Analisis dan penilaian prestasi lengah lepas tangan menggunakan protokol pencetusan sesi (SIP) bagi sistem terintegrasi UMTS-WLAN

Teknologi rangkaian tanpa vvayar 4G merupakan penggabungan beberapa teknologi rangkaian capaian yang berbeza seperti rangkaian Universal Mobile Telecommunication System (UMTS) dan Rangkaian Kawasan Setempat Tanpa Wayar (WLAN). Rangkaian 4G menyokong mobiliti tanpa kelim {seamless) dalam menjanjikan perhubungan dan perkhidmatan yang terbaik kepada pelanggan. Protokol Pencetusan Sesi (SIP) yang berada pada lapisan aplikasi telah diramalkan sebagai calon terbaik bagi menguruskan mobiliti di dalam rangkaian 4G. Rangkaian 4G yang menawarkan aplikasi multimedia dalam perkhidmatannya mesti mempunyai lengah lepas tangan yang rendah bagi mencapai objektif penubuhannya. Tujuan utama disertasi ini adalah untuk menilai lengah lepas tangan bagi sistem terintegrasi UMTSWLAN yang menggunakan SIP sebagai protokol pengisyaratan. Model simulasi menggunakan MATLAB dibangunkan untuk menilai prestasi lengah lepas tangan tersebut. Model simulasi menggambarkan pergerakan hos mobil ke rangkaian UMTS dan WLAN. Lengah lepas tangan yang berlaku diukur berdasarkan model analitik. Prestasi lengah lepas tangan dinilai berdasarkan perubahan kadar ralat kerangka (FER), kadar ketibaan sesi SIP dan halaju hos mobil (MIT) semasa MH bergerak ke rangkaian UMTS dan WLAN. Keputusan simulasi menunjukkan bahawa lengah lepas tangan meningkat dengan penambahan FER dan kadar ketibaan sesi SIP. Halaju kebolehgerakan pengguna memberi kesan terhadap nilai lengah lepas tangan. Keputusan juga menunjukkan lengah lepas tangan minimum yang berlaku sewaktu MH bergerak ke rangkaian UMTS adalah 1.9565 saat dengan lebar jalur saluran 128kbps dan ke rangkaian WLAN adalah sekitar 0.8651 saat dengan lebar jalur saluran 11 Mbps. Berdasarkan nilai ini, lengah lepas tangan semasa MH bergerak ke rangkaian UMTS atau WLAN adalah tidak boleh diterima untuk penjurusan multimedia. Di dalam kajian ini didapati capaian tanpa wayar GPRS menyumbang lengah terbesar daripada keseluruhan lengah lepas tangan ke rangkaian UMTS

Evaluation of alternative approach for suspension corner damping by the use of hydraulic top mounts

The scope of “Evaluation of alternative approach for suspension corner damping by the use of hydraulic top mounts” is the analysis of the benefit given by the implementation of a hydraulic mount as the top mount for a vehicle suspension system. The whole project is based on numerical simulations performed by means of MATLAB®/Simulink®. Therefore, the modelling of the selected hydraulic top mount by means of a system of springs, dampers and masses was the starting point of the project. Afterwards, the aforementioned hydraulic top mount model was inserted into a quarter car model and its performance was compared to that of an equivalent quarter car model employing a rubber top mount, instead. Therefore, the quarter car model with the rubber top mount represented the reference model to assess the performance of the new hydraulic top mount. In particular, both linear and nonlinear quarter car models were developed, the former were used to check the robustness of the model itself and the latter were used to carry out all the comparisons with the reference models. Different chirp signals were used as input for all the linear models, while random road and single asperity signals were employed as inputs for the nonlinear models. Furthermore, in order to explore the potential improvements that could be achieved by implementing the hydraulic top mount, a second arrangement for the relative position of the hydraulic top mount and the shock absorbed in the quarter car model was modelled and, then, tested. A slight better performance was recorded in the case of models containing the hydraulic top mount. Finally, for a better understanding of the characteristics of the hydraulic top mount, a Design of Experiments (DOE) that takes into account the parameters of the mount hydraulic components was carried out; DOE methodology allowed one to identify the most influential factors in the quarter car model performance. Additionally, the analysis of DOE results was employed as a starting point to perform a first optimization of the hydraulic top mount. The simulation carried out employing the optimized top mount showed a relevant improvement with respect to the base hydraulic top mount and, a fortiori, with respect to the rubber top mount case. Moreover, it was shown that the second arrangement for the hydraulic top mount in the quarter car model could give even better performance than the model with the standard arrangement

Mathematical modelling techniques for the computer simulation of vehicle dynamic performance and response

Abstract available: [p. 2

Ride and handling assessment of vehicles using four-post rig testing and simulation

