Pressure Control Approach Research Articles

Online multi-objective optimization for tunnel boring machine segment assembly considering stress concentration

To address stress concentration issues during the assembly of tunnel boring machine (TBM) segments, particularly in the context of synchronous excavation and segment assembly (SESA) TBMs, this paper presents an optimization framework focused on hydraulic cylinder pressure redistribution. The paper develops a Bayesian optimization extreme gradient boosting (BO-XGBoost) model for cylinder status detection and devises an online Archimedean optimization algorithm (AOA) for cylinder pressure redistribution. Verification of the proposed approach's effectiveness is conducted using a SESA TBM experimental bench. The results indicate that: 1) The proposed hydraulic cylinder status detection model effectively distinguishes various cylinder operating statuses, achieving a high F1-score of 0.9891. 2) Across the six segment assembly scenarios, the stress concentration phenomenon can be improved by 16.03%, 14.29%, 8.84%, 31.10%, 15.47%, and 11.11%, respectively. 3) In comparison to the offline optimization algorithm, the online algorithm reduces the maximum pressure by 36.69% and decreases algorithmic error by 30.50%. A key contribution from this paper is the introduction of an active pressure control approach integrated with the online multi-objective optimization algorithm, which is helpful in effectively improving the stress concentration phenomenon in the SESA TBM.

Patient preference for renal denervation therapy in hypertension: A cross-sectional survey in Chengdu, China.

This study investigated patient preferences for renal denervation (RDN) therapy in hypertension patients in Chengdu, China. A questionnaire-based cross-sectional study was conducted between August and December 2020. First, we collected and analyzed information on demographics, the duration of hypertension, the presence or absence of medication, the medication regimen, the duration of medication, maximal and minimal blood pressure levels, self-reported comorbidities, the willingness of patients to choose RDN as a blood pressure control strategy, choice determinants and expectations for RDN. In total, 485 patients were interviewed, and 402 questionnaires were eligible for analysis. The mean age of the participants was 61 years, 53.9% of the participants were male, and 32.6% of the patients demonstrated a willingness to choose RDN as a blood pressure control strategy. The proportion of patients who were already on medication was 34.7%, whereas the proportion of those who were not on medication was 23.3%. Furthermore, 47.3% of the patients would choose RDN treatment if the procedure could decrease their blood pressure by over 20 mmHg, while no patient would choose the device treatment if their blood pressure would decrease by less than 5 mmHg. In addition, 56.5% of the patients expected that they could take one less medication after RDN. Approximately 70% of the patients expected that RDN could consistently decrease their blood pressure for at least 15 years. In summary, among hypertensive patients in Chengdu, an estimated one-third were willing to choose RDN therapy as a blood pressure control approach; these patients were younger, more likely to be male, took more antihypertensive drugs, and had concomitant metabolic disorders. The perspectives of patients on RDN were not dependent on their education levels; also, their expectations for RDN were high.

Air flow rate and pressure control approach for the air supply subsystems in PEMFCs

Simultaneous control of the air flow rate and the cathode pressure plays an essential role in enhancing the performance and prolonging the service life of a polymer electrolyte membrane fuel cell (PEMFC). However, this is challenging to implement in practice due to the high complexity and coupled dynamics of the air supply subsystem in the PEMFC. This work, based on a simplified control-oriented model, puts forward a disturbance-observer-based multi-output feedback control strategy to address the issue of synergistically controlling the air flow rate and cathode pressure. The disturbances (Including humidity, temperature, water vapor, etc.) are estimated through an extended state observer (ESO). The final control law, which takes the disturbances observation into account, is designed through feedback linearization technique. A complex, high-order, nonlinear model is used as the high-fidelity plant in the validation process, and a series of simulations are implemented under different operational conditions. The outcomes show that the proposed control strategy offers a rapid dynamic response, precise steady-state tracking performance, and strong robustness against disturbances and unmodeled dynamics.

Pressure Prediction by Programme Logic Control Approach on Superplastic Forming in 7075 Al Alloy

A widespread problem in a superplastic forming process is to obtain a uniform thickness distribution in multiple geometry components. Hence, nowadays, the variable pressure control approach has been implementing in order to obtain uniform thickness variation in complex profiles. This paper observed the outcome of various stages in the superplastic forming process for multistage hemispherical die cavity in a newly developed pressure prediction method. Superplastic behaviour such as forming pressure, forming temperature, forming time and thickness distribution are analysed and optimised all parameters in multi-stage profile by using a new pressure prediction approach. Experimentally and numerically evaluated the superplastic parameters and the values are obtained from finite element methods agrees well with the experimental results.

