Large Settling Time Research Articles

Design of Adaptive PID Controller for Lower Limb Rehabilitation Robot Based on Particle Swarm Optimization Algorithm.

The proportional-integral-derivative (PID) is still the most common controller and stabilizer used in industry due to its simplicity and ease of implementation. However, in most of the real applications, the controlled system has parameters that slowly vary or are uncertain. Thus, PID gains must be adapted to cope with such changes.
 In this research, an Adaptive Proportional-Integral-derivative controller (APID) is proposed to control the 2-DOF lower limb rehabilitation robot system. The parameters gains of the proposed controller are optimized using the Particle Swarm Optimization algorithm (PSO). The simulation results show no overshoot and zero steady-state error, but large settling time (ts=3.654 sec. for link1 and ts=2.844 sec. for link2) for linear path, and the actual path tracks the desired path with a large error for the nonlinear path. The results illustrate that the robot's performance is inefficient for linear and nonlinear paths when using the APID controller to control the lower limb rehabilitation robot. Therefore, the controller needs to modify for controlling the robot efficiently.

Open-loop control of electrostatic levitation actuators to enhance the travel-range of optical switches

Command shaping is a driving technique for handling the large settling time of the high-Q-MEMS actuators. The strong nonlinearity due to the electrostatic actuation limits the linear operation range in cantilevered or torsional micro-mirrors where command shaping techniques can be applied for positioning. Experimental and simulation results of this research demonstrate the effectiveness of using electrostatic levitation to overcome the actuation nonlinearities and a significant increase in the operation range. The motivation for this research is that applying the nonlinear command shaping causes complexity in command manipulation and requires an accurate knowledge of the nonlinear terms involved in the system model. The large linear operation range generated by the levitating force allows using the practical simple command shaping methods for open-loop control.

Performance Comparison of ANFIS, FOPID-PSO and FOPID-Fuzzy Tuning Methodology for Optimizing Response of High-Performance Drilling Machine

A fractional-order proportional integral derivative (FOPID)controller has replaced the classical PID controller used in industries for process control application. FOPID is less sensitive to the change of control parameters than PID Controller, due to which better results are obtained. The FOPID provides a robust and stable system for a higher-order system as of iso- damping property. This study aims to find a stable and controlled structure by tuning the FOPID controller with the Particle Swarm Optimization (PSO) algorithm, fuzzy-based logic approach, and Adaptive Neuro-fuzzy inference system (ANFIS). The tuning of FOPID is done to overcome deficits of PID controller using the different types of optimization method to overcome large overshoot and large settling time. This paper presented useful techniques based on PSO, fuzzy logic, and ANFIS to optimize FOPID controlled high-performance drilling machines. On the analysis and comparisons of simulation findings, it is observed that the FOPID-PSO approach provides better performance over the Ziegler-Nichols (ZN)-FOPID and the above-mentioned intelligent techniques in terms of less settling time (ts=0.823sec.) & optimized peak overshoot (Mp=2.44%) for the mentioned target.

Design a Second Order Sliding Mode Controller for Electrical Servo Drive Systems

The aim of this paper is to design and study a powerful second-order sliding mode controller for electrical servo drive systems. The suggested controller can successfully overcome the chattering problem that was usually facing such systems during operation. The first (1-SMC) and second (2-SMC) sliding mode controllers are nonlinear controllers’ techniques capable of stabilizing the output of a plant, even though a disturbance and parameter uncertainty is present. The asymptotically stable is the significant property of 1-SMC as well as 2-SMC. Despite the robustness of the 1- SMC, in real-time but it suffers from a large settling time and a chattering (undesirable rapid oscillations) of system trajectory close to the sliding surface. The chattering must be reduced because of its negative impact on system stability. The chattering can be reduced by replacing the sign function, used in classical sliding mode, by a saturation function. In the current study, the Second Order Sliding Mode Controller (2-SMC) is used to overcome the drawbacks of 1- SMC by reducing both the chattering and the settling time of the control action. The Electrical Servo drive system was adopted in this paper for testing; both, the 1-SMC as well as the 2-SMC. The comparison of results between the two controllers indicated smaller chattering and settling time in the 2-SMC than that in the 1-SMC. The simulation results of this work were obtained by using the Matlab programming.

