Figure 1 - uploaded by Luis Miguel Castellanos Molina
Content may be subject to copyright.
Source publication
This paper presents an active magnetic levitation application that exploits the measurement of coil current and flux density to determine the displacement of the mover. To this end, the nonlinear behavior of the plant and the physical sensing principle are modeled with a finite element approach at different air gap lengths and coil currents. A line...
Contexts in source publication
Context 1
... magnetic levitation demonstrator consists of an electromagnet fixed to a frame and a levitated spherical body (mover), as illustrated in Figure 1. The electromagnet is an E-shaped core made of laminated soft iron with a coil wound on its central limb. ...
Context 2
... latter quantity is determined using an analog sensor installed on one of the side limbs of the electromagnet. Its role is to measure the flux density component B s which is orthogonal to the cross section of the sensing element (see Figure 1). The relation between λ, the current i and the vertical displacement q can be known either experimentally or from simulation. ...
Context 3
... 9 shows both, the estimates and the sensor measurements when a reference step change is applied. Similarly, Figure 10 shows a quasi-static estimation behaviour around the nominal air gap. The position estimates match the sensor measurements with enough precision. ...
Context 4
... slight but acceptable degradation of the position estimate is advisable when the sphere moves downwards and beyond the nominal operating point. Figure 11 shows the open loop steady state behavior of the measurements from both sensors and the resulting displacement estimates. The data is obtained in a ten-second sampling window by fixing manually the mover at the nominal air gap while keeping the bias constant (i.e., the steady state condition at the operating point with the control voltage u set to u 0 ). ...
Similar publications
Currently, there are no formalized methods for tuning non-integer order controllers. This is due to the fact that implementing these systems requires using an approximation of the non-integer order terms. The Oustaloup approximation method of the sα fractional derivative is intuitive and widely adopted in the design of fractional-order PIλD control...
Citations
... Magnetic levitation technology has garnered significant interest in various applications, including chip manufacturing [1][2][3][4], microscopic imaging [5][6][7][8], and force control [9][10][11][12]. Its advantages of being friction-less [13], non-polluting [14], and having high precision capabilities [15] make it highly desirable. ...
Precision machining fields often require worktables with different stroke sizes. To address the need for scalability and facilitate manufacturing, this study proposes a novel infinite expansion magnetically levitated planar motor (MLPM) based on PCB stator coils. Different from existing magnetic levitation systems that use PCB coils, the design presented in this paper utilizes smaller coil units, with each coil being independent of one another. The coils are structured in a spiral pattern on a 16-layer PCB, comprising 15 layers of coils, while the last layer is dedicated to wiring and other circuits. Magnetic field modeling is conducted for both the stator coil and the 2D Halbach array structure employed in the system. A simple table lookup method is employed to accurately account for the prevalent end effects observed during system motion. Additionally, the decoupling effect of magnetic force and torque is evaluated by solving for the current vector at different points along a specific trajectory. To verify the accuracy of the proposed system’s modeling, a prototype is developed and tested. Experimental results demonstrate that compared to traditional harmonic model methods, the proposed approach improves the calculation accuracy of magnetic force by 50.31% and torque by 70.65%. This study presents a new MLPM system with vast potential applications in precision manufacturing and robotics. The innovative design and improved performance characteristics make it a promising technology for enhancing the capabilities of worktables in precision machining fields.
... Feedback control is achieved through a novel approach based on inductive ux sensing. Flux measurement using sensing coils has certain advantages compared with other methods, such as those based on Hall sensors [13,21], as it provides direct measurements of the mean ux through the pole face and does not require the installation of sensors that take up space within the air gap. A main challenge for the control implementation is that the sensor signal is proportional to the rate of change of ux and therefore must be supplemented with position/current information to achieve stable control. ...
To reduce power consumption of active magnetic bearings (AMBs), permanent magnets (PMs) may be employed to generate a bias flux through the magnetic circuits connecting the actuators with the rotor. In this way, control algorithms based on zero-current operating points and linearized models may be used. This paper describes a new modular design of PM-biased AMB actuator involving a balanced-reluctance topology where the bias flux is set by an auxiliary air gap within the magnetic circuit. A theoretical model and design methodology for achieving a specified range of actuation forces are also defined. Each actuator unit within an AMB suspension system may by positioned freely and operated independently because, unlike many previous PM-biased designs, there is no flux linkage between actuators. To improve the robustness of the actuator control to uncertainty in material properties and air gap sizes, a feedback control scheme is proposed based on inductive sensing of the mean flux density at the actuator pole faces. Testing of the actuator with a current-cancelling flux-based control scheme shows that stable suspension with very low power consumption can be achieved over a range of operating conditions involving both static loading and unbalance excitation.
