Showing papers on "Proportional control published in 2015"

Experimental comparison of torque control methods on an ankle exoskeleton during human walking

Abstract: Few comparisons have been performed across torque controllers for exoskeletons, and differences among devices have made interpretation difficult. In this study, we designed, developed and compared the torque-tracking performance of nine control methods, including variations on classical feedback control, model-based control, adaptive control and iterative learning. Each was tested with four high-level controllers that determined desired torque based on time, joint angle, a neuromuscular model, or electromyography. Controllers were implemented on a tethered ankle exoskeleton with series elastic actuation. Measurements were taken while one human subject walked on a treadmill at 1.25 m·s−1 for one hundred steady-state steps. The combination of proportional control with damping injection and iterative learning resulted in the lowest errors for all high-level controllers. With time-based desired torque, root-mean-squared errors were 0.6 N·m (1.3% of peak desired torque) step by step, and 0.1 N·m (0.2%) on average. These results indicate that model-free, integration-free feedback control is suited to the uncertain dynamics of the human-robot system, while iterative learning is effective in the cyclic task of walking.

Direct torque control with feedback linearization for induction motor drives

Abstract: This paper describes a Direct Torque Controlled (DTC) Induction Machine (IM) drive that employs feedback linearization and sliding-mode control. A feedback linearization approach is investigated, which yields a decoupled linear IM model with two state variables: torque and stator flux magnitude. This intuitive linear model is used to implement a DTC type controller that preserves all DTC advantages and eliminates its main drawback, the flux and torque ripple. Robust, fast, and ripple-free control is achieved by using Variable Structure Control (VSC) with proportional control in the vicinity of the sliding surface. The VSC component assures robustness as in DTC, while the proportional component eliminates the torque and flux ripple. The torque time response is similar to DTC and the proposed solution is flexible and highly tunable due to the proportional controller. The controller design and its robust stability analysis are presented. The sliding controller is compared with a linear DTC scheme, and experimental results for a sensorless IM drive validate the proposed solution.

Distributed primary frequency control through multi-terminal HVDC transmission systems

Abstract: This paper presents a decentralized controller for sharing primary AC frequency control reserves through a multi-terminal HVDC grid. By using passivity 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.

An auto-tuning PID control system based on genetic algorithms to provide delay guarantees in Passive Optical Networks

Abstract: Passive Optical Networks (PONs) are the most important access architectures since their deployment is massive all around the world. However, the QoS (Quality of Service) and the efficient management of the network resources have become the key point, especially with the new emerging services and applications. In particular, the delay and the bandwidth are becoming important limiting factors for the user experience. As a consequence, in a previous research we proposed the implementation of PID (Proportional-Integral-Derivative) control strategies to manage these networks parameters in PONs, demonstrating higher efficiency and more robustness than other previous existing algorithms. It is worth emphasizing that this is the first time to apply this control strategy in PONs access networks. However, in this paper we improve the PID control strategy by automating the tuning process with a genetic algorithm. Indeed, we have developed a novel automatic tuning technique based on genetic algorithms to tune a P controller that provides delay guarantees. Simulation results show that the control strategy reduces the tuning time up to 64% in comparison with the Ziegler–Nichols manual technique (ZN). On the other hand, it is demonstrated that our proposal is more accurate and robust that ZN since the genetic algorithm automatically evolves to the best solutions of the tuning parameters in contrast to the manual experiments required for the ZN method. Furthermore, we have complemented the use of the P controller with a new dynamic Admission Control (AC) module. This module implements a policy to selectively transmit or drop packets and leads a better delay control. The simulation analysis reveals that the real time evolution of the delay with the dynamic AC is more stable when compare to a conventional and simple fixed AC, reaching differences near one order of magnitude in the delay fluctuations.

System of automated control of Hydraulic screw-down mechanisms of plate mill stand

Abstract: When rolling with automated profile control is introduced at the plate mill, it imposes strict requirements to accuracy of automated gauge control. The structure of the Hydraulic Gap Control (HGC) position controller of the 5,000 mm mill is considered, it includes a fast proportional control channel and a relatively slow channel of integral position regulation. The paper provides dependencies for calculation of the controller factors. It views the principle of automated gauge control implemented in the resource of the Automatic Gap Control system of TCS stand controller. The paper offers a scheme of the gauge controller and dependencies for factor calculation. It specifies functions of the RAC regulator designed for compensation of the tensile difference (gap spacing) at the stand sides. There are results of experimental investigations of the gauge controller and RAC regulator provided. High accuracy of control of the set technological parameters and a full compensation of roller gap spacing are proved to be ensured at the settings proposed.

