The Effect of Local Force Control on Punch Forces During Panel Forming

2018 ◽  
Author(s):  
William J. Emblom
Keyword(s):  
Closed Loop ◽  
Force Transducer ◽  
Open Loop ◽  
Control Panel ◽  
Closed Loop Control ◽  
Punch Force ◽  
Blank Holder ◽  
Loop Control ◽  
Operational Envelope ◽  
And Control

Methods for improving the robustness of panel forming including the introduction of process sensing and feedback and control has resulted in significant gains in the quality of parts and reduced failures. Initial efforts in implementing closed-loop control during panel forming used active tool elements to ensure that the total punch force followed prescribed trajectories. However, more recently local forces within the tooling have been demonstrated to not only follow desired force trajectories but have been shown to increase the operational envelope of the tooling compared to open-loop tests and even closed-loop test where the total punch force had been controlled. However, what has not been examined is the effect of local force, especially during closed-loop control panel forming operations on the total punch force measured during forming. This paper addresses this by comparing the results of both open-loop tests and closed-loop tests and examining the effects on both local and total punch forces. It was found that while open-loop forming with various constant draw bead depths resulted in varying total punch forces, once closed-loop control was implemented the total punch forces followed virtually identical trajectories. The tooling for this project included local force transducers and a total punch force transducer. In addition, active draw beads could be controlled during forming and a flexible blank holder with variable blank holder forces were part of the setup.

Strain Control in an Intelligent Die Based Upon Local Force Control and Blank Holder Forces

2009 ◽  
Author(s):  
William J. Emblom ◽  
Klaus J. Weinmann ◽  
John E. Beard
Keyword(s):  
Closed Loop ◽  
Open Loop ◽  
Die Design ◽  
Closed Loop Control ◽  
Blank Holder Force ◽  
Punch Force ◽  
Blank Holder ◽  
Loop Control ◽  
And Control ◽  
Bead Penetration

An experimental evaluation of the strains in an oval stamp forming die is presented. The die design included a flexible blank holder and active draw beads. The die was instrumented with local punch force and wrinkle sensors and control systems were developed in order to follow local punch force and wrinkle trajectories. Strains were measured after pan forming for both open and closed-loop tests. The relation between blank holder force, draw bead penetration, and strains were explored in the critical strain region of the formed pan. Closed-loop control of the local punch forces at the die ends was established using blank holder forces. The strains for tests with various lubrication conditions and draw bead penetrations were compared. It was observed that there is a tendency for the strains in critical locations to converge or remain constant for the closed-loop control tests while the strains tended to increase with blank holder force for open-loop tests. It was concluded that by controlling local punch forces, strain is indirectly controlled.

Improved Robustness Through Closed-Loop Control for Aluminum Sheet Metal Stamp Forming

2008 ◽  
Author(s):  
William J. Emblom ◽  
Klaus J. Weinmann
Keyword(s):  
Closed Loop ◽  
Experimental Tests ◽  
Open Loop ◽  
Closed Loop Control ◽  
Punch Force ◽  
Blank Holder ◽  
Loop Control ◽  
Stamp Forming ◽  
Process Disturbances ◽  
Bead Height

A stamp forming die, whose flexible blank holder was designed using FEA, was built. Tests were performed to evaluate the robustness of the die once closed-loop control was implemented. These results were compared to the results of open-loop tests presented earlier. The closed-loop tests were designed to determine the die and control system’s ability to reject process disturbances and demonstrate improved robustness in stamp forming when using a flexible blank holder and closed-loop control. Draw beads were used to control local punch forces and blank holder forces were used to control wrinkling. Experimental tests for the die demonstrated that closed-loop control of local punch forces using active draw beads improves robustness of the die. Two different lubricants and varying quantities of lubricant were evaluated for this study. Additionally, the ability to simultaneously use draw bead height to control local punch force and blank holder force to control wrinkles was demonstrated.

Robustness for Intelligent Tooling While Forming Shallow Aluminum Pans

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
William J. Emblom
Keyword(s):  
Control System ◽  
Design Process ◽  
Closed Loop ◽  
Open Loop ◽  
Closed Loop Control ◽  
Blank Holder ◽  
Loop Control ◽  
Stamp Forming ◽  
Tooling Design ◽  
Process Disturbances

This study examines the robustness of stamp forming tooling. An oval pan was formed using tooling that included a flexible blank holder, active draw beads, and closed-loop control of both wrinkling and local punch forces. The results were compared to open-loop tests using the same tooling and earlier work that utilized tooling that produced similar pans but included a rigid blank holder. For the current study, robustness was defined as the ability to delay wrinkling or tearing. A description of the tooling design process is provided as well as a synopsis of the development of the control system for the tooling. Open-loop and closed-control tests using AL 6111-T4 blanks were performed in order to evaluate the ability to reject process disturbances and demonstrate improved robustness of the tooling. During open-loop tests, the current tooling was shown to be more robust than the earlier tooling with the rigid blank holder. Control of wrinkling eliminated one form of part failure while closed-loop control of local punch forces significantly improved the robustness of the tooling by delaying tearing.

