Design and performance investigation of a novel 3DOF compact MR damper. - In: Smart materials and structures, ISSN 1361-665X, Bd. 31 (2022), 12, 125020, S. 1-14
Magnetorheological fluid (MR) based dampers have been established as an alternative to classical hydraulic dampers with proportional electromagnetic valves under vibration processes which demand adaptive damping forces. Almost all MR-dampers are spatially 1-Degree-of-Freedom (DOF) dampers, having only one axis or direction of damping force generation. In many technical applications there exist movements in more than one spatial DOF, eventually necessitating more than one damper. Because of this, the damping is required not only in one but in more spatial directions, yet adjustable. In this work, a new design of a spatial 3DOF MR damper is proposed to allow damping in three directions within one damping device. The underlying motivation is to spatially integrate three damping directions in one device to potentially reduce installation space compared to three separate 1 DOF dampers. The basic idea of the construction is to use one fluid chamber with several spatially distributed control elements at different positions of the fluid chamber. The control elements are electromagnets, generating the magnetic field in the fluid at different positions so that in total 3 spatial DOFs can be damped individually. Experiments and investigation are made, where the damper's behavior are analyzed not only in one single DOF but also in more than one DOF. It is shown, that the damping concept can generate damping in all three spatial DOFs, both individually or together. Moreover, the damping can be generated to be dominant in one specific direction, meanwhile minimum in the other direction orthogonal to it.
A compact 4-DoF MR damper with semi-independent damping adjustment. - In: IEEE Xplore digital library, ISSN 2473-2001, (2022), S. 101-104
Magnetorheological (MR) fluid-based damper systems have been known for their novel property to adjust its damping forces in milliseconds by changing the applied magnetic field strength. This adaptability comes along with a rather simple design compared to classical fluidic damper systems. However, the known operating modes of the MRF, such as shear, flow, squeeze, and pinch mode, are only able to generate damping in one specific direction. On the contrary, vibrations could occur not only in one direction but also in several directions. Therefore, it is desirable to have damping generated not only in one direction but also in several directions. In the worst case, N dampers would need to be installed to dampen vibrations in N translational and rotational directions. In this work, a damper design for a single and compact 4-DoF magnetorheological-based damper is proposed. The compactness is achieved by integrating several control elements to control the MR fluid. It is done by installing five electromagnets in one MR damper without adding any extra fluid chamber so that only one fluid chamber is needed for the damper system. Depending on the direction of the acting vibration, the corresponding electromagnet is then activated accordingly, which changes the state of the MR fluid in the chamber locally. Experimental investigations are conducted and the results are presented in this work. It can be seen from the results, that the design allows the MR damper to possess four degree-of-freedom by using only a single fluid chamber. Moreover, the damping can be adjusted, depending on the damping requirement.
Enhancement of shock absorption using hybrid SMA-MRF damper by complementary operation. - In: Actuators, ISSN 2076-0825, Bd. 11 (2022), 10, 280, S. 1-17
A hybrid damper concept is presented here using a combination of a Magnetorheological (MR) Fluid (MRF) and Shape Memory Alloy (SMA)-based energy dissipation. A demonstration is performed utilizing the shear operating mode of the MRF and the one-way effect of the SMA. The damping performance of different MRF-SMA configurations is investigated and the corresponding energy consumption is evaluated. We demonstrate that the operation of MRF and SMA dampers complement each other, compensating for each other's weaknesses. In particular, the slow response from the MR damper is compensated by passive SMA damping using the pseudoplastic effect of martensite reorientation, which can dissipate a significant amount of shock energy at the beginning of the shock occurrence. The MR damper compensates for the incapability of the SMA to dampen subsequent vibrations as long as the magnetic field is applied. The presented hybrid SMA-MR damper demonstrates superior performance compared to individual dampers, allowing for up to five-fold reduction in energy consumption of the MR damper alone and thereby opening up the possibility of reducing the construction volume of the MR damper.