Method and System for Testing the Working Characteristics of Vehicle Fuel Injector

Background: The vehicle fuel injector directly affects the power performance, emission characteristics and economic efficiency of the engine. At present, several testing standards are stipulated on accurate measurement of the working characteristics of fuel injectors. Objective: The purpose of this study is to provide an efficient patent about the method and system for testing the working characteristics of a vehicle fuel injector. Methods: Two key techniques are significant to establish a standard test environment. The patent about the pressure control approach and the injector driving method was proposed. The adaptive fuzzy PID approach was applied to control pressure. An adaptive multi-functional driver was designed and developed for both the voltage-driven and current-driven port fuel injectors. Results: The experiments on the two key technologies were conducted. During the dynamic flow test, the settling time using the system was 1ms. For the static flow test, the settling time was 1 s. The maximum changing rate of pressure fluctuation was 1%. Then, the system was verified by test on the flow characteristics and dynamic response of the voltage-driven and current-driven injectors. The linear deviation of each dynamic flow curve was between ± 3% to ± 6%. Furthermore, the deviation of the dynamic flow curves from the repeated test was small. The maximum deviation of the static flow results was less than 4% and the dynamic response of the injector varied with the change of the pressure. Conclusion: The system meets the requirements of the related standards. The experimental results prove that the system is stable and reliable.

Peak blood pressure-guided monitoring may serve as an effective approach for blood pressure control in the out-of-office setting.

We aimed to explore whether diurnal blood pressure (BP) peak characteristics have a significant influence on the association between left ventricular damage with the two BP components (morning BP vs. afternoon peak BP) in untreated hypertensives. This cross-sectional study included 1084 hypertensives who underwent echocardiography and 24-h ambulatory BP monitoring. Participants were stratified according to the relationship between morning systolic BP (MSBP; average SBP within 2h of waking up) and afternoon peak systolic BP (ASBP; average SBP between 16:00 and 18:00). Afternoon and morning hypertension was defined as≥135/85mm Hg. The morning and afternoon peak BPs occurred at around 7:00 and 17:00, respectively. In general hypertensives, morning BP and afternoon peak BP are significantly different in absolute values (for binary SBP, McNemar's χ2 =6.42; p=.014). ASBP was more pronounced than MSBP in 602 patients (55.5%), in whom 24-h SBP showed higher consistency with ASBP than with MSBP (Kappa value: 0.767 vs 0.646, both p<.01). In subjects with ASBP≥MSBP, ASBP was associated with left ventricular hypertrophy independent of MSBP (logistic regression analysis odds ratio: 1.046, p<.01), and left ventricular mass index was more strongly correlated with ASBP than with MSBP (multiple regression coefficient β: 0.453, p<.01), in which the relationships held true independently of 24-h SBP. The opposite results were obtained in subjects with MSBP>ASBP. Peak BP-guided monitoring may serve as an effective approach to out-of-office hypertension monitoring and control, providing the best consistency with 24-h average SBP and highest discrimination performance for target organ damage, independently of 24-h SBP.

Design and Experiment of Control Architecture and Adaptive Dual-Loop Controller for Brake-by-Wire System With an Electric Booster

Brake-by-wire (BBW) is a critical technology in modern automotive and lays a solid foundation for intelligent vehicles. A control strategy to take full advantage of this system both in the active brake and the conventional boosting brake is essential for the BBW system, which is a challenging issue because of its complex structure and high requirement for rapid dynamic response and control accuracy. To get satisfying performance and control effect, this article designs a new type of electric booster installing on the electrohydraulic brake (EHB) system that can realize active brake control and brake boosting simultaneously, and then, a synthetic control architecture special for this system is put forward. First, the system principle and detailed modeling are given. Then, an adaptive dual-loop brake pressure control approach is proposed where a modified PID controller is used as the outer control loop to track the desired pressure and an inner loop named adaptive current control is employed to guarantee the brushless direct electric motor (BLDC) performance of tracking current considering the parametric variation and system uncertainties. Besides, the stability of the inner loop control is proven. Meanwhile, a user-defined brake-boosting framework is designed to realize the electric boosting brake. Simulation and experimental validation are implemented to demonstrate the feasibility of the system and the effectiveness of the control strategy design eventually, manifesting that the proposed BBW system and its control strategy can obtain satisfying performance.

