Investigating the Capability of Precision in Robotic Grinding

Most robotic grinding focus on the surface finish rather than accuracy and precision. However ever increased demand on complex component manufacture requires to advance robot grinding capability so that more practical and competitive accurate systems can be developed. The current study focuses on improving the level of accuracy of robotic grinding, which is a significant challenge in robot application because the kinematic accuracy of robot movement is much more complex than normal CNC machine tools. Aiming to improve accuracy and efficiency the work considers all quality of measures including surface roughness and the accuracy of size and form. For that to be done, a repeatability test is firstly preformed to observe the distributions of the joint positions and how well the robot responds to its programmed position using a dial gauge method and a circuit trigger method. After that, a datum setting method is performed to assess the datum alignment with the robot. Hence, a mathematical model based on regression analyses applies towards the collected data to observe closely any error correlation when setting up a datum to perform the grinding procedure

Development of an integrated robotic polishing system

This thesis presents research carried out as part of a project undertaken in fulfilment of the requirements of Loughborough University for the award of Philosophical Doctorate. The main focus of this research is to investigate and develop an appropriate level of automation to the existing manual finishing operations of small metallic components to achieve required surface quality and to remove superficial defects. In the manufacturing industries, polishing processes play a vital role in the development of high precision products, to give a desired surface finish, remove defects, break sharp edges, extend the working life cycle, and meet mechanical specification. The polishing operation is generally done at the final stage of the manufacturing process and can represent up to a third of the production time. Despite the growth automated technology in industry, polishing processes are still mainly carried out manually, due to the complexity and constraints of the process. Manual polishing involves a highly qualified worker polishing the workpiece by hand. These processes are very labour intensive, highly skill dependent, costly, error-prone, environmentally hazardous due to abrasive dust, and - in some cases - inefficient with long process times. In addition, the quality of the finishing is dependent on the training, experience, fatigue, physical ability, and expertise of the operator. Therefore, industries are seeking alternative solutions to be implemented within their current processes. These solutions are mainly aimed at replacing the human operator to improve the health and safety of their workforce and improve their competitiveness. Some automated solutions have already been proposed to assist or replace manual polishing processes. These solutions provide limited capabilities for specific processes or components, and a lack of flexibility and dexterity. One of the reasons for their lack of success is identified as neglecting the study and implementing the manual operations. This research initially hypothesised that for an effective development, an automated polishing system should be designed based on the manual polishing operations. Therefore, a successful implementation of an automated polishing system requires a thorough understanding of the polishing process and their operational parameters. This study began by collaborating with an industrial polishing company. The research was focused on polishing complex small components, similar to the parts typically used in the aerospace industry. The high level business processes of the polishing company were capture through several visits to the site. The low level operational parameters and the understanding of the manual operations were also captured through development of a devices that was used by the expert operators. A number of sensors were embedded to the device to facilitate recording the manual operations. For instance, the device captured the force applied by the operator (avg. 10 N) and the cycle time (e.g. 1 pass every 5 sec.). The capture data was then interpreted to manual techniques and polishing approaches that were used in developing a proof-of-concept Integrated Robotic Polishing System (IRPS). The IRPS was tested successfully through several laboratory based experiments by expert operators. The experiment results proved the capability of the proposed system in polishing a variety of part profiles, without pre-existing geometrical information about the parts. One of the main contributions made by this research is to propose a novel approach for automated polishing operations. The development of an integrated robotic polishing system, based on the research findings, uses a set of smart sensors and a force-position-by-increment control algorithm, and transpose the way that skilled workers carry out polishing processes

Large Deployable Reflector (LDR) system concept and technology definition study. Volume 2: Technology assessment and technology development plan

