Variety Of Control Strategies Research Articles

Optimal phase-based gait guidance control on a lower-limb exoskeleton

Lower-limb exoskeletons, often used for assistance and rehabilitation, operate using a variety of control strategies, such as phase-based gait guidance controllers. Phase is a configuration-dependent scalar representing the progression of gait. In purely robotic systems, the definition of phase is largely arbitrary so long as it satisfies monotonic and diffeomorphic conditions. However, in applications involving an active user, the volitional inputs of the operator can alter system behavior. This can negatively influence the progression of phase throughout locomotion, impacting reference gait generation and user comfort. This paper investigates defining phase in a way that considers the influence of the user. Specifically, a series of walking experiments is conducted where recorded data from each experiment is used to optimally define phase for the subsequent experiment. In each iteration, phase is optimally defined to minimize its sensitivity to natural variability in gait. To evaluate whether the proposed method is able to improve phase progression and system behavior, three walking experiments were performed using a bilateral mixing gait guidance controller on an Indego Explorer exoskeleton with an able-bodied subject. The controller combines two single-support gait tracking controllers plus gravity compensation where the gravity compensation is proven to be preserved during double-support. In the final experiment, the root-mean-square error between the experimental and theoretical progression of phase was 0.0136 where phase nominally progresses monotonically from 0 to 1. For comparison, a walking experiment using the horizontal hip coordinate as phase, normalized from 0 to 1, resulted in a root-mean-square error of 0.0995. The progression of phase improved by 86% from the non-optimized to iteratively optimized definition. As a result, the commanded references tended to better resemble the desired nominal gait pattern. In conjunction with the gait guidance controller with optimized phase definition, an adaption law adjusted the reference gait based on walking speed estimated from foot displacement and timing. Experimental results show how the adaptive controller is able to predict walking speed and adjust the commanded reference accordingly.

Nearly‐optimal control for energy, thermal, and storage loads with energy disaggregation monitoring: A case of residential management for the elderly

AbstractThe increase in the ageing of the population calls for advanced monitoring and actuation systems for the smart control and management of elderly households that should manage to optimise multi‐objective control problems. This study proposes a state‐of‐art approach, based on Approximate Dynamic Programming, that tackles multiple challenges, aiming to maximise the energy efficiency, the electricity cost reduction, the user comfort, and the load monitoring of a typical Greek residency (simulated in EnergyPlus), including both controllable and uncontrollable loads, an energy storage system, and power generation units. The article presents the various simulated loads, pricing schemes under Greek regulations and variety of control strategies that are co‐ordinately used to minimise the defined objective functions in contrast to the current state‐of‐the‐art approaches. The latter either focus on single objective problems or use simpler iterative and often limited to specific variables, approaches for multi‐objective control. Finally, the presented results provide insights for the optimal and safe residential management and validate the performance of the proposed control strategy in comparison with alternative demand response strategies, offering improved performance by 20% in terms of energy efficiency, cost reduction, and thermal comfort.

Application of Fractional Order-PID Control Scheme in Automatic Generation Control of a Deregulated Power System in the Presence of SMES Unit

A fractional order PID (FOPID) control technique for automatic generation control (AGC) in a multi-area power system is presented in this study. To create a reliable controller, a variety of control strategies were used. The load frequency control (LFC) problem in a power system implementing different power transactions, such as bilateral and Poolco transactions, are investigated here. Because any control scheme’s performance is only as good as its parameters, the parameters of the designed control scheme were determined using the big bang big crunch (BBBC) algorithm. Furthermore, in this work, the effect of a superconductive magnetic energy storage (SMES) unit is addressed in the given test (two and four area) systems. When confronted with a fluctuation in immediate load, the SMES unit is thought to follow the initial drop in frequency and tie-line power in order to increase LFC. It is evident that the performance of an FOPID control scheme is improved in the presence of an SMES unit and it provides frequency, tie-line power, change in generation with reduced oscillations and settling time.

Seamless and intuitive control of a powered prosthetic leg using deep neural network for transfemoral amputees.

Powered prosthetic legs are becoming a promising option for amputee patients. However, developing safe, robust, and intuitive control strategies for powered legs remains one of the greatest challenges. Although a variety of control strategies have been proposed, creating and fine-tuning the system parameters is time-intensive and complicated when more activities need to be restored. In this study, we developed a deep neural network (DNN) model that facilitates seamless and intuitive gait generation and transitions across five ambulation modes: level-ground walking, ascending/descending ramps, and ascending/descending stairs. The combination of latent and time sequence features generated the desired impedance parameters within the ambulation modes and allowed seamless transitions between ambulation modes. The model was applied to the open-source bionic leg and tested on unilateral transfemoral users. It achieved the overall coefficient of determination of 0.72 with the state machine-based impedance parameters in the offline testing session. In addition, users were able to perform in-laboratory ambulation modes with an overall success rate of 96% during the online testing session. The results indicate that the DNN model is a promising candidate for subject-independent and tuning-free prosthetic leg control for transfemoral amputees.

