Showing papers on "Proportional control published in 2014"
01 May 2014
TL;DR: It is concluded that for reliable simultaneous and proportional myoelectric control, it is not necessary to achieve high accuracy in the mapping between EMG and kinematics, and this conclusion explains the possibility of accurate simultaneously and proportional control over multiple degrees of freedom when using unsupervised algorithms, such as NMF.
Abstract: In this paper, we present a systematic analysis of the relationship between the accuracy of the mapping between EMG and hand kinematics and the control performance in goal-oriented tasks of three simultaneous and proportional myoelectric control algorithms: nonnegative matrix factorization (NMF), linear regression (LR), and artificial neural networks (ANN). The purpose was to investigate the impact of the precision of the kinematics estimation by a myoelectric controller for accurately complete goal-directed tasks. Nine naive subjects performed a series of goal-directed myoelectric control tasks using the three algorithms, and their online performance was characterized by 6 indexes. The results showed that, although the three algorithms' mapping accuracies were significantly different, their online performance was similar. Moreover, for LR and ANN, the offline performance was not correlated to any of the online performance indexes, and only a weak correlation was found with three of them for NMF . We conclude that for reliable simultaneous and proportional myoelectric control, it is not necessary to achieve high accuracy in the mapping between EMG and kinematics. Rather, good online myoelectric control is achieved by the continuous interaction and adaptation of the user with the myoelectric controller through feedback (visual in the current study). Control signals generated by EMG with rather poor association with kinematic variables can still be fully exploited by the user for precise control. This conclusion explains the possibility of accurate simultaneous and proportional control over multiple degrees of freedom when using unsupervised algorithms, such as NMF.
194 citations
TL;DR: In this article, a direct grid current control strategy for LCL-filtered grid-connected inverters is proposed, where the virtual resistance based on capacitance current is used to realize active damping, zero compensation is brought in to enhance the stability, and the proportional resonant (PR) controller under two-phase static coordinate is designed to track the ac reference current as well as to avoid the strong coupling brought by the coordinate transformation.
Abstract: A direct grid current control strategy for LCL-filtered grid-connected inverters is proposed in this paper. The conventional current control strategies are analyzed and compared, and then the necessity of direct grid current control is presented to mitigate the grid voltage disturbance. In the proposed control strategy, the virtual resistance based on the capacitance current is used to realize active damping, zero compensation is brought in to enhance the stability, and the proportional resonant (PR) controller under two-phase static coordinate is designed to track the ac reference current as well as to avoid the strong coupling brought by the coordinate transformation. Under the distortion grid voltage, the PR plus harmonic compensator (PR+HC) structure is adopted to restrain the distortion of the grid current. Finally, the proposed control strategy is verified by the experimental results.
180 citations
25 Mar 2014
TL;DR: In this article, the authors proposed a distributed controller based on passivity properties of the system, which has the potential to deal with more complex models of dynamical networks and fairly rich classes of external perturbations.
Abstract: The power grid can be regarded as a large interconnected network of different subsystems, called control area’s. In order to guarantee reliable operation the frequency is tightly regulated around its nominal value, e.g. 50 Hz. Automatic regulation of the frequency in power grid is traditionally achieved by primary proportional control (droop-control) and a secondary PI-control on the generators, where economic considerations are largely neglected. Recently we proposed a novel distributed controller in [1] that controls power production such that the frequency is regulated in an economic efficient way. Main advantage of our approach, based on passivity properties of the system, is that it has the potential to deal with more complex models of dynamical networks and fairly rich classes of external perturbations.
174 citations
01 Jan 2014
TL;DR: Two novel proportional control algorithms for use with pattern recognition-based myoelectric control were designed to provide automatic configuration of motion-specific gains and to normalize the control space to the user's usable dynamic range.
