Double Suspension Research Articles

A method for determining the position of the center of gravity of a bulky cargo for safe reloading on a ship

Based on the analysis of the equilibrium equations of a two-link suspension system for bulky cargo, two methods for determining the position of the center of gravity of this cargo are proposed. The essence of the methods consists in double suspension of this system and measuring the angles of its deviation in the suspended equilibrium position. In this case, the difference in the angles of deviation of the system between suspensions is provided either by changing the height of the primary suspension (the length of the primary slings), or by changing the ratio of the masses of the traverse and the load. A comparative analysis of the accuracy and practical feasibility of both methods is carried out. It is shown that when carrying out cargo operations in a port or on a ship, a method in which the difference in the angles of deviation of the system between suspensions is carried out by changing the length of the primary slings (the height of the primary suspension) is practically feasible and more accurate. The work emphasizes that an important condition for ensuring the stability of the system when hanging and preventing overturning of the load is that the primary slings (connecting the hook and the traverse) must be of such length that the suspended load can virtually be inscribed inside the pyramid (safety pyramid) formed by the traverse and these slings. It is also shown that the length of the secondary slings (connecting the traverse and the load) does not matter, but they must be of equal length and parallel to each other, which will ensure their vertical position after hanging the system. The heavier the traverse (in comparison with the weight of the suspended cargo), the higher the safety pyramid, and therefore the more stable the cargo suspension system as a whole becomes. On the other hand, the longer the primary slings (the higher the safety pyramid), the smaller the angles of deviation of the traverse (and the system as a whole) from the initial position when suspended. To demonstrate the possibilities of the proposed new method for determining the position of the cargo center, a numerical example of its implementation is given.

Verification Of New Double Suspention Keofloat To Minimise Wave Height Inaccuracies In A Physical Model Resulting From Rotation In A 3D Wave Agitataion Study

A modification to the Keofloat system has been developed to address the effect that rotation about its vertical axes may have on the quantities effecting measurement accuracy of the system. The effect of rotation was not previously determined and was found to rarely occur in specific locations for some three-dimensional models. Consequently, the Keofloat design was modified from having a single suspension string to a double suspension string supporting it. A single and double suspension string Keofloat was tested in a wave flume to compare the modified Keofloat to what was previously used. Tests were conducted for regular waves between 0.5 mm and 23 mm and wave periods of 0.8 s and 1.6 s. The testing conducted, included two sets of tests, one for direct comparison where rotation was not present and the other where controlled and nonintrusive rotation was generated on the single suspension string Keofloat. The tests show that the double suspension string Keofloat compared extremely good to the single suspension string Keofloat and can reliably be used to measure small waves in a harbour basin where factors causing rotation of the Keofloat might be present.

Load Carrying Capacity Enhancing Design and Lubrication Investigation of the Magnetic-Water Double Suspension Elastic Support Thrust Bearing

Aiming at the problem that the traditional water-lubricated bearing cannot carry the heavy load and adapt to the constantly changing operating conditions for the high-power Rim Driven Thruster (RDT), the principle structure of the Magnetic Water-double-suspension Elastic-support Thrust Bearing (MWETB) is designed and the optimal structure parameters of the bearing are selected using simulation. To demonstrate the reliability of the MWETB under the RDTs’ actual working conditions, performance tests, which include the magnetic flux density, magnetic force, and lubrication performance, are carried out. The simulation and experimental results indicate that the optimal offset ratios are in two intervals, and the magnetic alignment and sheath materials have a great effect on the load reduction. The load-carrying force has obvious zoning characteristics with the change in bearing clearance. Besides, compared with the water-lubricated thrust bearings, the MWETB has advantages in terms of minimum film thickness and friction coefficient.

Decoupling control of radial 4 degree of freedom system of magnetic-liquid double suspension bearing based on generalized extended state observer.

