Offset Control Research Articles

An accurate and fast method for computing offsets of high degree rational Bézier/NURBS curves with user-definable tolerance

Abstract This paper focuses on the fast and accurate offset method of high degree rational Bezier/NURBS curves. Firstly, in order to solve the scaling problem of the subdivision error in the Bezier/NURBS curve offsetting, a novel dynamic offset error control method which is the extension of the fast subdivision method of Bezier curve, and can realize the fast offset of the Bezier/NURBS curves under the user's required offset accuracy is proposed. Secondly, for the interpolation of the offset points, the local interpolation is adopted, which can effectively solve the problem of the mass calculation caused by the re-segmentation of the original curve when the interpolation accuracy check fails. Finally, the paper validates the efficiency of the proposed method by comparing the offset accuracy of a series of Bezier/NURBS curves with those of other methods.

Performance of Plunge Depth Control Methods During Friction Stir Welding

Friction stir welding is a preferred solid state welding process for Al/Fe joints, and in friction stir lap welding, the plunge depth is the most critical parameter for joint strength. We compared three plunge depth control methods, namely conventional position control, offset position control, and deflection compensation control in the friction stir lap welding of 3 mm-thick Al 5083-O alloy over 1.2 mm-thick DP 590 steel. The desired plunge depth was 0.2 mm into the steel sheet. However, the pin did not reach the steel surface under conventional position control due to deflection of the vertical axis of the welding system. In offset position control, an additional offset of 0.35 mm could achieve the desired plunge depth with considerable accuracy. Nevertheless, a gradual increase of the plunge depth along the longitudinal direction was unavoidable, due to an in-situ decrease of the material yield strengths. In deflection compensation control, the deflection is estimated by the coaxially measured plunging force and the force-deflection relationship, and then corrected by feedback control. Thus, the plunge depth is stabilized along the longitudinal direction and is precisely controlled with a 3.3-μm standard deviation of error during the tool traverse phase. There is also a consistent bias of 32 μm caused by the resolution of the measuring system, and it can be easily calibrated in the feedback control system.

The impact of strained layers on current and emerging semiconductor laser systems

In this paper, we discuss how the deliberate and controlled introduction of strain can be used to improve the performance of semiconductor lasers. We show how strain-induced modifications of the electronic band structure give rise to significant changes in the valence band of III-V semiconductors which have been used to produce devices with lower threshold currents and higher efficiencies. We furthermore illustrate how the strain limit of semiconductor layers can be overcome by using strain compensation techniques and how this is being widely adopted in lasers based on a number of emerging III-V systems, enhancing device efficiency and output power and extending the wavelength of operation. We show how strained layers are also being used to optimize the performance of mid-infrared lasers through band offset control. Finally, we show how strain may be used to facilitate the production of lasers on silicon through controlling the conduction band valley splitting in group IV semiconductors or through the development of novel direct bandgap III-V systems that may be grown lattice matched to silicon. Such systems are expected to be of significant potential for the future convergence of electronic and photonic devices and highlight the ongoing importance of strain engineering in photonic devices.

Coupled rotational and translational modeling of two satellites connected by a tether and their robust attitude control using optimal offset approach

In this study, the robust sliding mode attitude control of a tethered satellite system using optimal tether offset in the presence of perturbations and uncertainties is investigated. The three main goals of this study are: (1) comprehensive modeling of two satellites connected by a tether considering the coupling between their attitude and position, (2) finding a robust attitude control for both satellites, and (3) reducing the reaction wheels’ power consumption for attitude control utilizing the tether tension. In this regard, the 6 DOF governing equations of the coupled nonlinear rotational and translational dynamics of a two-satellite tethered system in the presence of perturbing forces are derived. Additionally, the offset of the tether attachment points from the center of mass of both satellites is modeled, which results in the coupling of two satellites’ dynamics. The tether tension force acts as external force and moment on each satellite which is used by an optimization method for attitude control of satellites along with their reaction wheels. The simulation results show that the designed sliding mode control stabilizes the attitude of both satellites in the presence of uncertainties and perturbations. Moreover, the optimal offset control saves the energy usage of reaction wheels up to 55 percent.