The tuning of production road car suspension parameters in the development stage of a vehicle can be a lengthy and expensive procedure and commonly relies on the subjective judgements of test drivers to assess various aspects of ride and handling. The work in this thesis aims to create a testing and tuning technique using four-post rig testing and vehicle simulation to significantly reduce the amount of physical and subjective testing required within the development stage. A four-post rig testing technique is developed using modal sine sweep inputs to acquire the response of the vehicle in the heave, pitch, roll and warp modes of excitation. An analysis and parameter estimation method is developed based on four-post data and a 7 degree-of-freedom model, with four-post test data used to validate the parameter estimation and vehicle model simultaneously, obtaining satisfactory results in all but the roll mode of excitation. The BS 6841 [1] discomfort acceleration weightings are applied to the modal responses, with road input PSDs representative of standardised roads and driving cycles used to produce a comfort index value for a tested vehicle or setup. A novel performance index is created to estimate grip loss due to static and dynamic tyre properties for each axle, which allows the prediction of road input effects on the total grip and balance of the vehicle, as well as a driver requirement of steering input. MATLAB code is constructed for the parameter estimation procedure and for three general user interfaces to assist with the testing, tuning and benchmarking procedure. An objective-subjective validation exercise is carried out using a single vehicle with four different component setups which are tested on the four-post rig to determine comfort and performance index values, as well as recording the subjective assessments of three test drivers on two drive routes in the UK and Germany. The results show fair to good correlation for comfort measures but generally poor correlation to the performance index, mostly because of large variations between the drivers’ subjective assessment criteria

Implications of nonlinear suspension behaviour for feedforward control of road noise in cars

Active control offers a lightweight solution to the problem of low frequency structure-borne road noise in cars. Feedforward control of road noise is predominantly limited by the difficulty of finding reference signals that are highly coherent with the sound in the cabin. One factor that could restrict the coherence of the reference signals, and therefore the performance of a linear control system, is the behaviour of nonlinear components in the suspension. The purpose of this research is to identify potential sources of nonlinearity in a car’s suspension and investigate their influence on the propagation of structure-borne road noise into the cabin. The details of experiments and simulations are described that aim to quantify the role of nonlinearity in the suspension’s dynamics, and determine to what extent it limits the performance of a linear feedforward road noise control system. The results of experiments conducted on a Nissan Leaf test vehicle are presented that establish the theoretical maximum noise reduction that can be achieved with a linear control system using reference sensors placed at the wheel hubs. Laboratory experiments on the components in the Nissan Leaf’s suspension are presented that identify the hydraulic dampers as the main source of nonlinearity in the road noise transmission path. Models of the key components in a car suspension are developed based on the results of the experiments. Models for the front and rear dampers in the Nissan Leaf are validated up to 300 Hz, and analysed to reveal the mechanisms causing their nonlinear dynamics. Models for the bushings, springs and wishbone are developed and combined into a full suspension model. The suspension model’s predictions add to the evidence from the measurements that road noise transmission is strongly influenced by nonlinearity in the damper. Some implications of the suspension’s nonlinear dynamics for feedforward control of road noise are then explored. The linear control systems used currently are often limited to one reference sensor on each suspension; a simplified analysis of a two transmission path suspension system shows that, if one path is nonlinear, a linear control system with a single reference sensor can not cancel all of the noise generated at the wheel. This thesis presents strong evidence that nonlinear suspension dynamics limit the performance of feedforward road noise controllers. A nonlinear model of vibration transmission through a suspension is developed and guidelines are suggested for reference sensor selection.Bose Corporatio

A numerical investigation on active engine mounting systems and its optimization

In this paper, based on the previous research experiences in the lumped parameter modeling and study of active control mounts (ACM) model, an analytical model of active ACM in powertrain is developed and implemented in MATLAB. In order to validate this newly developed model in this work, a finite element analysis (FEA) method is conducted in ANSYS and the results of FEA is compared with analytical model for validation. After the validation, the control strategy is integrated into the analytical model by using the linear quadratic regulator (LQR) method. Numerical results show a good control performance. Furthermore, this work examines the application of genetic algorithms (GA) in optimizing the weight matrices of LQR. An optimal configuration is obtained and thus this approach could help the practical design of ACM systems

Optimisation of racing car suspensions featuring inerters

Racing car suspensions are a critical system in the overall performance of the vehicle. They must be able to accurately control ride dynamics as well as influencing the handling characteristics of the vehicle and providing stability under the action of external forces. This work is a research study on the design and optimisation of high performance vehicle suspensions using inerters. The starting point is a theoretical investigation of the dynamics of a system fitted with an ideal inerter. This sets the foundation for developing a more complex and novel vehicle suspension model incorporating real inerters. The accuracy and predictability of this model has been assessed and validated against experimental data from 4- post rig testing. In order to maximise overall vehicle performance, a race car suspension must meet a large number of conflicting objectives. Hence, suspension design and optimisation is a complex task where a compromised solution among a set of objectives needs to be adopted. The first task in this process is to define a set of performance based objective functions. The approach taken was to relate the ride dynamic behaviour of the suspension to the overall performance of the race car. The second task of the optimisation process is to develop an efficient and robust optimisation methodology. To address this, a multi-stage optimisation algorithm has been developed. The algorithm is based on two stages, a hybrid surrogate model based multiobjective evolutionary algorithm to obtain a set of non-dominated optimal suspension solutions and a transient lap-time simulation tool to incorporate external factors to the decision process and provide a final optimal solution. A transient lap-time simulation tool has been developed. The minimum time manoeuvring problem has been defined as an Optimal Control problem. A novel solution method based on a multi-level algorithm and a closed-loop driver steering control has been proposed to find the optimal lap time. The results obtained suggest that performance gains can be obtained by incorporating inerters into the suspension system. The work suggests that the use of inerters provides the car with an optimised aerodynamic platform and the overall stability of the vehicle is improved