Dynamics and Control of Global Instabilities in Open-Flows: A Linearized Approach

2010 ◽  
Vol 63 (3) ◽  
Author(s):  
Denis Sipp ◽  
Olivier Marquet ◽  
Philippe Meliga ◽  
Alexandre Barbagallo
Keyword(s):  
Closed Loop ◽  
Selection Process ◽  
Open Loop ◽  
Base Flow ◽  
Closed Loop Control ◽  
Mean Flow ◽  
Loop Control ◽  
Dynamics And Control ◽  
Global Modes ◽  
And Control

This review article addresses the dynamics and control of low-frequency unsteadiness, as observed in some aerodynamic applications. It presents a coherent and rigorous linearized approach, which enables both to describe the dynamics of commonly encountered open-flows and to design open-loop and closed-loop control strategies, in view of suppressing or delaying instabilities. The approach is global in the sense that both cross-stream and streamwise directions are discretized in the evolution operator. New light will therefore be shed on the streamwise properties of open-flows. In the case of oscillator flows, the unsteadiness is due to the existence of unstable global modes, i.e., unstable eigenfunctions of the linearized Navier–Stokes operator. The influence of nonlinearities on the dynamics is studied by deriving nonlinear amplitude equations, which accurately describe the dynamics of the flow in the vicinity of the bifurcation threshold. These equations also enable us to analyze the mean flow induced by the nonlinearities as well as the stability properties of this flow. The open-loop control of unsteadiness is then studied by a sensitivity analysis of the eigenvalues with respect to base-flow modifications. With this approach, we manage to a priori identify regions of the flow where a small control cylinder suppresses unsteadiness. Then, a closed-loop control approach was implemented for the case of an unstable open-cavity flow. We have combined model reduction techniques and optimal control theory to stabilize the unstable eigenvalues. Various reduced-order-models based on global modes, proper orthogonal decomposition modes, and balanced modes were tested and evaluated according to their ability to reproduce the input-output behavior between the actuator and the sensor. Finally, we consider the case of noise-amplifiers, such as boundary-layer flows and jets, which are stable when viewed in a global framework. The importance of the singular value decomposition of the global resolvent will be highlighted in order to understand the frequency selection process in such flows.

scholarly journals A Dynamic Model for the Evaluation of Aircraft Engine Icing Detection and Control-Based Mitigation Strategies

2017 ◽  
Author(s):  
Donald L. Simon ◽  
Aidan W. Rinehart ◽  
Scott M. Jones
Keyword(s):  
Closed Loop ◽  
Open Loop ◽  
Operating Conditions ◽  
Mitigation Strategies ◽  
System Level ◽  
Test Facility ◽  
Closed Loop Control ◽  
Turbofan Engine ◽  
Loop Control ◽  
And Control

Aircraft flying in regions of high ice crystal concentrations are susceptible to the buildup of ice within the compression system of their gas turbine engines. This ice buildup can restrict engine airflow and cause an uncommanded loss of thrust, also known as engine rollback, which poses a potential safety hazard. The aviation community is conducting research to understand this phenomena, and to identify avoidance and mitigation strategies to address the concern. To support this research, a dynamic turbofan engine model has been created to enable the development and evaluation of engine icing detection and control-based mitigation strategies. This model captures the dynamic engine response due to high ice water ingestion and the buildup of ice blockage in the engine’s low pressure compressor. It includes a fuel control system allowing engine closed-loop control effects during engine icing events to be emulated. The model also includes bleed air valve and horsepower extraction actuators that, when modulated, change overall engine operating performance. This system-level model has been developed and compared against test data acquired from an aircraft turbofan engine undergoing engine icing studies in an altitude test facility and also against outputs from the manufacturer’s customer deck. This paper will describe the model and show results of its dynamic response under open-loop and closed-loop control operating scenarios in the presence of ice blockage buildup compared against engine test cell data. Planned follow-on use of the model for the development and evaluation of icing detection and control-based mitigation strategies will also be discussed. The intent is to combine the model and control mitigation logic with an engine icing risk calculation tool capable of predicting the risk of engine icing based on current operating conditions. Upon detection of an operating region of risk for engine icing events, the control mitigation logic will seek to change the engine’s operating point to a region of lower risk through the modulation of available control actuators while maintaining the desired engine thrust output. Follow-on work will assess the feasibility and effectiveness of such control-based mitigation strategies.

