Showing papers on "Proportional control published in 2017"

Direct Torque Control With Feedback Linearization for Induction Motor Drives

Abstract: This paper describes a direct-torque-controlled (DTC) induction motor (IM) drive that employs feedback linearization and sliding-mode control (SMC). A new feedback linearization approach is proposed, 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 SMC with proportional control in the vicinity of the sliding surface. SMC assures robustness as in DTC, while the proportional component eliminates the torque and flux ripple. The torque time response is similar to conventional DTC and the proposed solution is flexible and highly tunable due to the P component. The controller design is presented, and its robust stability is analyzed in simulations. The sliding controller is compared with a linear DTC scheme with and without feedback linearization. Extensive experimental results for a sensorless IM drive validate the proposed solution.

Application of flower pollination algorithm in load frequency control of multi-area interconnected power system with nonlinearity

Abstract: This work presents an application of bio-inspired flower pollination algorithm (FPA) for tuning proportional–integral–derivative (PID) controller in load frequency control (LFC) of multi-area interconnected power system. The investigated power system comprises of three equal thermal power systems with appropriate PID controller. The controller gain [proportional gain (K p), integral gain (K i) and derivative gain (K d)] values are tuned by using the FPA algorithm with one percent step load perturbation in area 1 (1 % SLP). The integral square error (ISE) is considered the objective function for the FPA. The supremacy performance of proposed algorithm for optimized PID controller is proved by comparing the results with genetic algorithm (GA) and particle swarm optimization (PSO)-based PID controller under the same investigated power system. In addition, the controller robustness is studied by considering appropriate generate rate constraint with nonlinearity in all areas. The result cumulative performance comparisons established that FPA-PID controller exhibit better performance compared to performances of GA-PID and PSO-PID controller-based power system with and without nonlinearity effect.

Bioreactor temperature control using modified fractional order IMC-PID for ethanol production

Abstract: The product quality of a fermentation process depends on a number of factors such as temperature, pH, nutrient balance, dilution rate, dissolved oxygen and CO2 concentration etc. The present work focuses on the precise temperature control of the process and to achieve desired product quality. Therefore a novel control algorithm, which is an amalgamation of fractional mathematics and IMC-PID, having less design parameters is proposed. A fractional order IMC-PID is designed and then modified (MFOIMC-PID) by incorporating an extra control loop with proportional gain to reduce the offset error. A nature inspired optimization technique i.e. water cycle algorithm is utilized for estimation of optimum design parameters of proposed controller which leads to WMFOIMC-PID controller. Fractional order PID (FOPID) and conventional PID are also designed for comparative study. Simulation results show that the proposed controller reduces integral absolute error (IAE) by 57% and 72% in comparison to FOPID and PID respectively for set-point tracking. Similar reduction of IAE is observed for disturbance rejection and noise suppression. Thus WMFOIMC-PID proves to be more robust and efficient in comparison to the other designed controllers.

Particle swarm optimisation-based parameters optimisation of PID controller for load frequency control of multi-area reheat thermal power systems

Abstract: The current study presents the load frequency control (LFC) of multi-area reheat thermal power system with proportional-integral-derivative (PID) controller. The interconnected control areas are provided with a single stage reheat turbine in all areas. The proportional gain (KP), integral gain (KI) and derivative gain (KD) values of the PID controller are simultaneously optimised using recent and powerful evolutionary computational intelligence technique, namely the particle swarm optimisation (PSO) algorithm. The superiority of the PSO-based PID controller has been proved by comparing its performance to recent modern optimisation techniques such as hill climbing (HC) algorithm and genetic algorithm (GA) tuned controllers for the same multi-area thermal power system. For the analysis, the time domain specification and 1% step load perturbation (1% SLP) are considered in thermal area 1. The simulation result showed that the proposed PSO-based PID controller provides superior dynamic response over other optimisation technique (HC and GA)-based PID controller.

Fault-tolerant cooperative control for multiple UAVs based on sliding mode techniques

Abstract: This paper proposes a fault-tolerant cooperative control (FTCC) design approach for multiple unmanned aerial vehicles (UAVs), where the outer-loop control and the inner-loop fault accommodation are explicitly considered. The reference signals for the inner-loop of the follower UAV can be directly produced by resorting to a proportional control. In the presence of actuator faults, the estimation of the fault information can be completed within finite time. Moreover, the control of the inner-loop is reconfigured based on the fault information adaptation and sliding mode techniques, such that the deleterious effects due to failed actuators can be compensated within finite time. Simulations of UAV cooperative flight are conducted to illustrate the effectiveness of this FTCC scheme.