Abstract: This paper describes two novel proportional control algorithms for use with pattern recognition-based myoelectric control. The systems were designed to provide automatic configuration of motion-specific gains and to normalize the control space to the user's usable dynamic range. Class-specific normalization parameters were calculated using data collected during classifier training and require no additional user action or configuration. The new control schemes were compared to the standard method of deriving proportional control using a one degree of freedom Fitts' law test for each of the wrist flexion/extension, wrist pronation/supination and hand close/open degrees of freedom. Performance was evaluated using the Fitts' law throughput value as well as more descriptive metrics including path efficiency, overshoot, stopping distance and completion rate. The proposed normalization methods significantly outperformed the incumbent method in every performance category for able bodied subjects and nearly every category for amputee subjects. Furthermore, one proposed method significantly outperformed both other methods in throughput , yielding 21% and 40% improvement over the incumbent method for amputee and able bodied subjects, respectively. The proposed control schemes represent a computationally simple method of fundamentally improving myoelectric control users' ability to elicit robust, and controlled, proportional velocity commands.
101 citations
TL;DR: A feedforward friction observer (FFFO) is proposed as formulating an explicit analytical expression for the applied observation function that ensures the cancelation of friction disturbances and time variances at steady state.
Abstract: In motor drives, just as in other mechanical actuators, the friction compensation is extremely important as friction can have adverse impact on the overall control performance. In this paper, a feedforward friction observer (FFFO) is proposed as formulating an explicit analytical expression for the applied observation function. This ensures the cancelation of friction disturbances and time variances at steady state. The proposed observation scheme utilizes the two-state dynamic friction model with elastoplasticity (abbreviated as 2SEP), which is compact in parameterization and captures both the presliding and sliding phases of kinetic friction. The method to identify a motor drive plant with nonlinear friction in the frequency domain has been applied using only few frequency-response-function measurements. The feedback control design is performed with respect to the time delay detectable in the system, thus under additional constraints when determining the control gains. The optimal proportional-integral (PI) control designed this way is compared with the proportional control combined with the observer (P-FFFO). The simulation results show that P-FFFO control compensates faster for frictional disturbances at suddenly changing frictional conditions than PI control. In addition, an extensive experimental evaluation of velocity tracking control discloses P-FFFO as superior in terms of a faster steady-state convergence after various transient phases.
77 citations
TL;DR: In this article, the authors explored the relationship between dual decomposition and the consensus-based method for distributed optimisation by examining the similarities between the two approaches and their relationship to gradient-based constrained optimisation.
Abstract: In this paper, we explore the relationship between dual decomposition and the consensus-based method for distributed optimisation. The relationship is developed by examining the similarities between the two approaches and their relationship to gradient-based constrained optimisation. By formulating each algorithm in continuous-time, it is seen that both approaches use a gradient method for optimisation with one using a proportional control term and the other using an integral control term to drive the system to the constraint set. Therefore, a significant contribution of this paper is to combine these methods to develop a continuous-time proportional-integral distributed optimisation method. Furthermore, we establish convergence using Lyapunov stability techniques and utilising properties from the network structure of the multi-agent system.
70 citations
TL;DR: This is the first simultaneous proportional myoelectric control system demonstrated on a prosthesis affixed to the forearm of a subject and illustrates that PGT is a promising system training method for proportional control.
Abstract: Pattern recognition control of prosthetic hands take inputs from one or more myoelectric sensors and controls one or more degrees of freedom. However, most systems created allow only sequential control of one motion class at a time. Additionally, only recently have researchers demonstrated proportional myoelectric control in such systems, an option that is believed to make fine control easier for the user. Recent developments suggest improved reliability if the user follows a so-called prosthesis guided training (PGT) scheme. In this study, a system for simultaneous proportional myoelectric control has been developed for a hand prosthesis with two motor functions (hand open/close, and wrist pro-/supination). The prosthesis has been used with a prosthesis socket equivalent designed for normally-limbed subjects. An extended version of PGT was developed for use with proportional control. The control system’s performance was tested for two subjects in the Clothespin Relocation Task and the Southampton Hand Assessment Procedure (SHAP). Simultaneous proportional control was compared with three other control strategies implemented on the same prosthesis: mutex proportional control (the same system but with simultaneous control disabled), mutex on-off control, and a more traditional, sequential proportional control system with co-contractions for state switching. The practical tests indicate that the simultaneous proportional control strategy and the two mutex-based pattern recognition strategies performed equally well, and superiorly to the more traditional sequential strategy according to the chosen outcome measures. This is the first simultaneous proportional myoelectric control system demonstrated on a prosthesis affixed to the forearm of a subject. The study illustrates that PGT is a promising system training method for proportional control. Due to the limited number of subjects in this study, no definite conclusions can be drawn.