An Adaptive Resilient Control Approach for Pressure Control in Proton Exchange Membrane Fuel Cells

This paper introduces a novel controller design for pressure control in the proton exchange membrane (PEM) fuel cells. The proposed controller can control the system under the fault/failure of the actuators. The introduced design uses an artificial neural network for online fault detection and isolation in the pressure valves of the PEM fuel cell (PEMFC). We designed a nonlinear controller based on feedback linearization technique to compensate for the fault effects in real time. We also investigated the stability of the proposed design based on the Lyapunov theory. The simulation and the hardware in the loop results clearly show that the proposed active fault-tolerant control design is able to detect, estimate, and track the PEMFC actuators faults and failure accurately, and to compensate for their negative impacts while keeping the desired control performances in real time.

A study of the optimal control approach for a Kalina cycle system using a radial-inflow turbine with variable nozzles at off-design conditions

To maximize the exergy utilization efficiency of a Kalina cycle system with an ammonia-water radial turbine at off-design conditions, this study proposes a novel control approach named optimal control approach. An off-design model for ammonia-water radial-inflow turbine using variable nozzles is constructed. The optimal control approach is realized by changing the outlet angle of the radial-inflow turbine nozzle and the turbine inlet pressure. Design parameters of heat source (waste hot water) are 130 °C and 10 kg/s. To find out the performance advantage for the novel control approach, it is compared with two traditional control approaches. The results show that the proposed novel control approach presents the highest exergy utilization efficiency and net power at off-design conditions. The net power ratio of the optimal control approach to the traditional sliding pressure control approach reaches 111.22% as the heat source mass flow rate declines to 5 kg/s. Compared with the traditional approach for constant pressure control (changing turbine nozzle outlet angle), the optimal control approach has a potential to produce 3.11% more net power. The exergy utilization efficiency is generally declined with the elevated heat source mass flow rate at the approach for optimal control, while the system thermal efficiency is slowly increased.

Method to control an air conditioner by directly measuring the relative humidity of indoor air to improve the comfort and energy efficiency

In modern society, air conditioning systems are widely used in places where people tend to congregate, such as in homes, companies, schools and work sites. Both the dry-bulb temperature and relative humidity should be measured and controlled to achieve better comfort and to improve the energy efficiency of air conditioning systems. However, the current evaporation pressure control technique based on evaporator outlet pressure reading (EPCP) method only uses the dry-bulb temperature to control the evaporation pressure, making this method insufficient with regard to improving comfort. An evaporation pressure control approach based on the evaporator pressure and the relative humidity reading (EPCR) method is developed here. The EPCR method changes the evaporation pressure based on the dry-bulb temperature and the relative humidity of the air. The performance of an identical air conditioner is measured experimentally while switching the control method between the conventional EPCP method and the newly proposed EPCR method. The results demonstrate that the new EPCR method improves both the thermal comfort of indoor air and the energy efficiency.

A Flow Rate Control Approach on Off-Design Analysis of an Organic Rankine Cycle System

This study explored effects of off-design heat source temperature (TW,in) or flow rate (mW) on heat transfer characteristics and performance of an organic Rankine cycle system by controlling the flow rate of working fluid R245fa (i.e., the operation flow rate of R245fa was controlled to ensure that R245fa reached saturation liquid and vapor states at the outlets of the preheater and evaporator, respectively). The results showed that the operation flow rate of R245fa increased with TW,in or mW; higher TW,in or mW yielded better heat transfer performance of the designed preheater and required higher heat capacity of the evaporator; heat transfer characteristics of preheater and evaporator differed for off-design TW,in and mW; and net power output increased with TW,in or mW. The results further indicated that the control strategy should be different for various off-design conditions. Regarding maximum net power output, the flow rate control approach is optimal when TW,in or mW exceeds the design point, but the pressure control approach is better when TW,in or mW is lower than the design point.

Pneumatic Variable Series Elastic Actuator.

