Types Of Control Strategies Research Articles

Manipulator motion control in operational space using joint velocity inner loops

This paper addresses the operational space motion control—trajectory tracking—of robot manipulators endowed with joint velocity feedback inner loops. A general structure for model-based joint velocity controllers is proposed for the inner loop. The required joint velocity reference is provided by an outer loop inspired from the robot kinematic control approach. It is shown that above two-loops control schemes lead to a nice cascade structure for the corresponding closed-loop systems. A stability result adapted for analysis of this particular kind of systems is developed in the paper; sufficient conditions for global exponential stability of this class of cascade systems are obtained. The effectiveness of the proposed control approach is evaluated on a direct-drive mechanical arm, and compared with a typical control strategy based on inverse kinematics resolution for computation of the desired motion in joint space, and the use of the computed–torque technique. The experimental evidences show better performance of the proposed two-loops controller.

A Reinforcement Learning Approach to Streetcar Bunching Control

Transit agencies often implement operations control strategies so as to mitigate the effects of streetcar bunching along transit routes. Typical control strategies include vehicle holding, expressing, and short turning, which are usually implemented through manual means via field supervisors or central control centers. The objective of this study is to automate streetcar bunching control by means of multiple Reinforcement Learning (RL) agents that act on a series of successive signalized intersections. The multiple RL agents developed in this study include the “bunch–splitting,” “holding,” and “expressing” agents which work cooperatively to break up a streetcar bunch if one is detected and to build a reasonable headway between the paired streetcars. Various elements of the RL agents such as the action set, the reward, and the state space are set up under a traffic signal control context. Simulation results indicated that these multiple RL agents could split up a streetcar bunch and prevent it from forming again with a high success rate.

Design and Development of Speed Controller for Wheeled Walking Frames (Application of Internal Model Control and LQ Control with Servo Compensation)

The work presents the wheeled walking frames that are supporting equipments, to be used by elderly people or handicapped in rehabilitation. Mostly, standard frames have weakness in walking on upward/downward slope. People often need power assistance on upward, and need secure walking support without falling on downward. The purpose of this paper is to develop a speed control assisting unit for wheeled walking frames by using the generalized internal model control (GIMC) with LQ control. By selecting appropriate parameter, the control method has various type of control scheme. Effectiveness of the assisting unit is confirmed by comparative experiments on upward and downward slopes. The result shows that the proposed method is effective on speed control for the assisting unit of wheeled walking frames.

The control of ice slurry systems: an overview

This article outlines some typical control strategies for the basic components of an ice slurry system. From this review it became apparent that the control of terminal units is not fundamentally different from the control of classical single-phase secondary cooling systems, except from the fact that it must be based on the use of local pumps and the ON–OFF operation of actuators to avoid ice plugging problems. The safe control of the ice generator can be ensured with a simple thermostat, although the resulting ice concentration control would be approximate. It was also demonstrated that any ice accumulation in the storage tank would not prevent the ice slurry system from functioning safely. As a final precaution, it was not recommended to operate an ice slurry generator at low solute concentrations and temperatures greater than −3/−4 °C due to the risk of plugging up the distribution loop and causing mechanical wear to the ice generator.

General run-to-run (R2R) control framework using self-tuning control for multiple-input multiple-output (MIMO) processes

During recent years, run-to-run (R2R) control techniques have been developed and used to control various semiconductor manufacturing processes. The R2R control methodology combines response surface modelling, engineering process control, and statistical process control. The main objective of such control is to manipulate the recipe to maintain the process output of each run as close to the nominal target as possible. The primary focus of this research is on the multiple-input multiple-output self-tuning control of R2R processes. A general control scheme is presented that can compensate for a variety of noise disturbances frequently encountered in semiconductor manufacturing. The controller can also compensate for various system dynamics, including autocorrelated responses, deterministic drifts, and varying process gains and offsets. Self-tuning controllers are developed to provide on-line parameter estimation and control. A recursive least squares algorithm is normally used to provide on-line parameter estimation to the controller. This type of control strategy used in the proposed self-tuning controller applies the principle of minimizing total cost (in the form of an expected off-target and controllable factors adjustment) to obtain a recipe for the next run. It is shown through the simulation study that even if the control model is non-linear, the self-tuning controller offers satisfactory control performance for R2R applications as compared with those of the control actions provided by the optimizing adaptive quality controller module. At last, a relevant application to chemical mechanical planarization in semiconductor manufacturing, a critical fabrication step involving two quality characteristics (removal rate and within-wafer non-uniformity), is used to illustrate the proposed controller. In this case study, a multivariate statistical process control technique via the Hotelling T 2 statistic is also used as a dead-band for further investigation.

