Comparison of several robust observers for automotive damper force estimation

International audienceThis paper aims at comparing three robust observers used to estimate the damping force of of elec-trorheological (ER) damper in a vehicle suspension system. Firstly, a nonlinear quarter-car model, augmented with a first-order dynamical nonlinear damper model, is developed. The first two methods are designed considering the nonlinearity as an unknown input and minimizing the effect of the unknown input disturbances (including nonlinearity term, measurment noise, unknown road profile) on the estimation errors, by using an H 2 and H ∞ criterion, respectively. The latter method is to only minimize the effects of measurement noises and road profiles on the state variable estimation errors by using a H ∞ criterion while the nonlinearity is bounded through a Lipschitz condition. Two low-cost sensors signals (two accelerometers data from the sprung mass and the unsprung mass) are considered as inputs for the observer designs. Finally, the observers are implemented on the INOVE testbench from GIPSA-lab (1/5-scaled real vehicle) to assess and compare experimentally the performances of the approaches. Both simulations and experimental results demonstrate a better effectiveness of the latter observer in terms of the ability of estimating the damper force in real-time despite the nonlinearity, the measurement noises and the road disturbances

LPV force observer design and experimental validation from a dynamical semi-active ER damper model

International audienceThis paper presents an LPV damping force observer of ElectroRheological (ER) dampers for a real automotive suspension system, taking the dynamic characteristic of damper into account. First, an extended nonlinear quarter-car model is considered, where the time constant representing the damper dynamics is varying according to the control level. This is rewritten as an LPV model which is used to design an LPV observer. The objective of the LPV observer is to minimize the effects of bounded unknown input disturbances (unknown road profile and measurement noises) on the state estimation errors through an H ∞ criterion, while the damper nonlinearity is bounded using a Lipschitz condition. Two low-cost accelerometers (the sprung mass and the unsprung mass accelerations) are used as inputs for the proposed methodology only. To experimentally assess the proposed approach, it is implemented on the 1/5-scaled real vehicle-INOVE testbench of GIPSA-lab. This shows the ability of the observer to estimate the damper force in real-time, face to unknown inputs disturbance and sensor noises

Application of Grey System Theory in Construction Management

Materials are an important input in building construction. They account for a substantial proportion of investment capital and construction volume. However, as material prices are often affected by the market, choosing the right construction supplier is not an easy decision for contractors, especially for those materials required during the finishing phase of construction. As one of these finishing materials is paint, identifying core criteria for evaluating and selecting the best construction paint supplier is a crucial economic choice for construction contractors. Assessing the importance of these criteria is a complex multi-criteria decision-making problem. To reflect the risks and uncertainties in this problem, this paper presents a grey system theory approach to prioritize important criteria for selecting paint material suppliers in construction projects

Design of an LMI-based Polytopic LQR Cruise Controller for an Autonomous Vehicle towards Riding Comfort

In this paper, we present an LMI-based approach for comfort-oriented cruise control of an autonomous vehicle. First, vehicle longitudinal dynamics and a corresponding parameter-dependent state-space representation are explained and discussed. An LMI-based polytopic LQR controller is then designed for the vehicle speed to track the reference value in the presence of noise and disturbances, where the scheduling parameters are functions of the vehicle mass and the speed itself. An appropriate disturbance force compensation term is also included in the designed controller to provide a smoother response. Then we detail how the reference speed is calculated online, using polynomial functions of the given desired comfort level (quantified by the vertical acceleration absorbed by the human body) and of the road type characterized by road roughness. Finally, time-domain simulations illustrate the method’s effectiveness

EFL Agreeing and Disagreeing Discourses in Facebook

Agreeing and disagreeing are two common speech acts that occur in social conversations. Driven by the fact that there are direct and indirect way for expressing agreement and disagreement, and there are also mitigating strategies to protect interlocutors from face-threatening in disagreeing discourses, this study examined EFL students’ use of discourse strategies in their Facebook interaction. Thirty-four pre-intermediate EFL students at a university in Vietnam took part in this study. Data analysis shows that direct discourses is linguistically limited while indirect ones exhibit wider language use. Students also demonstrate two different directions of using mitigating strategies for their disagreeing discourses. Some pedagogical implications are also suggested in this study. Keywords: agreeing, disagreeing, direct, indirect, strategies DOI: 10.7176/JLLL/86-03 Publication date: February 28th 202

PREPARATION OF ORAL CURCUMIN DELIVERY FROM 3D-NANO-CELLULOSE NETWORKS MATERIAL PRODUCED BY ACETOBACTER XYLINUM USING OPTIMIZATION TECHNIQUE

Objective: To prepare oral curcumin delivery and optimize curcumin loading of 3D-nano-cellulose networks material (3DCM) by looking into the impact of process variables on the response utilizing response surface methodology (RSM) and Box-Behnken design. Methods: Optimization of curcumin loading of 3DCM was conducted using RSM and Box-Behnken model. Impact of four independent variables, including, the concentration of curcumin (X1), temperature (X2), shaking speed (X3), and time of loading (X4), was studied on one dependent response, that is, an amount of loaded curcumin (Y). Characterization of optimized 3DCM including curcumin was examined by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) analysis . Results: R2 value for Y was approximately 0.94. X1 possessed the biggest positive impact compared to X2, X3 and X4. Optimized conditions for curcumin loading of 3DCM were X1 at 3 mg/ml, X2 at 40 °C, X3 at 120 rpm and X4 at 120 min. SEM photograph of 3DCM surfaces were found including fibers creating a 3D network structure. FTIR spectra studies depicted that there was no interaction between curcumin and 3DCM. Conclusion: The data obtained in this study thus suggest that curcumin loaded 3DCM was successfully fabricated to give a potential oral delivery system of curcumin

Application of Google Docs in English for Specific Purposes Collaborative Writing

English language learners today have considerable opportunities to practice their writing skill via their peer interaction in Web 2.0 platforms, such as Blogs, Wikis, and Google Docs. Different studies have investigated the influence of these platforms on student writing collaboration and interaction, but few studies had explored factors that may affect English for Specific Purposes (ESP) student collaborative writing in Vietnamese settings. This study, therefore, attempts to explore the impact of four factors, namely gender, student attitudes towards learning English, student economic status, and availability of English at home on Google Docs-based interaction and collaborative writing outcome at a southern university in Vietnam. Fifty participants took part in this study and they worked collaboratively in small groups in Google Docs to finish two writing tasks and complete a survey afterwards. Analysis of their survey, interaction, and writing outcome suggests that gender, student attitudes towards learning English, and the number of books available at their homes have an impact on their writing outcome whereas their economic status did not seemingly affect their writing quality. Some pertinent pedagogical implications are also discussed in this paper. Keywords: Google Docs, collaborative writing, English for Specific Purposes DOI: 10.7176/JLLL/78-02 Publication date: April 30th 202