As the novel suspension bearing, Magnetic-Liquid Double Suspension Bearing (MLDSB) is mainly supported by magnetic suspension and supplemented by a liquid hydrostatic bearing. Due to its great bearing capacity and stiffness, rapid response, great active control, and so on, MLDSB is suitable for medium speed heavy loads and has a large carrying capacity and high operating stability. In addition, the radial inertia coupling and gyroscopic coupling between radial 4-DOF control channels can reduce control precision, operation stability, and reliability of MLDSB. Therefore, a mathematical model of radial 4-DOF rotor-dynamics of MLDSB is established in this paper, and the inherent coupling mechanism is explored. Taking inertial coupling, gyroscopic coupling, and external disturbance loads as lumped disturbances, a decoupled controller based on Generalized Extended State Observer (GESO) is established. The influence of the GESO controller on the decoupling and control performance of radial 4-DOF control channels is simulated. The results indicate that the decoupling effect of the GESO controller is great. Under the action of step signal, the steady displacement, maximum displacement, adjustment time, and peak time of the rotor after decoupling are all reduced, among which the steady displacement and maximum displacement are the most obvious. Under the sinusoidal signal, the steady displacement and maximum displacement are reduced by 90%, which can effectively avoid the "gap-impact" fault. Under the pulse signal, the steady displacement, maximum displacement, adjustment time, and peak time are all reduced, among which the maximum displacement is the most obvious. The research in this paper can provide a theoretical reference for the stable support and decoupling control of MLDSB.

Suspension homotopy of 6–manifolds

For a simply connected closed orientable manifold of dimension $6$, we show its homotopy decomposition after double suspension. This allows us to determine its $K$- and $KO$-groups easily. Moreover, for a special case we refine the decomposition to show the rigidity property of the manifold after double suspension.

Adjustment of Immunosuppressants to Facilitate Anti-COVID-19 Antibody Production after mRNA Vaccination in Liver Transplant Recipients.

Liver transplant recipients are immunocompromised and have low immunogenicity to produce antibodies in anti-COVID-19 vaccination. Whether immunosuppressant adjustment could facilitate anti-COVID-19 antibody production in anti-COVID-19 mRNA vaccination is undetermined. Our patients were informed to temporarily suspend mycophenolate mofetil (MMF) or everolimus (EVR) for 2 weeks during both the 1st and 2nd doses of Moderna mRNA-1273 vaccine. A total of 183 recipients receiving two doses of Moderna mRNA-1273 vaccine were enrolled and grouped into tacrolimus monotherapy (MT, n = 41), and dual therapy with non-adjustment (NA, n = 23), single suspension (SS, n = 19) and double suspension (DS, n = 100) of MMF/EVR in two-dose mRNA vaccination. A total of 155 (84.7%) patients had a humoral response to vaccines in this study. The humoral response rates were 60.9%, 89.5%, 91.0% and 80.5% in NA, SS, DS, and MT group patients, respectively (p = 0.003). Multivariate analysis showed that favorable factors for humoral response were temporary suspension of MMF/EVR and monotherapy, and unfavorable factors were deceased donor liver transplantation, WBC count < 4000/uL, lymphocyte < 20% and tacrolimus trough level ≥ 6.8 ng/mL. In conclusion, temporary two-week suspension of anti-proliferation immunosuppressants could create a window to facilitate antibody production during anti-COVID-19 mRNA vaccination. This concept may be applied to other vaccinations in liver transplant recipients.

Arthroscopic Medial Patellofemoral Ligament Reconstruction with a Double Suspension Technique

Arthroscopic Medial Patellofemoral Ligament Reconstruction with a Double Suspension Technique

Research on singular point characteristics and parameter bifurcation of single DOF nonlinear autonomous bearing system of magnetic-liquid double suspension bearing

Research on singular point characteristics and parameter bifurcation of single DOF nonlinear autonomous bearing system of magnetic-liquid double suspension bearing

Research on singular point characteristics and parameter bifurcation of single DOF nonlinear autonomous bearing system of magnetic-liquid double suspension bearing

Research on singular point characteristics and parameter bifurcation of single DOF nonlinear autonomous bearing system of magnetic-liquid double suspension bearing

A Double Suspension Technique for Laparoscopic Isolated Caudate Lobectomy.