A study was conducted to define reasonable and representative LDR system concepts for the purpose of defining a technology development program aimed at providing the requisite technological capability necessary to start LDR development by the end of 1991. This volume presents thirteen technology assessments and technology development plans, as well as an overview and summary of the LDR concepts. Twenty-two proposed augmentation projects are described (selected from more than 30 candidates). The five LDR technology areas most in need of supplementary support are: cryogenic cooling; astronaut assembly of the optically precise LDR in space; active segmented primary mirror; dynamic structural control; and primary mirror contamination control. Three broad, time-phased, five-year programs were synthesized from the 22 projects, scheduled, and funding requirements estimated

Geometrical Error Analysis and Correction in Robotic Grinding

The use of robots in industrial applications has been widespread in the manufacturing tasks such as welding, finishing, polishing and grinding. Most robotic grinding focus on the surface finish rather than accuracy and precision. Therefore, it is important to advance the technology of robotic machining so that more practical and competitive systems can be developed for components that have accuracy and precision requirement. This thesis focuses on improving the level of accuracy in robotic grinding which is a significant challenge in robotic applications because of the kinematic accuracy of the robot movement which is much more complex than normal CNC machine tools. Therefore, aiming to improve the robot accuracy, this work provides a novel method to define the geometrical error by using the cutting tool as a probe whilst using Acoustic Emission monitoring to modify robot commands and to detect surfaces of the workpiece. The work also includes an applicable mathematical model for compensating machining errors in relation to its geometrical position as well as applying an optimum grinding method to motivate the need of eliminating the residual error when performing abrasive grinding using the robot. The work has demonstrated an improved machining precision level from 50µm to 30µm which is controlled by considering the process influential variables, such as depth of cut, wheel speed, feed speed, dressing condition and system time constant. The recorded data and associated error reduction provide a significant evidence to support the viability of implementing a robotic system for various grinding applications, combining more quality and critical surface finishing practices, and an increased focus on the size and form of generated components. This method could provide more flexibility to help designers and manufacturers to control the final accuracy for machining a product using a robot system

NASA SBIR abstracts of 1990 phase 1 projects

The research objectives of the 280 projects placed under contract in the National Aeronautics and Space Administration (NASA) 1990 Small Business Innovation Research (SBIR) Phase 1 program are described. The basic document consists of edited, non-proprietary abstracts of the winning proposals submitted by small businesses in response to NASA's 1990 SBIR Phase 1 Program Solicitation. The abstracts are presented under the 15 technical topics within which Phase 1 proposals were solicited. Each project was assigned a sequential identifying number from 001 to 280, in order of its appearance in the body of the report. The document also includes Appendixes to provide additional information about the SBIR program and permit cross-reference in the 1990 Phase 1 projects by company name, location by state, principal investigator, NASA field center responsible for management of each project, and NASA contract number

A flexible manufacturing system for lawnmower cutting cylinders

The thesis is concerned with the conception and design of a FLEXIBLE MANUFACTURING SYSTEM (FMS) for the automation of the manufacture of lawnmower cutting cylinders at Suffolk Lawnmowers Ltd. A review of FMS definitions, planning methods and current systems is carried out for the development of a suitable FMS configuration for the final stages of manufacture of grass cutting cylinders having 21 different design specifications. This involves examination of the capabilities of robotics and microcontrollers to automate the technologies used in cylinder production. The company's current manual batch production system is analysed to determine the suitable form and requirements of the FMS. This includes analyses of annual volumes, throughputs, batch sizes, product and process mixes. Long term objectives to automate the system are identified from which short term objectives are derived. The FMS recommended for immediate development encompasses the short term objectives for the welding, hardening, grinding and transfer processes of 8 cutting cylinder specifications. It is shown that the MIG (Argon/C02) are welding, progressive flame hardening and wide-face cylindrical grinding processes can be developed successfully to automate cylinder production. The recommended system integrates these processes into an FMS through the'automatic handling of cylinders (through three process routes) by a robotic manipulator utilising a double gripper. 'A robotic welding station, manually loaded, is also recommended. ' The system is controlled overall by a 32K microcontroller with the process machines individually controlled by programmahle logic controllers with up to 6K of memory each. The economic appraisal of the FMS indicates a 4.4 year payback based on direct labour and material cost savings. The company's application for grant aid to implement the FMS design has led to an offer of a Department of Industry grant to cover 50% of all capital and revenue costs. The grant of £166,943 reduces the payback period to 2.3 years

