Open-loop Design Research Articles

Digital twin technology facilitates precision improvement in complex product assembly: A progressive deduction method of data-driven tolerance allocation

Advancements in aerospace technology have significantly increased the demands on assembly precision, particularly for large aircraft models. These developments require sub-millimeter precision to be achieved in assembly, posing new challenges for conventional tolerance allocation methods, which rely heavily on theoretical models and static simulations. To address these limitations, this paper proposes a digital twin system for online deduction of assembly tolerances (DTS-ODTA) using point cloud registration and free-form deformation (FFD). The proposed method includes three key innovations. First, a digital twin (DT)-based assembly process control framework supports the simulation of assembly deviations by integrating virtual and actual data. Second, a data-driven method models the actual surface shapes, ensuring synchronization between physical and digital states. Third, a progressive deduction strategy for tolerance allocation combines virtual and actual information, providing effective inputs for real-time assembly process control. This approach was validated through an industrial case study, achieving a prediction accuracy of 91.64 % for assembly precision and effectively preventing out-of-tolerance issues during product assembly. By promptly identifying and addressing potential assembly discrepancies, this method enhances the overall assembly quality and provides critical support for design decisions. In summary, this paper introduces a novel DT-based tolerance allocation method that shifts from traditional open-loop design to closed-loop control, thereby meeting the high precision demands of modern aerospace manufacturing.

Heat Consumer Model for Robust and Fast Simulations of District Heating Networks Using Modelica

Dynamic thermo-hydraulic simulations of district heating networks (DHN) are essential to investigate novel concepts for their sustainable design and operation. To develop solutions for a particular case study, numerous long-term simulations are required. Therefore, computational effort for simulation is critical. Heat consumers (HC) are numerous and determine the dynamics of mass flows and return temperatures in the DHN. Thus, the way in which HCs are modeled has significant impact on the computational effort and the results of the simulation. This article presents a novel Modelica-based model for HCs that builds on an existing simplified modeling approach (open-loop design). The calculation of mass flow and return temperature is improved in terms of robustness, plausible behavior and low computational effort. In particular, the model reacts to limited differential pressure and supply temperatures to ensure plausible behavior across all operating conditions, including undersupply situations. The model is successfully tested using an exemplary DHN. The analysis proves that the HC model itself requires little time to simulate. Nevertheless, it significantly influences the simulation time for the entire DHN, which varies by a factor of five for the investigated system depending on the HC model. Fast dynamics, including a bypass in the model and correction of deviations between set point and actual heat load increase the simulation time, so users should sensibly choose how to use these options. HC models triggering many state events result in high computational effort. Compared to other simple HC models, the proposed model produces more plausible results while maintaining at least equal simulation performance (for models without bypass) or even improving it (for models with bypass, CPU time is reduced by at least 35%).

DSPACE Implementation of Motor Drives using Asymmetric Converter

This paper deals with the dSPACE DS1104 based implementation of closed-loop motor drive system using asymmetric converter. The mathematical model of the drive has been simulated in the MATLAB/Simulink environment to analyze the performance of the drive system. The simulated results are then validated with the experimental investigation. For experimental work, the pulse width modulation (PWM) has been implemented in MATLAB environment with Simulink real-time interface. Meanwhile, the hardware implementation consisting of dSPACE digital signal processor, voltage source inverter and generator-coupled motor. Variable speed test was performed on the loaded motor in open loop and closed-loop design to obtain speed tracking response parameter as well as speed ripple. Overall performance of developed system is satisfactory where in low-speed operation, experimental results show good speed tracking performance with ripple within 20%.

Desain Simulasi dan Analisa Closed Loop Boost Converter Terintegrasi Solar PV Berbasis PID

The tendency for the price of using solar PV (photovoltaic) to become cheaper means that the portion of the use of this solar energy source is encouraged to be larger along with the addition of the portion of renewable energy (EBT) generators based on PLN's 2021-2030 Electricity Supply Business Plan (RUPTL). As a step to mitigate this problem, a power electronics circuit application is needed in the form of a boost converter or what can be called a step-up DC-DC converter. In this study, the boost converter design modeling is made a closed loop. There is feedback by adding a PID controller to adjust the duty cycle as a function of switching on or off MOSFET so that the output voltage is as desired (setpoint) and adjusts to needs of load. Open-loop design modeling is also included as a comparison. The design stage begins with determining the circuit design, calculating component specifications, and simulating using MATLAB R2013a software and hardware implementation. From the test results, it was found that the boost converter can increase the solar PV voltage varies (17.34-19.13 Volts). In the closed loop boost converter circuit with a constant load of 129.96 Ω with varying duty-cycle value set by PID controller with value of Kp=0.005 Ki=9.75 Kd=0.00000029, the average output voltage is 36. 0067 Volts and stable at the desired setpoint of 36 Volts.

