Magnetic Ball Research Articles

Adaptive variable gain linear active disturbance rejection control parameter optimization in magnetic levitation

The magnetic levitation ball system is characterized by strong nonlinearity, multiple disturbances, and intrinsic instability, which has long been a thorny problem in the field of control engineering. The magnetic levitation system can be continuously and stably levitated, even in a complex environment. In this thesis, the model of the magnetic levitation ball system is firstly constructed according to the kinetic theory and simplified according to the actual situation. After that, a linear active disturbance rejection control (LADRC) controller for the magnetic levitation ball system is designed. Considering that there are many parameters in the LADRC controller and it is difficult to obtain the optimal control effect by manual tuning, an adaptive variable gain LADRC algorithm is proposed to optimize the control strategy of LADRC parameters. An adaptive iterative algorithm is used to adaptively adjust the bandwidth of the linear extended state observer (LESO) in LADRC, and the convergence of the algorithm is demonstrated by using the Lyapunov function. To solve the problem that the proportional and differential gains of the LADRC controller can only be adjusted unidirectionally and simultaneously, this paper proposes an error variable gain algorithm. The aim is to realize the non-unidirectional and more detailed adjustment of the controller parameters, and it is rigorously analyzed and demonstrated through simulation and experiment. The results show that the proposed algorithm is better than proportional–integral–derivative (PID), sliding mode control (SMC), and LADRC in terms of dynamic performance, steady-state performance, and anti-interference.

Diagnosis and treatment of magnetic foreign bodies of the gastrointestinal tract is the experience of four centers

Abstract Introduction. Magnetic foreign bodies of the gastrointestinal tract are a relatively rare problem of pediatric urgent surgery, meanwhile, in the structure of foreign bodies they are the most difficult both in terms of timely diagnosis and treatment. There are no generally accepted therapeutic and diagnostic standards, traditional algorithms for managing patients with foreign bodies, focused on dynamic observation, are not correct; algorithms described in foreign literature contradict each other. The frequency of surgical interventions is high, and the risk of complications is high. Surgical tactics leave many "white spots". All of this leaves this issue open for discussion. Materials and methods. The experience of treating 76 patients with magnetic foreign bodies of the gastrointestinal tract in four pediatric surgical hospitals for the period 2010-2023 was analyzed. The study included patients with neodymium magnetic balls from the constructor – 38 people (50%), 30 people (39.5%) with neodymium magnets of a different shape and purpose, 6 people (7.9%) with ferrite magnets, 2 people (2.6%) with magnets of an unidentified nature. Results and discussion. The average age of the patients was 4 ± 3.65 years. The fact of ingestion of a foreign body was revealed in the anamnesis in 46 (60.5%) cases. Mental illnesses were diagnosed in 4 children – 5.3%, which is higher than the average in the child population. Clinical symptoms were found in 4 (11.8%) children with a single magnetic foreign body and in 33 (78.6%) with multiple. The main diagnostic method was an overview X-ray of the abdominal cavity (70 cases - 92%), which allowed to identify both a foreign body and possible complications (signs of obstruction, free gas in the abdominal cavity). Fibrogastroduodenoscopy was performed in 50 cases (65.8%), of which a foreign body was detected in 34 (68% of all cases), including in 28 cases the foreign body was removed. Other diagnostic methods (ultrasound, spiral computed tomography) were used much less frequently. Among the treatment methods, open types of surgical intervention prevailed – 32 cases (42%). Laparoscopy was used in isolated cases. Conclusion. Magnetic foreign bodies are the most difficult category of foreign bodies, both in terms of diagnosis and treatment. Diagnosis often depends on anamnesis data and, in its absence, is often delayed, and the frequency of intraoperative diagnosis remains high. Among the diagnostic methods, it is difficult to identify a universal one that can be recommended as the "gold standard", however, the most widely used and practical informative is an overview radiograph of the abdominal cavity and FGDS. Among the methods of surgical treatment, the role of laparoscopic technologies is relatively small, endoscopic removal is mainly performed, or "open" surgery is used.

