Skyhook surface sliding mode control on semi-active vehicle suspension systems for ride comfort enhancement

A skyhook surface sliding mode control method was proposed and applied to the control on the semi-active vehicle suspension system for its ride comfort enhancement. A two degree of freedom dynamic model of a vehicle semi-active suspension system was given, which focused on the passenger’s ride comfort perform-ance. A simulation with the given initial conditions has been devised in MATLAB/SIMULINK. The simula-tion results were showing that there was an enhanced level of ride comfort for the vehicle semi-active sus-pension system with the skyhook surface sliding mode controller

Attenuation Of Electromagnetic Acoustic Noise From A Variable Speed Induction Motor By Using Dynamic Vibration Absorber.pdf

Hingar akustik elektromagnetik mempunyai ciri ton hingar yang dihasilkan oleh motor induksi kelajuan boleh ubah mewujudkan suasana yang tidak selesa kepada pengendali mesin. Hingar yang berlaku pada frekuensi tinggi ini kebiasaannya berlakupada gandaan frekuensi pensuisan pada pembalik. Penyelesaian masalah hingar ini pada umumnya dicapai dengan rekabentuk elektromekanikal dan modulasi lebar denyut untuk membasmi harmonik yang menyebabkan hingar. Penggunaan penyerap getaran dinamik adalah antara alternatif yang dikaji di dalam penyelidikan ini. Ujian spektrum menunjukan bahawa daya tindakan elektromagnetik mempengaruhi secara langsung hingar elektromagnetik yang dihasilkan oleh motor induksi. Gandaan harmonik 3 kHz pada spektrum modulasi lebar denyut berlaku juga pada spektrum getaran permukaan dan spektrum hingar. Analisis mod dan ujian spektrum menunjukan bahawa hingar dengan frekuensi 6 kHz pada kelajuan 1250 rpm dan ke bawah adalah disebabkan oleh getaran paksa. Pada halaju di atas 1250 rpm, hingar 3 kHz adalah disebabkan resonans. Bolt M6 sepanjang 20 mm digunakan sebagai penyerap getaran dinamik dan dipasang pada permukaan motor untuk mengurangkan hingar pada 6 kHz. Penyerap getaran dinamik menyerap getaran sebanyak 20% hingga 86%pada permukaan motor dan pengurangan aras tekanan bunyi sebanyak 12 dB(A) dapat dicapai. Ia juga berkesan pada lokasi lain pada motor dan juga pada semua kelajuan operasi. Penyerap getaran dinamik telah terbukti untuk mengurangkan hingar elektromagnetik daripada motor induksi kelajuan boleh ubah. _________________________________________________________________________________________________________________________ Tonal electromagnetic acoustic noise radiated from variable speed induction motor can be annoying to human operator. Occurring at high frequency, it often occurs at multiples of the inverter switching frequency. Solutions for the noise attenuation have been generally by means of electromechanical design and pulse width modulation (PWM) strategy to remove harmonics leading to noise generation. Dynamic vibration absorber (DVA) as an alternative solution was implemented in this research. Spectral test revealed that the input electromagnetic excitation has direct influence on the radiated electromagnetic acoustic noise from the induction motor. The multiples of 3 kHz harmonics in PWM spectrum was also present in the surface vibration and sound pressure spectrum. From experimental modal analysis and spectral test, it was found that the 6 kHz acoustic noise was due to forced vibration for speed of 1250 rpm and below. While at above 1250 rpm, the 3 kHz noise was due to resonance. A 20mm M6 bolt was used as DVA and attached to a point on the motor housing for targeted noise attenuation at 6 kHz. The DVA was able to absorb the surface vibration in the range of 20 to 86% and maximum sound pressure level reduction of 12 dB (A) was achieved. It was also effective at other locations on motor as well as at different operating speed

Innovative magnetorheological devices for shock and vibration mitigation

Vibration and impact protection have been a popular topic in research fields, which could directly affect the passengers’ and drivers’ comfort and safety, even cause spines fracture. Therefore, an increasing number of vehicle suspensions and aircraft landing gears are proposed and manufactured. Magnetorheological fluids (MRFs), as a smart material, are growly applied into the above device owing to its unique properties such as fast response, reversible properties, and broad controllable range, which could improve the vibration/impact mitigation performance. MRF was utilized to achieve adaptive parameters of the vehicle suspensions by controlling the magnetic field strength of the MRF working areas. Generally, the magnetic field is provided by a given current, subsequently, it would consume massive energy from a long-term perspective. Thus, a self-powered concept was applied as well. This thesis reports a compact stiffness controllable MR damper with a self-powered capacity. After the prototype of the MR damper, its property tests were conducted to verify the stiffness controllability and the energy generating ability using a hydraulic Instron test system. Then, a quarter-car test rig was built, and the semi-active MR suspension integrated with the self-powered MR damper was installed on a test rig. Two controllers, one based on short-time Fourier transform (STFT) and a classical skyhook controller was developed to control the stiffness. The evaluation results demonstrate that the proposed MR damper incorporated with STFT controller or skyhook controller could suppress the response displacements and accelerations obviously comparing with the conventional passive systems