Inspired by human motor control theory, stiffness control is highly effective in manipulation and human-interactive tasks. The implementation of stiffness control in robotic systems, however, has largely been limited to closed-loop control, and suffers from multiple issues such as limited frequency range, potential instability, and lack of contribution to energy efficiency. Variable-stiffness actuator represents a better solution, but the current designs are complex, heavy, and bulky. The approach in this paper seeks to address these issues by using pneumatic actuator as a variable series elastic actuator (VSEA), leveraging the compressibility of the working fluid. In this work, a pneumatic actuator is modeled as an elastic element with controllable stiffness and equilibrium point, both of which are functions of air masses in the two chambers. As such, for the implementation of stiffness control in a robotic system, the desired stiffness/equilibrium point can be converted to the desired chamber air masses, and a predictive pressure control approach is developed to control the timing of valve switching to obtain the desired air mass while minimizing control action. Experimental results showed that the new approach in this paper requires less expensive hardware (on-off valve instead of proportional valve), causes less control action in implementation, and provides good control performance by leveraging the inherent dynamics of the actuator.

PLC-Based Pressure Control in Multi-Pump Applications

Abstract The paper is devoted to the centrifugal pumps represented the most popular type of pumping equipment used in different areas. The pressure control approach for variable speed driven (VSD) parallel connected centrifugal pumps is reported. The goal of the study is optimization of some quality indices, such as efficiency, consumed power, productivity, energy carrier temperature, heat irradiation, etc. One of them – efficiency – has been studied in the paper more carefully. The mathematical model of pumping process is discussed and a vector-matrix description of the multi-pump application is given. The program-based pressure control system is developed which productivity is changed by regulating the number of working pumps. The paper introduces new pressure control algorithms based on the working point estimation intended for programmable logical controllers (PLC). Experiments prove correctness of the offered methodology.

Triple‐step method to design non‐linear controller for rail pressure of gasoline direct injection engines

The precise control of rail pressure in gasoline direct injection (GDI) engines is considered as an important issue. This study presents a novel approach for rail pressure control of GDI engines. The control objective is to make the rail pressure track a given reference. Different from the existing non-linear controller design methods, the proposed method can be formalised as a triple-step procedure: (i) a steady-state control is deduced, playing the similar role of the map-based control strategy widely used in automotive control; (ii) a feed-forward control is derived concerning the variation of the tracking reference; and (iii) the previous two steps result in an explicit and affine expression of the tracking error dynamics, based on that a non-linear error feedback can be easily designed for enhancing the closed-loop performance and rearranged into a state-dependent PID. The structure of the designed non-linear controller is concise and is comparable to those widely used in modern automotive control. In addition, this procedure provides a concise design process so that the derivation of the control law is simplified and straightforward. A guideline of the control parameters tuning is given based on robustness analysis. Finally, the simulation results in the environment of AMESim with a realistic common rail injection system model show the efficiency of the proposed approach.

Effect of off-design heat source temperature on heat transfer characteristics and system performance of a 250-kW organic Rankine cycle system

This work investigated the effect of off-design heat source temperature on the heat transfer characteristics and system performance of a 250-kW organic Rankine cycle system. R245fa was used as a working fluid. The net power output was 243 kW and the system thermal efficiency was 9.5% under design conditions. For an off-design heat source temperature (TW,in), the operating pressure was controlled to meet that R245fa reached the saturation liquid and vapor states at the outlet of the preheater and evaporator, respectively. The results demonstrated that the increase rate in evaporation temperature was almost the same as that in TW,in; higher TW,in yields better heat transfer performance of the preheater and required a smaller evaporator heat capacity; and the net power output and system thermal efficiency increased linearly with increasing TW,in. The net power output increased by 41.9%, whereas the total heat transfer rate increased by only 7.0% for the studied range of TW,in. In conclusion, an off-design operation was studied by the pressure control approach within a heat source temperature variation of −10.3 °C to +19.8 °C from design, resulting in variations of −13.6% to +22.6% and −11.5% to +17.4% in the net power output and system thermal efficiency, respectively.

Efficient Thrust Distribution with Adaptive Pressure Control for Multinozzle Solid Propulsion System

An integrated approach for chamber pressure control and thrust distribution for multiple nozzles of a solid propulsion system is presented. In this study, a solid propulsion system with variable nozzle throat area controlled by a pintle actuator is considered. To keep the hardware configuration simple and lightweight, multiple nozzles share a combustion chamber. Consequently, changing the throat area of one nozzle results in an unintended change of chamber pressure and thrust from other nozzles. Therefore, pressure stabilization and thrust distribution for multiple nozzles should be conducted simultaneously to achieve the desired performance. For the inner control loop, an adaptive sliding mode controller with feedback linearization is used for pressure stabilization. With the pressure control loop working properly, a thrust distribution algorithm into 10 nozzles for translation and attitude maneuver is developed as an outer control loop.