QLPV Predictive Control - A Benchmark Study on State Space vs Input-Output Approach

This paper presents a comparison and evaluation of two approaches to Nonlinear Model Predictive Control (NMPC) via quasi-LPV modeling, by means of a benchmark problem: control of a 4 degree-of-freedom Control Moment Gyroscope (CMG). The use of quasi-LPV modeling allows us to recast the nonlinear optimization problem arising in NMPC, as a repeated quadratic program which can be solved efficiently. The difference between the two presented schemes lies in the modeling paradigm chosen to express the dynamics of the system, namely state space (SS) or input-output (IO) frameworks. In both cases, quasi-LPV models are obtained by performing a velocity-based linearization, which results in an exact representation of the nonlinear dynamics and enables offset free control. Both schemes are successfully implemented on a laboratory CMG, and the experimental results are compared and discussed. Furthermore, advantages and disadvantages of each control scheme are examined.

Study of Offset Control between Two Intersections with Different Green Splits

Study of Offset Control between Two Intersections with Different Green Splits

A novel two-loop large offset tracking control of an uncertain nonlinear system with input constraints

Under a large deviation between the initial state and the desired trajectory, the traditional single-loop control method usually fails to solve the output tracking of SISO nonlinear systems due to the inherent uncertainties, input saturation, and unmeasurable states. In this work, a novel tracking control system is proposed in the framework of two-loop control system to achieve high-accurate tracking performance and reconcile the contradiction between the system's available regulating capacity and the required tracking capacity. Specifically, an observer and command-filtered-based adaptive fuzzy controller are synthesized in the inner loop to guarantee a satisfying tracking accuracy and remain robust to uncertainties. A simplified fuzzy approximator is utilized to estimate the uncertainties with a single adaptive parameter. Then, a replanned reference trajectory is generated in the outer loop by online optimization to minimize the transient performance over the predictive horizon. Moreover, a tracking governor of reference trajectory is proposed to obtain an adaptive convergence rate with respect to the desired trajectory while only satisfying relatively loose constraints. Simulation results prove that the proposed two-loop scheme can not only improve the tracking accuracy; but also has the adaptability to fulfill the particular engineering problems that have a large difference between the initial condition and the desired trajectory.

A decoupled Mechanical Shim core control strategy for a pressurized water reactor using feedforward compensation and a multimodel approach

The advanced Mechanical Shim (MSHIM) core control strategy employs two separate and independent control rod banks, namely the MSHIM control banks (M-banks) and axial offset (AO) control bank (AO-bank), for automatic reactivity/temperature and axial power distribution control respectively. The M-banks and AO-bank are controlled by two closed-loop controllers, independently, called the coolant average temperature (Tavg) controller and the AO controller. Since the motion of the M-banks and AO-bank can both affect the Tavg and AO, an interlocking design between the Tavg controller and the AO controller is adopted in the MSHIM control strategy to avoid the interference between the two controllers during power maneuvers. This design can enhance the stability of the MSHIM control system by avoiding the simultaneous movement of the M-banks and AO-bank and keeping the priority of the M-bank movement. However, the AO control performance is degraded at the same time. In the present study, a feedforward compensation decoupling method and a multimodel approach have been used to eliminate the coupling effect between the two controllers in the MSHIM control system during a wide range of power maneuvers. A multiple feedforward compensation system has been designed with integration of the feedforward compensators for the Tavg and AO controllers at five equilibrium conditions using the multimodel approach. By implementing it in the MSHIM control system, the interlocking between the M-banks and the AO-bank can be released to realize the independent and decoupling control between the Tavg and AO. The effectiveness of the decoupled MSHIM control strategy has been verified by comparing its control performance with that of the original MSHIM control strategy during typical load change transients of the AP1000 reactor. The obtained results show that superior and decoupling control of the Tavg and AO can be achieved using the proposed decoupled MSHIM control strategy.