Performance, robustness and sensitivity analysis of the nonlinear tuned vibration absorber

The nonlinear tuned vibration absorber (NLTVA) is a recently-developed nonlinear absorber which generalizes Den Hartog's equal peak method to nonlinear systems. If the purposeful introduction of nonlinearity can enhance system performance, it can also give rise to adverse dynamical phenomena, including detached resonance curves and quasiperiodic regimes of motion. Through the combination of numerical continuation of periodic solutions, bifurcation detection and tracking, and global analysis, the present study identifies boundaries in the NLTVA parameter space delimiting safe, unsafe and unacceptable operations. The sensitivity of these boundaries to uncertainty in the NLTVA parameters is also investigated.Comment: Journal pape

Electromechanical pendulum for vibration control and energy harvesting

This paper presents the design of an experimental electromechanical device for vibration control and energy harvesting. Traditionally, when the broadband resonant response due to a selected mode of a lightly damped structure needs to be controlled a vibration absorber is used. The resonance frequency of the absorber can be chosen to minimise the response of the structure under control. Optimising the damping ratio to achieve this aim also dissipates the most power in the damper, but care must be taken not to exceed the maximum throw of the device at high excitation levels. The absorber may also be mistuned by changes in operation condition and thus underperform. It is thus important to be able to design tuneable vibration absorbers, able to adapt their resonance frequency and their damping ratio depending on the operation condition.In this paper an electromechanical device consisting of a pendulum connected to an electrical motor is proposed. It is shown that by shunting the terminal of the device with an appropriate electrical circuit it is possible to control both its resonance frequency and its damping ratio. The power dissipated in the resistive part of the shunt circuit could also be harvested and used to implement the tuning mechanism, or for other purposes

An optimized tuned mass damper/harvester device

Much work has been conducted on vibration absorbers, such as tuned mass dampers (TMD), where significant energy is extracted from a structure. Traditionally, this energy is dissipated through the devices as heat. In this paper, the concept of recovering some of this energy electrically and reuse it for structural control or health monitoring is investigated. The energy-dissipating damper of a TMD is replaced with an electromagnetic device in order to transform mechanical vibration into electrical energy. That gives the possibility of controlled damping force whilst generating useful electrical energy. Both analytical and experimental results from an adaptive and a semi-active tuned mass damper/harvester are presented. The obtained results suggest that sufficient energy might be harvested for the device to tune itself to optimise vibration suppression

The phase-switched screen

Conventional (passive) radar-absorbent materials operate either by phase cancellation or by absorbing incident electromagnetic energy and converting it into heat. This paper examines a new type of active "absorber," called the phase-switched screen (PSS). The PSS operates quite differently from passive absorbers in that it exhibits an apparently low value of reflectivity by redistributing the electromagnetic energy incident upon it over a bandwidth that is wide enough to ensure that little reflected energy falls within the pass-band of the receiver. The discussion considers the basic temporal and spectral properties of several PSS topologies, and includes measured data on both planar and cylindrical PSS structures

LFI 30 and 44 GHz receivers Back-End Modules

The 30 and 44 GHz Back End Modules (BEM) for the Planck Low Frequency Instrument are broadband receivers (20% relative bandwidth) working at room temperature. The signals coming from the Front End Module are amplified, band pass filtered and finally converted to DC by a detector diode. Each receiver has two identical branches following the differential scheme of the Planck radiometers. The BEM design is based on MMIC Low Noise Amplifiers using GaAs P-HEMT devices, microstrip filters and Schottky diode detectors. Their manufacturing development has included elegant breadboard prototypes and finally qualification and flight model units. Electrical, mechanical and environmental tests were carried out for the characterization and verification of the manufactured BEMs. A description of the 30 and 44 GHz Back End Modules of Planck-LFI radiometers is given, with details of the tests done to determine their electrical and environmental performances. The electrical performances of the 30 and 44 GHz Back End Modules: frequency response, effective bandwidth, equivalent noise temperature, 1/f noise and linearity are presented