... Compressors, turbomolecular pumps, blood pumps, blowers, spindles, generators, and other high-speed rotating machinery are relevant applications that exploit AMBs [11]. Recently, the research on AMBs has been mainly focused on the study of new actuator geometries and materials [10,13,15], development of advanced sensing and sensorless strategies [5,6,9,32,33], definition of more effective control strategies [4,23,26,29], integration of the levitation and motoring in the so-called bearingless configurations [12,19,31], and reduction of cost, weight and size [3,22,36]. ...
An Active Magnetic Bearing (AMB) is a mechatronic system that supports a rotating shaft by means of magnetic levitation. Cone-shaped Active Magnetic Bearings (AMB) can control the rotor motion in the axial and radial directions simultaneously with two bearings in a cone-shaped magnetic core. Although this configuration eliminates a dedicated axial actuator, it complicates the control due to the coupling of the axial and radial actions. Cone-shaped AMBs are nonlinear and unstable in open-loop. However, obtaining a linear plant model is usually preferred to facilitate the control design, as it can exploit classical control theory tools. Nevertheless, the control performance can deteriorate when the plant model is affected by uncertainty. In this context, this paper presents the identification of a linear and multi-variable cone-shaped AMB system using grey-box modeling. Firstly, the plant linear and nonlinear models are presented. Since the cone-shaped AMB has an unstable open-loop nature, a Linear Quadratic Regulator (LQR) is used to stabilize the plant. An experimental campaign is performed to obtain the plant response while applying persistent disturbance currents on each electromagnet. These measurements are then used to carry out the grey-box identification procedure. It is demonstrated that the identified model yields an experimental match improvement up to 10% when compared to the nominal model. This estimated model can be exploited in model-based control approaches to improve system performance.
... Many attempts have been made to control the MagLev system. For instance, some studies have verified the effectiveness of the classical PID control in levitating an object [14][15][16]. A subsequent study has shown that the sliding-mode control outperforms the classical PID control [17]. ...
... The proposed control law aims to enable the system output d to track the ideal output x re f under a semi-active approach. This means that the control is only activated in one direction, opposite to gravitational force, introducing a challenge control design, in contrast with, for instance, [14,18,23,[30][31][32], where the active approach is employed. Moreover, the maximum voltage is stated at 5 V; however, in the literature, its maximum is usually 12 V [19]. ...
This paper describes how to construct a low-cost magnetic levitation system (MagLev). The MagLev has been intensively used in engineering education, allowing instructors and students to learn through hands-on experiences of essential concepts, such as electronics, electromagnetism, and control systems. Built from scratch, the MagLev depends only on simple, low-cost components readily available on the market. In addition to showing how to construct the MagLev, this paper presents a semi-active control strategy that seems novel when applied to the MagLev. Experiments performed in the laboratory provide comparisons of the proposed control scheme with the classical PID control. The corresponding real-time experiments illustrate both the effectiveness of the approach and the potential of the MagLev for education.
... In this equation, i 0 is the current of electromagnet coil at equilibrium position, while z 0 is the suspension gap at equilibrium position. The linearization is accomplished near the equilibrium point, and the linearization model is obtained [5]. ...
The maglev train is a whole new method of transportation without wheels, consisting of 20 groups of symmetry suspension units. The magnetic levitation system plays a major role in suspending the maglev train stably and following the track quickly with the desired gap. However, vertical track irregularity in the maglev train line has a dreadful effect on the tracking performance of the magnetic levitation system. The investigations carried out by our team have revealed that the fluctuation of the suspension gap becomes more and more serious with increases in running speed. In this paper, a mathematical model with consideration of vertical track irregularity is established. In order to overcome and suppress the fluctuation of the suspension gap, we propose a new strategy which includes installing an accelerometer on the electromagnet to address this problem. This strategy has already been successfully implemented and applied to the suspension controller for a magnetic levitation system in the Changsha maglev express. Real operation data indicates the tracking performance of the magnetic levitation system was obviously improved.
... The topology of the maglev rotary actuator can refer to the magnetically levitated planar motor [17,18] or employ the axisymmetric structure in which the magnet and coil are distributed along the circumference [11]. Once a specific design structure is given, the next step is obtaining the magnetic force and torque model [19][20][21][22][23][24][25]. It is also called the wrench model and is the foundation of the motion-decoupling unit in a control system. ...
