Robustness of Adaptive Rotor Vibration Control to Structured Uncertainty

1997 ◽  
Vol 119 (2) ◽  
pp. 243-250 ◽  
Author(s):  
C. R. Knospe ◽  
S. M. Tamer ◽  
S. J. Fedigan
Keyword(s):  
Robustness Analysis ◽  
Stability Margin ◽  
Singular Values ◽  
Open Loop ◽  
Worst Case ◽  
Loop Control ◽  
Structured Uncertainty ◽  
Analysis Of Stability ◽  
And Performance ◽  
Performance Robustness

Recent experimental results have demonstrated the effectiveness of adaptive open-loop control algorithms for the suppression of unbalance response on rotors supported in active magnetic hearings. Herein, tools for the analysis of stability and performance robustness of this algorithm with respect to structured uncertainty are derived. The stability and performance robustness analysis problems are shown to be readily solved using a novel application of structured singular values. An example problem is presented which demonstrate the efficacy of this approach in obtaining tight bounds on stability margin and worst case performance.

Robustness of Adaptive Unbalance Control of Rotors with Magnetic Bearings

1996 ◽  
Vol 2 (1) ◽  
pp. 33-52 ◽  
Author(s):  
C.R. Knospe ◽  
R.W. Hope ◽  
S.M. Tamer ◽  
S.J. Fedigan
Keyword(s):  
Control Algorithm ◽  
Open Loop ◽  
Experimental Results ◽  
Magnetic Bearings ◽  
Worst Case ◽  
Actual Performance ◽  
Loop Control ◽  
And Performance ◽  
The Stability ◽  
Performance Robustness

Rotor unbalance in the primary cause of unacceptable vibration in rotating machinery. Over the last decade, researchers have explored different methods of taking advantage of the active nature of magnetic bearings to attenuate unbalance response including both feedback and adaptive open loop methods. An important issue in the application of this technology to industrial machines is the robustness of the unbalance control algorithm. The stability and performance robustness of a promising adaptive open loop control algorithm is examined. Expressions are derived for a number of unstructured uncertainties. Experimental results are then presented, which evaluate the algorithm's robustness with respect to three variations: gain schedule errors, random additive errors, and feedback loop gain. The robustness exhibited in these tests was quite good and, along with the excellent vibration attenuation obtained, recommend the algorithm for further testing and industrial application. The experimental results indicate that the theoretical robustness expressions do provide an upper bound on actual performance, however this bound is not tight. Although the conservatism in the results is partly due to the variations considered and the worst-case nature of the performance robustness guarantees, the results also indicate that further research is needed on unstructured performance robustness for this method of rotor vibration control.

scholarly journals Design and performance assessment of an underactuated hand for industrial applications

2011 ◽  
Vol 2 (1) ◽  
pp. 9-15 ◽  
Author(s):  
C. Meijneke ◽  
G. A. Kragten ◽  
M. Wisse
Keyword(s):  
Degrees Of Freedom ◽  
International Workshop ◽  
Input Voltage ◽  
Industrial Applications ◽  
Open Loop ◽  
Robotic Hand ◽  
Loop Control ◽  
Six Degrees Of Freedom ◽  
And Performance ◽  
Underactuated Robot

Abstract. The Delft Hand 2 (DH-2) is an underactuated robot hand meant for industrial applications, having six degrees of freedom (DoF), one actuator (DoA) and no sensors. It was designed to provide a cheap and robust hand to grasp a large range of objects without damaging them. The goal of this paper is to assess the design and performance of the DH-2, demonstrating how the design was optimized for its intended application area and how the hand was simplified to make it commercially attractive. Performance tests show that the DH-2 has a payload of 2 kg for an object range of 60 to 120 mm, it can close or open within 0.5 s, and it only uses open-loop control by means of the input voltage of the motor. The results demonstrate that the industrial need of a simple, cheap and effective robotic hand can be achieved with the principle of underactuation and the use of conventional components. This paper was presented at the IFToMM/ASME International Workshop on Underactuated Grasping (UG2010), 19 August 2010, Montréal, Canada.

scholarly journals Practical Design Considerations for Performance and Robustness in the Face of Uncertain Flexible Dynamics in Space Manipulators

2021 ◽  
Vol 8 ◽  
Author(s):  
Connor Holmes
Keyword(s):  
Control Strategies ◽  
Low Frequency ◽  
Open Loop ◽  
Unmodeled Dynamics ◽  
Loop Control ◽  
Stability Margins ◽  
Flexible Mode ◽  
Space Manipulators ◽  
The Face ◽  
And Performance