Adaptive control of magnetic levitation system based on fuzzy inversion

A novel adaptive tracking controller for magnetic levitation systems (MLS) is developed. The controller is based on a special adaptive control scheme incorporating fuzzy model of electromagnetic acceleration enabling fast and accurate fuzzy inversion. The controller ensures accurate tracking of any smooth desired position signal, despite unknown MLS parameters. The closed-loop system stability, in the sense of uniform ultimate boundedness (UUB) of error trajectories, is proved using Lyapunov approach. The closed-loop system performance is investigated during numerical experiments. Finally the proposed controller is verified by successful implementation on a DSP board controlling a typical magnetic levitation ball system. Performed tests and experiments demonstrate that the proposed control technique is robust against discretization and unknown MLS model parameters, provides high tracking accuracy, is easily implementable, and simple to tune.

Piezoelectric-electromagnetic wearable harvester for energy harvesting and motion monitoring

This paper proposes a piezoelectric-electromagnetic wearable harvester (PEWH). The device is used to harvest the energy generated when the upper limb swings and can perform the function of motion monitoring. The main structure of PEWH consists of the piezoelectric power generation module and electromagnetic sensing module. Among them, the piezoelectric sheet in the piezoelectric module deforms and outputs electric energy, and the magnetic ball in the electromagnetic module moves to generate induced electromotive force to achieve sensing and energy supply. Through experimental testing, PEWH output performance is optimal when the spring wire diameter is 0.8 mm and the distance between the spring connector where the spring located and the position of the top of the shaft is 65 mm. At a vibration excitation frequency of 2 Hz, the device’s output voltage reaches a peak-to-peak value of 57.84Vpp, accompanied by a maximum power of 115.52mW. A range of application experiments were conducted to confirm the output performance of the device, which can power 82 LEDs and the temperature and humidity sensor. The prototype can be worn on the arm to enable monitoring of the current movement status. PEWH can effectively capture the energy generated by human movement for self-powered and self-sensing motion detection.

RBF-ARX model-based trust region nonlinear model predictive control and its application on magnetic levitation ball system

RBF-ARX model-based trust region nonlinear model predictive control and its application on magnetic levitation ball system

A viscoelastic metamaterial beam for integrated vibration isolation and energy harvesting

Locally resonant metamaterials have low-frequency band gaps and the capability of converging vibratory energy in the band gaps at resonant cells. It has been demonstrated by several researchers that the dissipatioin of vibratory energy within the band gap can be improved by using viscoelastic materials. This paper designs an integrated viscoelastic metamaterial for energy harvesting and vibration isolation. The viscoelastic metamaterial is achieved by a viscoelastic beam periodically arrayed with spatial ball-pendulum nonlinear energy harvesters. The nonlinear resonator with an energy harvesting function is achieved by placing a free-rolling magnetic ball in a spherical cavity with an additional induction coil. The dynamic equations of viscoelastic metamaterials under transverse excitation are established, and the energy harvesting and vibration isolation characteristics within the dispersion relation of viscoelastic metamaterials are analyzed. The results show that the vibrations of the main body of the viscoelastic metamaterial beam are significantly suppressed in the frequency range of the local resonance band gap. At the same time, the elastic waves are limited in the nonlinear resonator with an energy harvesting function, which improves the energy output. Finally, an experimental platform of viscoelastic metamaterial vibration is established for validation purposes.

Deep Learning based Model Predictive Controller on a Magnetic Levitation Ball System

The magnetic levitation (maglev) ball system is a prototypical Single-Input-Single-Output (SISO) system, characterized by its pronounced nonlinearity, rapid response, and open-loop instability. It serves as the basis for many industrial devices. For describing the dynamics of the maglev ball system precisely in the pseudo linear model, the long short-term memory (LSTM) based auto-regressive model with exogenous input variables (LSTM-ARX) is proposed. Firstly, the LSTM network is modified by incorporating the auto-regressive structure with respect to sequence input, allowing it to deduce a locally linearized model without the need for Taylor expansion. Then, the LSTM-ARX model is transformed into a linear parameter varying (LPV) state space model, and upon this foundation, a model predictive controller (MPC) is proposed. Specifically, when deducing the MPC, the deep learning-based model is linearized by fixing its state input at the current state, so that the nonlinear, non-convex optimization problem can be converted to a finite-horizon quadratic programming problem, thereby deriving the explicit form of MPC. To further enhance the efficiency of the controller in real-time control tasks, a predictive functional controller (PFC) is proposed. It employs multiple nonlinear functions to fit the control sequence, thereby reducing the number of decision variables of the on-line optimization problem in MPC. The proposed controller was successfully applied to the real-time control of the maglev ball system. Simulation and real-time control experiments have validated the improvement in transient performance and efficiency of the LSTM-ARX model-based PFC (LSTM-ARX-PFC).

