Lambert W Function Controller Design for Teleoperation Systems

Soheil Ganjefar,Mohammad Hadi Sarajchi,Seyed Mahmoud Hoseini,Zhufeng Shao 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.1

Stability and transparency play key roles in a bilateral teleoperation system with communication latency. This study developed a new method of controller design, based on the Lambert W function for the bilateral teleoperation through the Internet. In spite of the time-delay in the communication channel, system disturbance, and modeling errors, this approach causes the slave manipulator tracks the master appropriately. Time-delay terms in the bilateral teleoperation systems result in an infinite number of characteristic equation roots making difficulty in the analysis of systems by traditional strategies. As delay differential equations have infinite eigenspectrums, it is not possible to locate all closed-loop eigenvalue in desired positions by using classical control methods. Therefore, this study suggested a new feedback controller for assignment of eigenvalues, in compliance with Lambert W function. Lambert W function causes the rightmost eigenvalues to locate exactly in desired possible positions in the stable left hand of the imaginary axis. This control method led to a reduction in the undesirable effect of time-delay on the communication channel. The simulation results showed great closed-loop performance and better tracking in case of different time-delay types.

Adaptive Wavenet Controller Design for Teleoperation Systems with Variable Time Delays using Singular Perturbation Method

Soheil Ganjefar 제어·로봇·시스템학회 2013 International Journal of Control, Automation, and Vol.11 No.3

The main goal of controller design in teleoperation systems is to achieve stability and optimal operation in presence of factors such as time delays, system disturbances and modeling errors. This paper proposes a new method of controller design based on wavenet with singular perturbation method for the bilateral teleoperation of robots through the internet. The wavenet controller could overcome the variable time delay in teleoperation system. This new method introduces a reduced-order structure for control and stability of teleoperation systems. By using singular perturbation method, teleoperation system is decomposed into two fast and slow subsystems. This method is a step towards reduced-order modeling. In this method, we use a feedback linearization method in master subsystem and a wavenet controller for slave subsystem. In wavenet controller, we used a learning method so that the system was Lyapunov stable. As the stability of the model is highly dependent on the learning of the system, we use Lyapunov stability in this method. It has been tried to reduce the tracking error between the master and the slave subsystems. In this structure the position of master-slave are compared together and controlling signal is applied to the slave so that they can track each other in the least possible time. In all schemes the effectiveness of the system is shown through the simulations and they have been compared with each other.

Controller Design Based on Wavelet Neural Adaptive Proportional Plus Conventional Integral-derivative for Bilateral Teleoperation Systems with Time-varying Parameters

Soheil Ganjefar,Mohammad Afshar,Mohammad Hadi Sarajch,Zhufeng Shao 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.5

In this study, a new controller method based on wavelet neural adaptive proportional plus conventional integral-derivative (WNAP+ID) controller through adaptive learning rates (ALRs) for the Internet-based bilateral teleoperation system is developed. The PID controller design suffers from dealing with a plant with an intricate dynamic model. To make an adaptive essence for PID controller, this study uses a trained offline self-recurrent wavelet neural network as a processing unit (SRWNN-PU) in parallel with conventional PID controller. The SRWNN-PU parameters are updated online using an SRWNN-identifier (SRWNNI) in order to reduce the controller error in realtime function. Using feedback linearization method and a PID controller, the presented control method reduced the tracking error in the subsystems of the teleoperation system, i.e., master and slave which are stabilized, respectively. Additionally, time-varying delay in teleoperation systems is considered as noise making the master signals be modulated because wavelt neural networks have a high susceptibility to remove the noise, thus the WNAP+ID controller is able to eliminate the noise effect. In this paper, we concentrated on the efficiency and stability of the teleoperation system with time-varying parameters through simulation outcomes. Moreover, the results of the WNNs are compared with those of multi-layer perceptron neural networks (MLPNNs).