Background: Laparoscopic isolated caudate lobectomy is still a challenging procedure for hepatobiliary surgeons because of its deep location and narrow operating space. Hilar exposure and adequate operation space play an important role during laparoscopic caudate lobectomy. Very few references are available on this technique, and in this study, we present a new suspension technique to assist laparoscopic caudate lobectomy. Materials and Methods: The data of patients with caudate hepatic tumors who underwent laparoscopic isolated caudate lobectomy with or without the double suspension technique at the Eastern Hepatobiliary Surgery Hospital were retrospectively analyzed. Results: A total of 25 patients underwent laparoscopic isolated caudate lobectomy at Eastern Hepatobiliary Surgery Hospital between June 2016 and March 2022. Eight patients had perioperative complications, and no patient died within 30 days after surgery. There were no significant differences between the two groups in terms of conversion rate (8.3% versus 7.7%; P = .954), complication rate (25.0% versus 38.5%; P = .480), length of stay (8.0 [6.0-11.0] days versus 9.0 [6.0-19.0] days; P = .098), and postoperative liver function changes. Patients who underwent resection in the suspension group had shorter operation time (154.9 ± 44.3 minutes versus 224 ± 86.3 minutes; P = .018), inferior vena cava dissection time (30.1 ± 5.4 minutes versus 44.8 ± 7.4 minutes; P < .001), and less bleeding (125.0 [20-800.0] mL versus 350 [80-850.0] mL, P = .011). Conclusions: This double suspension technique is a safe and feasible method to assist laparoscopic caudate lobectomy. It provides clear exposure and adequate surgical space, thereby shortening the operation time and reducing intraoperative blood loss.

Research on magneto-hydraulic proportional control strategy for single degree of freedom supporting system of magnetic-liquid double suspension bearing.

Compared with the traditional active electromagnetic bearing, the additional hydrostatic supporting concept is imported to form magnetic-liquid double suspension bearing (MLDSB) without affecting the support performance. Therefore, the bearing carrying capacity and stiffness are greatly increased and the operational stability and reliability of MLDSB are also improved. The controlling strategy and the regulating mode have the major impact on the safe and stable operation of MLDSB, which directly determines the performance quality. MLDSB adopts the magnetic-liquid coupling supporting mode with electromagnetic suspension as the main and hydrostatic supporting as the supplement, which greatly increases the complexity and difficulty of MLDSB. Therefore, the proportional control strategy and the magneto-hydraulic coupled nonlinear controller of MLDSB are explored in this paper. First, the regulation mechanism of the single degree of freedom (DOF) supporting system is revealed, and the proportional-integral-differential controller of the electromagnetic and hydrostatic closed-loop is designed. Then, the fuzzy control idea is introduced into the single DOF supporting system to design a magnetic-liquid variable proportional fuzzy controller, and the difference between the proportional/variable proportional control modes is compared. Finally, the rotor displacement following characteristics and anti-interference characteristics in the proportional/variable proportional control mode are compared on a magnetic-liquid double suspension test bench. The results show that compared with the proportional control method, the variable proportional control method combines the advantages of fast regulation speed of the electromagnetic system and the stable and reliable advantages of the hydrostatic system. In the same step signal, the rotor can achieve unbiased following under two control modes of proportional/variable proportion, and the adjustment time of the variable proportional control mode is shorter. In two control modes, the rotor can be restored to the original equilibrium position. The maximum offset under the variable proportional control mode is smaller, and with the continuous increase of the displacement, the performance of the variable proportional control method is more obvious. The stability control of MLDSB is provided on the theoretical basis in this article.