Using graphic warning labels to counter effects of social cues and brand imagery in cigarette advertising.

Exposure to cigarette advertising can increase the likelihood of youth smoking initiation and may encourage people who already smoke to continue. Requiring prominent, graphic warning labels could reduce these effects. We test whether graphic versus text-only warning labels in cigarette advertisements influence cognitive and emotional factors associated with youth susceptibility to smoking and adult intentions to quit. We conducted two randomized, between-subjects experiments with middle-school youth (n = 474) and adult smokers (n = 451). Both studies employed a two (graphic or text-only warnings) by two (advertisements with social cues or brand imagery) factorial design with a fifth, offset control group (social cue advertisements with the current US Surgeon General's Warning). Graphic warnings outperformed text-only warnings in reducing visual attention to the advertisement, generating visual attention to the warning and arousing more negative affect. Graphic warnings also reduced the appeal of cigarette brands among youth relative to social cue advertisements with the Surgeon General's warnings. None of the warnings (graphic or textual) influenced health risk beliefs. Graphic warning labels on cigarette advertisements appear to have effects similar to those observed on cigarette packs in previous work, with an added benefit of reducing cigarette brand appeal among youth.

An offset hub active vibration control system for mitigating helicopter vibrations during power loss: Simulation and experimental demonstration

In recent years, hub active vibration control (HAVC) technologies have been developed to attenuate blade pass frequency vibration on helicopters. While these systems provide superior vibration control with reduced weight compared to passive options, in the event of electrical power loss they can exacerbate the vibration problem in a manner that is problematic for helicopter and tiltrotor aircraft. This paper presents an offset hub active vibration control system (OHAVCS) designed to attenuate vibration during a power loss by offsetting the centers of rotation of two imbalance masses. The equations of motion for this system are developed using Lagrangian methods; analysis, simulation and experimental validation of these equations indicate that offsetting the imbalance masses effectively mitigates 1/Rev vibrations during a rotor hub power loss while continuing to cancel N/Rev vibrations during normal operation. These offsets create stabilizing centripetal torques that rotate each imbalance mass to a unique equilibrium angle. Experimental data also indicate that these offsets do not hinder control of the imbalance masses during normal (active) operation, though they do increase system power requirements.

A pneumatic Bionic Voice prosthesis-Pre-clinical trials of controlling the voice onset and offset.

Despite emergent progress in many fields of bionics, a functional Bionic Voice prosthesis for laryngectomy patients (larynx amputees) has not yet been achieved, leading to a lifetime of vocal disability for these patients. This study introduces a novel framework of Pneumatic Bionic Voice Prostheses as an electronic adaptation of the Pneumatic Artificial Larynx (PAL) device. The PAL is a non-invasive mechanical voice source, driven exclusively by respiration with an exceptionally high voice quality, comparable to the existing gold standard of Tracheoesophageal (TE) voice prosthesis. Following PAL design closely as the reference, Pneumatic Bionic Voice Prostheses seem to have a strong potential to substitute the existing gold standard by generating a similar voice quality while remaining non-invasive and non-surgical. This paper designs the first Pneumatic Bionic Voice prosthesis and evaluates its onset and offset control against the PAL device through pre-clinical trials on one laryngectomy patient. The evaluation on a database of more than five hours of continuous/isolated speech recordings shows a close match between the onset/offset control of the Pneumatic Bionic Voice and the PAL with an accuracy of 98.45 ±0.54%. When implemented in real-time, the Pneumatic Bionic Voice prosthesis controller has an average onset/offset delay of 10 milliseconds compared to the PAL. Hence it addresses a major disadvantage of previous electronic voice prostheses, including myoelectric Bionic Voice, in meeting the short time-frames of controlling the onset/offset of the voice in continuous speech.

