| 1. |
- Ingesson, Gabriel, et al.
(författare)
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Proportional–Integral Controller Design for Combustion-Timing Feedback, from n-Heptane to iso-Octane in Compression-Ignition Engines
- 2017
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Ingår i: Journal of Dynamic Systems, Measurement, and Control, ASME. - : ASME International. - 0022-0434 .- 1528-9028.
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Tidskriftsartikel (refereegranskat)abstract
- The problem of designing robust and noise-insensitive PI controllers for pressure-sensor based combustion-timing control was studied through simulation. Different primary reference fuels (PRF) and operating conditions were studied. The simulations were done using a physics-based, control-oriented model with an empirical ignition-delay correlation. It was found that the controllable region, in-between the zero-gain region for early injection timings and the misfire region for late injection timings is strongly PRF dependent. As a result, it was necessary to adjust intake temperature to compensate for the difference in fuel reactivity prior to the controller design. With adjusted intake temperature, PRF dependent negative-temperature coefficient behavior gave different system characteristics for the different fuels. The PI-controller design was accomplished by solving the optimization problem of maximizing disturbance rejection and tracking performance subject to constraints on robustness and measurement-noise sensitivity. Optimal controller gains were found to be limited by the high system gain at late combustion timings and high-load conditions, furthermore, the measurement-noise sensitivity was found to be higher at the low-load operating points where the ignition delay is more sensitive to variations in load and intake-conditions. The controller-gain restrictions were found to vary for the different PRFs, the optimal gains for higher PRFs were lower due to a higher system gain, whereas the measurement-noise sensitivity was found to be higher for lower PRFs.
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| 2. |
- Jonathan Muñoz-Vázquez, Aldo, et al.
(författare)
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An Exact Robust Differentiator Based on Continuous Fractional Sliding Modes
- 2018
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Ingår i: Journal of Dynamic Systems Measurement, and Control. - : American Society of Mechanical Engineers (ASME). - 0022-0434 .- 1528-9028. ; 140:9
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Tidskriftsartikel (refereegranskat)abstract
- The problem addressed in this paper is the online differentiation of a signal/function that possesses a continuous but not necessarily differentiable derivative. In the realm of (integer) high-order sliding modes, a continuous differentiator provides the exact estimation of the derivative f(over dot)(t), of f(t), by assuming the boundedness of its second-order derivative, f(over double dot)(t), but it has been pointed out that if f(over dot)(t) is casted as a Holder function, then fotthorn is continuous but not necessarily differentiable, and as a consequence, the existence of f(over dot)(t) is not guaranteed, but even in such a case, the derivative of f(t) can be exactly estimated by means of a continuous fractional sliding mode-based differentiator. Then, the properties of fractional sliding modes, as exact differentiators, are studied. The novelty of the proposed differentiator is twofold: (i) it is continuous, and (ii) it provides the finite-time exact estimation of f(over dot)(t), even if fotthorn does not exist. A numerical study is discussed to show the reliability of the proposed scheme.
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| 3. |
- Köroglu, Hakan, 1971, et al.
(författare)
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Platoon Control under a Novel Leader and Predecessor Following Scheme with the Use of an Advanced Aerodynamic Model
- 2018
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Ingår i: Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME. - : ASME International. - 0022-0434 .- 1528-9028. ; 140:4
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Tidskriftsartikel (refereegranskat)abstract
- The longitudinal platoon control problem is considered under a leader and predecessor following scheme with a novel velocity-dependent spacing policy. With this spacing policy, the steady-state inter-vehicle distances increase with increasing cruise velocity and more so for vehicles that are closer to the leader.} Since significant changes might be encountered in inter-vehicle distances during the travel due to the variations in the velocity of the leader, the problem is studied together with a more accurate modeling of aerodynamic effects within a platoon formation. Based on a standard feedback linearization approach, a dynamic output feedback synthesis problem is formulated with two H_infinity performance objectives. One of the performance objectives is linked to the string stability of the platoon formation, while the other can be shaped in a way to maintain small spacing errors without aggressive vehicle maneuvers. A synthesis procedure is then outlined based on linear matrix inequality optimization. The new control scheme is investigated for a three-vehicle platoon by using an advanced aerodynamic model developed based on extensive fluid dynamics simulations. It is observed in this investigation that a desirable platoon operation can be achieved even with a simple aerodynamic model, provided that the controller is designed in a way to ensure good disturbance attenuation. Nevertheless an accurate modeling of aerodynamic disturbances might be needed especially for the first vehicle after the leader when the cruising velocity varies over a wide range.
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| 4. |
- Vazquez, Carlos, et al.
(författare)
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Second-Order Sliding Mode Control of a Perturbed-Crane
- 2015
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Ingår i: Journal of Dynamic Systems Measurement, and Control. - : ASME International. - 0022-0434 .- 1528-9028. ; 137:8
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Tidskriftsartikel (refereegranskat)abstract
- A fiv degrees-of-freedom overhead crane system affected by external erturbaions is the topic f study. Existing method justhandle the nperturbed case or, in addition, the analysis is limited to three or wo degrees-of-freedom. A wide range of processes cannot be restricted o these scenarios and this paper goes a step forward proposing a ontrol solution for a five degrees-of-freedom system under the esence f matched and unmatched disturbances. The contribution includes a del escription and a second-order sliding mode (SOSM) control design nsuring the precise trajectory tracking for the actuated variables and t the same time the regulation of the unactuated variables. urthermore, the proposed approach is supported by the design of strong yapunov fnctions providing an estimation of the convergence time. imulations and experiments, including a comparison with roportional-integral-derivatie (PID) controller, verified the dvantages of the methodology.
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| 5. |
- Vodder Nielsen, Kraen, et al.