Partial nitritation at elevated loading rates: design curves and biofilm characteristics.

There is a need to develop low operational intensity, cost-effective, and small-footprint systems to treat wastewater. Partial nitritation has been studied using a variety of control strategies, however, a gap in passive operation is evident. This research investigates the use of elevated loading rates as a strategy for achieving low operational intensity partial nitritation in a moving bed biofilm reactor (MBBR) system. The effects of loading rates on nitrification kinetics and biofilm characteristics were determined at elevated, steady dissolved oxygen concentrations between 5.5 and 7.0mg O2/L and ambient temperatures between 19 and 21°C. Four elevated loading rates (3, 4, 5 and 6.5g NH4+-N/m2days) were tested with a distinct shift in kinetics being observed towards nitritation at elevated loadings. Complete partial nitritation (100% nitrite production) was achieved at 6.5g NH4+-N/m2days, likely due to thick biofilm (572µm) and elevated NH4+-N load, which resulted in suppression of nitrite oxidation.

Bees with attitude: the effects of directed gusts on flight trajectories.

ABSTRACTFlight is a complicated task at the centimetre scale particularly due to unsteady air fluctuations which are ubiquitous in outdoor flight environments. Flying organisms deal with these difficulties using active and passive control mechanisms to steer their body motion. Body attitudes of flapping organisms are linked with their resultant flight trajectories and performance, yet little is understood about how isolated unsteady aerodynamic phenomena affect the interlaced dynamics of such systems. In this study, we examined freely flying bumblebees subject to a single isolated gust to emulate aerodynamic disturbances encountered in nature. Bumblebees are expert commanders of the aerial domain as they persistently forage within complex terrain elements. By tracking the three-dimensional dynamics of bees flying through gusts, we determined the sequences of motion that permit flight in three disturbance conditions: sideward, upward and downward gusts. Bees executed a series of passive impulsive maneuvers followed by active recovery maneuvers. Impulsive motion was unique in each gust direction, maintaining control by passive manipulation of the body. Bees pitched up and slowed down at the beginning of recovery in every disturbance, followed by corrective maneuvers which brought body attitudes back to their original state. Bees were displaced the most by the sideward gust, displaying large lateral translations and roll deviations. Upward gusts were easier for bees to fly through, causing only minor flight changes and minimal recovery times. Downward gusts severely impaired the control response of bees, inflicting strong adverse forces which sharply upset trajectories. Bees used a variety of control strategies when flying in each disturbance, offering new insights into insect-scale flapping flight and bio-inspired robotic systems.This article has an associated First Person interview with the first author of the paper.

Genetic resistance: tolerance to vector-borne diseases and the prospects and challenges of genomics

Vector-borne diseases in cattle and small ruminants (e.g. trypanosomosis, Rift Valley fever and East Coast fever) are associated with major economic losses in tropical countries, and particularly on the African continent. A variety of control strategies (e.g. management, vaccination and/or acaricide treatments) are used to minimise their negative impacts. These strategies are often associated with environmental, technical and/or economic drawbacks. However, several indigenous livestock populations have been reported to show a level of genetic tolerance or resistance to such disease challenges (e.g. trypanotolerant N'Dama cattle and Djallonké sheep). Use of these populations represents a sustainable alternative approach to minimising the negative impact of such infection/infestation on livestock production. This review summarises the current understanding of the genetic control of these adaptations, identifies knowledge gaps and critically examines the possible impacts of genomics approaches to the genetic improvement of tolerance and/or resistance to vector-borne diseases.

Knowing the enemy: ant behavior and control in a pediatric hospital of Buenos Aires.

