“Intelligent robotic assembly” indicates a complete degree of autonomy and a high adaptability in performing assembly tasks. For instance, a highly flexible and intelligent assembly system appears to be one that can autonomously perform any assembly work in entirely unstructured environments. This system does not require organized, orderly forms of part transport and presentation devices, such as assembly jig and fixture, part feeding devices, tray, magazine, conveyor, etc., but needs only an assembly table where parts to be assembled are stacked up in a cluttered manner.

It is an established fact that a majority of a product's cost is determined by its design. Hence, effort should be directed to achieve a lower cost design without sacrificing the original functionality. A computer-aided product redesign system is proposed to provide help in generating assembly-oriented redesign by taking the robotic assembly constraints into consideration. The system operates in two phases: In the first phase, an objective evaluation of the input design is performed to determine whether there is a need for redesign. During the second phase, the focus is to aid the designer in searching for feasible design alternatives. Three quantitative measures have been proposed to evaluate the conformity of an input design to a list of DFA design guidelines. If the input design received a bad evaluation results on any of the three measures, a search for feasible redesign suggestions is initiated to derive suitable redesign suggestions.

The design of tolerances should take the functionality, manufacturability, assemblability and cost effectiveness of a product into consideration. This paper presents a method of analyzing and evaluating the assemblability of a product under given tolerance specifications in order to provide a tool to aide for tolerance design. Introduced is the range of feasible displacement of a part of an assembly as a result of the accumulation of clearances between mating parts along the serial as well as parallel chain of assembly, which can play a role of compensating for the pose error of the corresponding part due to the accumulation of tolerances. Assemblability is determined by the probability that all the parallel as well as serial chains of the assembly can be f ormed successfully under given statistical properties of tolerances. This requires to numerically compute the probability that a pair of mating parts forming a parallel chain can align themselves within the error margin defined by their mating clearance, accounting for the possible compensation of the ranges of pose errors associated with the mating parts due to tolerance accumulations by the ranges of feasible displacements of the mating parts due to clearance accumulations. Simulation results are shown.

This paper presents a design of an assembly sequence planner based on a “plan reuse” philosophy. Most of assembly planning research in the past has attempted to completely plan each problem from scratch. This research shows that stored cases of basic assembly configurations can be applied to a given assembly problem. It is observed that the number of such basic assembly configurations is quite small. The planner divides the assembly into a number of constituent configurations, which are called “loops”. These act as subgoals in its search for solutions. Plans retrieved for all subgoals are fused into a set of plans that are consistent with the constraints implied by each plan. Application specific constraints on the assembly are explicitly handled in the second phase of planning. Mechanisms for assembly representation and implementation details of the planner are also presented.

The frequent use of past experience by human engineers when solving new problems has led to an interest in the use of case based reasoning (CBR) to help automate engineering design. In engineering design it often occurs that many past exp eriences must be combined to solve a new problem, and thus the process of case based adaptation must efficiently and systematically combine information from many sources. We have developed a constraint based methodology for case combination that allows its application across a wide range of problems. We have shown that our approach provides an efficient adaptation methodology that ensures convergence upon a solution if one exists, provides a uniform representation of cases, and is generalizable beyond just one domain. Our technique is implemented in a case based reasoning system called COMPOSER, which ha s been tested in two design domains: assembly sequence design and configuration design.

The ability of manipulating flexible objects, such as rubber belts and paper sheets, is important in automated manufacturing systems. This paper describes a novel approach to vision-guided assembly of flexible objects. The operation dealt with in this paper is to assemble a rubber belt with fixed pulleys. By analyzing possible states of the belt based on the empirical knowledge of the belt, we can derive a method to have not only the action planning but also the visual verification planning. We have implemented a belt assembly system using the two manipulators and a laser range finder as the sensor, and succeeded in performing the belt-pulley assembly. The extension of our approach to other kinds of assembly of flexible objects is also discussed.

Assembly robots that use an active camera system for visual feedback can achieve greater flexibility, including the ability to operate in an uncertain and changing environment. Incorporating active vision into a robot control loop involves some inherent difficulties, including calibration, and the need for redefining the servoing goal as the camera configuration changes. In this paper, we propose a novel self-organizing neural network that learns a calibration-free spatial representation of 3D point targets in a manner that is invariant to changing camera configurations. This representation is used to develop a new framework for robot control with active vision. The salient feature of this framework is that it decouples active camera control from robot control. The feasibility of this approach is established with the help of computer simulations and experiments with the University of Illinois Active Vision System (UIAVS).

