Efficient active chatter mitigation for boring operation by electromagnetic actuator using optimal fractional order PDλ controller
TL;DR: It is observed that a fractional order PDλ controller designed by using combination of pseudo spectral and response optimization techniques is highly efficient in terms of the requirement of low amplitude of the peak force and simplicity of implementation.
About: This article is published in Journal of Materials Processing Technology.The article was published on 2020-02-01. It has received 9 citations till now. The article focuses on the topics: Open-loop controller & Delay differential equation.
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TL;DR: In this paper, a magnetorheological (MR) damper is introduced to increase the stability of the boring process, which significantly increases the chatter free depth of cut on the stability lobe diagrams.
18 citations
TL;DR: This paper improves the optimal chatter control through a more accurate modeling method which considers the cutting tool as a cantilever Euler–Bernoulli beam and the TMD as a two degrees of freedom system including translation vibration and rotation vibration of the mass block.
5 citations
TL;DR: In this paper , the authors systematically review previous studies on the identification of system dynamic characteristics, modeling and prediction of chatter stability, and chatter elimination/suppression methods and devices and conclude that existing problems are summarized, and future research is concluded.
Abstract: Thin−walled parts are widely used in many important fields because of performance and structural lightweight requirements. They are critical parts because they usually carry the core functions of high−end equipment. However, their high−performance machining has been facing severe challenges, among which the dynamics problem is one of the most important obstacles. The machining system is easily subjected to chatter due to the weak rigidity of the thin−walled structure and slender cutting tool, which significantly deteriorates the surface quality and reduces the machining efficiency. Extensive studies aiming at eliminating machining chatter have been carried out in the recent decades. This paper systematically reviews previous studies on the identification of system dynamic characteristics, modeling and prediction of chatter stability, and chatter elimination/suppression methods and devices. Finally, existing problems are summarized, and future research is concluded.
3 citations
TL;DR: In this article, the axial ultrasonic vibration-assisted boring (AUVB) method has been used for aviation deep-hole machining and the results demonstrate that AUVB has obvious advantages in reducing boring force, improving boring accuracy, suppressing vibration and promoting surface quality.
Abstract: Deep-holes are typical parts of aircraft structures, which is difficult to be machined. Boring assisted with ultrasonic vibration-assisted cutting has been proved to greatly enhance machining performance, especially for Ti6Al4V aviation alloy. This paper focuses on the machining extra-large aspect ratio (exceeding 20) of Ti6Al4V aviation deep-hole with the axial ultrasonic vibration-assisted boring (AUVB) method. First, the kinetics of the AUVB process is analyzed and a retrospective of its separation cutting feature is provided. Subsequently, a multi-stepped cantilever beam model of boring bar is established to analyze its static rigidity and dynamic stability. The aperture error is deduced, and then size coefficient is put forward to represent the static rigidity of the boring bar, which is inversely proportional to the diameter. In addition, two different vibration cases, namely modal-coupling vibration and regenerative vibration are considered for dynamic stability analysis. Next, the morphology of bored surface is analyzed, and the geometric height of peaks formed by AUVB and CB are calculated. Phase shift φ= π is suggested for obtaining a better surface in AUVB. Finally, the feasibility of AUVB on the machining of extra-large aspect ratio Ti6Al4V titanium alloy aviation deep-hole is verified through systematic experiments. Results demonstrate that AUVB has obvious advantages in reducing boring force, improving boring accuracy, suppressing vibration and promoting surface quality. Furthermore, the aperture error decreases to 50% and vibration amplitudes decrease to only 20–25%. The overall surface roughness of the deep-hole part stays below Ra=0.8μm with rotational speeds of 60r/min and 80r/min, and the surface residual stress state is transferred from the tensile state to a compressive one. As a result, not only AUVB can provide better boring accuracy and surface finish, but it also can enhance the surface fatigue properties.
1 citations
TL;DR: In this paper , the most important parameters affecting the electric and thermal fields' distribution in coal were investigated in order to identify the effective parameters that achieve the highest temperature increase rate and to reach the highest impact and efficiency of the system with the least amount of consumed energy.