Feasibility of intelligent drug control in the maintenance phase of general anesthesia based on convolutional neural network

BackgroundThe growth and aging process of the human population has accelerated the increase in surgical procedures. Yet, the demand for increasing operations can be hardly met since the training of anesthesiologists is usually a long-term process. Closed-loop artificial intelligence (AI) model provides the possibility to solve intelligent decision-making for anesthesia auxiliary control and, as such, has allowed breakthroughs in closed-loop control of clinical practices in intensive care units (ICUs). However, applying an open-loop artificial intelligence algorithm to build up personalized medication for anesthesia still needs to be further explored. Currently, anesthesiologists have selected doses of intravenously pumped anesthetic drugs mainly based on the blood pressure and bispectral index (BIS), which can express the depth of anesthesia. Unfortunately, BIS cannot be monitored at some medical centers or operational procedures and only be regulated by blood pressure. As a result, here we aim to inaugurally explore the feasibility of a basic intelligent control system applied to drug delivery in the maintenance phase of general anesthesia, based on a convolutional neural network model with open-loop design, according to AI learning of existing anesthesia protocols. MethodsA convolutional neural network, combined with both sliding window sampling method and residual learning module, was utilized to establish an "AI anesthesiologist" model for intraoperative dosing of personalized anesthetic drugs (propofol and remifentanil). The fitting degree and difference in pumping dose decision, between the AI anesthesiologist and the clinical anesthesiologist, for these personalized anesthetic drugs were examined during the maintenance phase of anesthesia. ResultsThe medication level established by the “AI anesthesiologist” was comparable to that obtained by the clinical anesthesiologist during the maintenance phase of anesthesia. ConclusionThe application of an open-loop decision-making plan by convolutional neural network showed that intelligent anesthesia control is consistent with the actual anesthesia control, thus providing possibility for further evolution and optimization of auxiliary intelligent control of depth of anesthesia.

Is Recycled Mixed Plastic an Environmentally Effective Solution as a Replacement for Exterior Treated Wood? Combating the Myth of Down-Cycling with an Open-Loop Design Approach

Is Recycled Mixed Plastic an Environmentally Effective Solution as a Replacement for Exterior Treated Wood? Combating the Myth of Down-Cycling with an Open-Loop Design Approach

Geometric robustness and dynamic response management by structural topometry optimisation to reduce the risk for squeak and rattle

Abstract Historically, squeak and rattle (S&R) sounds have been among the top quality problems and a major contributor to the warranty costs in passenger cars. Geometric variation is among the main causes of S&R. Though, geometric variation analysis and robust design techniques have been passively involved in the open-loop design activities in the predesign-freeze phases of car development. Despite the successful application of topometry optimisation to enhance attributes such as weight, durability, noise and vibration and crashworthiness in passenger cars, the implementation of closed-loop structural optimisation in the robust design context to reduce the risk for S&R has been limited. In this respect, the main obstacles have been the demanding computational resources and the absence of quantified S&R risk evaluation methods. In this work, a topometry optimisation approach is proposed to involve the geometric variation analysis in an attribute balancing problem together with the dynamic response of the system. The proposed method was used to identify the potential areas of a door component that needed structural reinforcement. The main objective was to enhance the design robustness to minimise the risk for S&R by improving the system response to static geometrical uncertainties and dynamic excitation.

Closing the Loop With Cortical Sensing: The Development of Adaptive Deep Brain Stimulation for Essential Tremor Using the Activa PC+S.