Development and experimental characterization of a pneumatic valve actuated by a dielectric elastomer membrane

Abstract: Due to their many features including lightweight and low energy consumption, dielectric elastomer (DE) membrane actuators are of interest for a number of industrial applications, such as pumping systems or valve control units. In particular, the use of DEs in valve control units offers advantages over traditional solenoid valves, including lower power requirements and relative simplicity in achieving proportional control. Additionally, DEs generate low thermal dissipation and are capable of virtually silent operation. The contribution of this work is the development of a new valve system based on a circular DE membrane pre-loaded with a linear spring. The valve is designed for pressurized air and operates by actuating a lever mechanism that opens and closes an outlet port. After presenting the operating principle and system design, several experiments are presented to compare actuator force, stroke, and dissipated energy for several pressure differentials and associated volume flows. It is observed that the DE-driven valve achieves a performance similar to a solenoid-based valve, while requiring a significantly lower amount of input energy. In addition, it is shown that DE-membrane valves can be controlled proportionally by simply adjusting the actuator voltage.

Torque Control in Legged Locomotion

Abstract: Many torque control approaches have been proposed for robotic devices used in legged locomotion, but few comparisons have been performed across controllers in the same system. In this study, we compared the torque-tracking performance of nine control strategies, including variations on classical feedback control, model-based control, adaptive control, and iterative learning. To account for interactions between patterns in desired torque and tracking performance, we tested each in combination with four high-level controllers that determined desired torque based on time, joint angle, a neuromuscular model, or electromyographic measurements. Controllers were implemented on an ankle exoskeleton with series elastic actuation driven by an off-board motor through a uni-directional Bowden cable. The exoskeleton was worn by one human subject walking on a treadmill at 1.25 m⋅ s −1 for one hundred steady-state steps under each condition. We found that the combination of proportional control, damping injection and iterative learning resulted in substantially lower root-mean-squared error than other torque control approaches for all high-level controllers. With this low level torque controller, RMS errors can be as low as 1.3% of peak torque for real-time tracking, and 0.2% for the average stride. Model-free, integration-free feedback control seems to be well suited to the uncertain, changing dynamics of the human–robot system, while iterative learning is advantageous in the cyclic task of walking.

Robust proportional ECMS control of a parallel hybrid electric vehicle

Abstract: Improved fuel efficiency in hybrid electric vehicles requires a delicate balance between the internal combustion engine usage and battery energy, using a carefully designed energy management control algorithm. Numerous energy management strategies for hybrid electric vehicles have been proposed in literature, with many of these centered on the equivalent consumption minimisation strategy (ECMS) owing to its potential for online implementation. The key challenge with the equivalent consumption minimisation strategy lies in estimating or adapting the equivalence factor in real-time so that reasonable fuel savings are achieved without over-depleting the battery state of charge at the end of the defined driving cycle. To address the challenge, this paper proposes a novel state of charge feedback ECMS controller which simultaneously optimises and selects the adaption factors (proportional controller gain and initial equivalence factor) as single parameters which can be applied in real time, over any driving cy...

Memory feedback PID control for exponential synchronisation of chaotic Lur'e systems

Abstract: This paper studies the problem of exponential synchronisation of chaotic Lur'e systems (CLSs) via memory feedback proportional-integral-derivative (PID) control scheme. First, a novel augmented Lyapunov–Krasovskii functional (LKF) is constructed, which can make full use of the information on time delay and activation function. Second, improved synchronisation criteria are obtained by using new integral inequalities, which can provide much tighter bounds than what the existing integral inequalities can produce. In comparison with existing results, in which only proportional control or proportional derivative (PD) control is used, less conservative results are derived for CLSs by PID control. Third, the desired memory feedback controllers are designed in terms of the solution to linear matrix inequalities. Finally, numerical simulations of Chua's circuit and neural network are provided to show the effectiveness and advantages of the proposed results.

Analysis and compensation for the cascade dead-zones in the proportional control valve.

Abstract: The four-way proportional directional control valve has been widely used as the main stage spring constant for the two-stage proportional control valve (PDV). Since a tradeoff should be made between manufacturing costs and static performance, two symmetry dead-zones are introduced in the main stage spring constant: the center dead-zone caused by the center floating position and the intermediate dead-zone caused by the intermediate position. Though the intermediate dead-zone is much smaller than the center dead-zone, it has significant effect on the dynamic position tracking performance. In this paper, the cascade dead-zones problem in a typical two-stage PDV is analyzed and a cascade dead-zones model is proposed for the main stage spring constant. Then, a cascade dead-zones inverse method is improved with gain estimation and dead-zone detection to compensate the dead-zone nonlinearity. Finally, a digital controller is designed for verification. The comparative experimental results indicate that it is effective to reduce the large position tracking error when the proposed method is applied.