Strains in Aluminum Stamp Formed Pans Resulting From Closed-Loop Control of Local Forces

2015 ◽  
Author(s):  
William J. Emblom
Keyword(s):  
Control System ◽  
Closed Loop ◽  
Open Loop ◽  
Smith Predictor ◽  
Forming Limit ◽  
Closed Loop Control ◽  
Blank Holder ◽  
Loop Control ◽  
Closed Loop Control System ◽  
Loop Control System

A stamp forming die, whose flexible blank holder was designed using FEA, was built. A closed-loop control system was used to control local punch forces and wrinkling by controlling both blank holder forces and draw bead penetration. The controllers for the draw beads featured an advanced PID controller with a Smith Predictor and Kalman Filter. A Bang-bang controller was also incorporated into the control system in order prevent control saturation. Fuzzy logic was used to transition from once controller to the other. Once closed-loop was implemented, tests were performed to evaluate the strains in the pans for various forming conditions. These results were compared to open-loop tests and it was found that the strains measured from closed-loop control tests resulted in more uniform strains and that the strains were further from the forming limit curves than strains from tests that were performed under open-loop conditions. Furthermore, it was seen that the strains in the regions were local force were controlled resulted in more uniform strain fields. Hence it was concluded that controlling local punch forces resulted in the strain control of critical regions.

Indirect Strain Control in Aluminum Stamp Formed Pans

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
William J. Emblom
Keyword(s):  
Control System ◽  
Feedback Loop ◽  
Closed Loop ◽  
Open Loop ◽  
Smith Predictor ◽  
Forming Limit ◽  
Closed Loop Control ◽  
Blank Holder ◽  
Loop Control ◽  
Critical Regions

A stamp forming die whose flexible blank holder (BH) was designed using finite element (FE) analysis was built. The tooling also included active draw beads, local wrinkling sensors, and local force transducers. Wrinkling was controlled using a proportional–integral–derivative (PID) feedback loop and blank holder force (BHF). Local forces in the tooling were also controlled using blank holder forces in a PID feedback loop. A third closed-loop control system that could be used to control local punch forces (LPF) near draw beads featured an advanced PID controller with a Smith Predictor and Kalman Filter. A Bang–bang controller was also incorporated into that control system in order to prevent control saturation. Fuzzy logic was used to transition from one controller to the other. Once closed-loop control was implemented, tests were performed in order to evaluate the strains in the pans for various forming conditions. These results were compared to open-loop tests and it was found that the strains' paths for closed-loop control tests resulted in convergence and were further from the forming limit than strains from open-loop control tests. Furthermore, it was seen that the strains in critical regions had more uniform strain fields once closed-loop control of local punch forces was implemented. Hence, it was concluded that controlling local punch forces resulted in the indirect control of strains in critical regions.

Open-loop versus closed-loop control of processor loading

1990 ◽  
Vol 11 (3) ◽  
pp. 201-208
Author(s):  
Frits C. Schoute
Keyword(s):  
Closed Loop ◽  
Open Loop ◽  
Closed Loop Control ◽  
Loop Control

A Control Strategy for Intelligent Stamp Forming Tooling

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
William J. Emblom ◽  
Klaus J. Weinmann
Keyword(s):  
Fuzzy Logic ◽  
Control Systems ◽  
Control Strategy ◽  
Pid Controller ◽  
Closed Loop ◽  
Closed Loop Control ◽  
Linear Quadratic ◽  
Blank Holder ◽  
Loop Control ◽  
Stamp Forming

This paper describes the development and implementation of closed-loop control for oval stamp forming tooling using MATLAB®’s SIMULINK® and the dSPACE®CONTROLDESK®. A traditional PID controller was used for the blank holder pressure and an advanced controller utilizing fuzzy logic combining a linear quadratic gauss controller and a bang–bang controller was used to control draw bead position. The draw beads were used to control local forces near the draw beads. The blank holder pressures were used to control both wrinkling and local forces during forming. It was shown that a complex, advanced controller could be modeled using MATLAB’s SIMULINK and implemented in DSPACE CONTROLDESK. The resulting control systems for blank holder pressures and draw beads were used to control simultaneously local punch forces and wrinkling during the forming operation thereby resulting in a complex control strategy that could be used to improve the robustness of the stamp forming processes.

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