A Power-Enhanced Active Rectifier with Offset-Controlled Comparator for Self-Powered PEH Systems

In this paper, a power-enhanced active rectifier with high precision of current detection for piezoelectric energy harvesting (PEH) system is presented. A traditional two-stage active rectifier is adopted, which includes a first-stage negative voltage converter and an active diode. A comparator with offset control technique is proposed; thus the input-referred offset voltage of the proposed comparator can be less than 1[Formula: see text]mV. The current detected accuracy of the proposed offset-controlled comparator (OCC) is improved by more than 10 times over a traditional comparator. Output oscillations of the OCC are dramatically reduced attributing to the high precision of current detection. In addition, the OCC is also able to prevent the reverse leakage current. The design is implemented in an SMIC 0.18[Formula: see text][Formula: see text]m standard CMOS technology with a chip area of 0.22[Formula: see text]mm2. The measurement results show that the maximum output power, power conversion efficiency and figure of merit are 23.3[Formula: see text][Formula: see text]W, 90%, and 0.9, respectively, when the open-circuit voltage is 2.4[Formula: see text]V. The proposed rectifier can be self-powered without the additional external supply.

On the First Hyperchaotic Hyperjerk System With No Equilibria: A Simple Circuit for Hidden Attractors

A fourth-order hyperchaotic hyperjerk system with no equilibria has never been reported, whereas a search for its existence has been an open research problem. A new system in a rare type of 4D seven-term no-equilibrium hyperchaotic systems is proposed and also compared with two existing systems of such a rare type. The proposed system offers 10 concurrent advantages, six of which appear to be superior to both existing systems, that is; 1) the first report of a fourth-order hyperchaotic hyperjerk system with no equilibria; 2) a much simpler circuit based on only 21 electronic components; 3) a higher value of the Lyapunov dimension at 3.2280; 4) a higher value of the largest Lyapunov exponent at 0.2525; 5) a large two-parameter space of hyperchaos; and 6) a boostable variable for offset control. The other four advantages offer either equal or better features, that is; 7) the number of nonlinear terms is two; 8) no potential dangers of multistability; 9) hyperchaos, chaos, and periodic behavior are possible; and 10) attractors are readily hidden attractors. The system is unique in the sense that there are no equilibria in both dynamical and hyperjerk forms.

Dynamics and offset control of tethered space-tug system

Tethered space-tug system is regarded as one of the most promising active debris removal technologies to effectively decrease the steep increasing population of space debris. In order to suppress the spin of space debris, single-tethered space-tug system is employed by regulating the tether. Unfortunately, this system is underactuated as tether length is the only input, and there are two control objectives: the spinning debris and the vibration of tether. Thus, it may suffer great oscillations and result in failure in space debris removal. This paper presents the study of attitude stabilization of the single-tethered space-tug system using not only tether length but also the offset of tether attachment point to suppress the spin of debris, so as to accomplish the space debris removal mission. Firstly, a precise 3D mathematical model in which the debris and tug are both treated as rigid bodies is developed to study the dynamical evolution of the tethered space-tug system. The relative motion equation of the system is described using Lagrange method. Secondly, the dynamic characteristic of the system is analyzed and an offset control law is designed to stabilize the spin of debris by exploiting the variation of tether offset and the regulation of tether length. Besides, an estimation formula is proposed to evaluate the capability of tether for suppressing spinning debris. Finally, the effectiveness of attitude stabilization by the utilization of the proposed scheme is demonstrated via numerical case studies.

Offset Free Tracking Predictive Control Based on Dynamic PLS Framework

This paper develops an offset free tracking model predictive control based on a dynamic partial least square (PLS) framework. First, state space model is used as the inner model of PLS to describe the dynamic system, where subspace identification method is used to identify the inner model. Based on the obtained model, multiple independent model predictive control (MPC) controllers are designed. Due to the decoupling character of PLS, these controllers are running separately, which is suitable for distributed control framework. In addition, the increment of inner model output is considered in the cost function of MPC, which involves integral action in the controller. Hence, the offset free tracking performance is guaranteed. The results of an industry background simulation demonstrate the effectiveness of proposed method.

