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"Flatness"
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Data preprocessing for flatness measurements of large precision workpieces
Measuring the flatness error of large precision workpieces quickly and accurately is a difficult problem. A new method for preprocessing flatness measurement data based on MSE (mean squared error) is proposed. A mathematical model of a new data preprocessing method was established, and the mathematical formula for model solving was derived in detail. The data were measured by digital level on the plane of the granite base with dimensions of 2340 m×1540 mm. The new method and SmartLevel (basic measurement system of the level computer) were used to calculate and process the data. The flatness errors after diagonal evaluation were 4.07 μm and 3.90 μm, respectively. The relative error of the two was 4.36%, which confirmed the reliability and accuracy of the new method. The data results show that this method can be effectively used for the engineering measurement of the flatness of large precision workpieces.
Journal Article
Theoretical and numerical research on effect of tension mechanisms in strip flatness electromagnetic control rolling mills
To achieve stable rolling, the influence of a tension mechanism of a large diameter ratio roll system on the rolling process of a strip flatness electromagnetic control rolling mill is studied. Through the analysis of the rolling deformation zone, the deformation zone composition form of a large diameter ratio roll system and a calculation formula of neutral angle under tension are proposed. To analyze the effect of front and post tensions on the rolling characteristic and the strip flatness control characteristic, a three-dimensional rolling finite element (FE) model of a large diameter ratio roll system with the function of roll profile electromagnetic control is established by FE software and verified by a strip flatness electromagnetic control rolling mill. Based on the model, the strip thickness characteristic, metal transverse flow, strip flatness state, and adjustment range of the loaded roll gap are analyzed for different front and post tensions setting values. The results show that changing the front or post tension setting values can improve the single-pass reduction rate of a large diameter ratio roll system and have little effect on the flatness control ability of the strip flatness electromagnetic control rolling mill.
Journal Article
Machine-learning for automatic prediction of flatness deviation considering the wear of the face mill teeth
The acceptance of the machined surfaces not only depends on roughness parameters but also in the flatness deviation (Δfl). Hence, before reaching the threshold of flatness deviation caused by the wear of the face mill, the tool inserts need to be changed to avoid the expected product rejection. As current CNC machines have the facility to track, in real-time, the main drive power, the present study utilizes this facility to predict the flatness deviation—with proper consideration to the amount of wear of cutting tool insert’s edge. The prediction of deviation from flatness is evaluated as a regression and a classification problem, while different machine-learning techniques like Multilayer Perceptrons, Radial Basis Functions Networks, Decision Trees and Random Forest ensembles have been examined. Finally, Random Forest ensembles combined with Synthetic Minority Over-sampling Technique (SMOTE) balancing technique showed the highest performance when the flatness levels are discretized taking into account industrial requirements. The SMOTE balancing technique resulted in a very useful strategy to avoid the strong limitations that small experiment datasets produce in the accuracy of machine-learning models.
Journal Article
Active Inference and Functional Parametrisation: Differential Flatness and Smooth Random Realisation
This paper is a first attempt to marry constructive nonlinear control theory techniques with active inference. Specifically, we are interested in the relationship between differential flatness and the design of generative models for use in control settings. We place specific emphasis on the pathwise properties of differentially flat systems that inherit from their definition in terms of successive temporal derivatives and relate this to the use of generalised coordinates of motion in formulating continuous-time generative models in active inference. To illustrate the basic concepts, we appeal to the example of oculomotor control.
Journal Article
Differential-flatness-based finite-time anti-swing control of underactuated crane systems
In this paper, we consider the finite-time regulation controller for the underactuated crane systems in 2-dimensional (2D) space with both constant cable length and varying cable length. The differential-flatness-based approach is applied to the development of finite-time control laws. The elegantly designed controller can simultaneously suppress the payload swing and regulate the trolley to the desired destination within a finite time for the 2D bridge crane system in the case of constant cable length. Considering cable length variation, the flatness-based tracking controller is presented meticulously in a separately two-step program. Specifically, the finite-time technique is first used to achieve the simultaneous motion regulation and payload swing suppression and elimination within a finite time. Then, we propose a Lyapunov-based tracking control method, under which the cable can track a predefined trajectory. Simulation results are provided to demonstrate both the efficiency and the robustness against external disturbances of the addressed control algorithms.