Multi-loop control of UPS inverter with a plug-in odd-harmonic repetitive controller.

Abstract: This paper proposes an improved multi-loop control scheme for the single-phase uninterruptible power supply (UPS) inverter by using a plug-in odd-harmonic repetitive controller to regulate the output voltage. In the suggested control method, the output voltage and the filter capacitor current are used as the outer and inner loop feedback signals, respectively and the instantaneous value of the reference voltage feedforwarded to the output of the controller. Instead of conventional linear (proportional-integral/-resonant) and conventional repetitive controllers, a plug-in odd-harmonic repetitive controller is employed in the outer loop to regulate the output voltage, which occupies less memory space and offers faster tracking performance compared to the conventional one. Also, a simple proportional controller is used in the inner loop for active damping of possible resonances and improving the transient performance. The feedforward of the converter reference voltage enhances the robust performance of the system and simplifies the system modelling and the controller design. A step-by-step design procedure is presented for the proposed controller, which guarantees stability of the system under worst-case scenarios. Simulation and experimental results validate the excellent steady-state and transient performance of the proposed control scheme and provide the exact comparison of the proposed method with the conventional multi-loop control method.

Climate control in greenhouse using intelligent control algorithms

Abstract: Greenhouse climate control problem has received considerable attention in agriculture engineering research. The greater part of accomplishing ensured farming within the greenhouse environment is achieved by controlling the temperature and relative humidity. As the result of process dead times and extreme interdependence of these parameters, the control problem is classified to be non-linear and multivariable. With the advances in intelligent control systems, more and more decisions involved in greenhouse control can be automated. Thus, more emphasis can be placed on emulating the abilities of the expert operator. In this paper, intelligent and non-intelligent control techniques for addressing the problem of automated climate control in a greenhouse are investigated. These include proportional-integral-derivative (PID) and Linear-Quadratic regulator (LQR) as a ‘non-intelligent’ technique and fuzzy PID and fuzzy immune PID as ‘intelligent’ technique. The new study is made for implementing the nonlinear fuzzy immune PID controller for greenhouse climate control. This controller has a simple structure and its parameters can be conveniently adjusted. It consists of a PID controller and a basic immune proportional controller in cascaded connection, the nonlinear function of the immune proportional controller is realized using fuzzy reasoning. Thus, controller parameters are adjusted online by the rules of immune feedback controller and fuzzy controller. The simulation results are compared for the effectiveness and applicability to greenhouse environmental problem.

Altitude control of quadrotor using fuzzy self tuning PID controller

Abstract: This paper presents fuzzy self-tuning PID controller for controlling the altitude of the quadrotor. Although the PID controllers have many advantages, it has a limitation that the main term gains called proportional gain, integration gain, and derivative gain have to be tuned manually. One of a solution to manage its limitation is adding the special feature called self-tuning. So, a fuzzy self-tuning PID controller is proposed to adjust the gain parameter of PID controller. As a result, two control techniques were then developed and synthesized for comparing; a linear PID controller only and fuzzy self-tuning PID controller. A complete simulation was then implemented on MATLAB/Simulink relying on the derived mathematical model of the quadrotor.

Comparison of methods for controllers design of single phase inverter operating in island mode in a microgrid: Review

Abstract: In recent years, new strategies of electric power generation are being developed and these are based on distributed generation systems ( DG ). With this new strategy of electric power generation based on renewable sources, there is a need to implement interfaces that allow the connection of these sources to the grid, as well as feed loads directly when operating in island mode or disconnected from the grid. Such interfaces are known as microgrids and the energy conversion systems that integrate them are very important. Therefore, the design of these units of energy conversion is a priority; therefore in this work we present the comparison of three methods of controllers design and the model of a single phase inverter for island mode operation in a microgrid. Particularly, the mathematical model is represented using transfer functions. This model describe the mathematical relationships that enable design in a simple and direct way the controllers of the different control loops that make up the energy conversion system. For the controller design in this operation mode, a conventional direct current method based on frequency method was first developed, from which a proportional-integral PI controller is designed. Second, an approximate method based on direct current to alternating current transformation ( dc-ac ), that allows the design of a proportional controller add generalized integrator ( P+IG ). This controller is obtained from the PI controller design in direct current. Third, an exact method is developed, which consists in applying a general methodology based on the frequency analysis. In particular, this work distinguishes the advantages of the second method, considering that its application allows the controllers design in a simple way for the different inverter control loops.