Transformerless Three Phase Variable Output Voltage DC/AC Standalone Power Converter Using Modified Restrictive Control Set Model Predictive Control

This paper proposes a new technique for regulating the amplitude of line–line voltage of a voltage source converter (VSC) with standalone linear or nonlinear load by using the concept of restrictive control set model predictive control (RCS-MPC). Conventionally, the line–line voltage is regulated by regulating the amplitude modulation ratio ( $m_{a}$ ) in sinusoidal pulsewidth modulation (SPWM) technique. However, the total harmonic distortion (THD) increases with the decrease in $m_{a}$ . Moreover, the conventional approach also has some restraint in the large settling time. This problem is addressed by suggesting RCS-MPC for controlling the amplitude of line–line voltage of VSC. Through RCS-MPC, the value of slider gain in the cost function is adjusted accurately to regulate the output line–line voltage. The proposed approach increases the linear region from 0.612 to 0.648, limits the THD of output voltage below 5% during the variation in the output voltage from zero to the maximum value. From the proposed approach, settling time reduces from 0.035 s to a minimum of 0.005 s. The use of the restricted control horizon ensures a low computational load by undergoing the computational time complexity analysis of the MPC algorithm. The stability analysis is performed using the phase portrait and the effect of parameter variation is also discussed. The practicability of the recommended method is verified by MATLAB/Simulink and it is also verified experimentally.

Application of finite-time control Lyapunov function in low-power PMSG wind energy conversion systems for sensorless MPPT

This paper discusses the problem of observer-based finite-time control (FTC) of a grid-connected wind turbine and a low-power permanent magnet synchronous generator (PMSG). An adaptive nonlinear observer is employed to estimate the mechanical variables. Maximum power point tracking (MPPT) is obtained using the estimation of rotor speed and torque from the adaptive observer, and excluding the wind speed sensor. Improvement of the MPPT technique through the designed FTC is investigated. The proposed controller stabilizes the WECS and tracks the reference trajectories in a short pre-known time alternative to common nonlinear controllers with large settling time. The suggested controller is also robust against uncertainties in WECS parameters. Parameters’ variations are compensated by robust control design. Finite time stability and robustness of the proposed WECS controller is mathematically proved. Moreover, the advanced performance of the suggested FTC is demonstrated by simulation and is compared to a conventional asymptotic convergent controller (ACC). The proposed FTC provides fast and robust rotor speed regulation and thus enhances the sensorless MPPT. The proposed FTC improves the WECS performance for tracking of ramp references and robustness against parameter uncertainties. Furthermore, advanced control of the grid-side converter yields improved resiliency and reliability.

Fuzzy Sliding Mode Control of a Switched Reluctance Motor

The simplicity, ruggedness, and low cost of a switched reluctance motor (SRM) makes it a viable candidate for various general-purpose adjustable-speed and servo-type applications. Sliding mode control (SMC) is one of the popular strategies to deal with uncertain control systems. The Fuzzy Sliding Mode Controller (FSMC) combines the intelligence of a fuzzy inference system with the sliding mode controller.PI controllers are generally used for the speed control of SRM main drawback of PI controller is high overshoot and large settling time. The main reason for this high overshoot and large settling time is due to the fixed nature of the controller parameters. In this paper, mathematical modelling of 6/4 SRM has been developed, speed performance of the motor using PI controller and FSMC has been analysed. Results of this study show that the overshoot is completely eliminated and the speed of response is improved when Fuzzy SMC is used for the speed control of SRM.

Chattering free robust control of LCL filter based shunt active power filter using adaptive second order sliding mode and resonant controllers

Abstract This paper proposes a new robust adaptive controller for LCL filter based shunt active power filters in order to solve the control problems of high overshoot and large settling time in the DC link voltage. To this end, the second order sliding mode with the adaptive gain super-twisting control law and proportional-resonant controllers with active damping are used in the DC bus voltage control loop and d–q axis current control loops respectively. The control objectives are fourfold: (i) driving the DC bus voltage to a reference signal; (ii) forcing the d–q axis current errors to zero; (iii) assuring a satisfactory power factor correction and a high harmonic performance in relation to the AC source; and (iv) eliminating the chattering effect. In the closed loop control system, three phase grid currents, LCL capacitor currents and the DC link voltage are available for feedback. As a result, the proposed controller has the advantages of zero overshoot response and fast acting chattering-free behavior. Results of experimental studies prove that the proposed control system guarantees to track reference signals with a high harmonic performance despite external disturbance uncertainties.

A simple nonlinear PD controller for integrating processes

Many industrial processes are found to be integrating in nature, for which widely used Ziegler–Nichols tuned PID controllers usually fail to provide satisfactory performance due to excessive overshoot with large settling time. Although, IMC (Internal Model Control) based PID controllers are capable to reduce the overshoot, but little improvement is found in the load disturbance response. Here, we propose an auto-tuning proportional-derivative controller (APD) where a nonlinear gain updating factor α continuously adjusts the proportional and derivative gains to achieve an overall improved performance during set point change as well as load disturbance. The value of α is obtained by a simple relation based on the instantaneous values of normalized error (eN) and change of error (ΔeN) of the controlled variable. Performance of the proposed nonlinear PD controller (APD) is tested and compared with other PD and PID tuning rules for pure integrating plus delay (IPD) and first-order integrating plus delay (FOIPD) processes. Effectiveness of the proposed scheme is verified on a laboratory scale servo position control system.