Magnetic levitation system control research based on improved linear active disturbance rejection

In this study, we propose an improved linear active disturbance rejection control (I-LADRC) method to achieve stable suspension of magnetic levitation balls. This method can not only solve the overshoot problem but also enhance the anti-interference capability. The control algorithm is designed, and the convergence of the control system is verified by derivation. To verify the effectiveness of the proposed control algorithm, we conduct simulation experiments and analyze the dynamic performance, tracking effect, and anti-interference ability of four controllers: sliding mode control (SMC), LADRC, longitudinal error-LADRC (LE-LADRC), and I-LADRC. Simulation results show that I-LADRC outperforms SMC, LADRC, and LE-LADRC regarding tracking effect and anti-interference ability. We also experimentally verify the control performance of I-LADRC. The experimental results show that I-LADRC has strong anti-interference ability and robust performance, which is 100% and 50% higher than LADRC and LE-LADRC, and has good dynamic performance, which verifies the effectiveness of the simulation experiment, which exhibits better robustness and dynamic performance.

Foreign bodies of the stomach with the introduction into the mucous membrane of a 9-year-old child

A description of the clinical observation of a 9-year-old child with foreign bodies of the stomach (2 magnetic balls) and their introduction into the mucous membrane is presented. Timely endoscopic and X-ray examinations contributed to the establishment of the exact localization of foreign objects, and videoesophagogastroscopy using a magnetic extractor made it possible to extract magnets from the mucous membrane with minimal damage to the stomach tissues and prevent the development of complications in this patient.

Implantable magnetically-actuated capsule for on-demand delivery

Many implantable drug delivery systems (IDDS) have been developed for long-term, pulsatile drug release. However, they are often limited by bulky size, complex electronic components, unpredictable drug delivery, as well as the need for battery replacement and consequent replacement surgery. Here, we develop an implantable magnetically-actuated capsule (IMAC) and its portable magnetic actuator (MA) for on-demand and robust drug delivery in a tether-free and battery-free manner. IMAC utilizes the bistable mechanism of two magnetic balls inside IMAC to trigger drug delivery under a strong magnetic field (|Ba| > 90 mT), ensuring precise and reproducible drug delivery (9.9 ± 0.17 μg per actuation, maximum actuation number: 180) and excellent anti-magnetic capability (critical trigger field intensity: ∼90 mT). IMAC as a tetherless robot can navigate to and anchor at the lesion sites driven by a gradient magnetic field (∇ Bg = 3 T/m, |Bg| < 60 mT), and on-demand release drug actuated by a uniform magnetic field (|Ba| = ∼100 mT) within the gastrointestinal tract. During a 15-day insulin administration in vivo, the diabetic rats treated with IMAC exhibited highly similar pharmacokinetic and pharmacodynamic profiles to those administrated via subcutaneous injection, demonstrating its robust and on-demand drug release performance. Moreover, IMAC is biocompatible, batter-free, refillable, miniature (only Φ 6.3 × 12.3 mm3), and lightweight (just 0.8 g), making it an ideal alternative for precise implantable drug delivery and friendly patient-centered drug administration.

Endoscopic removal of multiple magnetic foreign bodies in the stomach of a 2-year-old child

Introduction. Foreign bodies in the gastrointestinal tract (GIT) is a serious problem in pediatric surgery. In recent years, the incidence of cases when children swallow magnets has increased significantly. Foreign bodies in the stomach, small and large intestines can cause their perforation.Purpose. To demonstrate a successful endoscopic removal of multiple magnetic foreign bodies which were in the stomach of a 2–yearold child for a long time.Description of clinical observation. Boy, 2 y.o., was admitted by the ambulance to the Clinical and Research Institute of Emergency Pediatric Surgery and Trauma in Moscow with suspected presence of multiple magnetic foreign bodies in the stomach and complaints of melena during the last 2 months, about which his parents repeatedly consulted their pediatrician. Two days before the admission, the parents found several magnetic balls in child's faeces and decided to visit the pediatrician for the second time. This time the child had X-ray examination and was transferred to the hospital. At the survey radiography and ultrasound examination of the abdominal cavity, the diagnosis of multiple foreign bodies in the stomach was confirmed. Esophagogastroduodenoscopy revealed a conglomerate of multiple magnetic foreign bodies that filled ½ of the stomach lumen. Under general anesthesia, 209 pieces of magnetic beans were endoscopically removed. Postoperative course was uneventful.Conclusion. If there is the slightest suspicion of a foreign body in the gastrointestinal tract and if there is a clinical picture of gastrointestinal bleeding, the child must be sent to surgical hospital for further examination and, if possible, for endoscopic management.