Fully integrated high quality factor <i>G</i><sub>m</sub><i>C</i> bandpass filter stage with highly linear operational transconductance amplifier

Abstract. This paper presents an electrical, fully integrated, high quality (Q) factor GmC bandpass filter (BPF) stage for a wireless 27 MHz direct conversion receiver for a bendable sensor system-in-foil (Briem et al., 2016). The core of the BPF with a Q factor of more than 200 is an operational transconductance amplifier (OTA) with a high linearity at an input range of up to 300 mVpp, diff. The OTA's signal-to-noise-and-distortion-ratio (SNDR) of more than 80 dB in the mentioned range is achieved by stabilizing its transconductance Gm with a respective feedback loop and a source degeneration resistors RDG. The filter stage can be tuned and is tolerant to global and local process variations due to offset and common-mode feedback (CMFB) control circuits. The results are determined by periodic steady state (PSS) simulations at more than 200 global and local process variation parameter and temperature points and corner simulations. It is expected, that the parasitic elements of the layout have no significant influence on the filter behaviour. The current consumption of the whole filter stage is less than 600 µA.

“I Forgot I Wasn’t Saving the World”: the Use of Formative and Summative Assessment in Instructional Video Games for Undergraduate Biology

This study examined the role of formative and summative assessment in instructional video games on student learning and engagement. A 2 (formative feedback: present vs absent) × 2 (summative feedback: present vs absent) factorial design with an offset control (recorded lecture) was conducted to explore the impacts of assessment in video games. A total of 172 undergraduates were randomly assigned to one of four instructional video game conditions or the control. Results found that knowledge significantly increased from the pretest for players in all game conditions. Participants in summative assessment conditions learned more than players without summative assessment. In terms of engagement outcomes, formative assessment conditions did not significantly produce better learning engagement outcomes than conditions without formative assessment. However, summative assessment conditions were associated with higher temporal disassociation than non-summative conditions. Implications for future instructional video game development and testing are discussed in the paper.

Offset Voltage Control Scheme for Modular Multilevel Converter Operated in Nearest Level Control

This paper proposes an offset voltage control scheme for the modular multilevel converter (MMC) operated in nearest level control (NLC) to improve the total harmonic distortion (THD) of AC phase voltages. The offset (neutral-to-zero-point) voltage is adjusted so that the magnitude of each AC pole voltage maintains constant value with N + 1 level in the range of whole modulation index (MI). The validity of the proposed scheme was confirmed by computer simulations for the MMC with 22.9 kV/25 MVA and experimental works for the scaled MMC with 380 V/10 kVA. It was confirmed that the proposed control scheme can generate linearly variable AC phase voltages with improved THD in the over-modulation region as well as the normal-modulation region.

Unknown Offset Free MPC for Buck Converter

Buck converters are commonly used as DC power supplies. To deal with the parameters uncertainty in R-L (resistance-inductance), an Unknown Offset Free Model Predictive Control (UOFMPC) method for buck converters have been proposed in this paper. Firstly, a continuous model for buck converters is established. Based on it, a discrete model with fixed sampling time is derived and the output of controller is set as the direct switch on/off signals. Secondly, one-step MPC method aimed at optimizing the output voltage with recursive least squares algorithm for parameters identification is given to satisfy the ability of adaptation in parameters. Finally, both the model and control scheme are validated by simulation in MATLAB/Simulink.

Offset control of traffic signal using cellular automaton traffic model

This paper deals with an offset control of traffic signals using a cellular automaton traffic model. A stochastic optimal control method for distributed traffic signals is modified to achieve coordinated traffic signal control with the proposed offset control method. In the proposed coordinated traffic signal control method, splits of each cycle and common cycle length are calculated using a modified stochastic optimal control method, and then the offset is calculated using an estimation method based on a modified CA traffic model at intervals. Also, simulations are carried out at multiple intersections using a micro traffic simulator. The effectiveness of the proposed coordinated control method is proved by comparing with other traffic signal control methods such as pre-timed signal control, two types of the traditional coordinated control and distributed control.