The Federal Conference on Intelligent Processing Equipment

Research and development projects involving intelligent processing equipment within the following U.S. agencies are addressed: Department of Agriculture, Department of Commerce, Department of Energy, Department of Defense, Environmental Protection Agency, Federal Emergency Management Agency, NASA, National Institutes of Health, and the National Science Foundation

Hibrit artık robot kolu kullanarak yüksek performanslı taşlama işlemi geliştirmesi.

Automatic grinding using robot manipulators, requires simultaneous control of the robot endpoint and force interaction between the robot and the constraint surface. In robotic grinding, surface quality can be increased by accurate estimation of grinding forces where significant tool and workpiece deflection occurs. Tool deflection during robotic grinding operation causes geometrical errors in the workpiece cross-section. Also, it makes controlling the grinding cutting depth difficult. Moreover small diameter of the tool in robotic grinding causes different behavior in the grinding process in comparison with the tools that are used by universal grinding machines. In this study, a robotic surface grinding force model is developed in order to predict the normal and tangential grinding forces. A physical model is used based on chip formation energy and sliding energy. To improve the model for robotic grinding operations, a refining term is added. In order to include the stiffness of the tool and setup in the force model, penetration tests are implemented and their results are used in refining term of the force model. The model coefficients are estimated using a linear regression technique. The proposed model is validated by comparing model outputs with experimentally obtained data. Evaluation of the test results demonstrates the effectiveness of the proposed model in predicting surface grinding forces. In this thesis, a method is proposed for calculation of the tool deflection in normal and tangential directions based on grinding force feedback in these directions. Based on calculated values, a real-time tool deflection compensation algorithm is developed and implemented. Implementing surface grinding with constant normal force is a well-known approach for improving surface quality. Tool deflection in the robotic grinding causes orientation between the force sensor reference frame and tool reference frame. This means that the measured normal and tangential forces by the sensor are not actual normal and tangential interaction forces between the tool and workpiece. In order to eliminate this problem, a resultant grinding force control strategy is designed and implemented for a parallel hexapod-robotic light abrasive surface grinding operation. Due to the nonlinear nature of the grinding operation, a supervised fuzzy controller is designed where the reference input is identified by the proposed grinding force model. Evaluation of the experimental results demonstrates significant improvement in grinding operation accuracy using the proposed resultant force control strategy in parallel with a real-time tool deflection compensation algorithm. The final aim of this thesis is to develop a posture optimization strategy for robotic grinding operation using 12 DOF hybrid redundant manipulator. The 12 DOF redundant hybrid manipulator of present study is composed of a 6 DOF serial ABB IRB2000 robot and a 6 DOF PI H-824 hexapod where the parallel hexapod is connected to the end of the serial ABB manipulator. Here the fifth joint (wrist) of the ABB serial manipulator is the weakest joint in the robot, so the computed torque of this joint is selected as the cost function. The aim is to minimize this factor by finding the best configuration of the hybrid manipulator using genetic algorithm approach. For such a purpose, a complete kinematic and dynamic model of the 12 DOF manipulator is developed where the output of the grinding force model is fed into the dynamic model as external reaction forces. The computed torque of the wrist joint is given to the optimization module and new configuration is generated by the module and is given to the dynamic model. This process continues until converge to the minimum computed torque value. Then the optimal configuration is chosen for the grinding operation. The evaluation of this posture optimization approach shows its great ability to decrease the necessary actuating torques of the redundant manipulator joints.Ph.D. - Doctoral Progra