A comparison of adaptive trajectory tracking controllers for wheeled mobile robots

Abstract: Two adaptive trajectory tracking controllers for wheeled mobile robots are tested in this work. Adaptively tuned proportional control is one approach, where as the other controller uses a Universal Adaptive Stabilization (UAS) based technique. Using simulations, the robustness of the above controllers is quantified in the presence of measurement noise. The robustness is measured in terms of the Integral of absolute magnitude of the error (IAE), the Integral of square of the error (ISE), and the Integral of time multiplied by the absolute value of the error (ITAE) criteria. It is observed that the UAS based technique shows fast convergence in the absence of noise. To combat the effect of noise, the authors reset the adaptation gains after the adaptation gains reach a preset bound. With this technique it is found that the UAS based technique converges to the trajectory being tracked faster than the adaptively tuned proportional controller, and also faster than a traditional inputoutput state feedback linearization based controller.

Intelligent proportional trajectory tracking controllers: Using ultra-local model and time delay estimation techniques

Abstract: This paper presents a new intelligent proportional control (iPs) for trajectory tracking of nonlinear affine-in control systems with unknown internal dynamics. The referred proposed controller which is based on an ultra-local model and a time-delay estimation technique has a very simple structure and easily to be regulated. Moreover with the systems output feedback, the proposed controller dose not require any knowledge of nonlinear internal dynamics ensuring the trajectory tracking of systems output. Finally, to validate the proposed method, a nonlinear cart system which includes different kind of frictions have been considered to compare with different model free controls of time delay estimation based control (TDEC) and recursive model free control (RMFC), and illustrates its corresponding performance and robustness.

Steady-State Gain Identification and Control of Multivariable Unstable Systems

Abstract: A method is presented to identify the steady-state gain matrix of a multivariable (SSGM) unstable system under closed-loop control. Effects of disturbances and measurement noise on the identification of SSGM were also studied. Davison's method (Davison, 1976) was modified to design single-stage multivariable PI controllers using only the steady-state gain matrix of the system. Since the overshoots in the responses are larger, a two-stage P-PI control system is proposed. Based on the SSGM, a simple proportional controller matrix was designed by the modified Davison's method (1976) to stabilize the system. Based on the gain matrix of the stabilized system, diagonal PI controllers were designed. The performance of the two-stage control system was evaluated and compared with that of single-stage multivariable controllers. Simulation results on two examples show the effectiveness of the proposed methods for both servo and regulatory problems.

A Control Strategy with Tactile Perception Feedback for EMG Prosthetic Hand

Abstract: To improve the control effectiveness and make the prosthetic hand not only controllable but also perceivable, an EMG prosthetic hand control strategy was proposed in this paper The control strategy consists of EMG self-learning motion recognition, backstepping controller with stiffness fuzzy observation, and force tactile representation EMG self-learning motion recognition is used to reduce the influence on EMG signals caused by the uncertainty of the contacting position of the EMG sensors Backstepping controller with stiffness fuzzy observation is used to realize the position control and grasp force control Velocity proportional control in free space and grasp force tracking control in restricted space can be realized by the same controller The force tactile representation helps the user perceive the states of the prosthetic hand Several experiments were implemented to verify the effect of the proposed control strategy The results indicate that the proposed strategy has effectiveness During the experiments, the comments of the participants show that the proposed strategy is a better choice for amputees because of the improved controllability and perceptibility

Advanced Control Strategy of Back-to-Back PWM Converters in PMSG Wind Power System

Abstract: This paper proposes a control scheme of back-to-back PWM converters for the permanent magnet synchronous generator (PMSG) wind turbine system. The DC-link voltage can be controlled at the machine-side converter (MSC), while the grid-side converter (GSC) controls the grid active power for a maximum power point tracking (MPPT). At the grid fault condition, the DC-link voltage controller is designed using a feedback linearization (FL) theory. For the MPPT, a proportional control loop is added to the torque control to reduce the influence of the inertia moment in the wind turbines, which can improve its dynamic performance. The validity of this control algorithm has been verified by the simulation of the 2-MW PMSG wind turbine system.

Average current mode control of multi-phase switching power converters

Abstract: Exemplary embodiments are related to switching power converters. A switching power converter may comprise a plurality of control unit configured for average current mode control, wherein each control unit of the plurality comprises a dedicated proportional control unit. The switching power converter may further comprise an integrator coupled to each control unit of the plurality of control unit and configured to convey a signal to each control unit.