Study on the Contamination Characteristics of V-Type Double Suspension Rod Insulators Based on the Influence of Wake Flow

The insulators of the catenary of the Lanzhou-Xinjiang High-speed Railway in windy areas suffer from serious contamination, which has led to frequent flashover accidents. The catenary of the Lanzhou-Xinjiang High-speed Railway has adopted the unique external insulation of V-type double suspension rod insulators. To further determine the contamination characteristics of this type of insulator, a contamination simulation model of insulator is established in this paper based on the principles of fluid mechanics, which is used to analyze the contamination characteristics of the V-type double suspension rod insulators under the influence of wake flow. The research results show that wind speed directly determines the static pressure on the surface of the insulator, the wind speed and particle concentration are proportional to the contamination volumes on the windward and crosswind sides of insulator, while the particle size is inversely proportional to the contamination volume on the leeward side of the insulator. The direction of wake flow is consistent with the direction angle of external incoming flow, and the wake flow generating area affects the contamination characteristics of the insulator. When the incoming flow is at a prevailing wind direction of 0°, focus should be put on the windward and crosswind sides of the two insulators during insulator cleaning, and the contamination distributions on these two insulators are similar; when the incoming flow is at a prevailing wind elevation of 0°∼60°, focus should be put on the entire surface of 1# insulator and the windward and crosswind sides of 2# insulator during insulator cleaning.

Comparing constructions of the classifying space for the fibre of the double suspension

The different constructions of a classifying space for the fibre of the double suspension by Gray and the authors are shown to be essentially the same, up to a homotopy equivalence. We go on to compare a variety of maps Ω2S2np+1⟶S2np−1 that are of degree p on the bottom cell.

Supporting performance of magnetic-liquid double suspension bearing under wear of magnetic poles

Supporting performance of magnetic-liquid double suspension bearing under wear of magnetic poles

Influence of Controller’s Parameters on Static Bifurcation of Magnetic-Liquid Double Suspension Bearing

Magnetic-Liquid Double Suspension Bearing (MLDSB) is composed of an electromagnetic supporting and a hydrostatic supporting system. Due to greater supporting capacity and static stiffness, it is appropriate for occasions of middle speed, overloading, and frequent starting. Because of the complicated structure of the supporting system, the probability and degree of static bifurcation of MLDSB can be increased by the coupling of hydrostatic force and electromagnetism force, and then the supporting capacity and operation stability are reduced. As the key part of MLDSB, the controller makes an important impact on its supporting capacity, operation stability, and reliability. Firstly, the mathematical model of MLDSB is established in the paper. Secondly, the static bifurcation point of MLDSB is determined, and the influence of parameters of the controller on singular point characteristics is analyzed. Finally, the influence of parameters of the controller on phase trajectories and basin of attraction is analyzed. The result showed that the pitchfork bifurcation will occur as proportional feedback coefficient Kp increases, and the static bifurcation point is Kp = −60.55. When Kp &lt; −60.55, the supporting system only has one stable node (0, 0). When Kp &gt; −60.55, the supporting system has one unstable saddle (0, 0) and two stable non-null focuses or nodes. The shape of the basin of attraction changed greatly as Kp increases from −60.55 to 30, while the outline of the basin of attraction is basically fixed as Kp increases from 30 to 80. Differential feedback coefficient Kd has no effect on the static bifurcation of MLDSB. The rotor phase trajectory obtained from theoretical simulation and experimental tests are basically consistent, and the error is due to the leakage and damping effect of the hydrostatic system within the allowable range of the engineering. The research in the paper can provide theoretical reference for static bifurcation analysis of MLDSB.