Abstract: In coal mining operations, coalbed methane is one of the potential hazards that must be extracted to prevent an explosion of the accumulated gas and environmental pollution. One of the mechanisms is using microwave irradiation so that the thermal stress caused by microwave heating generates fractures. In this research, we investigated the most important parameters affecting the electric and thermal fields’ distribution in coal in order to identify the effective parameters that achieve the highest temperature increase rate and to reach the highest impact and efficiency of the system with the least amount of consumed energy. In this paper, using Maxwell equations, heat transfer, mass transfer and coupling them by COMSOL, we have simulated the radiation of electromagnetic field and heat in the cavity and coal, and we have also shown the temperature dispersion inside the coal. The parameters studied included the amount of coal moisture (type of coal), operating frequency, input power and heating time, location of the waveguide, the size of the waveguide and the location of the coal, and finally the parameters were re-examined in a secondary standard cavity to separate the parameters related to the size of the environment and the cavity from the independent parameters. The results of this study show that the most effective parameter on the electric and thermal fields’ distribution within coal is the size of the resonance chamber. Additionally, the results show that the moisture of 5%, the highest input power and cutoff frequency close to the operating frequency cause the highest average temperature inside the coal, but many parameters such as operating frequency, waveguide location and coal location should be selected depending on the chamber size.
1 citations
References
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TL;DR: In this article, a 3 degrees of freedom linear magnetic actuator was proposed to increase the stiffness of flexible structures during machining, and the magnetic force was linearized with respect to the input current using magnetic configuration design strategy.
Abstract: Parts and cutting tools with large structural flexibility experience both forced and chatter vibrations during machining, resulting in poor surface finish or damage to the machine. This paper presents the design principles of a novel 3 degrees of freedom linear magnetic actuator which increases the damping and static stiffness of flexible structures during machining. The proposed actuator can deliver 248 N force in two radial (x, y) directions and 34 N×m (torque) in torsional (θ) direction up to 850 Hz. The force and torque reduces to 107 N and 14.5 N×m at 2000 Hz, hence it can actively damp a wide range of structural modes. The magnetic force is linearized with respect to the input current using magnetic configuration design strategy. Loop shaping controllers are designed for active damping of boring bar vibrations. The static and dynamic stiffnesses of the boring bar were considerably increased with the designed actuator, leading to a significant increase in chatter-free material removal rates during cutting tests.
64 citations
01 Aug 2005
TL;DR: In this paper, a numerical stability analysis is performed using the root locus method and it is shown that, along with the structural poles, eigenvalues due to the delay parameter may contribute to instability.
Abstract: The motivation of the work is twofold: (a) understand the physics behind regenerative chatter and the influence of structural damping and (b) demonstrate an active damping technique based on collocated actuator/sensor pairs. A numerical stability analysis is performed using the root locus method and it is shown that, along with the structural poles, eigenvalues due to the delay parameter may contribute to instability. Since experimental demonstration of chatter in real machines is difficult, an alternative way of demonstration via a mechatronic simulator is presented, using the ‘hardware-in-the-loop’ concept. The mathematical model of the regenerative cutting process in turning is simulated in a computer and this is interfaced to a beam, representing the structural dynamics of the machine, via a displacement sensor and force actuator. In this way, a hardware and a software loop are combined. In a second step, an additional control loop is added, consisting of an accelerometer sensor and a collocat...
62 citations
TL;DR: In this paper, an adaptive control system based on a novel design of the boring bar containing an Electrorheological fluid, automatically adjusts the dynamics of the bar according to the information from the monitored sensor signal.
60 citations
TL;DR: In this article, an active system integrated into a spindle unit is proposed to mitigate chatter vibrations in milling. But the authors only consider the dynamics of the machine structure in the controller design and minimizes the influence of cutting forces on tool tip deviations.
55 citations
15 Sep 1994-Jsme International Journal Series C-mechanical Systems Machine Elements and Manufacturing
TL;DR: In this article, an active damping system for chatter suppression is described, which is based on the application of active dampers to a slender boring bar, and it has been confirmed in cutting tests that the active damper system adapts to change and fluctuation of the chatter frequency and suppresses chatter well.
Abstract: The chatter suppression described in this paper is based on the application of active dampers to a slender boring bar. Chatter vibration signals detected by a pickup are fed to a computer. After calculating the chatter frequency and the corresponding phase shift parameter, the computer supplies the amplified signals to piezoelectric actuators with the same phase as that of the vibration velocity of the boring bar. As a result of this, the actuators generate damping forces ; that is, they act as active dampers. It has been confirmed in cutting tests that the active damping system adapts to change and fluctuation of the chatter frequency and suppresses chatter well. Furthermore, it has become clear that there is an optimum position of the active damper for chatter suppression.
55 citations