Flight control of a small-diameter spin-stabilized projectile using imager feedback

Abstract: Small-diameter gun-launched projectiles pose a challenging platform on which to implement closed-loop guidance and control. This paper presents a novel imager-based guidance and control algorithm for small-diameter spin-stabilized projectiles. The control law is specifically formulated to rely on feedback only from a strapdown detector and roll angle sensors. Following introduction of the projectile nonlinear dynamic model, an integrated guidance and control algorithm is presented in which control commands are computed directly from detector feedback using a gain-scheduled proportional control. Time-varying controller gains are derived through a surrogate modeling approach, and controller performance is further enhanced through use of an observer that filters unwanted angular motion components from detector feedback. Example closed-loop flight simulations demonstrate performance of the proposed control system, and Monte Carlo analysis shows a factor of 2 accuracy improvement for the closed-loop system ove...

Simple digital current control strategy for single-phase grid-connected converters

Abstract: This study proposes a simple digital current control technique for single-phase grid-connected voltage source converters. Unlike conventional strategies, the proposed method does not require any proportional-integral or proportional-resonant controller, fictitious phase generation, reference frame transformation and decoupling network; thus, it has the advantages of simplicity and reduced computational efforts. The suggested digital technique only uses a simple proportional controller in its structure and can be directly implemented on available digital signal processors. A digital controller parameter design procedure is proposed which ensures stability and near-zero steady-state error under all circumstances. Simulation and experimental results confirm that the proposed technique provides a fast and accurate current tracking with minimum harmonic distortions.

A novel current controller scheme for doubly fed induction generators

Abstract: This paper presents a novel current control methodology for grid connected doubly-fed induction generator (DFIG) based wind energy conversion systems. Controller is based on a proportional controller with additional first order low pass filter disturbance observer which estimates the parameter dependent nonlinear feed-forward terms. The results in simulations and experimental test bed obviously demonstrate that decoupled control of active and reactive power is achieved without the necessity of additional machine parameter.

Real-time implementation of decentralized adaptive formation control on multi-quadrotor systems

Abstract: In this study, we focus on real-time implementations of a practical distributed adaptive formation control scheme for a multi-quadrotor system with uncertain inertial system parameters. We design a decentralized controller based on the leader-follower formation approach to motion control of such a system in rigid formation. The proposed control approach has a two-level structure: At the high level, a distributed control scheme is designed for the kinematic formation control problem. In the low-level, we analyze each single quadrotor control design in three parts. The first is an adaptive linear quadratic controller under consideration of inertial uncertainties for the pitch and roll dynamics, and in this case, we design an on-line parameter estimation with the least squares approach, excepting yaw and altitude dynamics. The second is proportional controller for the yaw motion. The third is proportional-integral-derivative controller for altitude. Throughout the formation control implementations, the controllers successfully satisfy the formation maintenance objective. Simulations and experimental results are presented considering various scenarios, demonstrating the effectiveness of our algorithm.

Composite PID fuzzy control method applied to transformer cooling system

Abstract: The invention discloses a composite PID fuzzy control method applied to a transformer cooling system. The method comprises the following steps of obtaining a temperature value through a thermodetector; solving input quantity deviation E and deviation change EC, performing fuzzification after quantization; calculating a fuzzy control table, and checking the fuzzy control table to obtain the fuzzy control quantity; solving the practical control quantities , and , and making the ,the and the serve as the input quantities of PID; solving the control quantity y(t) and outputting the control quality to a frequency converter. According to the composite PID fuzzy control method applied to the transformer cooling system, the fuzzy control and the PID control are combined, the fuzzy control is introduced on the basis of the conventional PID control to form the composite PID fuzzy control method, the dynamic response speed is increased by utilizing the proportional control of PID, and steady state errors are eliminated by utilizing the integral control of PID, so that the steady-state performance of the fuzzy control is improved, and the energy-saving effect of the operation of the transformer cooling system is further improved.

Improved smith predicting controller

Abstract: An improved Smith predicting controlling algorithm comprises the following steps: designing a fuzzy adaptive PID controller to replace an original PID controller, wherein the fuzzy adaptive PID controller mainly comprises a PID control regulator and a fuzzy inference engine, and modifying a PID control parameter according to a fuzzy control rule in real time by using an error e and the change rate ec of the error as the input of the controller and the kp, ki and kd of the PID control parameter as the output, so as to meet the requirements of e and ec for the self-regulation of the PID parameter at different moments; adding an inner feedback loop, sending a feedback signal to a predicting model and an input end of an actually-controller object by the inner feedback loop at the same time, comparing the feedback signal with the output of a main controller, using the difference as an input signal of the actually-controlled object and the predicting model and introducing an adaptive regulator. Therefore, the problem of deviation caused by the change of an open-loop gain parameter is solved by changing the value of a proportional controller continuously.

