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Design of semiactive rear damper for electrobikes
Uhlíř, Radim ; Růžička, Bronislav (referee) ; Strecker, Zbyněk (advisor)
When riding off-road motorcycle, the rider's comfort and the grip of the driven wheel are crucial factors. That is why efforts are constantly being made to develop better shock absorbers that provide better comfort and rideability. Semi-actively controlled magnetorheological dampers can provide a significant improvement in vibroisolation properties. The aim of this thesis was to design, manufacture and test a fast magnetorheological damper for the rear structure of the Kuberg Freerider off-road electric motorcycle. The design damping characteristics were based on those of the factory DNM Burner RCP-2S damper. The magnetic circuit of the damper was designed using magnetostatic FEM analysis and the time response of the piston group was verified using transient electromagnetic FEM analysis. Subsequently, structural analysis of selected parts was performed, and the damper was fabricated and tested. A function sample of the magnetorheological damper with a 240 mm pitch, 76 mm stroke, dynamic range of 9.1 at a piston velocity of 0.1 m/s and an average time response of 6.6 ms has been created.
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Semi-actively controlled magnetorheological damper of electric motor fork
Blahuta, Jiří ; Vimmr, Jan (referee) ; Kubík, Michal (advisor)
The passive dampers used today, which work by dissipating energy using an oil fill, allow only limited damping force adjustment, which must be set before driving. Passive dampers are at their peak in terms of design and no further advances in ride comfort are expected. This is where magnetorheological dampers have the potential to increase ride comfort and improve handling with semi-active control. They achieve better performance thanks to a rapid change in damping force, which can then be controlled almost instantly according to the current driving conditions. MR dampers are already successfully used in the automotive sector but have not yet made a commercial breakthrough in the cycling segment. The main reason is their high weight compared to current passive dampers. The aim of this work is to design a lightweight and fast MR damper for the fork of a Kuberg electric motorbike. For the success of the product, the weight of the design needs to be minimized. For the proper operation of a semi-active damper, it is necessary to achieve a fast time response of the damping force, which is most affected by the occurrence of eddy currents in the magnetic circuit. Another problem is to achieve sufficient damping force in the activated state, so a suitable prediction model must be used. The design of the damper also needs to be able to fit into the limited space of the fork and the damper must be fitted with sensors. The result of this work is the design of two generations of MR damper and the fabricated working sample. Generation I MR damper was used for testing and verification of the model. Generation II MR damper is then the final design with reduced mass. The weight of the generation II damper is only 19% higher than the original passive damper. The total weight of the MR damper is 1,6 kg. The new MR damper retains the original dimensions and stroke and has integrated sensors in the design. The proposed MR damper has the potential to be successful in the electric bicycle segment and other electric single-track vehicles where its implementation is most advantageous. However, it can also be used in conventional mountain bikes. Together with a semi-active control unit, it allows for better ride comfort and handling characteristics.
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Reconstruction of undetachable LORD MR damper
Lochman, Vít ; Macháček, Ondřej (referee) ; Mazůrek, Ivan (advisor)
The bachelor´s thesis deals with the design and the realization of the modification of the non-demountable magnetorheological damper LORD, which has gained an atypical Fv characteristic in the course of time. The first part of the thesis deals with the operation of the magnetorheological liquid and the various design variants of the magnetorheological dampers. The practical part is devoted to the reverse engineering and the design of the damper modification itself. The complete drawing documentation of the original and the modified damper is included in this work.
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Design of fast magnetorheological damper piston group using selective laser melting technology
Vítek, Petr ; Růžička, Bronislav (referee) ; Strecker, Zbyněk (advisor)
The diploma thesis deals with the development of the magnetic circuit of Magnetoreological (MR) dampers with a short time response. To achieve a short response time, a shape approach was chosen whereby the geometry of the magnetic circuit was chosen to significantly eliminate the occurrence of eddy currents. The influence of structures on magnetic properties was first examined on a simpler toroidal core and then the optimization was subjected to the magnetic circuit of the MR damper itself. Geometry optimization was done using FEM simulations. The resulting geometry was made of pure iron using Selective Laser Melting technology (SLM). In addition, a MR damper was completed and its properties on air and with MR fluid were measured, which were then compared with previously developed rapid MR dampers. It has been found that the newly designed magnetic circuit achieves similar time responses as all other compared fast MR dampers and reaches a higher dynamic range than most of the compared variants. The proposed magnetic circuit also has a significantly reduced weight.