Decoupling Control of Multi-DOF Supporting System of MLDSB

Magnetic liquid double suspension bearing (MLDSB) is composed of an electromagnetic system and hydrostatic system and its bearing capacity and stiffness can be greatly improved. It is very suitable for occasions of medium speed, heavy load, and starting frequently. Due to the gyroscopic effect and interference between the supporting system, the space state of the rotor can be affected and the operation stability of the MLDSB can be reduced greatly. Therefore, the coupling features of the multi-degree of freedom (multi-DOF) system are analyzed and a decoupling controller is designed and verified in the paper. Firstly, the paper introduces the structural characteristics, stress forms, and control regulation mechanism. Then, the mathematical transfer function of the multi-DOF supporting system is established and the coupling principle is revealed. The state feedback decoupling controller is designed by means of a state feedback decoupling, and its decoupling effect is analyzed by the Simulink module. Finally, the single-DOF decoupling system is independently controlled by the use of the root locus method. The coupling characteristics between channel x and channel y are tested experimentally, and the decoupling controller is added and its effect tested. The results show that the state feedback decoupling controller can effectively reduce the coupling degree in the multi-DOF system and convert the multi-DOF coupling problem into a single-DOF independent control problem. The coupling effect of channel x and channel y is reduced by using the decoupling controller, with the subsequent displacement characteristic of the rotor increased, and then the operation stability of the MLDSB is improved greatly. This paper can enrich the support system of the MLDSB and provide a theoretical reference for stability control.

Double Closed-Loop Compound Control Strategy for Magnetic Liquid Double Suspension Bearing

As a new type of suspension bearing, the magnetic liquid double suspension bearing (MLDSB) is mainly supported by electromagnetic suspension and supplemented by hydrostatic support. At present, the MLDSB adopts the regulation strategy of “electromagnetic-position feedback closed-loop, hydrostatic constant-flow supply” (referred to as CFC mode). In the equilibrium position, the external load is carried by the electromagnetic system, and the hydrostatic system produces no supporting force. Thus, the carrying capacity and supporting stiffness of the MLDSB can be reduced. To solve this problem, the double closed-loop control strategy of “electromagnetic system-force feedback inner loop and hydrostatic-position feedback outer loop” (referred to as DCL mode) was proposed to improve the bearing performance and operation stability of the MLDSB. First, the mathematical models of CFC mode and DCL mode of the single DOF supporting system were established. Second, the real-time variation laws of rotor displacement, flow/hydrostatic force, and regulating current/electromagnetic force in the two control modes were plotted, compared, and analyzed. Finally, the influence law of initial current, flow, and controller parameters on the dynamic and static characteristic index were analyzed in detail. The results show that compared with that in CFC mode, the displacement in DCL mode is smaller, and the adjustment time is shorter. The hydrostatic force is equal to the electromagnetic force in DCL mode when the rotor returns to the balance position. Moreover, the system in DCL mode has better robustness, and the initial flow has a more obvious influence on the dynamic and static characteristic indexes. This study provides a theoretical basis for stable suspension control and the safe and reliable operation of the MLDSB.

Impact-Rubbings Dynamics Behavior of Magnetic-Liquid Double Suspension Bearing in Electromagnetic Failure Model

Magnetic-liquid double suspension bearing (MLDSB) is a new type of suspension bearing with electromagnetic suspension as the main part and hydrostatic supporting as the auxiliary part. It can greatly improve the bearing capacity and stiffness of rotor bearing system and is suitable for medium speed, heavy load, and frequent starting occasions. The electromagnetic system adopts PD control, and hydrostatic system adopts constant pressure supply model to adjust and control the rotor’s displacement in real time. Once bearing electromagnetic system fails, the “dropping-collision” phenomenon of the rotor will be triggered in operation process, leading to cracking and shedding of magnetic sleeve plating and magnetic pole plating. Then the operational reliability and stability of MLDSB will be greatly reduced. So in this paper, Firstly, the drop impact-rubbing equation of the single DOF bearing system under four failure models (upper unit failure, lower unit failure, bilateral failure, and power amplifier failure) is established. Secondly, the paper simulates influence laws of different structure and operation parameters (plating/liquid film thickness and oil pocket pressure, bias current) on falling rotor impact-rubbings behavior. The results show that: (1) the degree of “dropping-collision” of the rotor under the four failure models is successively as follows: power amplifier failure &gt; upper unit failure &gt; bilateral failure &gt; lower unit failure. (2) Due to the impact-rubbing damping effect of hydraulic oil, it plays a certain inhibitory and buffering role on the phenomenon of “drop-collision”. The degree and probability of “dropping-collision” of rotor can be effectively reduced by increasing the pressure of oil chamber appropriately. (3) The rotor drop impact-rubbing behavior obtained from the test is basically consistent with the theoretical simulation, and the correctness of the theoretical simulation can be effectively verified. The research provides a theoretical basis for fault prevention and diagnosis of MLDSB.

