The application of nonlinear model reference pid controller for a planar robot arm

Structural analysis of fuzzy controllers with nonlinear input fuzzy sets in relation to nonlinear PID control with variable gains

Structural analysis of fuzzy controllers with nonlinear input fuzzy sets in relation to nonlinear PID control with variable gains*1

This paper presents a practical implementation for a new formula of nonlinear PID (NPID) control. The purpose of the controller is to accurately trace a preselected position reference of one stage servomechanism system. The possibility of developing a transfer function model for experimental setup is elusive because of the lack of system data. So, the identified model has been developed via gathering experimental input/output data. The performance of the enhanced nonlinear PID (NPID) controller had been investigated by comparing it with linear PID controller. The harmony search (HS) tuning system had built to determine the optimum parameters for each control technique based on an effective objective function. The experimental outcomes and the simulation results show that the proposed NPID controller has minimum rise time and settling time through constant position reference test. Also, the NPID control is faster than the linear PID control by 40% in case of variable position reference test.

Two-way shear failure of slabs is a sudden one, which has catastrophic outcomes. Slabs with large spans may be subjected to in-plane tensile forces due to thermal or earthquake loading. There is a lack of agreement between various design codes regarding the significance of in-plane tensile forces on the two-way shear strength. Two-way shear failure of slabs is a sudden one, which has catastrophic outcomes. Slabs with large dimensions may be subjected to in-plane tensile forces due to restraint or earthquake loading. There is a lack of agreement between various design codes regarding the significance of in-plane tensile forces on the two-way shear strength. The purpose of this study is to explore, propose a simplified two-way shear strength model, which includes the effect of in-plane tensile forces on the strength. A review for the experimental investigations, existing models, design codes for two-way shear of slabs is presented, with emphasis on in-plane tensile forces. The loading method used in the current experimental testing is misleading, where the two-way shear and the in-plane forces are independent. A comparative study was conducted between the existing formula and design codes for this case. The comparison between different codes with the experimental results show that the new proposed Eurocode design code was found to be the most accurate one. However, it did not include the effect of the in-plane tensile forces in a physically sound manner. In addition, more full testing of concrete slabs under combined two-way shear and tensile forces are required to refine this existing two-way shear design code provisions or develop new formulas or mechanical models.

Nonlinear PID (N-PID) Controller for SSSP Grid Connected Inverter Control of Photovoltaic Systems

Nonlinear proportional-integral-derivative (NPID) is realized by modulating the control gains of a conventional linear controller in response to system state or error. Performance benefits such as increased damping or reduced tracking error have been experimentally demonstrated. Previous results (2000) have established Lyapunov stability of NPID control for full-state knowledge and for special cases of partial-state knowledge; but the general problem of stability with arbitrary state knowledge remained unsolved. In the present work, design methods for NPID control are extended to the case of arbitrary partial-state knowledge. Given any combination of a stabilizable linear system and NPID control law, an upper bound on control effort can be determined for which global asymptotic stability is assured. The result is based on a Lyapunov stability proof and is applied to establish the stability of NPID control for the Sarcos dexterous manipulator.

Model-based synthesis of nonlinear PI and PID controllers

This paper investigates the performance of adaptive particle swarm optimization (APSO) algorithm to find the best optimal gain parameters (Kp, Ki, Kd) in linear PID (L-PID) and nonlinear PID (NL-PID) controllers for the trajectory control of a nonlinear dynamical system (NLDS). Mathematical modeling, stability and performance analysis of a NLDS are being carried out with L-PID and NL-PID controllers. It is found that the APSO based tuning of NL-PID controller provides better tracking of NLDS than L-PID controller in respect of its search domain, premature convergence, and computational efficiency. Simulation analysis of various variables of controllers and system response such as error, cost function, and response of NLDS and their comparison to that of APSO tuned L-PID controller is described.

International audience

A novel Non-Linear Fractional order PID controller (NLF-PID) is designed for control of coupled and non-linear 2-link rigid robot. The structure of proposed controller comprises of non-linear hyperbolic function of instantaneous error and current state cascaded with Fractional Order PID (FO-PID). Non-linear function provides adaptive control ability while incorporation of fractional operator enhances flexibility of designed controller. To examine the comparative merits of NLF-PID controller, Non-linear PID (NL-PID), FO-PID and traditional PID schemes are also implemented. Design variables of controllers are optimally tuned using multi objective Non-dominated Sorting Genetic Algorithm II (NSGA-II) for small variation in control and error signal. Results prove that NLF-PID provides robust and efficient control of robotic arm as compared to other designed controllers for reference tracking, model uncertainty, disturbance and noise due to inherent shortcoming of sensor.