Modeling and Identification of High Speed High Accuracy Lightweight Stages with Flexible Arms

Light-weight structures operating at high speeds may suffer from significant vibration problems, thus degrading positioning accuracy and exhibiting large settling time. High-performance vibration and motion controllers are usually designed based on precise dynamic model. This paper addresses the problem of modeling and identification of a high speed high accuracy lightweight positioning stage with flexible arm. A simplified state space model for vibration motion control purpose is given. A separated identification method is proposed. The parameters related to rigid body part and flexible body part are identified, separately. Rigid body dynamics is firstly identified by employing unbiased Least Squares technique. Subsequently, flexible body dynamics is identified by impact test and nonlinear LS technique. The experiment results show that applying proposed identification strategy can get more precise low frequency rigid body dynamic parameters without loss the identification precision of high frequency parameters.

Voltage and frequency control in power generating system using hybrid evolutionary algorithms

A power generating system has the responsibility to ensure that adequate power is delivered to the load, both reliably and economically. The quality of power supply is affected due to continuous and random changes in load during the operation of the power system. Hence, a power system control is required to maintain a continuous balance between power generation and load demand. Load Frequency Controller and Automatic Voltage Regulator play an important role in maintaining constant frequency and voltage in order to ensure the reliability of electric power. In order to improve the performance and stability of these control loops, proportional-integral-derivative (PID) controllers are normally used. But these fixed gain controllers fail to perform under varying load conditions and hence provide poor dynamic characteristics with a large settling time, overshoot and oscillations. In order to achieve a better dynamic performance, system stability and sustainable utilization of generating systems, PID gains must be well tuned. In this paper, Evolutionary Algorithms like, Enhanced Particle Swarm Optimization, Multi Objective Particle Swarm Optimization, and Stochastic Particle Swarm Optimization are proposed to find the optimum gains of the PID controller to control the voltage and frequency of the generating system within the permissible limit. These algorithms offer a more stable and faster convergence towards the best PID gains and also with minimum computational time. These algorithms are appropriate to model the uncertainties found in the power demand and improve the flexible nature of the controllers. Simulation results demonstrate that the proposed controllers adapt themselves appropriately to varying loads and hence provide better performance characteristics with respect to settling time, oscillations and overshoot.

DC offset control with application in a zero-IF 0.18 μm CMOS Bluetooth receiver chain

A compact DC offset correction circuit based on the intrinsic properties of quasi-floating gate (QFG) transistors is presented. The proposed scheme uses a tuning mechanism to make its initial response faster improving the traditional large settling time of these circuits. A zero-IF baseband receiver chain suitable for Bluetooth that includes the proposed dc offset correction has been designed in a 0.18 μm CMOS technology at 1.2 V supply voltage.

A new coordinated control strategy for boiler-turbine system of coal-fired power plant

This paper presents the new development of the boiler-turbine coordinated control strategy using fuzzy reasoning and autotuning techniques. The boiler-turbine system is a very complex process that is a multivariable, nonlinear, slowly time-varying plant with large settling time and a lot of uncertainties. As there exist strong couplings between the main steam pressure control loop and the power output control loop in the boiler-turbine unit with large time-delay and uncertainties, automatic coordinated control of the two loops is a very challenging problem. This paper presents a new coordinated control strategy (CCS) which is organized into two levels: a basic control level and a high supervision level. Proportional-integral derivative (PID) type controllers are used in the basic level to perform basic control functions while the decoupling between two control loops can be realized in the high level. A special subclass of fuzzy inference systems, called the Gaussian partition with evenly (GPE) spaced midpoints systems, is used to self-tune the main steam pressure PID controller's parameters online based on the error signal and its first difference, aimed at overcoming the uncertainties due to changing fuel calorific value, machine wear, contamination of the boiler heating surfaces and plant modeling errors. For the large variation of operating condition, a supervisory control level has been developed by autotuning technique. The developed CCS has been implemented in a power plant in China, and satisfactory industrial operation results demonstrate that the proposed control strategy has enhanced the adaptability and robustness of the process. Indeed, better control performance and economic benefit have been achieved.

Electronic Cavendish device

The Cavendish torsion–balance method of detecting gravitational forces, while elegant and highly educational, is difficult to arrange as a lecture demonstration. The chief reason for this is the large settling time for torque-induced rotation. Described here is an apparatus in which the torsion bar does not appreciably rotate. A simple electronic servomechanism is used to maintain rotational equilibrium as an external mass is introduced. The resulting servo correction voltage is proportional to the torque induced by gravity. This effect can be observed in tens of seconds.

Electronic Cavendish device

The Cavendish torsion–balance method of detecting gravitational forces, while elegant and highly educational, is difficult to arrange as a lecture demonstration. The chief reason for this is the large settling time for torque‐induced rotation. Described here is an apparatus in which the torsion bar does not appreciably rotate. A simple electronic servomechanism is used to maintain rotational equilibrium as an external mass is introduced. The resulting servo correction voltage is proportional to the torque induced by gravity. This effect can be observed in tens of seconds.