Improved proportional-integral voltage controller for a piezoelectric energy harvesting system converter utilizing lightning search algorithm

Abstract: This paper presents a relatively new meta-heuristic optimization technique known as the Lightning Search Algorithm (LSA) for developing an optimal proportional-integral (PI) voltage controller for a piezoelectric energy harvesting system (PEHS) converter. In the conventional PI voltage controller, a trial and error procedure is normally used to obtain optimal values for the proportional gain (Kp), and integral gain (Ki). This procedure is time consuming and does not conduct to suitable solutions. To overcome the exhaustive traditional trial-and-error procedure, the LSA optimization algorithm is proposed for obtaining optimal Kp and Ki values for the PI voltage controller.

Microgrid Power Architecture

Abstract: Power converters, and microgrids driven by such a power converter, in which the converter is controlled by a proportional controller which operates directly on AC waveforms, preferably without conversion to a DC type signal; preferably with use of voltage compensation to remove inherent error of proportional controller; and preferably with use of individual phase RMS voltages in the voltage compensation, to allow for normal operation under any load condition. Undervoltage of one or two phases is automatically compensated by adjusting the voltage of all phases, to retain balance. Line-starting of a motor load is automatically detected, and frequency droop is driven, apart from the other control relations in the system, to complete the line-starting operation as quickly as possible.

Neutral network theory-based non-linear system adaptive proportional integral control method

Abstract: The invention discloses a neutral network theory-based non-linear system adaptive proportional integral control method. The method comprises the following steps: in a first step, a mathematical model for a non-linear system is built; in a second step, a smooth function is used for approximating a non-smooth performer saturation function; in a third step, a neutral network adaptive proportional plus integral controller is designed for control. According to the method disclosed in the invention, as for a non-linear system with input saturation, the smooth function is used for approximating the performer saturation function, a BLF is referenced, that neutral network input is maintained in a bounded compact set range can be ensured, and normal operation of a neutral network can be ensured; compared with a conventional PI gain adjustment, an adjustment method put forward in the invention is advantageous in that 1) proportion integral gain of the PI controller is not a fixed constant but a time variant; 2) proportional gain and integral gain are not designed individually but associated with each other via a certain coefficient, and therefore system analysis can be facilitated; 3) the method has certain robustness for nondeterminacy and input saturation of the system.

Controlling Mackey-Glass chaos.

Abstract: The Mackey–Glass equation is the representative example of delay induced chaotic behavior. Here, we propose various control mechanisms so that otherwise erratic solutions are forced to converge to the positive equilibrium or to a periodic orbit oscillating around that equilibrium. We take advantage of some recent results of the delay differential literature, when a sufficiently large domain of the phase space has been shown to be attractive and invariant, where the system is governed by monotone delayed feedback and chaos is not possible due to some Poincare–Bendixson type results. We systematically investigate what control mechanisms are suitable to drive the system into such a situation and prove that constant perturbation, proportional feedback control, Pyragas control, and state dependent delay control can all be efficient to control Mackey–Glass chaos with properly chosen control parameters.

Optimal tuning of cascaded control architectures for nonlinear HVAC systems

Abstract: Cascaded controllers have been shown in recent literature to significantly reduce hunting behavior and improve the performance of a variety of HVAC systems. The cascaded architecture uses multiple proportional-integral-derivative loops, standard in industry and building automation controls, to minimize the effects of load dependent nonlinearities. This article builds on previous work by defining and demonstrating the properties of two nonlinear gap metrics that quantify the closed-loop linearization of the cascaded control structure and enable proper tuning of the inner-loop proportional gain. This is followed by the development of a linear quadratic framework that enables simultaneous tuning of inner- and outer-loop control gains. The proposed gap metrics and tuning procedures are demonstrated with two case studies. A simple single input, two output example plant is used to demonstrate the benefits of the proposed tuning method compared to standard proportional-integral-derivative control and successive ...

Chatter suppression in boring with tool position feedback control

Abstract: Regenerative self-excited vibrations (chatter) often occur in boring operation due to low stiffness of a slender cantilever holder of a tool. These vibrations lead to significant defects of a machined surface and cutting tool damages. The new chatter suppression method is proposed in the paper. Displacement signal measured in the direction which is orthogonal to machined surface is used for generating a control action in the feed direction. Linear proportional control law is applied. Mathematical model of boring process dynamics with control has been developed for validation of the proposed method efficiency and searching better values of feedback gain.