A manually actuated continuum robot research platform for deployable shape-memory curved cannulae in stereotactic neurosurgery. - In: IEEE Xplore digital library, ISSN 2473-2001, (2022), S. 10-13
In this paper, a research platform for concentric tube continuum robots is developed in order to enable advances in deploying curved cannulae for stereotactic neurosurgery. The system consists of a manually operated high-precision actuation apparatus and a photogrammetric system with measurement errors in the range of 100 micrometer. With this platform, previously planned curved paths can be analyzed ex-situ w.r.t., e.g., target precision, follow-the-leader-behavior, and hysteretic phenomena. Regarding research towards an in-vivo application in human brains, first tests with porcine brain cadavers inside an intraoperative CT are conducted in order to pave the way for histological as well as target reachability studies.
Optimal path planning for stereotactic neurosurgery based on an elastostatic cannula model. - In: IFAC-PapersOnLine, ISSN 2405-8963, Bd. 55 (2022), 20, S. 600-605
In this paper, we propose a path-planning problem for stereotactic neurosurgery using concentric tube robots. The main goal is to reach a given region of interest inside the brain, e.g. a tumor, starting from a feasible point on the skull with an ideally short path avoiding certain sensitive brain areas. To describe the shape of the entire cannula from an entry point to the point of interest we use an existing mechanical model for continuum robots. We show numerically that our approach enables the surgeon to reach areas within the brain that would be impossible with a straight cannula as it is currently state of the art.
Review: a survey on configurations and performance of flow-mode MR valves. - In: Applied Sciences, ISSN 2076-3417, Bd. 12 (2022), 12, 6260, S. 1-22
Magnetorheological (MR) actuators are semi-active devices controlled by magnetic stimuli. The technology has been commercialized in the automotive industry or high-quality optical finishing applications. It harnesses the rheology of smart fluids to result in the unique application of the material. By a wide margin, the most common example of an MR actuator is a flow-mode single-tube housing with a control valve (electromagnet with a fixed-size air gap filled with the MR fluid) operating in a semi-active vibration control environment. The analysis of the prior art shows that the developed configurations of MR valves vary in size, complexity, the ability to generate adequate levels of pressure, and the interactions with the MR fluid’s rheology resulting in various performance envelopes. Moreover, miscellaneous testing procedures make a direct valve-to-valve comparison difficult. Therefore, in this paper we present a detailed and systematic review of MR control valves, provide classification criteria, highlight the operating principle, and then attempt to categorize the valves into groups sharing similarities in the design and performance envelope(s). Moreover, a simple performance metric based on the shear stress calculation is proposed, too, for evaluating the performance of particular valving prototypes. In the review, we discuss the key configurations, highlight their strengths and weaknesses and explore various opportunities for tuning their performance range. The review provides complementary information for the engineers and researchers with a keen interest in MR applications, in general. It is an organized and and critical study targeted at improvements in the categorization and description of MR devices.
Numerical and experimental investigation of a semi-active vibration control system by means of vibration energy conversion. - In: Energies, ISSN 1996-1073, Bd. 14 (2021), 16, 5177, insges. 19 S.
A vibration control concept based on vibration energy conversion and storage with respect to a serial-stiffness-switch system (4S) has previously been proposed. Here, we first present a rotational electromagnetic serial-stiffness-switch system as a novel practical vibration control system for experimental validation of the concept and, furthermore, an improved control strategy for higher vibration suppression performance is also proposed. The system consists of two spring-switch elements in series, where a parallel switch can block a spring. As an alternating mechanical switch, the experimental system uses two electromagnets with a shared armature. By connecting the armature to the rotating load or the base, the electromagnets decide which of the two spiral springs is blocked, while the other is active. A switching law based on the rotation velocity of the payload is used. Modelling and building of the experimental system were carried out. The corresponding experiment and simulation were executed and they matched well. These results prove that our serial-stiffness-switch system is capable of converting vibration energy and realizing vibration reduction under a forced harmonic disturbance. The effects of disturbance frequency, disturbance amplitude and sampling frequency on the system performance are shown as well. A position feedback control-based switching law is further put forward and experimentally verified to improve the repositioning accuracy of the disturbed system.
Modellierung und Entwurf eines schnell schaltenden Moving-Magnet-Antriebs für Mittelspannungsschalter. - In: Symposium Elektromagnetismus 2021, (2021), S. 155-164
Parallel field segmentation concept in ER/MR dampers for a simpler control system. - In: Actuator 2021, (2021), S. 385-388
Electromagnetic actuators. - In: Actuator 2021, (2021), S. 24-29