Foreign bodies of the gastrointestinal tract in children: a retrospective analysis of medical cases

Foreign bodies of the gastrointestinal tract in children are a fairly common reason for seeking help in surgical departments. Purpose. The study aims at identifying dependencies between the type of foreign bodies, the tactics of their detection and removal in different age periods. Material and methods. Retrospective analysis of 100 case histories of patients with a diagnosis of «Foreign body of the gastrointestinal tract”; 64 boys included. Results. Preschool children were more often diagnosed with «Foreign body of the gastrointestinal tract.» The children rarely complained. The most commonly used diagnostic method is overview radiography, and the method of extracting a foreign body is endoscopy. The most frequent finds were coins. Magnetic balls and batteries led to injury of the organ where they were located. Conclusion. When contacting a medical and preventive institution in the first hours after swallowing the object, the risk of complications is minimal. If the foreign body is a magnetic ball, magnet, or battery, the presence of which is associated with high risks of complications, it is necessary to remove them from the body as soon as possible.

A flexible omnidirectional rotating magnetic array for MRI-safe transdermal wireless energy harvesting through flexible electronics.

Magnetic resonance imaging (MRI)-safe implantable wireless energy harvester offers substantial benefits to patients suffering from brain disorders, hearing impairment, and arrhythmias. However, rigid magnets in cutting-edge systems with limited numbers of rotation axis impose high risk of device dislodgement and magnet failure. Here, a flexible omnidirectional rotating magnetic array (FORMA) and a flexible MRI-safe implantable wireless energy-harvesting system have been developed. Miniaturized flexible magnetic balls 1 millimeter in diameter achieved by molding three-dimensional printed templates can rotate freely in elastomer cavities and supply a magnetic force of 2.14 Newtons at a distance of 1 millimeter between an implantable receiver and a wearable transceiver. The system can work stably under an acceleration of 9g and obtain a power output of 15.62 decibel milliwatts at a transmission frequency of 8 megahertz. The development of the FORMA may lead to life-long flexible and batteryless implantable systems and offers the potential to promote techniques for monitoring and treating acute and chronic diseases.

Performance recovery of uncertain nonaffine systems by active disturbance rejection control

This paper studies performance recovery problem of a class of uncertain nonaffine strict-feedback systems with mismatched uncertainties. First, the strict-feedback nonaffine system with mismatched system dynamics is transformed into an integrator-chain nonaffine system by a diffeomorphism. Second, the transformed system is converted to an affine one by constructing an auxiliary control input term, and dynamical uncertainties and external disturbances are viewed as total disturbance of the affine system. Then, a two-time-scale active disturbance rejection controller (ADRC) is designed for the transformed affine system. Under some mild assumptions, it can be proved that the proposed ADRC-based closed-loop system can achieve performance recovery and weak performance recovery in different cases of mismatched system dynamics, respectively. Experimental results on a magnetic levitation ball system demonstrate the effectiveness of the proposed control scheme.

Workspace Characterization for Hybrid Tendon and Ball Chain Continuum Robots.

Continuum robots have attracted considerable attention for applications in minimally invasive diagnostics and therapeutics over the past decade [1]. The primary reason is their ability to navigate narrow and tortuous anatomical passageways, while guaranteeing safe inter- action with the anatomy. In designing such robots, an important goal is create a robot with a workspace appropriate for the clinical task. A significant limitation of many continuum designs re- lates to the minimum radius of curvature that a particular design can achieve. While multiple bending sections can be concatenated to provide more degrees of freedom, the orientations by which a point in the workspace can be approached are often limited. To overcome this limitation, this paper investigates a hybrid design that combines the advantages of tendon- actuated [2] and magnetic ball chain robots [3] as shown in Fig. 1. In this hybrid design, a proximal tendon- actuated section positions the robot with respect to the goal tip location while a distal ball chain section orients the robot tip with respect to the goal location. This abstract describes how the hybrid kinematics can be modeled and illustrates how the hybrid design possesses a dextrous workspace of finite extent.

