Chatter Suppression With Multiple Time-Varying Parameters in Turning

1999 ◽  
Author(s):  
Fulun Yang ◽  
Bi Zhang ◽  
Junyi Yu
Keyword(s):  
Rake Angle ◽  
Machining Process ◽  
New Method ◽  
Multiple Time ◽  
Time Varying ◽  
Varying Parameters ◽  
Chatter Suppression ◽  
Time Varying Parameter ◽  
Time Varying Parameters ◽  
Theoretical Analyses

Abstract This paper presents a new method, multiple time-varying parameter (MTVP) turning for chatter suppression. Compared to the single time-varying parameter (STVP) turning, the new method uses both time-varying spindle speed and time-varying rake angle to suppress chatter. The paper provides theoretical analyses on the MTVP turning and experimental results to justify the analytical results. It compares the effects of chatter suppression between the MTVP and STVP turnings, and discusses the possible mechanisms of chatter suppression. The paper then concludes that the MTVP turning method is more effective in chatter suppression than the STVP turning method because of the combined effect of the multiple time-varying parameters. It is demonstrated that the MTVP turning method can suppress chatter by 80%, and can be applied to suppress all kinds of chatter in a machining process.

Adaptive Estimation of Time-Varying Parameters in Linearly Parametrized Systems

2005 ◽  
Vol 128 (3) ◽  
pp. 691-695 ◽  
Author(s):  
Yongliang Zhu ◽  
Prabhakar R. Pagilla
Keyword(s):  
Adaptive Estimation ◽  
Parameter Estimate ◽  
Time Varying ◽  
Time Intervals ◽  
Varying Parameters ◽  
Time Varying Parameter ◽  
Time Varying Parameters ◽  
Parametrized Systems ◽  
Simulation Results ◽  
Estimation Of Time

Adaptive estimation of time-varying parameters in linearly parametrized systems is considered. The estimation time is divided into small intervals; in each interval the time-varying parameter is approximated by a time polynomial with unknown coefficients. A condition for resetting of the parameter estimate at the beginning of each interval is derived; the condition guarantees that the estimate of the time-varying parameter is continuous and also allows for the coefficients of the polynomial to be different in various time intervals. A modified version of the least-squares algorithm is provided to estimate the time-varying parameters. Stability of the proposed algorithm is shown and discussed. Simulation results on an example are given to validate the proposed method.

Adaptive Control of Mechanical Systems With Time-Varying Parameters and Disturbances

2004 ◽  
Vol 126 (3) ◽  
pp. 520-530 ◽  
Author(s):  
Prabhakar R. Pagilla ◽  
Yongliang Zhu
Keyword(s):  
Adaptive Control ◽  
Finite Length ◽  
Mechanical Systems ◽  
Adaptive Controller ◽  
Projection Algorithm ◽  
Time Interval ◽  
Time Varying ◽  
Varying Parameters ◽  
Time Varying Parameter ◽  
Time Varying Parameters

A new adaptive control algorithm for mechanical systems with time-varying parameters and/or time-varying disturbances is proposed and investigated. The proposed method does not assume any structure to the time-varying parameter or disturbance. The method is based on the expansion of the time-varying parameter/disturbance using Taylor’s formula. This facilitates expanding a time-varying function as a finite length polynomial and a bounded residue. The coefficients of the finite-length polynomial are estimated in a small time interval so that they can be assumed to be constant within that interval. A gradient projection algorithm is used to estimate the parameters within each time interval. Stability of the proposed adaptive controller is shown and discussed. A novel experiment is designed using a two-link planar mechanical manipulator to investigate the proposed algorithm experimentally. Results of the proposed adaptive controller are compared with an ideal nonadaptive controller that assumes complete knowledge of the parameters and disturbances. A representative sample of the experimental results is shown and discussed.

Real-Time Identification of Time-Varying ARMAX Systems Based on Recursive Update of Its Parameters

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Saied Reza Seydnejad
Keyword(s):  
Real Time ◽  
Basis Functions ◽  
New Method ◽  
Recursive Least Squares ◽  
Time Varying ◽  
Computationally Efficient ◽  
Algorithm Selection ◽  
Varying Parameters ◽  
Original Algorithm ◽  
Time Varying Parameters

A new method for identification of time-varying ARMAX systems is introduced. This method is based on expansion of time-varying parameters of the ARMAX model onto a set of basis functions. A recursive formulation for updating the coefficients of the basis functions of the time-varying parameters of the system is proposed. Similar to non-real-time basis-function methods, the proposed real-time method has the capability of tracking fast changes in the parameters of a time-varying system much better than the standard Kalman and recursive least-squares (RLS) methods. A computationally efficient version of the algorithm is also presented with a small degradation in tracking properties of the original algorithm. Selection of different types of basis functions makes the new method very flexible for different applications.

scholarly journals Improving Parameter Transferability of GR4J Model under Changing Environments Considering Nonstationarity

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2029
Author(s):  
Ling Zeng ◽  
Lihua Xiong ◽  
Dedi Liu ◽  
Jie Chen ◽  
Jong-Suk Kim
Keyword(s):  
Hydrological Model ◽  
Predictive Ability ◽  
Western China ◽  
Model Parameters ◽  
Time Varying ◽  
Varying Parameters ◽  
Changing Environments ◽  
Time Varying Parameter ◽  
Time Varying Parameters ◽  
Set Up

