Multidimensional Time-Frequency Control of Micro-Milling Instability

2013 ◽  
pp. 177-198
Keyword(s):  
Frequency Control ◽  
Micro Milling ◽  
Time Frequency

Simultaneous Time-Frequency Control of Multi-Dimensional Micro-Milling Instability

2012 ◽  
Author(s):  
Meng-Kun Liu ◽  
Eric B. Halfmann ◽  
C. Steve Suh
Keyword(s):  
Frequency Response ◽  
High Speed ◽  
Frequency Control ◽  
External Perturbation ◽  
Micro Milling ◽  
Time Frequency ◽  
System A ◽  
Control Concept ◽  
The Time Domain ◽  
Tool Damage

A novel control concept is presented for the online control of a high-speed micro-milling model system in the time and frequency domains concurrently. Micro-milling response at high-speed is highly sensitive to machining condition and external perturbation, easily deteriorating from bifurcation to chaos. When losing stability, milling time response is no longer periodic and the frequency response becomes broadband, rendering aberrational tool chatter and probable tool damage. The controller effectively mitigates the nonlinear vibration of the tool in the time domain and at the same time confines the frequency response from expanding and becoming chaotically broadband. The simultaneous time-frequency control is achieved through manipulating wavelet coefficients, thus not limited by the increasing bandwidth of the chaotic system — a fundamental restraint that deprives contemporary controller designs of validity and effectiveness. The feedforward feature of the control concept prevents errors from re-entering the control loop and inadvertently perturbing the sensitive micro-milling system. Because neither closed-form nor linearization is required, the innate, genuine features of the micro-milling response are faithfully retained.

Multi-dimensional time-frequency control of micro-milling instability

2012 ◽  
Vol 20 (5) ◽  
pp. 643-660 ◽  
Author(s):  
Meng-Kun Liu ◽  
Eric B Halfmann ◽  
C Steve Suh
Keyword(s):  
Frequency Control ◽  
Micro Milling ◽  
Time Frequency

The Optimization of Time-Frequency Control: Using Non-Autonomous Time-Delay Feedback Systems as Example

2016 ◽  
Author(s):  
Chi-Wei Kuo ◽  
C. Steve Suh
Keyword(s):  
Time Delay ◽  
Dynamic Instability ◽  
Frequency Control ◽  
Frequency Resolution ◽  
Control Technique ◽  
Time Step ◽  
Time Frequency ◽  
Control Scheme ◽  
Fxlms Algorithm ◽  
On Line

A novel time-frequency nonlinear scheme demonstrated to be feasible for the control of dynamic instability including bifurcation, non-autonomous time-delay feedback oscillators, and route-to-chaos in many nonlinear systems is applied to the control of a time-delayed system. The control scheme features wavelet adaptive filters for simultaneous time-frequency resolution. Specifically Discrete Wavelet transform (DWT) is used to address the nonstationary nature of a chaotic system. The concept of active noise control is also adopted. The scheme applied the filter-x least mean square (FXLMS) algorithm which promotes convergence speed and increases performance. In the time-frequency control scheme, the FXLMS algorithm is modified by adding an adaptive filter to identify the system in real-time in order to construct a wavelet-based time-frequency controller capable of parallel on-line modeling. The scheme of such a construct, which possesses joint time-frequency resolution and embodies on-line FXLMS, is able to control non-autonomous, nonstationary system responses. Although the controller design is shown to successfully moderate the dynamic instability of the time-delay feedback oscillator and unconditionally warrant a limit cycle, parameters are required to be optimized. In this paper, the setting of the control parameters such as control time step, sampling rate, wavelet filter vector, and step size are studied and optimized to control a time-delay feedback oscillators of a nonautonomous type. The time-delayed oscillators have been applied in a broad set of fields including sensor design, manufacturing, and machine dynamics, but they can be easily perturbed to exhibit complex dynamical responses even with a small perturbation from the time-delay feedback. These responses for the system have a very negative impact on the stability, and thus output quality. Through employingfrequency-time control technique, the time responses of the time-delay feedback system to external disturbances are properly mitigated and the frequency responses are also suppressed, thus rendering the controlled responses quasi-periodic.