Combined Use of Command-Proportional Control of External Robotic Devices Based on Electromyography Signals

Abstract: S.А. Lobov, Phd, Researcher, Laboratory for development of intellectual Biomechatronic Technology, Centre for Biotechnology development, institute of Biology and Biomedicine; V.I. Mironov, Junior Researcher, Vice-Head of Laboratory for development of intellectual Biomechatronic Technology, Centre for Biotechnology development, institute of Biology and Biomedicine; I.А. Kastalskiy, Junior Researcher, Laboratory for development of intellectual Biomechatronic Technology, Centre for Biotechnology development, institute of Biology and Biomedicine; V.B. Kazantsev, dSc, Head of the department of Neurotechnology, institute of Biology and Biomedicine, Vice-Rector for Research and innovations

The local control scheme for switching consensus value in multi-agent systems

Abstract: A local control strategy is presented to switch the consensus value for the first-order multi-agent system. When the local proportional controller is employed in the multi-agent systems, the Laplacian matrix of the system is changed. It is proved that the changed Laplacian has the same properties as the Laplacian matrix of the original multi-agent system for the consensus. Based on this, the parameter of the local controller, which can guarantee that all the agents change the original consensus value into the desired one, is determined in terms of the matrix calculation and the stability criterion. In practice, the control system must be implemented in the discrete form. Thus, the influence of the sampling period on the stability of the discrete multi-agent system with the local controller is analysed. The simulation results show the validity of the proposed method.

Improve Safety by Optimal Steering Control of a Converter Dolly Using Particle Swarm Optimization for Low-Speed Maneuvers

Abstract: This paper offers a solution to the problem of poor path-following performance of high capacity transport (HCT) vehicles, such as A-double combinations, causing safety issue for the vulnerable road users during low-speed turning maneuvers. An advanced control strategy is developed which only demands the axles of the converter dolly of such vehicle to be actively steerable so that existing tractor and semitrailers can be used without any further modification. The control strategy described in this paper allows the change of forward speed and even to stop the vehicle completely during the turning maneuver without any performance degradation. The controller utilizes the delays of tractor front axle steering angle and the articulation angles measured not in traditional time but in path-distance domain. The optimal controller is achieved using particle swarm optimization (PSO) technique. Finally the optimal vehicle performance is compared with a baseline non-steerable converter dolly case and also with a proportional control case. Significant improvement in path-following performance is observed.

Hydraulic-feedback proportional valve design for construction machinery:

Abstract: Due to the increasing demand for large-tonnage construction machinery, the manufacturers call for a reliable and inexpensive proportional control valve with large flow capacity. In this work, a nov...

Optimal control of fuel over-pressure in a polymer electrolyte membrane fuel cell system during load change

Abstract: This paper, presents an optimal control approach for maintaining the differential pressure between the anode and cathode sides, known as fuel over-pressure, in a polymer electrolyte membrane (PEM) fuel cell using model predictive control. In order to achieve the performance requirements, a proportional control valve is used and the state-space representation of the system is linearly approximated around each operating condition, and the overall model has been verified experimentally. Numerical simulation results are also provided to show the controller performance using experimental data from a 9-cell PEM fuel cell stack. These proof-of-concept results show the effectiveness of the controller to provide the optimal control input while satisfying the constraints of the problem.

Direction-cosine-matrix-based attitude control subject to actuator saturation

Abstract: Set-point attitude control of a rigid body explicitly preventing actuator saturation is considered. The attitude control approach developed does not employ any sort of direction-cosine-matrix (DCM) parameterisation, such as Euler angles or quaternions. Rather, the DCM is used directly within the feedback control algorithm. Together a proportional control term and an angular velocity control term make up the attitude controller. The angular velocity control is composed of a strictly positive real system subject to a special input non-linearity. The specific form of the proportional control and angular velocity control ensure control torques are below the saturation level of the on-board actuators. Two controller synthesis methods are considered. The first uses the linearised system, the solution to the linear quadratic regulator problem, and the Kalman–Yakubovich–Popov lemma to design the controller. The second employs a simple low-pass filter that is guaranteed to stabilise the closed-loop system; tuning the low-pass filter is also considered. Numerical simulation results demonstrate effective closed-loop control in the presence of plant disturbances and sensor noise.

Dynamic Self-Adaptive Reliability Control for Electric-Hydraulic Systems

Abstract: The high-speed electric-hydraulic proportional control is a new development of the hydraulic control technique with high reliability, low cost, efficient energy, and easy maintenance; it is widely ...

Autonomous charging management system for electric vehicles

Abstract: The autonomous charging management system for electric vehicles utilizes a voltage feedback control structure that compares the system voltage at the point of charging against a reference, while also taking into account the EV battery state of charge (SOC) A proportional control structure reduces the EV charging as the system voltage approaches the reference Moreover, the control structure does not require any communication between the EV and the utility