Toward Quantitative Coarse-Grained Models of Lipids with Fluids Density Functional Theory.

We describe methods to determine optimal coarse-grained models of lipid bilayers for use in fluids density functional theory (fluids-DFT) calculations. Both coarse-grained lipid architecture and optimal parametrizations of the models based on experimental measures are discussed in the context of dipalmitoylphosphatidylcholine (DPPC) lipid bilayers in water. The calculations are based on a combination of the modified-iSAFT theory for bonded systems and an accurate fundamental measures theory (FMT) for hard sphere reference fluids. We furthermore discuss a novel approach for pressure control in the fluids-DFT calculations that facilitates both partitioning studies and zero tension control for the bilayer studies. A detailed discussion of the numerical implementations for both solvers and pressure control capabilities are provided. We show that it is possible to develop a coarse-grained lipid bilayer model that is consistent with experimental properties (thickness and area per lipid) of DPPC provided that the coarse-graining is not too extreme. As a final test of the model, we find that the predicted area compressibility moduli and lateral pressure profiles of the optimized models are in reasonable agreement with prior results.

Nonuniqueness of the Solution of the Sound Field Reproduction Problem with Boundary Pressure Control

This paper studies the circumstances under which the problem of reproducing a desired sound field using the boundary pressure control approach has a unique solution. The sound field reproduction problem is formulated as an inverse problem, in which the reproduction of the target sound field is attempted in the interior of a bounded control region surrounded by a continuous distribution of secondary sources. The determination of the secondary source strength is an ill-posed problem. A general formula for the solution is derived (assuming its existence) and it is shown that nonuniqueness arises when the wavenumber is one of the Dirichlet eigenvalues of the control region. It is shown that, when this is not the case, the solution of the problem is unique. Some strategies are presented that enable the nonuniqueness to be overcome. The case is also studied of the wavenumber being one of the Dirichlet eigenvalues of the region bounded by the secondary source distribution, which contains but generally does not coincide with the control region. The results derived are illustrated for a two dimensional problem with a finite number of secondary sources.

Blood Pressure in Firefighters, Police Officers, and Other Emergency Responders

Elevated blood pressure is a major risk factor for cardiovascular morbidity and mortality. Increased risk begins in the prehypertensive range and increases further with higher pressures. The strenuous duties of emergency responders (firefighters, police officers, and emergency medical services (EMS) personnel) can interact with their personal risk profiles, including elevated blood pressure, to precipitate acute cardiovascular events. Approximately three-quarters of emergency responders have prehypertension or hypertension, a proportion which is expected to increase, based on the obesity epidemic. Elevated blood pressure is also inadequately controlled in these professionals and strongly linked to cardiovascular disease morbidity and mortality. Notably, the majority of incident cardiovascular disease events occur in responders who are initially prehypertensive or only mildly hypertensive and whose average premorbid blood pressures are in the range in which many physicians would hesitate to prescribe medications (140-146/88-92). Laws mandating public benefits for emergency responders with cardiovascular disease provide an additional rationale for aggressively controlling their blood pressure. This review provides a background on emergency responders, summarizes occupational risk factors for hypertension and the metabolic syndrome, their prevalence of elevated blood pressure, and evidence linking hypertension with adverse outcomes in these professions. Next, discrepancies between relatively outdated medical standards for emergency responders and current, evidence-based guidelines for blood pressure management in the general public are highlighted. Finally, a workplace-oriented approach for blood pressure control among emergency responders is proposed, based on the seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure.

Improved web break strategy using a new approach for steam pressure control in paper machines

This paper presents a new strategy for steam pressure control during web breaks in the paper machine. The aim was to restart paper production with the same drying properties of the cylinder as before the break. A detailed physical dynamic model of the drying cylinder has been developed. The accuracy of the model has been verified through experiments made at the M-real paper mill in Husum, Sweden. Verifications are made both during normal operation and during web breaks. The dynamic model has been reduced in order to derive simple transfer functions which were used to find the optimal steam pressure trajectory during web breaks. The resulting strategy has been tested on a paper machine with good results and it has been well received at the mill.