Nonlinear Time-Frequency Control of Permanent Magnet Synchronous Motors

2016 ◽  
Author(s):  
Xin Wang ◽  
C. Steve Suh
Keyword(s):  
Permanent Magnet ◽  
Frequency Control ◽  
Permanent Magnet Synchronous Motor ◽  
Synchronous Motor ◽  
Discrete Wavelet ◽  
Permanent Magnet Synchronous Motors ◽  
Synchronous Motors ◽  
Time Frequency ◽  
Essential Components ◽  
Wide Range

Permanent magnet synchronous motors are essential components in a wide range of applications in which their unique benefits are explored. However, in order for a permanent magnet synchronous motor to achieve satisfactory performance, particular control frameworks are essential. After all, permanent magnet synchronous motor is an AC machine, which is characterized by its complex structure and strongly coupled system states. Therefore, in order for it to achieve satisfactory dynamic performance, advanced control techniques are the only solution. This paper presents a precise speed control of permanent magnet synchronous motors using the nonlinear time-frequency control concept. The novel aspect of this nonlinear time-frequency control, which is an integration of discrete wavelet transformation and adaptive control, is its ability in analyzing the fundamental temporal and spectral qualities inherent of a permanent magnet synchronous motor and exerting control signals accordingly. Simulation results verifies that the proposed nonlinear time-frequency control scheme is feasible for alleviating the nonlinear behavior of the permanent magnet synchronous motor which hampers the tracking of speed with desired precision.

A Novel Nonlinear Time-Frequency Control Strategy for Underactuated Mechanical System

2019 ◽  
Author(s):  
Zilong Zhang ◽  
C. Steve Suh
Keyword(s):  
Finite Impulse Response ◽  
Frequency Control ◽  
Equations Of Motion ◽  
Control Technique ◽  
System Response ◽  
Primary Control ◽  
Least Mean Square ◽  
Nonlinear Controller ◽  
Control Approach ◽  
Time Frequency

Abstract In this paper, a novel nonlinear time-frequency control methodology is presented to address the stabilization of an underactuated surface vessel (USV). The wavelet-domain based time-frequency control technique augmented by the adaptive filters and filtered-x least-mean-square algorithm is employed as the primary control framework. A nonlinear three degrees-of-freedom planar dynamic model for the USV with only two available control inputs is considered in the study. The equations of motion are derived based on the Newton’s Second law of motion. By using wavelet transform and filter banks, the proposed nonlinear control algorithm requires no mathematical simplification or linearization of the physical system, thus retaining all the true nonlinear dynamics of the USV model. The presented nonlinear controller consists of two adaptive finite impulse response (FIR) filers that operate on wavelet coefficients: the first one is used to model the dynamic system on-line and provide a priori information in real-time while the second one serves as a feed-forward controller and rejects the uncontrollable input signal based on the first FIR filter. The proposed nonlinear time-frequency controller properly mitigates dynamical deterioration in both the time and frequency domains and regulates the system response with the desired stability. Numerical simulations are performed in MATLAB Simulink and the results validate the effectiveness of the proposed nonlinear time-frequency control approach.

Active Magnetic Bearings for High Speed Spindle Design With Nonlinear Time-Frequency Control

2015 ◽  
Author(s):  
Mengke Liu ◽  
C. Steve Suh
Keyword(s):  
High Speed ◽  
Frequency Control ◽  
Air Gap ◽  
Magnetic Bearings ◽  
Lms Algorithm ◽  
Significant Implication ◽  
Active Magnetic Bearings ◽  
Gyroscopic Effect ◽  
Electromagnetic Actuators ◽  
Time Frequency