Machine learning apparatus for learning gain optimization, motor control apparatus equipped with machine learning apparatus, and machine learning method

Abstract: A machine learning apparatus according to one embodiment of the present invention is a machine learning apparatus for learning a condition associated with adjustment of a current gain parameter in electrical machine control, and comprises: a state observing unit which acquires actual current as well as an integral gain function and a proportional gain function in a current control loop, and observes state variables which include the integral gain function, the proportional gain function, and at least one of an amount of overshoot, an amount of undershoot, and a rise time of the actual current occurring in response to a step-like torque command; and a learning unit which learns the condition associated with the adjustment of the current gain parameter in accordance with a training data set constructed from the state variables.

Control Method Experimental Research of Micro Chamber Air Pressure via a Novel Electromagnetic Microvalve

Abstract: This work presents the control method of micro chamber air pressure via a novel electromagnetic microvalve for pneumatic control of microfluidic chips to improve controling precision. The control method of Bang-Bang, k (Proportional control) plus PWM (Pulse Width Modulation), and composite control method are developed to control the micro chamber air pressure. Both advantages and disadvantages of three control methods are compared and analyzed. Experimental results demonstrate that with the composite control method, the control performance can be greatly improved, and pressure fluctuation can be largely reduced. Our control method can effectively improve the steady-state accuracy and greatly reduce the pressure fluctuations for pneumatic microfluidic chips.

PID Controller of Sprayer Chassis by Sliding Mode

Abstract: In order to solve the straight line drive coordinated control problem of the four-wheel independent drive sprayer chassis, the dynamic model of sprayer chassis and electromagnetic proportional valve controlled hydraulic motor model are established. The additional yaw moment is designed to rectify the deviation with sliding mode variable structure control. PID control strategy is used to calculate the control voltage adjustment of the electromagnetic proportional valve. The simulation results show that the accumulative deviation of the chassis is 0.2 m out of 100 m when the coordinated control strategy is adopted on different adhesive coefficient pavement, which is much smaller than the value without control. The test results of test prototype show that the yaw acceleration of the chassis can be as low as −0.0132 m/s2 on different adhesive coefficient pavement with coordinated control, which is smaller than the value without control, and the straight line drive requirements are met. It is feasible to combine sliding mode variable structure with PID control and use the electromagnetic proportional control technology in the straight line drive coordinated control of sprayer chassis by adding the yaw moment to rectify the deviation of chassis based on the yaw acceleration detection.

Proportional-control high-precision propelling hydraulic system for earth pressure balance shield tunneling machine and control method

Abstract: The invention relates to a proportional-control high-precision propelling hydraulic system for an earth pressure balance shield tunneling machine and a control method. The proportional-control high-precision propelling hydraulic system for the earth pressure balance shield tunneling machine comprises a PLC, a variable pump, an overflow valve, a proportional pressure reducing valve, a first one-way valve, a second one-way valve, a first hydraulic-control one-way valve, a second hydraulic-control one-way valve, a two-position and three-way electromagnetic reversing valve, a three-position and four-way electromagnetic reversing valve, a displacement sensor, an execution mechanism, and a pressure sensor. The proportional pressure reducing valve and the variable pump are used for controlling the pressure and flow of the system, and closed-loop control is formed by the proportional pressure reducing valve, the variable pump and the pressures sensor and the displacement sensor of the execution mechanism, so that the speed and pressure control precision of the system is improved, the shield tunneling machine can make axial movement and accurately achieve synchronous movement according to a specific route track during tunneling construction, and the problem of low efficiency of a hydraulic system can be solved.

Voltage and current double closed loop control method and device of adjustable invertor inertial effect

Abstract: The present invention discloses a voltage and current double closed loop control method and device of an adjustable invertor inertial effect. In the frame of the routine voltage and current double closed loop control, the inertial current component is added in an inverter current inner ring instruction to realize the equivalent control of the inverter inertia property and is indirectly generated through an inertial control system connected in parallel on the voltage outer ring. The inertial control system is formed by three parts connected in series, wherein the three parts include a low pass filter, a proportional controller and a differential arithmetical unit. The size of the inertial current component and the intensity level of the grid-connected inverter inertial effect can be flexibly controlled through the proportional controller in the inertial control system. The voltage and current double closed loop control method of the adjustable invertor inertial effect does not need to change the hardware portion of the current grid-connected inverter system, completely maintains the current basic control frame of the software portion, has good compatibility, can be applied to a double-fed wind turbine system and a photovoltaic power generation system, and has good engineering application values.