Ant control is difficult in systems even where a variety of control strategies and compounds are allowed; in sensitive places such as hospitals, where there are often restrictions on the methods and toxicants to be applied, the challenge is even greater. Here we report the methods and results of how we faced this challenge of controlling ants in a pediatric hospital using baits. Our strategy was based on identifying the species present and analyzing their behavior. On the one hand, we evaluated outdoors in the green areas of the hospital, the relative abundance of ant genera, their food preferences and the behavioral dominances. On the other hand, control treatments were performed using separately two boron compounds added to sucrose solution which was not highly concentrated to avoid constrains due to the viscosity.Most of the species in the food preference test accepted sugary food; only one species was recorded to visit it less than the protein foods. This result was consistent with the efficacy of control treatments by sugary baits within the rooms. For species that showed good acceptance of sugar solutions in the preference test outdoors, sugar bait control indoors was 100& effective. Conversely, for the only species that foraged significantly less on sugar food, the bait treatment was ineffective. This work reveals the importance of considering the behavior and feeding preferences of the species to be controlled by toxic baits.

Implementation of an iterative headway-based bus holding strategy with real-time information

In high frequency bus service lines buses often come irregularly at the stops, often in bunches, due to the uncertainty of the passenger demand and behavior and unexpected conditions on the roads. Vehicle holding is a commonly used strategy among a variety of control strategies in transit operation in order to reduce bus bunching and regulate bus headways. This paper investigates a control strategy of holding a group of buses at a single or multiple control point(s). By incorporating any passenger boarding activities during holding, a single control point problem is developed and extended to multiple control points to reduce the variance of headways for the downstream stops. The problem is a non-convex optimization problem with linear constraints that minimizes the total passenger waiting time both on-board and at stops. A heuristic is then developed that is easy and fast to implement, which makes it suitable for real-time implementation. The model is evaluated with a simulation case study by using the real-time bus operation data (i.e., Automatic Vehicle Location and Automatic Passenger Count Data) from the Chicago Transit Authority (CTA). The simulation results show that considering the boarding activities in the total waiting time, our model mitigates the error propagation and maintains steady performance, compared to the common models in the literature, which do not consider boarding while holding.

Real-time haptic-teleoperated robotic system for motor control analysis

A versatile teleoperated robotic system was created as an assessment device for testing upper-extremity motor control adaptation using different control strategies. While many systems display output virtually on a computer monitor, this system was designed to output in three-dimensional physical space. The system accepts haptic force and torque input, and outputs robot end-effector displacements and rotations in three spatial dimensions. Benefits of this system include flexibility to conduct a variety of dissimilar tasks and reality of user feedback in physical space. Two separate experiments validated the teleoperated robotic system. The first experiment tested unimanual human motor control and the second tested bimanual motor control. This teleoperated robotic system can be used as an assessment device to study neuromuscular adaptability via a variety of control strategies providing a new and functional approach to human motor control analysis.

A model of ruddy duck Oxyura jamaicensis eradication for the UK

Summary Non‐native species are the second most important threat to global biodiversity after habitat loss. The North American ruddy duck Oxyura jamaicensis established a feral population in the UK more than 40 years ago, and it is now threatening the endangered white‐headed duck Oxyura leucocephala through hybridization. We utilized a simple generic model, which includes uncertainty in parameter estimates and can be used for any invasive species, to assess the time frame for successful control. A simple spreadsheet‐based model was produced to provide the UK government with an assessment of whether sufficient ruddy ducks could be culled to allow the UK population to be reduced to fewer than 175 individuals (> 97% population reduction) within 10 years. Data on changes in numbers of ruddy duck at the main UK wintering sites were collected during a regional control trial, and a stochastic Monte Carlo simulation model was constructed to project the UK population under a variety of control strategies. Three variables were included in the model: cull rate per person (i.e. by how much each control officer could reduce the national population per year), number of control officers, and changes in the ruddy duck population growth rate as the population was reduced. Parameter estimation was kept to a minimum by using historical annual population growth rates as a basis for future growth rates. The historical data show a reduction in both the mean growth rate and in its variability when the population is in excess of 2000 birds. Density‐dependent and density‐independent models were produced. These all gave similar times to reach the target population, with some difference in the variance estimates between models. Simulations were run with a maximum annual population reduction of between 0·50 and 0·80, and between 12 and 20 control officers. A total of 8000 simulations was performed for each of the 63 different scenarios for each of the models. The mean time to reduce the UK ruddy duck population by 97% was predicted to be between 3 and 5 years, with 14 or 15 control officers reducing the population by between 65% and 70% per year. There was an 80% certainty that the population could be reduced to this level by 16 control officers within 4–6 years if annual reductions of more than 60% were achieved. Synthesis and applications. The novel spreadsheet model presented here can easily be applied to a range of eradication schemes where limited data are available on population size and culling efficacy. This would allow funding bodies to have a greater degree of certainty about the cost and outcome of a trial eradication programme.