Reliable flexible assembly workstations depend ultimately on the physics of assembly tasks performed. Multiple-peg insertions, as a practical assembly class, is complicated by the large number and kind of interaction between mating parts.

In this article, geometric and quasi-static analyses of multiple-peg insertions are presented. First, a possible contact-state enumeration, geometric conditions for each contact-state, and the force-moment equations for static-equilibrium states of two dimensional dual-peg insertions are derived. The jamming diagrams and the taxonomy of dual-peg insertions are obtained. Then, an experiment to verify the analysis is presented.

This paper presents an approach for analyzing the dynamics of initial impact during robotic parts mating represented by peg-in-hole assembly. Lagrange's impact model is used to derive a general form of impact equations for an industrial manipulator performing peg-in-hole assembly. Specific impact equations can then be generated for a given robot to analyze part motions and contact forces in the mating of parts. The impact equations of a SCARA robot are obtained and utilized to investigate how the system parameters affect force impulse and departure angle in the assembly of a peg with a chamfered hole. The resulting information is useful to robot manufacturers in design of robotic equipment and to robot users in determining optimal operational conditions. It is also useful for building an intelligent robot controller capable of deciding on proper values of operation parameters.

The MARK III FAA (Flexible Automatic Assembly) cell was designed to minimise the risk factors associated with FAA. This FAA cell is stepwise upgradeable and adopts the sub-batch principle and reversed material flow solutions. It allows for the assembly of products with an annual volume normally too low to justify automation. The MARK III FAA cell was implemented with the FACE programming and control system, a PC-based, modular programming and control platform for FAA cells. It enables the management of unpredictable order schemes and leads to very low programming costs.

JAPAN

New challenges face the robot industry of tomorrow. ‘It is estimated that the Japanese robot industry increased its production to Yen550billion in 1997,’ writes Seiuemon Inaba, Chairman of the Japan Robot Association in his New Year message . ‘This is 17% up over the preceding year, due chiefly to the rapid recovery of exports, in addition to the active domestic demand that has continued since 1996. The figures also reflect a firm trend of capital investment. ’ Although rec ent economic conditions have led to some uncertainties about future developments of the business climate, the industry's production in 1998 is likely to regain the Yen600billion level, an all-time high which was reached in the previous peak period,' he adds. ‘In respect of the fundamental economic and social needs for robots in Japan, we believe it is essential to further development of the nation's manufacturing industry-based economy that steps are taken to meet the requirements of industry, particularly in the strengthening of its international competitive abilities through the improvement of productivity and the establishment of a more efficient production system, ' writes Mr Inaba. ’In addition, the industry is called on to meet various other requirements, including measures to compensate for the shortage of skilled workers, the development of an intellectual, comfortable working environment to arrest the tendency of young workers to defect from the manufacturing sector , the release of workers from the so-called ‘three-D (dangerous, dirty and difficult) jobs, and the reduction of working hours,' declares Mr Inaba. ‘These requirements are expected to bring about mid-to-long-term active demand for automat ion equipment, especially robots and factory automation systems,’ writes Mr Inaba. ‘At present robots are used mostly in the conventional manufacturing industy, but in the years ahead, their application will be expanded to the personal sector, covering household uses and support systems for the daily life of the elderly and handicapped, as well as to non-manufacturing industries, including construction, nuclear power, ocean development, medical care and services.’ Mr Inaba adds: ‘St renuous research and development efforts for high technologies are essential to meeting such a wide range of economic and social needs in Japan. Among 15 new and growth sectors covered by a government programme for economic restructuring and creation, pre-arrangements are being made for a research and development project on ‘human co-operating and coexi sting robots’ for which the programme calls on interested parties to immediately set about development and commercialisation tasks. The robot industry intends to participate actively in the project when it comes to the implementation stage. “Thus the Japan Robot Association intends to carry out actively on various operations aimed at further development of the industry. For this purpose, we request the competent government agencies and other interested parties for continued guidance, assistance and co-operation” concludes Mr Inaba.