66 citations
TL;DR: In this paper, a PID controller optimization is proposed based on the frequency response of a process G p ( s ) and maximization of the proportional gain, under constraints on the desired sensitivity to measurement noise, desired maximum sensitivity and desired maximum complementary sensitivity.
49 citations
TL;DR: In this paper, a set-point controller composed of a proportional control term and an angular velocity control term is presented, which is a function of the vector measurements and a set of desired vector measurements that are used to compute the orientation error of the rigid body.
Abstract: Set-point regulation and tracking control of a rigid body is considered. The rigid body, which could be a spacecraft, underwater vehicle, or unmanned aerial vehicle, is equipped with various sensors, including those that provide unit-length vector measurements. At no point is the rotation matrix associated with the rigid-body’s orientation parameterized. The control algorithms developed in this paper are posed directly on the special orthogonal group of rigid-body rotations SO(3). The set-point controller presented is composed of a proportional control term and an angular velocity control term. The proportional control term is a function of the vector measurements and a set of desired vector measurements that are used to compute the orientation error of the rigid body. Passive systems theory is used to motivate the use of a strictly positive real angular velocity controller. The set-point regulator is robust to modeling errors associated with the mass distribution of the body. Tracking control is also con...
36 citations
TL;DR: In this article, a proportional-integral-derivative (PID) controller optimized by predictive functional control (PFC) is proposed and tested on liquid level in the industrial coke fractionation tower.
34 citations
TL;DR: A space-learning control is designed for the tracking of planar curves whose uncertain curvature is L-periodic in the curvilinear abscissa and the behaviour of a human driver, who repetitively learns the correct action from the past experience, is mathematically reproduced.
TL;DR: A segmented predict negative feedback control method, based on the advance proportional control one, is proposed and verified by experiments to overcome the shortcomings of PID temperature control and demonstrate that the optimal output performance of PEMFC can be realized.
Journal Article•
TL;DR: This paper deals with diabetes type 1 as a nonlinear model, which has been simulated in MATLABSIMULINK environment by the means of Gap Metric method and Genetic Algorithm amends the controller by improving fuzzy membership functions.
Abstract: This paper deals with diabetes type 1 as a nonlinear model, which has been simulated in MATLABSIMULINK environment by the means of Gap Metric method. A proportional controller turns three independent linear integrals into this nonlinear model. To enhance the system performance, a Fuzzy algorithm independent coefficient has been implemented. In this study, Genetic Algorithm amends the controller by improving fuzzy membership functions. Finally, the control method tuned by standard tuning procedure and the optimized form of it are compared.
TL;DR: In this article, a mathematical model of the steam turbine unit, developed based on the continuity equation, was used to determine the simulation diagram for the turbine with high, medium and low pressure sections.
Posted Content•
TL;DR: This paper presents a decentralized controller for sharing primary AC frequency control reserves through a multi-terminal HVDC grid that is shown to stabilize the equilibrium of the closed-loop system consisting of the interconnected AC andHVDC grids, given any positive controller gains.
Abstract: This paper presents a decentralized controller for sharing primary AC frequency control reserves through a multi-terminal HVDC grid. By using Lyapunov arguments, the proposed controller is shown to stabilize the equilibrium of the closed-loop system consisting of the interconnected AC and HVDC grids, given any positive controller gains. The static control errors resulting from the proportional controller are quantified and bounded by analyzing the equilibrium of the closed-loop system. The proposed controller is applied to a test grid consisting of three asynchronous AC areas interconnected by an HVDC grid, and its effectiveness is validated through simulation.
TL;DR: The proposed state-based method could be a suitable alternative for commercial myoelectric devices, providing reliable and intuitive control of two DoFs, and to achieve precise force control in grasping.
