Masao Sugi

Agile Assembly System by “Plug and Produce”

Abstract For highly flexible and agile assembly systems, installation of manufacturing devices is indispensable technology. In this paper, we propose a “Plug & Produce” concept. It is a methodology to introduce a new manufacturing device into a manufacturing system easily and quickly. It can also remove the device easily from the system. It is designed by analogy of Plug & Play concept in computer world. A holonic assembly system is installed using proposed Plug & Produce architecture. The validity of the proposed architecture is verified by experiments with robots and a belt conveyor. A robot will be installed to an existing cell in a short time. The proposed concept can enhance the agility of assembly systems greatly.

Holonic assembly system with Plug and Produce

Abstract An assembly system based on holonic concept has been newly installed. The system consists of three manipulators, one belt-conveyor and two warehouses. The system assembles several parts into a product. Its sequences are planned by negotiation among the assembly devices by means of contract net protocol. Thus, even though the parts are supplied at different warehouses, the system can generate a sequence of transportation automatically. Utilizing the characteristics of distributed autonomous systems, a new concept Plug and Produce is proposed. A device can be installed easily and then immediately start to work. This system has high robustness against the reconfiguration and sudden changes of products. Experiments were made for two kinds of assembly tasks and verified the efficiency of the system.

A holonic architecture for easy reconfiguration of robotic assembly systems

Proposes a flexible assembly system, where autonomous manufacturing devices and production management agents communicate with one another to accomplish production tasks. This architecture allows the system to arrange manufacturing devices independently of the type of products assembled and to assemble multiple products in parallel and asynchronous progress. This system also supports plug and produce, a system function that realizes easy reconfiguration. Thus, the system can return quick responses to breakdowns and changes in production quantities. This paper also presents an index for the general evaluation of reconfigurable manufacturing systems. With this index and the plug-and-produce function, the system can be reconfigured appropriately to adapt to changes in the manufacturing environments.

Motion Control of Self-Moving Trays for Human Supporting Production Cell “Attentive Workbench”

We propose “Attentive Workbench (AWB),” a new cell production system in which an intelligent system supports human workers. Using cameras, projectors, planar motor driven self-moving trays and other devices, the system supports workers from both physical and information aspects, recognizing worker’s condition and intention. This paper outlines AWB and deals with physical assembly support using self-moving parts trays. Two different schemes, centralized and decentralized, for controlling multiple parts trays are evaluated through experiments and simulations. The centralized control scheme is found to have the higher performance than the decentralized control scheme.

Automated calibration of robot coordinates for reconfigurable assembly systems

Abstract To achieve higher reconfigurability of an assembly line, quick plug-in and plug-out of devices such as robots is essential. When a new device is installed into the assembly line, calibration should be made. This research deals with an automated calibration system of relative position/orientation based on the Direct Linear Transformation method using two CCD cameras. The cameras are freely positioned, and then a set of motions is commanded to each manipulator. By detecting the motion with the cameras, the relative position of the two robots is obtained. The resultant accuracy is 0.16 mm rms at the best.

Deskwork support system based on the estimation of human intentions

We have proposed a system called an attentive workbench (AWB) that is designed to support desktop work. AWB is the system which estimates a workers condition using some sensors and assists a worker using movable trays and projectors from both physical and informational viewpoints. A method for estimating an AWB users intention is proposed and presented. An AWB user expresses his/her intention by pointing a finger at a necessary tray. For estimating which tray a user needs, the system uses dynamic Bayesian network to integrate the sensor data obtained from users pointing gestures and users past action sequences. A description of the experimental results are demonstrated the usefulness of the method proposed here.

Estimation of handgrip force using frequency-band technique during fatiguing muscle contraction

In this paper, we propose a force estimation model to compute the handgrip force from SEMG signal during fatiguing muscle contraction tasks. The appropriate frequency range was analyzed using various combinations of a wavelet scale, and the highest accuracy was achieved at a range from 242 to 365 Hz. After that, eight healthy individuals performed a series of static (70%, 50%, 30%, and 20% MVC) and dynamic (0-50% MVC) muscle contraction tasks to evaluate the performance of this technique in comparison with that of former method using the Root Mean Square of the SEMG signal. Both methods had comparable results at the beginning of the experiments, before the onset of muscle fatigue. However, differences were clearly observed as the degree of muscle fatigue began to increase toward the endurance time. Under this condition, the estimated handgrip force using the proposed method improved from 17% to 134% for static contraction tasks and 40% for dynamic contraction tasks. This study overcomes the limitation of the former method during fatiguing muscle contraction tasks and, therefore, unlocks the potential of utilizing the SEMG signal as an indirect force estimation method for various applications.

Assembly Information System for Operational Support in Cell Production

In cell production, the output depends heavily on the performance of the worker. Assembly information support is useful to support the worker. The objective of this study is to develop a framework to organize assembly information to support production operation. It is illustrated by an application of a production operation in laboratory simulation. Assembly motion of skilled worker is extracted and the assembly process is decomposed into operational units, which linked with support information to set up the information database. New assembly process with information support can then be generated and implemented with multimodal system to assist production operation.

Order scheduling of multiple stacker cranes on common rails in an automated storage/retrieval system

An order scheduling method for improving the work efficiency of multiple cranes on a common rail in an automated storage/retrieval system (AS/RS) is proposed in this paper. Most AS/RSs are equipped with one stacker crane. However, this is logistically challenging, and higher work efficiency in warehouses, such as those using more than one stacker crane, is required. In this paper, a warehouse with multiple stacker cranes working simultaneously is proposed. Unlike warehouses with only one crane, order scheduling is very difficult because there are multiple cranes working simultaneously and collisions are possible. Warehouse order must be maintained while avoiding collisions. Sometimes, detours are necessary to avoid collisions. As a result, work efficiency will decrease if a sequence of orders is not properly planned. Nevertheless, as transport works in AS/RSs are occurring randomly, scheduling cannot be conducted in advance, which makes the order scheduling of multiple cranes difficult. A fast order scheduling method is proposed here. Several orders are combined into an order cluster, and dynamic programming is used to obtain the best combination of order clustering. By utilising this method, cranes can work cooperatively, improving work efficiency to 0.95 with a two-crane AS/RS and to 0.78 with a three-crane AS/RS.

Simultaneous measurement of force and muscle fatigue using frequency-band wavelet analysis

Static and dynamic handgrip experiments are performed in order to evaluate the effectiveness of utilizing frequency-band wavelet analysis in measuring force and muscle fatigue simultaneously. SEMG signals are recorded from flexor muscle and analyzed using continuous wavelet transform (CWT). The wavelet coefficients are grouped into high frequency (65Hz – 350Hz) and low frequency (5Hz – 45Hz) band. A significant correlation is discovered between amplitude of high frequency band and force level. On the other hand, the amplitude of low frequency band is associated with muscle fatigue. These results have an important implication for estimating force and muscle fatigue simultaneously especially during dynamic contraction.