The nonlinear fuzzy PID control strategy, which combines nonlinear control, fuzzy control and PID control, is put forward in this paper to deal with the control of a class of nonlinear and large inertia plants under complicated and large variation conditions. The proposed control strategy can adjust control parameters timely and appropriately according to the dynamic characteristics of the systems, so as to achieve fast transient response and good steady-state accuracy. Moreover, the control strategy has good robustness and self-adaptive ability to the changes of model parameters. Take the case of the three-tank water system, the control strategy is investigated by simulation and experimentation. Experimental results, which agree with simulation results, show the control strategy suggested in the paper is correct and feasible. The design and implementation of it is simple and convenient, and it may have important reference value for the control of a class of continuous nonlinear and large inertia plants such as heating furnace and multi-capacity level plant in complicated conditions.

This paper presents two nonlinear PID (NPID) controllers which control the glycol temperature of a regasification system for LNG-fuelled engines. The NPID controllers have a parallel structure of the three nonlinear P, I, D actions or the linear P, D actions and nonlinear I action. A nonlinear function is employed to scale the error as input of the integral and implemented as a Takagi-Sugeno (T-S) fuzzy model. The controller parameters are optimally tuned by using a genetic algorithm. Furthermore, the stability problem of the overall system is verified based on the circle criterion. A set of simulation works is carried out to validate the efficiency of the two proposed controllers.

Electric load simulator (ELS) plays a vital role in the ground test and simulation of the electromechanical actuator (EMA) of an unmanned aerial vehicle (UAV), which is preferred by researchers for its dynamic response and high precision. However, clearance is an inevitable problem of the ELS system which can introduce backlash influencing the stability of the system. The backlash nonlinear can induce mechanical impact and impose limitations on the quality of loading torque control. In order to increase the accuracy of loading torque, a switching control method is presented to compensate for the backlash nonlinear. A time-optimal sliding mode control (TOSMC) method is used when the ELS system entering backlash, and a nonlinear proportional integral derivative (PID) controller is presented for the different system dynamic. A switching controller is also introduced to acquire suitable moment switching from TOSMC to nonlinear PID controller, ensuring the stability of the system. Experimental tests show that compared with the traditional PID control, this method can effectively reduce the torque overshoot when ELS crossing backlash and guarantee torque tracking speed and precision of ELS.

Rear-cabin pressure control system of high-altitude test facility has the characteristics of large time-delay, nonlinearity and strong disturbances. In China, the rear-cabin pressure control system uses the conventional PID control method which can’t nonlinearly regulate pressure very well; especially in engine transient experiments, it can’t automatically turn PID parameters to adapt the changes of system’s nonlinearities, which has seriously affected the dynamic regulation and control accuracy of the rear-cabin pressure. Therefore, in this paper, firstly the dynamics of hydraulic butterfly valve is modeled and the nonlinear characteristics of exhaust diffuser are analyzed and the simulation model of the rear-cabin pressure control system is established. Secondly, the nonlinear PID controller is developed based on extremum seeking and its parameters are turned online according to the pressure errors between the setting valves and system outputs of the pressure system by minimizing the cost function. Finally, with and without engine flow disturbances, some simulation results of the linear and nonlinear PID control are given for pressure regulation to show that the proposed nonlinear PID based on extremum seeking can not only turn the controller parameters online, but also reject time-varying and large amplitude disturbances, so it has effectively enhanced the nonlinear adaptability of controller and improved the control accuracy of transient responses of the rear-cabin pressure control system.

Nonlinear tracking-differentiator and nonlinear combination were used to improve the behavior of classical PID controller. The result nonlinear PID controller has better adaptability and robustness. An anti-windup compensator was used on the nonlinear PID controller to deal with input constraints in winged missile control system. The use of nonlinear PID controller releases us from complicated work of making gain scheduling table. Characteristic point simulation and full trajectory simulation show validity of the anti-windup NLPID controller.