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Magnetorheological shock absorber with short response time for train bogie
Šebesta, Karel ; Špalek, Petr (referee) ; Kubík, Michal (advisor)
The diploma thesis deals with the design of a magnetorheological damper with a short response time of the damping force for the bogie of a rail vehicle. The largest component, which slows down the response, is the eddy currents generated in the piston group of the MR damper. A rapid onset of damping force is achieved by using a shape approach in magnetic circuit design. The shape approach increases the distance that the eddy currents must travel, and therefore it helps to reduce them. The shape approach is realized by grooving the core and the shell of the MR damper. The proposed fast version of the MR damper is measured on a hydraulic pulsator and its results show a sufficient time response of the damping force. This response does not exceed 8 ms for the primary onset of the damping force. The new fast design of the MR damper combines the greatest advantages of the technology and enables to meet new requirements for damping elements in the rolling stock chassis.
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Adjustable dampers
Doležal, Kamil ; Blaťák, Ondřej (referee) ; Vančura, Jan (advisor)
This thesis elaborates with information about basic types of dampers, which are used nowadays. There is a description of primary parts and function of passive, adaptive, semiactive and active suspension systems. A part of a work is also evaluation of their advantages and disadvantages.
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Adaptive control of magnetorheological dampers
Míša, Jiří ; Porteš, Petr (referee) ; Zháňal, Lubor (advisor)
The topic of this master´s thesis is the design of adaptive damping algorithm for the prototype magnetorheological dampers, which are used for Formula Student vehicle. The prime output is the development and optimization of the control algorithm which included usage of the MBS software and real data from race track. Temperature compensation to supress the effect of dynamic viscosity of magnetorheological fluid due to the increase in operating temperature and testing of the vertical dynamic of the car on 4 - post test rig was realized as well. The main goal was to obtain better control of the car in transient situations and increase usability of tires via changes in damping based on actual conditions and status of the vehicle.
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Limiting and Degradation Processes of Magnetorheological Suspension Dampers
Roupec, Jakub ; Bauer, František (referee) ; Ondrůšek, Čestmír (referee) ; Dobeš, Petr (referee) ; Mazůrek, Ivan (advisor)
This work deals with the research of degradation of magnetorheological (MR) fluid during long-term loading under conditions that correspond to the real load in the linear MR devices such as dampers. The behaviour of MR fluid is described by a Bingham model of viscoplastic fluid. The parameters of this model are the yield stress and viscosity. Their values are determined by the shear rate from 1 to 2,8104 s-1. Results of durability tests show a significant decrease in viscosity of MR fluid, a gradual increase in yield stress in the off-state and a significant decrease in MR effect. The paper also described the effect of temperature on these parameters and there is also designed a method of non-assembly diagnostic of the MR fluid state in the damper using the "rate of pulsation."
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Design of semiactive seat suspension for agricultural machines
Zindulka, Martin ; Čížek, Petr (referee) ; Strecker, Zbyněk (advisor)
The thesis deals with design of a semiactive seat suspension system for an agriculture machines and design of dynamic model of the system, which includes real parameters of a magnetorheological (MR) damper. The dynamic model is a single degree of freedom model and it is made in program Matlab. In the model, response time of the MR damper and three control algorithms are implemented (two-state Skyhook, Skyhook linear approximation damper control and Acceleration Driven Damper control). Based on the results of the simulations, the damping characteristics are defined, and the MR damper is modified to achieve fast response time. A test seat is designed to test transmission of vibrations to the driver. The simulation results provide a comparison of efficiency of the seat suspension depending on the response time and control algorithm, as well as a comparison with a passive suspension system. On the designed test seat with MR damper with a fast response time, the vibration transmission is reduced up to 25 % compared with the best passive seat suspension setup.
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