Impact-Rubbing Dynamic Behavior of Magnetic-Liquid Double Suspension Bearing under Different Protective Bearing Forms

The magnetic-liquid double suspension bearing (MLDSB) is a new type of suspension bearing, with electromagnetic suspension as the main part and hydrostatic supports as the auxiliary part. It can greatly improve the bearing capacity and stiffness of rotor-bearing systems and is suitable for a medium speed, heavy load, and frequent starting occasions. Compared with the active electromagnetic bearing system, the traditional protective bearing device is replaced by the hydrostatic system in MLDSB, and the impact-rubbing phenomenon can be restrained and buffered. Thus, the probability and degree of friction and wear between the rotor and the magnetic pole are reduced drastically when the electromagnetic system fails. In order to explore the difference in the dynamic behavior law of the impact-rubbing phenomenon between the traditional protection device and hydrostatic system, the dynamic equations of the rotor impact-rubbing in three kinds of protection devices (fixed ring/deep groove ball bearing/hydrostatic system) under electromagnetic failure mode are established, and the axial trajectory and motion law of the rotor are numerically simulated. Finally, the dynamic behavior characteristics of the rotor are compared and analyzed. The results show that: Among the three kinds of protection devices (fixed ring/deep groove ball bearing/hydrostatic system), the hydrostatic system has the least influence on bouncing time, impact-rubbing force, and impact-rubbing degree, and the maximum impact-rubbing force of MLDSB is greatly reduced. Therefore, the protective bear is not required to be installed in the MLDSB. This study provides the basis for the theory of the “gap impact-rubbing” of MLDSB under electromagnetic failure, and helps to identify electromagnetic faults.

Influence of Design Parameters on Static Bifurcation Behavior of Magnetic Liquid Double Suspension Bearing

Magnetic liquid double suspension bearing (MLDSB) includes electromagnetic system and hydrostatic system, and the bearing capacity and stiffness can be greatly improved. It is very suitable for the occasions of medium speed, heavy load, and starting frequently. Due to the mutual coupling and interaction between electromagnetic system and hydrostatic system, the probability and degree of static bifurcation are greatly increased and the operation stability is reduced. And flow of bearing cavity, coil current, oil film thickness, and galvanized layer thickness are the key parameters to ensure operation safe and stable, which has an important influence on the static bifurcation behavior. So this article intends to establish the coupling model of MLDSB to reveal the range of parameter combination in the case of static bifurcation. The influences of different parameter groups on the singularity characteristics, phase trajectory, x − t curves, and suction basin of the single DOF bearing system are analyzed. The result shows that there are nonzero singularities and static bifurcation occurs when ε 2 &gt; 0 or δ 2 &gt; 0 . As the flow of bearing cavity, coil current, oil film thickness, and galvanized layer thickness changes in turn, the singularities will convert between stable focus, unstable focus, stable node, and saddle point, and then the stable limit cycle may be generated. The attractiveness of singularity will change greatly with the flow of the bearing cavity and coil current changes slightly in the case of small current or large flow. The minimal change of galvanized layer thickness will lead to the fundamental change of the final stable equilibrium point of the rotor, while the final equilibrium point is slightly affected by the oil film thickness. This study can provide a reference for the supporting stability of MLDSB.