Magnetic levitation technology shows promise for realizing multiple degrees of free precision motion for modern manufacturing, as the bearing and guiding parts are not used. However, motion decoupling in a magnetically levitated (maglev) system is difficult because it is hard to derive accurate magnetic force and a torque model considering the translation and rotation in all axes. In this work, a magnetic levitation rotary table that has the potential to realize unlimited rotation around the vertical axis and a relatively long stroke in the horizontal plane is proposed and analyzed, and the corresponding real-time numerical decoupling method is presented. The numerical magnetic force and torque model solves the current to magnetic force and torque transformation matrix, and the matrix is used to allocate the exact current in each coil phase to produce the required motion in the magnetically levitated (maglev) system. Next, utilizing a high-level synthesis tool and hardware description language, the proposed motion-decoupling module is implemented on a field programmable gate array (FPGA). To realize real-time computation, a pipelined program architecture and finite-state machine with a strict timing sequence are employed for maximum data throughput. In the last decoupling module of the maglev system, the delay for each sampling point is less than 200 μ s. To illustrate and evaluate real-time solutions, they are presented via the DAC adapter on the oscilloscope and stored in the SD card. The error ratios of the force and torque results solved by the numerical wrench model were less than 5 % and 10 % using the solutions from the boundary element method (BEM) program package RadiaTM as a benchmark.
... Therefore, the direct measurement with a dedicated sensor still has the widest acceptance and represents the most effective and performing solution. Direct measurement exploits a variety of technologies such as capacitive, optical, magnetic, and electromagnetic sensing [1,9,10]. Capacitive measuring method allows having high resolution (around 20 nm on a measuring range of 1 mm) but is expensive and very sensitive to dirt and dust [9,11]. ...
This paper presents a resonant inductive sensor for radial displacement in Active Magnetic Bearing (AMB) systems. The device consists of a wire coil wound around a tooth of a conventional eight-pole radial actuator of the bearing. The proposed device is different from standard inductive sensor schemes since the sensing coil is excited by the electromagnetic field generated by the actuation coil and not by an external oscillator. The electromagnetic flux linked by the sensing coil is a function of the distance between the sensor and the levitated object whose position has to be measured. The output measurement voltage is amplified by means of an electric resonator circuit obtained by installing a capacitor on the terminals of the sensing coil. A qualitative model is developed and compared to an experimental apparatus. This model captures well the sensing phenomenon and can be used for designing such a sensor. The proposed device demonstrates good properties of resolution and sensitivity with a small and low-cost layout. Additionally, such sensor allows obtaining an inherent sensor/actuator collocation along the longitudinal direction of rotors, which is an advantage in AMB systems for rotating machinery since it allows simplifying the layout and avoiding instability problems.
The zero-power permanent-electro magnetic suspension (PEMS) system features the magnetic levitation system that consists of the electromagnet and the floating magnet. Since the payload gravity is balanced by the attractive magnetic force between the iron core and the magnet, the excitation current in the coil stabilizes the magnet and fluctuates about the zero value. However, the accurate distance measurement between the iron core and the magnet is still a technical challenge against the hardware cost and the external disturbance. This work proposes a symmetric hall-effect-based distance sensor for the zero-power PEMS system. Under the small excitation current, the proposed sensor eliminates the magnetic field linearly excited by the current and outputs the magnetic field produced by the magnet to calibrate the floating distance. Additionally, the simulation results also indicate its outstanding performance against the tilting angle and the lateral offset of the floating magnet. Nevertheless, the experimental demonstration shows the functionality of the proposed sensor.
The measurement for levitation gap is a very important part of levitation control system. The traditional levitation gap sensors have some shortcomings such as small measurement range and specific installation requirements, and usually need nonlinear correction and temperature compensation to meet the control requirements of the magnetic levitation system. In our work, two novel measurement methods for levitation gap based on computer vision are proposed. Firstly, the levitation gap is measured by calculating the image pixel area of the region of interest (ROI). The error of the Pixel area model can be limited within 0.250mm, and the mean absolute error (MAE) is 0.095mm for full scale (F.S.). Secondly, the model named SelfConvNet based on convolutional neural network (CNN) is designed for measuring the levitation gap. The error of SelfConvNet model can be limited within 0.048mm, and the MAE is 0.013mm for full scale. The measurement results show that the SelfConvNet model is better than SqueezeNet and Visual Geometry Group 16 (VGG16) models, which has high measurement accuracy and strong anti-interference ability. The method based on pixel area has lower measurement accuracy but higher processing speed. Finally, the proposed gap measurement methods have been verified in closed-loop experiment of maglev ball control system.