Deep Brain Stimulation (DBS) is an important tool in the treatment of pharmacologically resistant neurological movement disorders such as essential tremor (ET) and Parkinson's disease (PD). However, the open-loop design of current systems may be holding back the true potential of invasive neuromodulation. In the last decade we have seen an explosion of activity in the use of feedback to “close the loop” on neuromodulation in the form of adaptive DBS (aDBS) systems that can respond to the patient's therapeutic needs. In this paper we summarize the accomplishments of a 5-year study at the University of Washington in the use of neural feedback from an electrocorticography strip placed over the sensorimotor cortex. We document our progress from an initial proof of hardware all the way to a fully implanted adaptive stimulation system that leverages machine-learning approaches to simplify the programming process. In certain cases, our systems out-performed current open-loop approaches in both power consumption and symptom suppression. Throughout this effort, we collaborated with neuroethicists to capture patient experiences and take them into account whilst developing ethical aDBS approaches. Based on our results we identify several key areas for future work. “Graded” aDBS will allow the system to smoothly tune the stimulation level to symptom severity, and frequent automatic calibration of the algorithm will allow aDBS to adapt to the time-varying dynamics of the disease without additional input from a clinician. Additionally, robust computational models of the pathophysiology of ET will allow stimulation to be optimized to the nuances of an individual patient's symptoms. We also outline the unique advantages of using cortical electrodes for control and the remaining hardware limitations that need to be overcome to facilitate further development in this field. Over the course of this study we have verified the potential of fully-implanted, cortically driven aDBS as a feasibly translatable treatment for pharmacologically resistant ET.

Experimental evaluation of feedforward tuning rules

This paper presents a practical comparison for some of the most relevant tuning rules for feedforward compensators that have been published in the recent years. The work is focused on the rejection of disturbances that affect the process output. The different tuning rules are evaluated in simulation and several performance indices are calculated in order to provide a quantitative comparison. All the tuning rules are compared against a standard feedback controller and the classical open-loop design method for feedforward compensators. Furthermore, two of the analysed tuning rules are tested in a real process for the first time. To that end, a traditional greenhouse was selected as a test bed for an experimental evaluation of the feedforward controllers in the context of a challenging control problem with significant disturbances.

Designing temporal networks that synchronize under resource constraints

Being fundamentally a non-equilibrium process, synchronization comes with unavoidable energy costs and has to be maintained under the constraint of limited resources. Such resource constraints are often reflected as a finite coupling budget available in a network to facilitate interaction and communication. Here, we show that introducing temporal variation in the network structure can lead to efficient synchronization even when stable synchrony is impossible in any static network under the given budget, thereby demonstrating a fundamental advantage of temporal networks. The temporal networks generated by our open-loop design are versatile in the sense of promoting synchronization for systems with vastly different dynamics, including periodic and chaotic dynamics in both discrete-time and continuous-time models. Furthermore, we link the dynamic stabilization effect of the changing topology to the curvature of the master stability function, which provides analytical insights into synchronization on temporal networks in general. In particular, our results shed light on the effect of network switching rate and explain why certain temporal networks synchronize only for intermediate switching rate.

Passive optical phase noise cancellation.

We report on the realization of an optical phase noise cancellation technique by passively embedding the optical phase noise information into a radio frequency signal and creating a copy of the optical frequency signal, which is pre-corrected by the amount of phase noise introduced by optical phase perturbations. Neither phase discrimination nor an active servo controller is required due to the open-loop design, mitigating some technical problems, such as the limited compensation speed and finite phase/timing jitter, in conventional phase noise cancellation. We experimentally demonstrate that this technique maintains the same delay-limited bandwidth and phase noise suppression capability as in conventional techniques, but significantly shortens the response speed and phase recovery time. Passive decoupling optical phase perturbation represents a powerful technique in the domains of optical frequency standard comparisons and tools for future optical atomic clocks, which are now under investigation for a potential redefinition of the International Time Scale.

Sustainable open-loop supply chain network design considering location routing problem: A hybrid approach based on FAHP, FTOPSIS and mathematical programming

This paper proposes a two-stage approach for designing the sustainable reverse supply chain network. In the first stage of the proposed approach, the values of potential locations from the social perspective will be evaluated and computed using a hybrid approach of fuzzy analytic hierarchy process (FAHP) and fuzzy TOPSIS (FTOPSIS). Then, in the second stage, a multi-objective mixed-integer linear programming model is applied to develop a sustainable open-loop supply chain network for cost minimisation and for the maximisation of the social value of the established locations. In the proposed model, location-routing decisions, discounts on purchases from suppliers, storage, and encountering with shortages are simultaneously taken into account. Finally, the proposed model is validated using the data of a PET manufacturing company in Iran. The results confirm the efficiency and effectiveness of the proposed approach.