Hydrological nonstationarity has brought great challenges to the reliable application of conceptual hydrological models with time-invariant parameters. To cope with this, approaches have been proposed to consider time-varying model parameters, which can evolve in accordance with climate and watershed conditions. However, the temporal transferability of the time-varying parameter was rarely investigated. This paper aims to investigate the predictive ability and robustness of a hydrological model with time-varying parameter under changing environments. The conceptual hydrological model GR4J (Génie Rural à 4 paramètres Journalier) with only four parameters was chosen and the sensitive parameters were treated as functions of several external covariates that represent the variation of climate and watershed conditions. The investigation was carried out in Weihe Basin and Tuojiang Basin of Western China in the period from 1981 to 2010. Several sub-periods with different climate and watershed conditions were set up to test the temporal parameter transferability of the original GR4J model and the GR4J model with time-varying parameters. The results showed that the performance of streamflow simulation was improved when applying the time-varying parameters. Furthermore, in a series of split-sample tests, the GR4J model with time-varying parameters outperformed the original GR4J model by improving the model robustness. Further studies focus on more diversified model structures and watersheds conditions are necessary to verify the superiority of applying time-varying parameters.

On the Adaptive Control of Mechanical Systems With Time-Varying Parameters and Disturbances

2002 ◽  
Author(s):  
Prabhakar R. Pagilla ◽  
Yongliang Zhu
Keyword(s):  
Adaptive Control ◽  
Finite Length ◽  
Control Algorithm ◽  
Mechanical Systems ◽  
Time Interval ◽  
Time Varying ◽  
Varying Parameters ◽  
Time Varying Parameter ◽  
Time Varying Parameters ◽  
Adaptive Control Algorithm

In this paper, we propose and investigate a new adaptive control algorithm for mechanical systems with time-varying parameters and/or time-varying disturbances. The proposed method does not assume any structure to the time-varying parameter or disturbance. The idea is based on the expansion of the time-varying parameter/disturbance using the Taylor series expansion; this facilitates expanding a time-varying function as a finite length polynomial and a bounded residue; the coefficients of the finite length polynomial are estimated in a time interval small enough so that they can be assumed to be constant within that interval. A novel experiment is designed using a two-link mechanical manipulator to investigate the proposed algorithm experimentally. Simulation and experimental results validate the proposed new adaptive control algorithm; we discuss these results and also give some future research directions.

scholarly journals THE TECHNIQUE OF DETERMINATION OF THE MODE OF MECHANICAL TREATMENT IN THE CONDITIONS OF UNCERTAINTY OF TECHNOLOGICAL INFORMATION WITH TIME-VARYING PARAMETERS

2021 ◽  
Vol 23 (3) ◽  
pp. 62-68
Author(s):  
A.N. Unyanin ◽  
◽  
P.R. Finageev ◽  
Keyword(s):  
Mathematical Models ◽  
Mutual Influence ◽  
Processing Parameters ◽  
Machining Process ◽  
Model Parameters ◽  
Time Varying ◽  
Varying Parameters ◽  
Technological Information ◽  
Controllable Factors ◽  
Time Varying Parameters

To reduce the error in the appointment of the mode in the conditions of uncertainty of information for the first time developed mathematical models and algorithms that provide for the correction of the model parameters relating the input and output parameters of the process, according to the current information about the output parameters. Developed a plan of varying the controllable factors of the technological process, the methodology and the algorithm used to generate mathematical models of the machining process with time-varying parameters. Models take into account the mutual influence of the tool state parameters and the current processing parameters and their impact on the output parameters and allow you to calculate the output parameters of the process at different times. This makes it possible to create prerequisites for the purpose of machining mode with time-varying parameters in the conditions of uncertainty of technological information.

Chatter Suppression via an Oscillating Cutter

1999 ◽  
Vol 121 (1) ◽  
pp. 54-60 ◽  
Author(s):  
F. Yang ◽  
B. Zhang ◽  
J. Yu
Keyword(s):  
Experimental Studies ◽  
Rake Angle ◽  
Transmission Mechanism ◽  
Machining Process ◽  
Chatter Suppression ◽  
Critical Issues ◽  
The Stability ◽  
Cutting System ◽  
Theoretical Analyses

Chatter is one of the critical issues in a machining process since it deteriorates the surface quality of a workpiece and reduces machining efficiency. A new method is developed to suppress chatter in which an oscillating cutter is used to machine the workpiece through a stepping motor and a transmission mechanism so as to vary tool rake angle continuously and periodically in process. Theoretical analyses are performed on the stability of the cutting system, and verified by the experimental studies. Both theoretical analyses and experimental results indicate that the method can suppress chatter in a turning process effectively. With the application of an oscillating cutter, the amplitude can be reduced by 80 percent in cutting a steel workpiece.

Synchronization of Chaotic Systems with Uncertain Time-Varying Parameters

2015 ◽  
Vol 9 (6) ◽  
pp. 568
Author(s):  
Ahmad Al-Jarrah ◽  
Mohammad Ababneh ◽  
Suleiman Bani Hani ◽  
Khalid Al-Widyan
Keyword(s):  
Chaotic Systems ◽  
Time Varying ◽  
Varying Parameters ◽  
Time Varying Parameters ◽  
Uncertain Time
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