Abstract: Current clinical myoelectric systems provide unnatural prosthesis control, with limited functionality. In this study, we propose a proportional state-based control method, which allows switching between functions in a more natural and intuitive way than the traditional co-contraction switch method. We validated the ability of the proposed system to provide precise control in both position and velocity modes. Two tests were performed with online visual feedback, involving target reaching and direct force control in grasping. The performance of the system was evaluated both on a subject with limb deficiency and in 9 intact-limbed subjects, controlling two degrees of freedom (DoF) of the hand and wrist. The system allowed completion of the tasks involving 1-DoF with task completion rate >96% and of those involving 2-DoF with completion rate >91%. When compared with the clinical/industrial state-of-the-art approach and with a classic pattern recognition approach, the proposed method significantly improved the performance in the 2-DoF tasks. The completion rate in grasping force control was >97% on average. These results indicate that, using the proposed system, subjects were successfully able to operate two DoFs, and to achieve precise force control in grasping. Thus, the proposed state-based method could be a suitable alternative for commercial myoelectric devices, providing reliable and intuitive control of two DoFs.
TL;DR: In this paper, a new oscillation mitigation method is introduced to demonstrate its effectiveness in solving the instability problems of open-loop constant voltage/frequency (v/f) adjustable speed drive (ASDs).
Abstract: Open-loop constant voltage/frequency (v/f) adjustable speed drives (ASDs) can often experience undesirablesustained oscillations. Factors affecting these oscillation states include induction machine (IM) parameters, dead time,dc-link capacitor size, IM saturation, output voltage, carrier frequency, and IM speed. Many literatures have discussedthe instabilities in light-load or low-frequency operating conditions. Quite a few methods have been proposed forstabilizing such a system. However, the instability problems, at different power levels, have not been completelydescribed. This paper analyzes the causes of this instability for constant v/f drives as power levels change. The 2.2-and 15-kW low-voltage IMs and the 746-kW medium-voltage IM are evaluated to illustrate how the motor parameters affectthe system stability. Additionally, a new oscillation mitigation method is introduced to demonstrate its effectivenessin solving the instability problems. It is based on the synchronous reference frame dynamic current feedback through itsmagnetic flux current component bandpass filtering and proportional control. In a theoretical stability analysis beforeand after the current feedback compensation, simulation studies are presented and verified through a 15-kW 380-V 50-HzIM ASD experimental system.
TL;DR: In this paper, a methodology for the design of broadband electroacoustic resonators for low-frequency room equalization is presented, where the benefits of using PID control and phase compensation techniques to improve the overall performance of the electroacoustical resonator are evaluated.
TL;DR: A fuzzy controller to regulate the pressurizer inventory control is developed and compared to the current proportional controller used at DNGS to show the fuzzy controller performs better than the proportional controller in terms of settling time and overshoot.
TL;DR: In this article, a RC controller is proposed to track the dc component and restrain the low-frequency even-order ac harmonics, which can distort the arm currents, increase the power loses, and cause higher current stresses on the semiconductor devices.
Abstract: Modular multilevel converters (MMCs) have emerged as the most promising topology for high and medium voltage applications for the coming years. However, one particular negative characteristic of MMCs is the existence of circulating current, which contains a dc component and a series of low-frequency even-order ac harmonics. If not suppressed, these ac harmonics will distort the arm currents, increase the power loses, and cause higher current stresses on the semiconductor devices. Repetitive control (RC) is well known due to its distinctive capabilities in tracking periodic signals and eliminating periodic errors. In this paper, a novel circulating current control scheme base on RC is proposed to effectively track the dc component and to restrain the low-frequency ac harmonics. The integrating function is inherently embedded in the RC controller. Therefore, the proposed circulating current control only parallels the RC controller with a proportional controller. Thus, conflicts between the RC controller and the traditional proportional integral (PI) controller can be avoided. The design methodologies of the RC controller and a stability analysis are also introduced. The validity of the proposed circulating current control approach has been verified by simulation and experimental results based on a three-phase MMC downscaled prototype.
TL;DR: In this paper, a software control method for harmonic content evaluation in the dq synchronous rotating reference frame for grid side VSIs (Voltage Source Inverters) used in DPGS (distributed power generation systems) applications is presented.