Two-degree-of-freedom Design Between Intersample and Sample Responses: Closed-loop State-space Approach Based on Steady-state Characteristics

A dual-rate sampled-data control system is designed in which the sampling interval of measured signals is twice as long as the holding interval of a control input. In the proposed method, a control law is extended based on the null space and intersample ripples are eliminated without changing the sampled output trajectory in the steady state. Polynomial and state-space approaches are conventional open-loop design methods based on the null space. However, conventional methods are ineffective for unstable systems and are unavailable when the null space of the plant model is only the zero vector because the controlled plant is not arbitrarily selectable. On the other hand, the proposed method is effective for unstable systems, as well as stable systems, even when the null space of the plant model is only the zero vector, because the proposed controller is designed based on a closed-loop system.

Mechanically Flexible Sensor Array for Current Measurement

Contactless galvanically isolated magnetic field-based current sensors utilizing hard ferromagnetic cores are widely used in many applications, for example, power converters for drives or wind turbines. New measurement methods, e.g., circular arrays of magnetic field sensors, offer some advantages, such as low weight, mechanical flexibility, and independence of the nonlinear and hysteretic behavior of the core. Those sensor arrays can be operated in an open-loop manner or in a closed-loop manner with an additional compensation coil. The advantages of the open-loop design, which we use in this article, are lower cost, lower weight, and the opportunity to realize a mechanically flexible sensor array. In this article, we show the theoretical and experimental influence of the mechanical bending on the accuracy of circular arrays of magnetic field sensors used for current measurement. Furthermore, the inner displacement of the conductor in combination with different bendings is considered. The experimental results were taken with 12, 6, 4, and 3 Hall effect sensors that were uniformly placed on the circular array.

Multi-node optical frequency dissemination with post automatic phase correction

We report a technique for coherence transfer of laser light through a fiber link, where the optical phase noise induced by environmental perturbation via the fiber link is compensated by remote users with passive phase noise correction, rather than at the input as is conventional. Neither phase discrimination nor active phase tracking is required due to the open-loop design, mitigating some technical problems such as the limited compensation speed and the finite compensation precision as conventional active phase noise cancellation. We theoretically analyze and experimentally demonstrate that the delay effect introduced residual fiber phase noise after noise compensation is a factor of 7 higher than the conventional techniques. Using this technique, we demonstrate the transfer laser light through a 145-km-long, lab-based spooled fiber. After being compensated, the relative frequency instability in terms of overlapping Allan deviation is 1.9E-15 at 1s averaging time and scales down 5.3E-19 at 10,000 s averaging time. The frequency uncertainty of the light after transferring through the fiber relative to that of the input light is -0.36+-2.6E-18. As the transmitted optical signal remains unaltered until it reaches the remote sites, it can be transmitted simultaneously to multiple remote sites on an arbitrarily complex fiber network, paving a way to develop a multi-node optical frequency dissemination system with post automatic phase noise correction for a number of end users.

Design and Analysis of a Swashplate Control System for an Asymmetric Axial Piston Pump

Abstract Based on the previously developed fixed-displacement asymmetric axial piston pump, a variable displacement asymmetric axial piston pump (VDAAPP) with three independent suction/delivery ports is proposed. A basic linear model of VDAAPP is established to get open-loop bode diagram. Based on open-loop Bode diagram features and design requirements, P-controller is determined for VDAAPP. Then VDAAPP's performance is investigated by advanced modeling environment for performing simulations of engineering systems (AMESim) and automatic dynamic analysis of mechanical systems (ADAMS) joint simulation, and some key design parameters are obtained. Next, a VDAAPP prototype with a maximum displacement of 40 cc/rev is designed and manufactured, ratio of flow rates at ports A, B and T is 1:0.6:0.4. Due to hard limitations of the test bench, the performance only under the conditions of the opposite passive loads is tested. Preliminary test results indicate that VDAAPP prototype works normally and meets the design requirements for flow ratio, and the maximum rise time of the test pressure is about 0.32 s. However, due to special design of VDAAPP valve plate, the swash plate torque severely limits system dynamic response. Therefore, an improved swashplate control system based on asymmetric-valve-controlled asymmetric-piston scheme is presented as well, it is found to be an effective way to suppress the negative impact of swash plate torque on system dynamic performance. This provides a direction for the optimization of the swashplate control system for asymmetric axial piston pumps in the future.