A novel concept applicable to the control of spindles at high speed is developed by using active magnetic bearings (AMBs) that are non-contact and of low vibration. Though former studies are abundant and demonstrating promising potentials, however, two major issues hamper the broader application of AMBs. The first is the disregard for the gyroscopic effect and geometry coupling that influence the magnitude as well as distribution of the electromagnetic force in AMBs. Not considering the two has a significant implication for the proper control of AMBs. This paper considers the gyroscopic effect and explores the geometry coupling of the electromagnetic actuators to the formulation of a comprehensive nonlinear AMB-rotor model. The model provides the basis for the creation of a novel time-frequency control algorithm whose derivation requires no linearization or mathematical simplification of any kind, thus allowing the model system to retain its true fundamental characteristics. Unlike proportional-integral-derivative (PID) controllers that are dominant in most if not all AMB configurations, the controller developed for the research is inspired by the wavelet-based nonlinear time-frequency control methodology that incorporates the basic notions of online system identification and adaptive control. Due to the fact that dynamic instability is characterized by time-varying frequency and non-stationary spectrum, the control of AMBs needs be executed in the time and frequency-domain concurrently to ensure stability and performance at high speed. Wavelet filter banks and filtered-x least-mean-square (LMS) algorithm are two of the major salient physical features of the controller design, with the former providing concurrent temporal and spectral resolutions needed for identifying the nonlinear state of motion and the latter ensuring the dynamic stability of the AMB-rotor system at extremely high speed. It is shown that the vibration of the rotor is unconditionally controlled by maintaining a mandatory 0.55 mm air gap at 187,500 rpm subject to a tight spatial constraint (tolerance) of the order of 0.1375mm, which is the 25% of the air gap.

Nonlinear Time-Frequency Control of Electromagnetic Solenoid Valve

2016 ◽  
Author(s):  
Jacob D. Southern
Keyword(s):  
Response Time ◽  
Frequency Control ◽  
Solenoid Valve ◽  
Rapid Response ◽  
Time Frequency ◽  
Signal Transformation ◽  
Automotive Transmission ◽  
Frequency Controller ◽  
Port Location ◽  
The Way

The main objective of this study is to prove that an electromagnetic solenoid valve can be controlled accurately and have a rapid response time while not having to linearize the system. An electromagnetic solenoid valve can neither be slow nor have large amounts of error due to the small distances between the pressure ports and the accuracy of the system they are used to control. The valve modeled for this study was an automotive transmission solenoid valve. The solenoid valve has three ports: supply, exhaust, and controlled pressure. For simplification, this model only considers moving the spool to a specific port location, which will be user specified. The controller used for this system was a nonlinear time-frequency controller that uses Daubechies-3 wavelets for signal transformation. Once, the controller was optimized it was able to control the system accurately and with a rapid response time. The system is able to reach the desired input and maintain zero error in two tenths of a second with out greatly over shooting the desired input. Overall, this system is physically possible to control the way the simulation predicts because all of the parameters used in the simulation are from a real solenoid valve.

Simultaneous Time-Frequency Control of Active Magnetic Bearing

2013 ◽  
Author(s):  
Meng-Kun Liu ◽  
C. Steve Suh
Keyword(s):  
Control Theory ◽  
High Speed ◽  
Frequency Control ◽  
Dynamic Stiffness ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Time Frequency ◽  
Highly Nonlinear ◽  
Nonlinear Character ◽  
On Line

Active magnetic bearings enable greater spindle dynamic stiffness through higher attainable bearing surface speeds. However, the active magnetic bearing system is highly nonlinear due to the interaction between electromagnetic field and rotor dynamics. Its nonlinear character becomes prominent when rotating in high speed. The operation undergoes route-to-chaos and is vulnerable to external excitation, which eventually leads to detrimental failure. A novel simultaneous time-frequency control theory is developed for controlling the active magnetic bearing at high speed. The control theory is able to tolerate the uncertainties in the system due to on-line identification and the deterioration in both time and frequency domain can be restrained.

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