Control of power electronic interfaces in distributed generation microgrids

Technological advances and environmental pressures are driving the interconnection of renewable energy sources to the distribution network. The interconnection of large amounts of non-traditional generation however causes problems in a network designed for ‘conventional’ operation. The use of power electronics interfaces and the ‘bundling’ of micro-generation and loads into so-called Microgrids, offers a potential solution. Each Microgrid is designed to operate as a ‘good citizen’ or near ideal conventional load. This paper discusses the various elements of the new Microgrid concept and presents suggestions for some typical control strategies for the various system elements.

A family of co‐robotic surgical set‐ups

The paper describes co‐robotic devices, aiming at accomplishing surgical operations by remote overseeing and manipulation. The concept design of a modular layout is presented, assuring body penetration by curved and twisted paths, with minimal impact. The fixture develops as an articulated snake‐like forearm, carrying a wrist and the pertinent effectors; scalpels, scissors, sewing rigs, cameras, etc. The fixture is a good example of a micro electro mechanical system, with force‐actuation and shape‐control being intrinsic properties. Different options are studied and the related basic operational characteristics are summarised and compared. The jointed forearm might include one to six blocks. Specifically, task‐oriented end‐effectors are considered, e.g. a self‐operating sewing rig, able to operate with a single thread. The robot co‐operation will drastically modify surgery practice, giving freedom from anthropocentric bounds; the paper introduces such opportunities, with comments on typical control strategies and hints on actual performance, inferred by testing on virtual reality and digital mock‐ups.

Adjusting irrigation abstraction to minimise the impact on stream flow in the East of Scotland

Abstractions of surface and groundwater for irrigation in Scotland are currently subject to control in only two small catchments. Under the terms of the EU Water Framework Directive, it will be necessary to introduce new legislation to control abstractions elsewhere. To help in the development of appropriate policy for Scotland a study has been carried out to examine the significance of irrigation and the effectiveness of different types of control strategies in terms of the economics of potato cropping and stream hydrology in Scotland. This paper presents the findings of the hydrological study and highlights some of the spatial and temporal issues that need to be considered in the selection of control mechanisms, if they are to be successful in achieving objectives for environmental improvement. The study was focussed on two catchments in the east of Scotland, the Tyne and West Peffer. The effectiveness of several different abstraction control strategies was examined to see how stream flows in the catchment would be modified by their implementation. The results of the study demonstrated that the West Peffer catchment in particular is significantly affected by irrigation abstractions. Control mechanisms based on allowable monthly abstraction volumes and flow-based abstraction bans would be of considerable help in restoring stream flows to their natural levels, but would modify the hydrological regime in slightly different ways. A spatial analysis of stream flows demonstrated that implementation of controls based on a single monitoring point may be ineffective at maintaining acceptable levels of flow throughout the catchment and that this may require a tighter control at the monitoring point.

Intelligent Feedback Linearization for Active Vehicle Suspension Control

Effective control of ride quality and handling performance are challenges for active vehicle suspension systems, particularly for off-road applications. Off-road vehicles experience large suspension displacements, where the nonlinear kinematics and damping characteristics of suspension elements are significant. These nonlinearities tend to degrade the performance of active suspension systems, introducing harshness to the ride quality and reducing off-road mobility. Typical control strategies rely on linear, time-invariant models of the suspension dynamics. While these models are convenient, nominally accurate, and tractable due to the abundance of linear control techniques, they neglect the nonlinearities and time-varying dynamics present in real suspension systems. One approach to improving the effectiveness of active vehicle suspension systems, while preserving the benefits of linear control techniques, is to identify and cancel these nonlinearities using Feedback Linearization. In this paper the authors demonstrate an intelligent parameter estimation approach using structured artificial neural networks that continually “learns” the nonlinear parameter variations of a quarter-car suspension model. This estimation algorithm becomes the foundation for an Intelligent Feedback Linearization (IFL) controller for active vehicle suspensions. Results are presented for computer simulations, real-time experimental tests, and field evaluations using an off-road vehicle (a military HMMWV). Experimental results for a quarter-car test rig demonstrate 60% improvements in ride quality relative to baseline (non-adapting) control algorithms. Field trial results reveal 95% reductions in absorbed power and 65% reductions in peak sprung mass acceleration using this IFL approach versus conventional passive suspensions.

Primary and secondary control strategies for managing health and financial stress across adulthood.