TL;DR: In this paper, the necessary and sufficient condition for stabilizability of a closed-loop FOPDT process by a proportional controller is found. And an algorithm is proposed for estimating the order and the parameters of an unstable fractional order model by using the mentioned data.
TL;DR: In this paper, an individual voltage balancing control scheme for multilevel cascade active-front-end rectifier is proposed to allow a different voltage setting capability among different dc outputs in series.
Abstract: In this study, a novel individual voltage balancing control scheme for multilevel cascade active-front-end rectifier is proposed to allow a different voltage setting capability among different dc outputs in series. First, the proportional resonant controller and admittance compensation controller are introduced for the active inner-current control loop of cascade active-front-end rectifier to achieve better steady-state and dynamic performance. Second, an assumption based on conservation of energy is proposed to decouple a series connected ac-dc system into several individual subsystems to facilitate the individual dc-bus controller design. Both simulation and experimental results based on the cascade two-unit cascade dual-buck/boost-type active-front-end rectifier proved the effectiveness of the proposed individual balancing control scheme, which also verified the proposed assumption.
16 Apr 2014
TL;DR: The use of IP controller enhances system dynamic response and reduces undesirable peak overshoot compared to conventional PI controllers and also reduces system's sensitivity to controller gains.
Abstract: Closed loop control strategy is indispensable in power converters to meet the desired load requirements PI controller is one among the existing control schemes This scheme has a single loop arrangement with proportional and integral gains in the forward path A double loop control strategy having proportional gain in the feedback path and integral gain in the forward path called the Integral Proportional - IP controller is proposed in this paper for Buck converter control The use of IP controller enhances system dynamic response and reduces undesirable peak overshoot compared to conventional PI controllers IP controller also reduces system's sensitivity to controller gains Responses of both controllers are analyzed by performing output voltage regulation of Buck Converter with the help of PSIM software Simulation results show that the IP controller has better response than PI Such a control arrangement is essential in applications, where a smooth power output is inevitable
TL;DR: In this article, an optimal time-varying P-controller is presented for a class of continuous-time underactuated nonlinear systems in the presence of process noise associated with systems inputs.
Abstract: In this manuscript, an optimal time-varying P-controller is presented for a class of continuous-time underactuated nonlinear systems in the presence of process noise associated with systems’ inputs. This is a state feedback control strategy where the optimization is performed on a time-varying feedback operator (herein called the feedback control gain). The main goal of the current manuscript is to provide a framework for multi-input multi-output nonlinear systems which yields a satisfactory tracking performance based on the optimal time-varying feedback control gain. Unlike other feedback control techniques that perform dynamic linearization of system models, the proposed time-varying Pcontroller provides the full-state feedback control to the original nonlinear system model. Hence, this P-controller guarantees global asymptotic state-tracking. Furthermore, the bounded system’s process noise is taken into consideration to measure the controller’s robustness. The proposed P-controller is tested for its nonlinear trajectory tracking and fixed-point stabilization capabilities with two nonholonomic systems in the presence of input noise.
TL;DR: Compared with the conventional PID-P and MPC-P cascade control methods, the proposed cascade control strategy can effectively decrease fluctuations of hydro-turbine speed under non-Gaussian disturbance conditions in practical hydropower plants.
Abstract: In this paper, an improved cascade control strategy is presented for hydroturbine speed governors. Different from traditional proportional-integral-derivative (PID) control and model predictive control (MPC) strategies, the performance index of the outer controller is constructed by integrating the entropy and mean value of the tracking error with the constraints on control energy. The inner controller is implemented by a proportional controller. Compared with the conventional PID-P and MPC-P cascade control methods, the proposed cascade control strategy can effectively decrease fluctuations of hydro-turbine speed under non-Gaussian disturbance conditions in practical hydropower plants. Simulation results show the advantages of the proposed cascade control method.
TL;DR: In this paper, a numerical controlled machine axis was studied through a lumped parameter model, where a linear model was derived in order to apply a modal analysis to estimate the first mechanical frequency of the system as well as its damping coefficients.