Magnetic Ball Chain Robots for Endoluminal Interventions.

This paper introduces a novel class of hyperredundant robots comprised of chains of permanently magnetized spheres enclosed in a cylindrical polymer skin. With their shape controlled using an externally-applied magnetic field, the spherical joints of these robots enable them to bend to very small radii of curvature. These robots can be used as steerable tips for endoluminal instruments. A kinematic model is derived based on minimizing magnetic and elastic potential energy. Simulation is used to demonstrate the enhanced steerability of these robots in comparison to magnetic soft continuum robots designed using either distributed or lumped magnetic material. Experiments are included to validate the model and to demonstrate the steering capability of ball chain robots in bifurcating channels.

Closed-form Kinematic Model and Workspace Characterization for Magnetic Ball Chain Robots.

Magnetic ball chains are well suited to serve as the steerable tips of endoluminal robots. While it has been demonstrated that these robots produce a larger reachable workspace than magnetic soft continuum robots designed using either distributed or lumped magnetic material, here we investigate the orientational capabilities of these robots. To increase the range of orientations that can be produced at each point in the workspace, we introduce a comparatively-stiff outer sheath from which the steerable ball chain is extended. We present an energy-based kinematic model and also derive an approximate expression for the range of achievable orientations at each point in the workspace. Experiments are used to validate these results.

Based on Sliding Mode and Adaptive Linear Active Disturbance Rejection Control for a Magnetic Levitation System

The magnetic levitation system has evident advantages in reducing energy consumption, but its nonlinear characteristics increase the difficulty of control. This study proposes a control method that combines the improved particle swarm optimisation algorithm with sliding mode control and adaptive linear active disturbance rejection control (IPSO–SMC–ALADRC) to address the problems of weak anti‐interference ability and stability in the application of traditional control methods in single‐point magnetic levitation ball systems. First, a mathematical model of a single‐point magnetic levitation ball is established. Second, the proportional and differential coefficients of LADRC are adjusted using adaptive laws, and the adaptive LADRC is combined with SMC to achieve stable control of the magnetic levitation ball. Moreover, an improved particle swarm optimisation algorithm is proposed to address the considerable number of adjustable parameters in the controller. The convergence and stability of the control algorithm were demonstrated using the Lyapunov equation. Finally, PID and LADRC are introduced for simulation and experimental comparison to verify the effectiveness of this control method. Results indicate that IPSO–SMC–ALADRC has excellent stability and anti‐interference performance. This study addresses the problem of weak stability and anti‐interference performance in the application of traditional control methods in the maglev system and further promotes the application of active disturbance rejection control in the magnetic levitation system.

An electromagnetically actuated ball and socket joint for applications in 3D metrology

The design, development and application of a novel magnetically actuated ball-and-socket joint has been presented here. The joint comprises a current-carrying conductor acting as the socket and a permanent magnet ball. External solenoid coils are employed to orient the ball in any desired direction. A novel strategy, based on providing a small vibratory input, is proposed to eliminate static friction. The joint has been fabricated and experimentally demonstrated to rotate over a large range of about ± with a low cross-axis rotation, of about 8%, and with negligible hysteresis. The developed joint has been employed as a touch-trigger probe in a coordinate measurement machine to access all the three surfaces in a cuboidal corner of a sample.

Self-Insertion of Newspaper into Bladder: An Unusual Case of Foreign Body.

Foreign bodies are most frequently observed in the bladder among the genitourinary organs. Many different foreign bodies such as needles, wires, Foley's catheter fragments, and magnetic balls have been observed in the bladder previously. In the present case, a 50-year male patient presented to the hospital with fever and acute urinary retention. Despite antibiotic therapy, the urinary tract infection did not regress, and the patient's suspicious statements were associated with the foreign body. Examination of the patient necessitated further enquiry upon the detection of newspaper pieces in the bladder. It was discovered that the patient had folded the newspaper in an attempt to commit suicide and pushed it into the bladder. Such a case has never been observed previously in the literature. An 8-cm rolled piece of newspaper was detected in the bladder using a cystoscope and was removed with open surgery. Key Words: Bladder, Foreign body, Newspaper.