The study examined the relation among three types of control strategies (persistence, positive reappraisals, lowering aspirations) and subjective well-being across adulthood (N = 3,490). Specifically, the authors investigated whether age-adapted endorsement of control strategies is conducive to subjective well-being if individuals experience health or financial stress. The results reveal an overall enhanced reliance on control strategies in older as compared with younger adults. In addition, persistence showed a stronger positive relation to subjective well-being in young adulthood as compared with old age. In midlife and old age, positive reappraisals had a stronger positive relation to subjective well-being than persistence. Lowering aspirations was negatively related to subjective well-being, independent of age. Age differences in the relation of control strategies to subjective well-being were particularly salient in individuals who faced either health or financial stress.

An experimental study of adaptive force/position control algorithms for an industrial robot

Presents the results of an experimental study of force/position control algorithms for an industrial robot with open control architecture, equipped with a wrist force sensor. The robot's end effector is in contact with a compliant surface of unknown stiffness. Two types of control schemes are considered which respectively achieve regulation and tracking of position on the contact surface and force along the direction normal to the surface. The desired position is scaled along the constrained direction so as to fulfill the force control objective; adaptive mechanisms are designed for the two schemes to compute the scaling factor, which depends on the unknown stiffness coefficient of the environment. A number of case studies are developed throughout the paper to illustrate the effectiveness of the force/position control algorithms under nonideal conditions.

A more accurate analytical model on blocking probability of multicast networks

Multicast communication is one of the most important collective communication operations and is highly demanded in telecommunication environments and scalable parallel and distributed computing systems. In this paper, we consider the issue of supporting multicast in the widely used a three-stage Clos network or /spl upsi/(m,n,r) network. We improve a previously proposed analytical model (Yang and Wang 1998) for the blocking probability of the /spl upsi/(m,n,r) multicast network by introducing more reasonable assumptions based on the properties of multicast communication and the Clos network. We also compare the improved analytical model with the simulation results under three typical routing control strategies. As can be seen, the improved model matches better with the simulation results and further confirms that a /spl upsi/(m,n,r) network with a comparable cost to a permutation network is almost nonblocking for multicast connections.

Benefit Sensitivities of Adaptive Traffic Control Strategies at Isolated Traffic Signals

A study of the possible benefits of using traffic adaptive and actuated signal control strategies at traffic signals is described here. The study indicated that delay estimates produced by INTEGRATION closely matched the delay estimates of the 1997 revision to the U.S. Highway Capacity Manual. Second, benefits of time-of-day control and adaptive control became more pronounced as the level of demand peaking increased. Third, well-designed time-of-day plans easily outperform fixed-time and adaptive strategies when the prevailing traffic demands match the controller’s expectations. Adaptive strategies performed better than simple fixed-time control strategies, which were optimized only for the average demand level. It was also observed that all types of control strategies, especially adaptive control strategies, could be improved by introducing signal actuation. Finally, it was found that actuation improved the performance of the intersection for both uniform and random departure headways. Improvements were greatest when an adaptive control strategy was being implemented and the departure headway was random.

The necessary conditions for Clos-type nonblocking multicast networks

Efficient interconnection networks are critical in providing low latency, high bandwidth communication in parallel and distributed computing systems with hundreds or thousands of processors. The well-known Clos network or v(m, n, r) network can be extended to provide full one-to-many or multicast capability. In this paper, we consider several typical routing control strategies for Clos-type nonblocking multicast networks and derive the necessary conditions under which this type of network is nonblocking for arbitrary multicast assignments in the strict sense as well as under these control strategies. The necessary conditions obtained are represented as the number of middle stage switches m/spl ges//spl Theta/(n[log r/log log r]). These results match the sufficient nonblocking condition for the currently best available explicitly constructed, constant stage nonblocking multicast network, and provide a basis for the optimal design of this type of multicast network.

Prenatal Exposure to Alcohol Affects the Ability to Maintain Postural Balance

Prenatal exposure to alcohol is known to affect gross motor functioning. Animal studies have shown that balance is particularly affected, and there is some evidence that similar deficits exist in alcohol-exposed children. In the current study, postural balance, or the ability to maintain equilibrium, was assessed in a group of alcohol-exposed children (ALC group; n = 11) and controls (NC group; n = 11) individually matched for age and sex. Balance was measured across six conditions designed to systematically manipulate or eliminate visual or somatosensory information. Equilibrium and strategy scores for each condition and a derived composite balance score were analyzed. Although the ALC group had a lower mean composite balance score, their performance was similar to that of the NC group on all conditions where somatosensory input was reliable. However, when somatosensory input was manipulated, and when both somatosensory and visual input were inaccurate, the ALC group performed more poorly than controls. Interestingly, there were no differences between the ALC group and NC group in the type of control strategy used to maintain balance. These results suggest that alcohol-exposed children are overly reliant on somatosensory input. When this input is atypical, alcohol-exposed children display significantly greater anterior-posterior body sway and are unable to compensate using available visual or vestibular information. These deficits may be related to cerebellar anomalies previously reported in fetal alcohol syndrome children.