An industrial application of multivariable linear quadratic control to a cement mill circuit

There are a variety of control strategies that one may consider for cement mill circuit control and often several methods for implementing each strategy. Ideally, the control strategy selected and methodology used in it's implementation should not only optimize circuit performance in terms of productivity but also be able to optimize quality. A linear quadratic multivariable controller has been applied to milling circuits and these goals successfully accomplished. The results are a stable circuit with mill and separator optimized, producing a consistent quality product of a predictable fineness. This enables one to use cement quality as the single circuit control set point.

Measurement Effects in Comparing Voter Learning from Television News and Campaign Advertisements

Studies of media effects on political knowledge have used exposure and attention to measure television watching and confidence and accuracy to measure knowledge. These studies have employed a variety of control strategies. Although measurements and control strategies are known to affect the magnitude of the resulting independent-dependent correlation, this study investigates whether they can affect research outcomes in any other way. The topic of substance, which we use as an example, is whether voters learn more from political advertisements than from television news. The results indicate that different methods can lead to different, or even opposite, conclusions.

The Value of Animal Test Information in Environmental Control Decisions

Value of information (VOI) analytic techniques are used to evaluate the benefit of performing animal bioassays to provide information about the cancer potency of specific chemical compounds. These tools allow the identification of the conditions in which the cost of reducing uncertainty about potency, by performing a subchronic or chronic bioassay, is justified by the benefit of having improved information for making control decisions. The decision analytic results are readily scaled to apply to a range of human contact rates (exposures) and a variety of control strategies. The sensitivity of results to uncertainty about animal to human extrapolation and the design of the bioassay is explored. An evaluation of the possible gains in general understanding about the mechanisms of carcinogenicity resulting from chronic bioassays is beyond the scope of this approach.

Interaction between process design and process control: economic analysis of process dynamics

Abstract A method is presented to assess the impact of disturbances on plant economic performance. The method is suitable for use during process design, and can be used to help evaluate alternative process structures or alternative control schemes for a given process. Non-linear steady-state optimization is performed to determine the best operating point in the absence of disturbances. Frequency response analysis of a linearized plant dynamic model is used to estimate the effects of plant disturbances on this ideal performance under a variety of control strategies. The method is illustrated on a case study involving minerals flotation circuit design.

Public perceptions of predators, particularly the wolf and coyote

This paper explores American attitudes toward, and knowledge of, predators, particularly the wolf and coyote. The data for this paper were derived from a national study of animal-related attitudes, knowledge, and behaviours among 3107 randomly selected Americans residing in the 48 contiguous states and Alaska. Each respondent was personally interviewed in his or her home for approximately one hour. Additionally, special mail surveys of cattle and sheep producers and trappers were conducted. Responses to questions regarding attitudes toward wolves, coyotes, and a variety of other predators were analysed. Comparisons were made among a variety of demographic groups distinguished by age, sex, region of residence, urban-rural residence, education, and occupation. The views of livestock producers—mainly cattlemen and sheep producers—were also explored. Attitudes toward the wolf, coyote, and other predators were compared with attitudes toward other species, and factors identified as possibly accounting for these differences in species preference. Knowledge of animals and, in particular, predators was also examined and compared across various demographic groups. Additionally, groups characterized by relatively great like or dislike of predators were contrasted regarding basic attitudes toward animals. Finally, the study explored attitudes toward predator control, in particular alternative methods for limiting coyote depredations of livestock. Attitudes toward a variety of control strategies were examined, and distinguished among the general public and livestock producers.

Royal Society/Confederation of British Industry Lecture, 1983 Control engineering and economic modelling: a collaboration aimed at improving control of the national economy

Control engineering techniques, founded on a well structured set of theoretical disciplines, have in recent years claimed a striking level of success in providing control systems for the most diverse and complex dynamical systems, enabling them to function in an optimal manner, either by reducing overall costs or by improving the quality of the end product. A national economy is just such a dynamical system, so one could expect that the application of control system theory would be equally relevant. This is indeed the case, but there are formidable difficulties to overcome; sheer system complexity is one, and achieving a consensus on what is to be regarded as ‘optimal’ is another. The lecture discusses various aspects of economic modelling and the ways in which control techniques can be brought to bear on the behaviour of the economy. Extensive simulations using a number of models of the U. K. economy have indicated the benefits that might ensue under a variety of control strategies.

An Approach to Evaluating Effects of Alternative Controls for Douglas-Fir Tussock Moth

The objective of our working group is essentially two-fold: To generate the physical impacts of tussock moth outbreaks under a variety of control strategies that range from doing nothing to using a variety of chemicals or biological controls and, second, to translate these impacts into measures for decision makers and managers to use in evaluating the trade-offs between control alternatives.