Reconfigurable manufacturing systems: Key to future manufacturing

Presented in this article is a review of manufacturing techniques and introduction of reconfigurable manufacturing systems; a new paradigm in manufacturing which is designed for rapid adjustment of production capacity and functionality, in response to new market conditions. A definition of reconfigurable manufacturing systems is outlined and an overview of available manufacturing techniques, their key drivers and enablers, and their impacts, achievements and limitations is presented. A historical review of manufacturing from the point-of-view of the major developments in the market, technology and sciences issues affecting manufacturing is provided. The new requirements for manufacturing are discussed and characteristics of reconfigurable manufacturing systems and their key role in future manufacturing are explained. The paper is concluded with a brief review of specific technologies and research issues related to RMSs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46513/1/10845_2004_Article_268791.pd

A Zero-placement Technique for Designing Shaped Inputs to Suppress Multiple-mode Vibration

than traditionally designed shapers of comparable duration. Computer simulations of a single-mode system demonstrated the advantages of the new shapers. MACE results collected aboard the Space Shuttle Endeavor demonstrated the shapers' vibration-reducing abiUty on real structures. Acknowledgments W

Force and Motion Control of a Constrained Flexible Robot Arm

The results of a study on the combined joint motion control, vibration control, and force control of a constrained rigid-flexible robot arm for both regulation and tracking are presented. A nonlinear modified Corless-Leitmann controller is proposed for control of the flexible motion using only joint actuators. Experimental studies, which demonstrate the effectiveness of the proposed method, are described

Nonlinear Feed Effect in Machining Chatter Analysis

Regenerative chatter is a major limitation to the productivity and quality of machining operations due to the excessive rate of tool wear and scrap parts which are produced. Machining chatter analysis techniques examine the stability of the closed-loop model (force process and machine tool-part structure) of the machining operation to determine the stable process parameter space. Almost all chatter analysis techniques assume a linear force process and develop stability lobe diagrams (i.e., plots of the stable and unstable regions in the process parameter space) for a specific feed. It is well known that machining force processes inherently contain a nonlinear relationship between the force and the feed, which is typically described by a power law. In this paper, the linear chatter analysis technique developed by Budak and Altintas is extended to account for the force-feed nonlinearity. The analysis provides insight into the effect feed has on chatter in machining operations. Also, by directly including the force-feed nonlinearity in the chatter analysis, the need to calibrate the force process model at different feeds is alleviated. The analysis is developed for turning and face milling operations and is validated via time domain simulations for both operations and by experiments for a face milling operation. The analyses show excellent agreement with both the time domain simulations and the experiments. Further, several end milling experiments were conducted that illustrate the nonlinear effect feed has on chatter in machining operations

Model-Based Machining Force Control

Regulating machining forces provides significant economic benefits by increasing operation productivity and improving part quality. Machining force regulation is a challenging problem since the force process varies significantly under normal operating conditions. Since fixed-gain controllers cannot guarantee system performance and stability as the force process varies, a substantial research effort has been invested in the development of adaptive force controllers. However, adaptive controllers can be difficult to develop, analyze, implement, and maintain due to their inherent complexity. Consequently, adaptive machining force controllers have found little application in industry. In this paper, a model-based machining force control approach, which incorporates detailed force process models, is introduced. The proposed design has a simple structure and explicitly accounts for the changes in the force process to maintain system performance and stability. Two model-based machining force controllers are implemented in face milling operations. The stability robustness of the closed-loop system with respect to model parameter uncertainties is analyzed, and the analysis is verified via simulation and experimental studies

Supervisory Control of a Face Milling Operation in Different Manufacturing Environments

The promise of improved productivity and quality has lead to numerous research investigations in machining process monitoring and control. Recent studies have demonstrated that careful attention must be paid to the regulation of multiple process modules within a single operation such that each module performs its function properly and adverse interactions between modules do not occur. This had lead to the development of supervisory control; particularly to the development of methodologies to systematically construct and implement these controllers. However, no research study has investigated the effect of the production environment on the design of supervisory controllers. In this paper, the design of supervisory controllers for various production environments is studied. The design approach given in Landers and Ulsoy (1998) is applied to construct two supervisory machining controllers that are experimentally implemented in a face milling operation. Comparisons with an experimental implementation without process control illustrate the benefits of utilizing process controllers that are coordinated properly. The results also show that the given design approach may be used to construct supervisory controllers for different types of production environments

Machining Force Control Including Static, Nonlinear Effects

Regulating machining forces provides significant economic benefits by increasing productivity and improving part quality. The traditional machining force control approach employs linear, model-based techniques, assuming the machining force of interest is proportional to the feed and the depth-of-cut. However, the force-feed and force-depth relationships are nonlinear. Adaptive control techniques augment the traditional approach to ensure controller stability in the presence of these nonlinearities. Approaches employing linearization and transformation techniques have been developed which approximately account for the static, nonlinear effects. This paper demonstrates through simulation and experimental results that ignoring these nonlinearities reduces the performance of common machining force controllers. A model-based methodology is introduced which exactly accounts for the static, nonlinear effects. A change of variable accounts for the force-feed effect and the controller gains are adjusted to account for the force-depth effect. The proposed approach preserves the ease of design of linear, model-based techniques while ensuring controller performance specifications are met. The proposed approach is compared to the traditional, linearization, and log transform approaches via simulations and experiments and the advantages of this new technique are demonstrated

Nonlinear Feed Effect in Machining Chatter Analysis

Regenerative chatter is a major limitation to the productivity and quality of machining operations due to the excessive rate of tool wear and scrap parts which are produced. Machining chatter analysis techniques examine the stability of the closed-loop model (force process and machine tool-part structure) of the machining operation to determine the stable process parameter space. Almost all chatter analysis techniques assume a linear force process and develop stability lobe diagrams (i.e., plots of the stable and unstable regions in the process parameter space) for a specific feed. It is well known that machining force processes inherently contain a nonlinear relationship between the force and the feed, which is typically described by a power law. In this paper, the linear chatter analysis technique developed by Budak and Altintas is extended to account for the forcefeed nonlinearity. The analysis provides insight into the effect feed has on chatter in machining operations. Also, by directly including the force-feed nonlinearity in the chatter analysis, the need to calibrate the force process model at different feeds is alleviated. The analysis is developed for turning and face milling operations and is validated via time domain simulations for both operations and by experiments for a face milling operation. The analyses show excellent agreement with both the time domain simulations and the experiments. Further, several end milling experiments were conducted that illustrate the nonlinear effect feed has on chatter in machining operations