Prenatal Exposure to Alcohol Affects the Ability to Maintain Postural Balance

Prenatal exposure to alcohol is known to affect gross motor functioning. Animal studies have shown that balance is particularly affected, and there is some evidence that similar deficits exist in alcohol-exposed children. In the current study, postural balance, or the ability to maintain equilibrium, was assessed in a group of alcohol-exposed children (ALC group; n=11) and controls (NC group; n= 11) individually matched for age and sex. Balance was measured across six conditions designed to systematically manipulate or eliminate visual or somatosensory information. Equilibrium and strategy scores for each condition and a derived composite balance score were analyzed. Although the ALC group had a lower mean composite balance score, their performance was similar to that of the NC group on all conditions where somatosensory input was reliable. However, when somatosensory input was manipulated, and when both somatosensory and visual input were inaccurate, the ALC group performed more poorly than controls. Interestingly, there were no differences between the ALC group and NC group in the type of control strategy used to maintain balance. These results suggest that alcohol-exposed children are overly reliant on somatosensory input. When this input is atypical, alcohol-exposed children display significantly greater anterior-posterior body sway and are unable to compensate using available visual or vestibular information. These deficits may be related to cerebellar anomalies previously reported in fetal alcohol syndrome children.

Safe implementations of supervisory commands

Two different types of control strategy used to safely implement supervisory commands of hybrid dynamical systems are compared. Both approaches considered switch between members of a family of control agents to ensure that constraints on the plant state are not violated at any time. The first approach is motivated by a hybrid system architecture outlined by Kohn and Nerode (1993) and uses a Fliess functional series of the plant's output to form a system of linear inequalities characterizing safe control inputs. Control signals are determined by solving a sequence of linear programs. The second approach is a model reference control approach to hybrid systems introduced by Lemmon and Bett (1996) and uses a known safe dynamical reference model to characterize the desired plant behaviour. The controller is determined by representing the resulting error dynamics as a linear parameter varying system and applying linear robust control techniques to enforce a bounded amplitude performance level. The fundamental results underlying each of the methods are derived; the approaches are compared with regard to their complexity, performance and sensitivity to modelling uncertainty. A numerical example is included for illustration.

Automated Control and Monitoring of Thermal Processing Using High Temperature, Short Time Pasteurization

High temperature, short time pasteurization was used to evaluate a computer-based system for controlling the pasteurization process, acquiring data, and monitoring records. Software was used for the control of hot water temperature, flow rate through the centrifugal timing pump, and diversion of underprocessed product. Three types of control strategies were conducted: single loop, cascade, and multivariable. The single loop control strategy showed the most rapid responses to temperature changes, but the temperature response curve was slowest to return to its set point. The cascade control strategy showed slower recoveries to temperature changes, but the temperature response curve was smoother. The multivariable control strategy responded slightly faster than the cascade control strategy, and the temperature response curve was slightly smoother than the cascade control strategy. The multivariable control strategy was able to control the flow diversion valve by the use of a lethality controller.The data acquisition system, used to monitor the data obtained from the high temperature, short-time pasteurization system, was within ±0.1°C of the temperature recorded by the safety thermal limit recorder. Reliability was determined by examining the changes in the position of the flow diversion valve to identify process deviations and by comparing the changes to the event marker on circular charts. The data acquisition system was an effective alternative for monitoring the completeness of data.

Experiments in contact control

The implementation, experimentation, and application of contact control schemes for a 7-DOF Robotics Research arm is presented. Three types of control schemes are presented: compliance cntrol, force control, and dual-mode control. This presentation is concluded with the application of the proposed schemes to perform a contact-based eddy-current inspection task.

Inconsistent nurturing as control theory: Implications for communication‐based research and treatment programs

Abstract Relatively little theorizing has focused on the role of the significant other in sustaining or reducing undesired behavior. Inconsistent Nurturing as Control (INC) theory argues that (1) the paradoxical nature of the power structure in functional‐afflicted relationships places limits on the types of control strategies that functional partners can use in attempts to extinguish undesired behavior, and (2) functional partners may unintentionally encourage undesirable behavior through well‐intentioned efforts to discourage the same behavior (Le Poire, 1992, p. 1465). This article explains INC as it applies to all couples including functional and afflicted partners and proposes a communication‐based method of assessing and treating relationships in which the afflicted partner is substance‐dependent.