Abstract: This paper reports how a numerical controlled machine axis was studied through a lumped parameter model. Firstly, a linear model was derived in order to apply a modal analysis, which estimated the first mechanical frequency of the system as well as its damping coefficients. Subsequently, a nonlinear system was developed by adding friction through experimentation. Results were validated through the comparison with a commercial servoaxis equipped with a Siemens controller. The model was then used to evaluate the effect of the stiffness of the structural parts of the axis on its first natural frequency. It was further used to analyse precision, energy consumption, and axis promptness. Finally a cost function was generated in order to find an optimal value for the main proportional gain of the position loop.
04 Jun 2014
TL;DR: The geometric approach introduced in [12] to address the control issue without computing the analytic trajectory of the costate is employed, and an alternative approach based on a proportional controller accounting for the limits of the control action can be tuned to resemble to the time optimal solution.
Abstract: In this paper, we analyze and discuss the time optimal control problem for bridge cranes. Specifically, we employ the geometric approach introduced in [12] to address the control issue without computing the analytic trajectory of the costate. As a second contribution, we show that an alternative approach based on a proportional controller accounting for the limits of the control action can be tuned to resemble to the time-optimal solution, but with simpler and more robust implementation. The above ideas are validated by means of some simulation examples.
Patent•
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01 Jan 2014
TL;DR: In this article, a ship steering device is characterized in which comprises a power pump set, a main oil way, an oil return way, a proportional amplifier, and an oil tank.
Abstract: The utility model relates to a ship steering device which comprises a both-way balance valve (1), a duplex safety valve (9), a helm shifting mechanism (8) and an electric-hydraulic proportional control valve set. The ship steering device is characterized in that the electric-hydraulic proportional control valve set comprises a power pump set, a main oil way, an oil return way, an electric-hydraulic proportional reversing valve (2), a proportional amplifier (3) and an oil tank (10). The power pump set is connected to the main oil way, the main oil way forms the oil return way through the electric-hydraulic proportional reversing valve (2), the proportional amplifier (3) is connected to the electric-hydraulic proportional reversing valve (2), and the electric-hydraulic proportional reversing valve (2) is provided with an oil inlet (2P), an oil return opening (2T) and reversing oil openings (2A and 2B). The oil tank (10) is arranged at one end of the main oil way, the liquid level is elevated through the power pump set, and the main oil way is connected with the oil inlet (2P). The oil return opening (2T) of the electric-hydraulic proportional reversing valve (2) is connected with the oil return way to return to the oil tank (10). Pipes are connected to the reversing oil openings (2A and 2B) of the electric-hydraulic proportional reversing valve (2), and the electric-hydraulic proportional reversing valve (2), the both-way balance valve (1), the duplex safety valve (9) and the helm shifting mechanism (8) are sequentially connected. According to the ship steering device, manual steering by a steering person is not required, dynamic control is achieved, the helm angles are corrected, the heading retentivity is improved, stable working motion of a steering engine is guaranteed, and impact and abrasions caused by a hydraulic system are effectively reduced.
Patent•
19 Feb 2014
TL;DR: In this article, a power grid synchronous signal real-time detection system based on the reference frequency was proposed, where negative feedback and proportional control were introduced into a low-pass filtering link in the detection process so that satisfying indexes of correction of phase deviation can be obtained.
Abstract: The invention discloses a power grid synchronous signal real-time detection method and system based on reference frequency, and relates to the field of voltage synchronous signal detection. According to the method, negative feedback and proportional control are introduced into a low-pass filtering link in the detection process so that satisfying indexes of correction of phase deviation can be obtained. The problem that due to frequency deviation of a power grid, large phase deviation occurs to a detected synchronous signal is solved. Single-phase power grid voltage and sine and cosine signal operations of reference frequency are detected only, and even if under the condition that a three-phase power grid distorts and is unbalanced, the power grid synchronous signal can be accurately detected. The invention further discloses a power grid synchronous signal real-time detection system based on the reference frequency. According to the system, negative feedback and proportional control enable phase deviation to be obviously corrected, according to a deducted expression of phase deviation and a proportional control coefficient K, a value is obtained, a satisfying result can be obtained, and as is proved, the power grid synchronous signal real-time detection system has correctness and validness.