contact forces can be changed or adjusted depending on the object by scaling up or down by changing the gains of the feedback. These outlined procedures should be followed in order to have a workable polishing robot. The steel metals are used in the design of the base and top link because they are the points that receive the maximum load. This is because they have higher tensile and yield strength compared to aluminium. The wrist tubing is designed by use of aluminium. The representation below summarizes the outline working of a polishing robot. Figure 1: representation of the outline working of a polishing robot Some of the limitation in the design and operation of a robot is the aspect of wear and tear as a result of friction between moving parts. PID Controller reduces the disturbances caused by inertia and measurement noise. Assumption The construction of a polishing robot assumes or does not take into consideration the factor of friction. It lowers the efficiency of the machine. Advantages of the system 1. Intelligent control With the use of a polishing robot, there is use of less human effort thus lead work efficiency and saves time. 2. Aid record keeping Robots do programmable tasks such that the records can be tracked and retrieved. Calculations and analysis According to Ranking theory in the design of links Design of the links involves: Maximum load occurs at the end of the joint between the links. Total load supported =350lbs When under yield stress W=load x factor of safety x dynamic load factor 350x1.25x2= 875 Under ultimate stress =350x1.5x2= 1050 Area of link= breadth x thickness For a good link, b= 3t Hence A=b x t= 3t x t =3 Moment of inertia on the base link x t = 1/12x xt= Radius of gyration is given K= Stress = From the above calculated Yield stress 875 Equating linking’s constant a=1/7500 Therefore, t=0.86inches Assumption, since we cannot have a negative thickness, the sign is neglected. Since Area= bxt= 3x .86^2=2.22 inches2 Hence, b=3x0.86=2.58inches Allowable stress= Mpa (kpsi) Ultimate stress Mpa (kpsi) Stress=F/A Maximum force leading to yield stress=stress x area= 24x2.22= 53.28 Newton Maximum force leading to ultimate stress = 36.67x2.22=80.674 Newton Therefore, the maximum load that the link can support without breaking is 80.674 Newton Figures Construction assembly of a manipulator. Before assembling (48in) Base link shoulder top link wrist After assembling Figure 2: an assembled manipulator. Conclusion The above discussed framework is a task-based methodology construction of robot manipulators. It highlights some of the important key factors that should be followed in the design and construction of a robotic system. The performance can also be hindered due to the interaction between the join motion and the angular motion of the surface. Conclusively, the programming code is the most requirement in the construction of a robot as it is the driving mechanism that operates everything. Additionally, in the construction set up of a robotic polishing system, the steel metals were used in both the base and top link due to their higher tensile and yield strength forces. The aluminum was used in the wrist part of the structure because of its flexibility. References Shi, Z.,Fung, E.H.K. and Li, Y. C. (1999). Dynamic modelling of rigid-flexible manipulator for constrained motion task control. Applied mathematics modelling. Yim, W. & Singh, S. N. (1995). Inverse Force and motion control of Constrained elastic robots. ASME Transactions Journal on Dynamic System, Measurement and Control 117, pp. 374. Ulsoy, G. & Hu, F. L. (1994). Force and motion control of a constrained flexible robot arm. ASME Transactions Journal on Dynamic System, Measurement and Control 116, pp. 336-343. Read More