Low frequency dynamics introduced by structural flexibility can result in considerable performance degradation and even instability in on-orbit, robotic manipulators. Although there is a wealth of literature that addresses this problem, the author has found that many advanced solutions are often precluded by practical considerations. On the other hand, classical, robust control methods are tractable for these systems if the design problem is properly constrained. This paper investigates a pragmatic engineering approach that evaluates the system’s stability margins in the face of uncertain, flexible perturbation dynamics with frequencies that lie close to or within the bandwidth of the nominal closed-loop system. The robustness of classical control strategies is studied in the context of both collocated (joint rate) and non-collocated (force/torque and vision-based) feedback. It is shown that robust stability and performance depend on the open-loop control bandwidth of the nominal control law (as designed for a simplified, rigid plant). Namely, the designed bandwidth must be constrained to be lower than the minimum flexible mode frequency of the unmodeled dynamics by a given factor. This strategy gives credence to popular heuristic methods commonly used to reduce the effect of unmodeled dynamics in complex manipulator systems.

Sensitivity and Stability Analysis of Mu-Synthesis AMB Flexible Rotor

2010 ◽  
Vol 164 ◽  
pp. 313-318 ◽  
Author(s):  
Arkadiusz Mystkowski
Keyword(s):  
Weighting Function ◽  
Stability Margin ◽  
Experimental Tests ◽  
Element Model ◽  
Open Loop ◽  
Mode Analysis ◽  
Flexible Rotor ◽  
Displacement Sensors ◽  
Mu Synthesis ◽  
And Performance

The paper presents the sensitivity and stability margin analyses of the flexible rotor supported by active magnetic bearings (AMBs) with the robust optimal vibrations control. The modal representation of the rotor finite element model (FEM) is investigated. Then, the open-loop system of the AMBs flexible rotor is established and critical speed analysis due to variation of bearing stiffness is performed. For the open-loop setup, the non-collocation effect of displacement sensors and magnetic actuators due to control stability problem is considered. The frequency mode analysis of the collocation and non-collocation system is presented. Next, the -synthesis control of 4-DOF AMBs rotor is investigated. The design process of -controllers, which cover uncertainty design and performance shape by chosen weighting function is shortly described. Then, the sensitivity function is calculated and used to evaluate the AMBs rotor stability margin for the -control and the PID control. The performance of the -controller are verified in experimental tests.

Stability and Performance Robustness Analysis of Repetitive Control Systems Using Structured Singular Values

1996 ◽  
Vol 118 (3) ◽  
pp. 593-597 ◽  
Author(s):  
Levent Gu¨venc¸
Keyword(s):  
Time Delay ◽  
Control Systems ◽  
Repetitive Control ◽  
Singular Values ◽  
Parametric Modeling ◽  
Singular Value ◽  
Plant Performance ◽  
Structured Singular Value ◽  
And Performance ◽  
Performance Robustness

The structured singular value method is applied to continuous-time SISO repetitive control systems in order to determine their stability and performance robustness in the presence of structured parametric modeling error in the plant. Performance measures for repetitive control systems are introduced and the robust performance analysis using structured singular values is modified, taking the alternating magnitude behaviour of the sensitivity function of a repetitive control system into account. The analysis procedure is simplified considerably in the case of large time delay by noting that the upper and lower envelopes of the structured singular value plots are obtained from corresponding finite dimensional systems without any time delay. The analysis procedures developed are applied to an example on repetitive control of an electrohydraulic material testing machine, available in the literature, to demonstrate their usefulness.

Synthesis of Robust Gain Matrices for Adaptive Rotor Vibration Control

1997 ◽  
Vol 119 (2) ◽  
pp. 298-300 ◽  
Author(s):  
C. R. Knospe ◽  
S. M. Tamer ◽  
S. J. Fedigan
Keyword(s):  
Steady State ◽  
Control Strategy ◽  
Synthesis Method ◽  
Open Loop ◽  
Active Magnetic Bearings ◽  
Open Loop Control ◽  
Rotor Vibration ◽  
Loop Control ◽  
Structured Uncertainty ◽  
Steady State Performance

Experimental results have recently demonstrated that an adaptive open-loop control strategy can be highly effective in the suppression of the unbalance induced vibration of rotors supported in active magnetic bearings. A synthesis method is presented for determining the adaptive law’s gain matrix such that the adaptation’s stability and steady-state performance are robust with respect to structured uncertainty.

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