(författare)
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Control-Oriented Model of Molar Scavenge Oxygen Fraction for Exhaust Recirculation in Large Diesel Engines
- 2017
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Ingår i: Journal of Dynamic Systems Measurement, and Control. - : ASME. - 0022-0434 .- 1528-9028. ; 139:2
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Tidskriftsartikel (refereegranskat)abstract
- Exhaust gas recirculation (EGR) systems have been introduced to large marine engines in order to reduce NOx formation. Adequate modeling for control design is one of the bottlenecks to design EGR control that also meets emission requirements during transient loading conditions. This paper therefore focuses on deriving and validating a mean-value model of a large two-stroke crosshead diesel engine with EGR. The model introduces a number of amendments and extensions to previous, complex models and shows in theory and practice that a simplified nonlinear model captures all essential dynamics that is needed for EGR control. Our approach is to isolate and reduce the gas composition part of the more complex models using nonlinear model reduction techniques. The result is a control-oriented model (COM) of the oxygen fraction in the scavenge manifold with three molar flows being inputs to the COM, and it is shown how these flows are estimated from signals that are commonly available. The COM is validated by first comparing the output to a simulation of the full model, then by comparing with measurement series from two engines. The control-oriented nonlinear model is shown to be able to replicate the behavior of the scavenge oxygen fraction well over the entire envelope of load and blower speed range that are relevant for EGR. The simplicity of the new model makes it suitable for observer and control design, which are essential steps to meet the emission requirements for marine diesel engines that take effect from 2016.
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| 6. |
- Xinhua, Liu, et al.
(författare)
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Improved Neural Network Control Approach for a Humanoid Arm
- 2019
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Ingår i: Journal of Dynamic Systems Measurement, and Control. - : ASME Press. - 0022-0434 .- 1528-9028. ; 141:10, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- This study extended the knowledge over the improvement of the control performance for a seven degrees-of-freedom (7DOF) humanoid arm. An improved adaptive Gaussian radius basic function neural network (RBFNN) approach was proposed to ensure the reliability and stability of the humanoid arm control. Considering model uncertainties, the established dynamic model for the humanoid arm was divided into a nominal model and an error model. The error model was approximated by the RBFNN learning to compensate the uncertainties. The contribution of this study mainly concentrates on employing fruit fly optimization algorithm (FOA) to optimize the basic width parameter of the RBFNN, which can enhance the capability of the error approximation speed. Additionally, the output weights of the neural network were adjusted using the Lyapunov stability theory to improve the robustness of the RBFN-based error model. The simulation and experiment results demonstrate that the proposed approach is able to optimize the system state with less tracking errors, regulate the uncertain nonlinear dynamic characteristics, and effectively reduce unexpected interferences.
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| 7. |
- Yin, Lianhao, et al.
(författare)
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Nonlinear Estimation of Variables for Heat Release Calculation Using a Gradient Method
- 2019
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Ingår i: Journal of Dynamic Systems, Measurement, and Control, ASME. - : ASME International. - 0022-0434 .- 1528-9028. ; 141:6
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Tidskriftsartikel (refereegranskat)abstract
- Advanced combustion such as the partially premixed combustion (PPC) is characterized by high energy efficiency. However, they are sensitive to the inlet condition and injection of a combustion engine. Therefore, it is essential to use combustion feedback. The accuracy of the feedback variables, derived from the cylinder pressure signal, is crucial for effective combustion feedback control. This paper proposes a nonlinear least-squares regression method to estimate the pressure offsets and variable polytropic exponent in heat release calculation automatically. The combustion feedback variables derived from the auto-tuned heat-release rate were applied to a heavy-duty compression ignition (CI) engine burning with gasoline fuel.
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| 8. |
- Gorges, Martin, et al.
(författare)
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Hypothalamic atrophy is related to body mass index and age at onset in amyotrophic lateral sclerosis
- 2017
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Ingår i: Journal of Neurology, Neurosurgery and Psychiatry. - : BMJ. - 0022-3050 .- 1468-330X. ; 88:12, s. 1033-1041
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Our objective was to study the hypothalamic volume in a cohort of patients with amyotrophic lateral sclerosis (ALS) including symptomatic and presymptomatic ALS mutation carriers.Methods: High-resolution three-dimensional T1-weighted MRI datasets from 251 patients with sporadic ALS, 19 symptomatic and 32 presymptomatic ALS mutation carriers and 112 healthy controls (HC) were retrospectivally registered for manual delineation of the hypothalamus. The volume of the hypothalamus, in total or subdivided, was normalised to the intracranial volume and adjusted to age. Correlation analyses were performed with clinical and metabolic outcomes. Pathologically defined ALS stages were determined in vivo by diffusion tensor imaging (DTI).Results: We observed a severe atrophy of the hypothalamus both in patients with sporadic ALS (-21.8%, p<0.0001) and symptomatic ALS mutation carriers (-13.4%, p<0.001). The atrophy in patients with sporadic ALS was observed in both the anterior (-27.6% p<0.0001) and the posterior parts of the hypothalamus (-17.7%, p<0.0001). Notably, this atrophy was also observed in presymptomatic ALS mutation carriers (-15.5%, p<0.001) and was unrelated to whole brain volume atrophy or disease stage as assessed using DTI or functional status. Hypothalamic volume was correlated with body mass index (BMI) in patients with sporadic ALS (p=0.0434, Ρ=+0.1579), and this correlation was much stronger in patients with familial ALS (fALS) (p=0.0060, Ρ=+0.6053). Anterior hypothalamic volume was correlated with age at onset, but not with survival after MRI.Conclusions: Hypothalamus is atrophied in ALS, even in premorbid stages, and correlates with BMI, especially in fALS. Decreased anterior hypothalamic volume is associated with earlier onset of disease.
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