An experiment on heat extraction from a deep geothermal well using a downhole coaxial open loop design

We report a field heat extraction test from a deep geothermal well using a downhole coaxial open loop design in Tanggu, Tianjin China, which is different from most previous studies in that the well casing is closed to the geothermal reservoir. A downhole pump installed in the inner tube pumped the geothermal fluids to the surface. After releasing heat by flowing through a plate heat exchanger, the geothermal fluid returned to the aquifer completely and naturally by gravity through the annular section between the inner tube and the borehole wall. The proposed design realizes a sustainable and clean way of “no water withdrawn but heat only” in geothermal utilization. The experimental test well was used as a reinjection well for two years, and the maximum measured temperature in the well before the experiment was only 51 °C. The experimental results show that the proposed configuration worked very well in extracting heat from a deep geothermal reservoir. The system’s stable heat output can reach approximately 275 kW after two weeks of continuous heat extraction, which was much larger than the theoretically calculated value for deep borehole heat exchangers by using the heat conduction model.

Wide-Bandwidth, High-Linearity, 2.8-GS/s, 10-bit Accurate Sample and Hold Amplifier in 130-nm SiGe BiCMOS

This paper presents a highly linear BiCMOS sample and hold amplifier (SHA) providing 2.8-GS/s intermediate frequency (IF) sampling for a 1-GHz input bandwidth spanning from 1.5 to 2.5 GHz. A single-transistor hold-mode feedthrough cancellation technique is implemented to remove distortion resulting from the nonlinear parasitic capacitance at the sampling node. The SHA is designed in a mainstream 130-nm BiCMOS technology using SiGe heterojunction bipolar transistors to buffer and sample the wideband input. The proposed SHA enables monolithic integration with a high-speed analog-to-digital converter core to realize a high-performance converter solution. This independent sampling front end occupies a core chip area of 0.6 mm2 and consumes an average power of 1.26 W. The SHA is a pseudo-differential open-loop design that includes two cascaded track-and-hold amplifiers, a high-speed clock driver, and externally adjustable current mirror biases. The high-speed clock drivers and buffers add 170 mW to the total power consumption. The measurements of the fabricated SHA show a 10-bit effective resolution across the 1-GHz IF bandwidth and < −61-dBc HD2 and HD3.

A 54.2-dB Current Gain Dynamic Range, 1.78-GHz Gain-Bandwidth Product CMOS VCCA2

A voltage-controlled current amplifier/attenuator in a standard 0.35- ${\mu }\text{m}$ CMOS technology is presented. It is based on the resistive mirror method, using non-saturated MOSFETs. An open-loop design with no compensation capacitors provides a high stability and a small occupied chip area of 0.0126 mm2. A current gain dynamic range of 513 (54.2 dB), a gain-bandwidth product of 1.78 GHz at the largest current gain of 35.9 dB, and a maximum power consumption of 250 ${\mu }\text{W}$ with a single supply voltage of 1.3 V are achieved. In addition, an AC current source has been designed, integrated on the same chip, and used as the input of the proposed voltage-controlled amplifier/attenuator.

A novel open loop design technique for frequency selective surface miniaturization

AbstractIn this letter, a highly miniaturizedal‐band frequency selective surface (FSS) is designed and experimentally verified. The proposed structure has orthogonally meandered metallic strips with an opening at one point in the loop. This single sided FSS operates at 1.23 and 3.3 GHz with a compact unit cell size dimension of 0.033λ0 × 0.033λ0 × 0.003λ0 where λ0 stands for the free space wavelength at the lower resonating frequency. Parametric and circuit analyses of the formulated structure has been carried out to have a comprehensive understanding of the model. The structure has stable resonance for TE and TM polarizations at various incident angles. The presented FSS is fabricated and measured. A good similitude between the simulation and measurement has been obtained.