A Passive Compliant Wrist Design for Robot Manipulators

Robot assembly in manufacturing systems is still a work-intensive process. A main difficulty that arises when trying to automate an assembly task with a robot is the precision required to position and orient the parts. This difficulty arises in several sources of error, such as robot accuracy, the gripping and presentation precision of pieces, and part tolerance. High requirements for part insertion also present a greater possibility for jamming of parts and bottlenecking of the assembly line. Using a compliant device mounted between the end effector of the robot and the gripper mechanism may relieve this situation. In order to achieve the reality of cheaper automation solutions by using robots in high precision insertion tasks, a passive compliant gripper device would need to be used. A passive design would supply the user with a “bolt-on” device that did not require any extra controllers or interfacing between the compliant wrist and the robot main controller, as is the case with an active or hybrid design. Using the wrist in operation, the number of damaged parts and the number of crashes by the robot would be reduced. Other compliant devices that are currently offered by commercial companies are compared with the proposed design and debated. After a study of existing compliant devices, a novel approach is presented. Utilizing an earthquake protection device for buildings as an initial idea fountain, a new compliant wrist design is formulated. The Passive Compliant Wrist design, based on a building support system, is exhibited in detail. A comprehensive discussion of the wrist in operation is also presented. The final design has also been verified using the dynamic motion simulation program, Working Model, by Knowledge Revolution.

A Multi-Agent Interactive Approach to Assembly Modeling

This paper introduces a new interactive multi-agent approach to automate the assembly modeling problem in order to generate the parts precedence relations of a product starting from its design data. Assembly parts are considered as self-interested intelligent agents with local information and goals. Centralized approaches based on graphical representation resulted so far in both combinatorial and information complexity, especially when dealing with actual complex industrial products. The proposed decentralized approach overcomes exhaustive combinatorial search, while the ability to store and exchange dynamic information among agents reduces the oversimplification of graphical representation. Furthermore, the incorporation of human agents helps the system to overcome the limitations of artificial intelligence. This approach offers a promising platform for assembly planning automation with minimum human intervention especially for all-new products.

A Workcell Based Robot Design Program

This paper discusses a computer graphics program that helps to design a robot based on an existing workcell that would be difficult or costly to modify. Standard robot bases, as well as tracked robots, are located to minimize the error of the desired taught robot gripper positions. Error levels are established based on the angle of the misalignment and the length of the required loading or unloading motion. Program implementation is detailed.

Development of a Methodology for Cost Estimation in Robot Assembly

The developments in today’s industries put the companies under increasing pressure concerning time and costs. This forces them to, among other measures, rationalize and automates the manufacturing systems, including the assembly systems. To reduce the risks of investments and enhance the investment planning, accurate calculation methodologies for assembly planning systems are necessary. There are a number of ways to lay out an assembly system. An assembly system may be designed for a manual operation, an automatic operation, or a flexible operation. Industrial robots are extensively used in such flexible assembly systems. Production volume and cost per assembled part depend heavily on how such a flexible cell is designed and on the robot being used. Boothroyd and Dewhurst have proposed an approach to arrive at evaluating robot integrated assembly cells. This approach is based on the manipulation of the part before presenting it for an assembly and the number of robot arms in the assembly cell. It does not account for the flexibility (number of robot axes, specific types of robots) the various industrial robots offer. Consequently, any evaluation made on this basis is expected to provide inaccurate answers.

Modular Automation Concepts: Opportunities and Challenges in Industry

The goals of Modular Automation Concepts (MAC) for the automation field are presented. In order to demonstrate the strategies, the packaging automation industry is reviewed to find new opportunities for production machines. These new machines were designed with the MAC techniques. Other challenges from the industrial side to Modular Design are also discussed.

Uncertainty Analysis of Planar Robots With Joint Clearance

Joint clearance in mechanisms and robots leads to uncertainty in function deviation. Unlike the impact of the link tolerance on the performance quality, the uncertain effect of the joint clearance to the performance can not be eliminated by calibration because of the random nature. In this paper, based on the probability theory, a general probability density function for the output of planar robots is established for any probability density function of joint clearance. The result is demonstrated by a uniform distribution in the joint clearance and a table of the resulting functions is presented. These distribution functions and the table provide a convenient way to obtain the probability value for a planar robot to position its end point within a desired deviation zone and to determine the joint clearance value based on the concerned shape of tolerance zone and the specified probability value of repeatability.

An Automated Assembly Sequence Planing System for Mechanical Parts

This work provides a software system, which can automatically determine the assembly sequence of a product from its parts, given only a geometric description of the assembly. A simple closed envelope method for product geometry representation, and an efficient matrix method to represent contact and interference relations among the parts were successfully used in this work. The possible sub-assemblies are automatically detected by satisfying some mathematical conditions applicable to these matrices. Possible assembly sequences are generated for each sub-assembly and for the whole product. Furthermore, the algorithms are successfully examined with several industrial products.

Evaluation of a Mechanical Assembly Using Manual and Robotic Methods

This paper attempts to evaluate the assembly of a conventional paper dispenser using manual as well as robotic method. The main thrust of the paper is using the Boothroyd and Dewhurst DFA charts for the assembly evaluation and analysis and commenting critically on the effectiveness of the charts. Thus the paper presents a case study in the analysis of assemblies using Boothroyd and Dewhurst DFA charts.