Journal Article
Antiswing control of offshore cranes under ship rolling disturbances: an active disturbance rejection control based approach
The offshore crane is an indispensable transportation tool on the sea, which is one of the core technical equipment in various scenes of marine engineering. In recent years, the demand for offshore cranes has increased, so it is necessary to improve its safety performance and intelligent operation as soon as possible. The offshore crane is not only a complex underactuated system, but also faces the special application environment on the sea, which makes the control task more difficult. In order to improve the anti-swing control performance of offshore cranes under ship rolling disturbance, an active disturbance rejection control method is designed by using differential flatness technology. This method can efficiently realize the control under the influence of ship rolling motion. Specifically, we prove the differential flatness of the system, solve the problem of state couplings, and construct effective flat outputs. Then, the control task of the offshore crane is further transformed into the control problem of flat outputs. Based on this, using the constructed flat outputs, an active disturbance rejection controller is designed. Finally, sufficient simulation tests and experimental tests are carried out to comprehensively verify the control performance of the proposed method.
Journal Article
Design of Continuous Class-F Mode Power Amplifier with High Gain Flatness
In this letter, a novel RF power amplifier (PA) with high gain flatness and high efficiency operating in continuous Class-F mode is introduced. Since most continuous Class-F PAs can’t meet the requirement of high gain flatness, a new structure which can achieve high gain flatness is presented. A 1.7-2.5GHz PA is designed, which uses CGH40010F GaN device. Simulation results show that the drain efficiency (DE) of the continuous Class-F PA is between 69% and 79%, output power is more than 41dBm across the whole bandwidth. Gain is between 11dB and 11.8dB, and gain flatness is 0.8dB.
Journal Article
Simulation and control of high-order flatness defect in rolling wide titanium strip with 20-high mill
In the wide titanium strip cold rolling process, the high-order flatness defect is one of the most difficult problems to be solved. Based on the finite element method, considering the anisotropic mechanical characteristics of titanium, an implicit integration calculation model of rolls-strip for 20-high mill was developed, which can simulate the dynamic rolling process. The model was used to analyze the adjustment characteristics of high-order flatness on the 20-high mill. The simulation revealed as the increasing of the 1# and 7# AS-U or 2# and 6# AS-U reduction adjustment, the high-order flatness defect was more aggravated; and as the increase of 3# and 5# AS-U or 4# AS-U reduction adjustment, the high-order flatness defect was alleviated to some extent. In addition, the high-order flatness cannot be effectively adjusted by roll shifting. Finally, the industrial test showed that increasing 4# AS-U reduction adjustment can effectively relieve the high-order flatness defect. After 6 months of strategy test, the high-order flatness defect rate decreased by 33.47%.
Journal Article
Research on the Detection Method of Tunnel Surface Flatness Based on Point Cloud Data
The curved surface of the tunnel is symmetrical. The curved surface of the tunnel can be roughly divided into the left and right arch walls along the direction of the central axis of the tunnel. The symmetry of the tunnel needs to be analyzed when the flatness inspection of the tunnel engineering is carried out. The flatness of the initial support of the tunnel project is an important indicator of the quality inspection and acceptance of the tunnel project. The three-dimensional laser scanner (3DLS) can be used to detect its rapidity effectively. According to the points obtained by the scanner, the surface fitting method based on B-spline interpolation and the SG bar initial support value processing method are used to optimize the tunnel surface to obtain the initial degree calculation reference. Based on the method, a calculation system for the initial flatness of the tunnel based on 3DLS technology is established. At the same time, the calculation method of the overall field of view distance and the development of small blocks is proposed. Through its application and comparison with traditional methods, the analysis shows that the three-dimensional laser scanning technology is feasible in the detection of the initial branch of the tunnel, and achieves a high degree of accuracy requirements.
Journal Article