Variable Speed Wind Turbine Control Using the Homotopy Perturbation Method

Arefe Shalbafian,Soheil Ganjefar 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.1

In this study, we present a method to obtain optimal control of the variable-speed fixed-pitch wind turbine using the homotopy perturbation method (HPM). In general, the optimal control problem for nonlinear systems should solve the Hamilton–Jacobi–Bellman (HJB) equation. The partial differential HJB equations that arise in optimal control problem, give closed-loop control law and it is difficult to obtain an exact solution of them for nonlinear systems. The main objective of this work is to employ the homotopy perturbation method to solve the HJB equation for a two-mass model of a wind turbine to capture the maximum power from the wind in below-rated wind speed. By applying this strategy, we obtained an approximate solution of the HJB equation for a two-mass model of the wind turbine with high accuracy. In the simulation section, we compare the results of the proposed HPM strategy with the nonlinear static state feedback control (NSSFE) approach. The presented results confirm that the HPM controller produces more electrical power while minimizing low-speed shaft oscillations by improving dynamic characteristics.

Quarter Car Active Suspension System: Minimum Time Controller Design Using Singular Perturbation Method

Younes Mohammadi,Soheil Ganjefar 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.6

Suspension systems have been widely applied to vehicles. Every vehicle moving on the randomly profiledroad is exposed to vibration and shocks which is harmful both for the passengers in terms of comfort andfor the durability of the vehicle itself. From this point of view, it is important to reset to zero displacement, velocityand acceleration of car in minimum time. So, this paper proposes a new minimum time controller basedon bang-bang control for the quarter car active suspension systems. First by using singular perturbation methodthe original suspension system is decomposed into two fast and slow singular subsystems in theory, and then byPontryagain’s Minimum Principle (PMP) and switching functions, the controller is designed for each subsystemand finally the optimal final time is obtained as maximum optimal time concluded of two subsystems. By using adegree of stability technique with two parameters (instead of four parameters), the optimal time is more reducedand leads to great simplifications in practical implementation. The performance of the controller is compared withthe Sub optimal Linear Quadratic Regulator (SLQR) controller using two types of road profiles (step and bump)implemented in MATLAB/Simulink. Test results demonstrate the proposed controller is very more effective andsimpler in eliminating fluctuations in suspension systems that finally provide the passengers comfort.

Intelligent Control of Static Synchronous Series Compensator via an Adaptive Self-Tuning PID Controller for Suppression of Torsional Oscillations

Mohsen Farahani,Soheil Ganjefar 제어·로봇·시스템학회 2012 International Journal of Control, Automation, and Vol.10 No.4

In this paper, an intelligent controller is proposed to control a static synchronous series compensator (SSSC) in order to mitigate subsynchronous resonance (SSR) oscillations in a power system. This in-telligent controller is an adaptive self-tuning PID controller. To train the PID controller, the gradient descent method is employed where the learning rate is adapted in every iteration in order to accelerate the speed of convergence. This control scheme also requires a wavelet neural network (WNN) to identify the controlled system dynamic. To update the parameters of WNN, the gradient descent (GD) along with the adaptive learning rates derived by the Lyapunov method is used. The computer simulations are used to show the ability of the proposed controller. In addition, the performance of the proposed controller is compared with another self-tuning PID controller. The results demonstrate that the proposed controller has a successful performance in minimizing the SSR.

Adaptive Controller Design Based On Predicted Time-delay for Teleoperation Systems Using Lambert W Function

Mohammad Hadi Sarajchi,Soheil Ganjefar,Seyed Mahmoud Hoseini,Zhufeng Shao 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.6

This study develops an approach of controller design, on the basis of Lambert W function structure for Internet-based bilateral teleoperation systems. Actually, time-delay terms in bilateral teleoperation systems lead to an infinite number of characteristic equation roots making difficulty in analysis of systems by classical methods. As delay differential equations (DDEs) have infinite eigenspectrums, all closed-loop eigenvalues are not feasible to locate in desired positions by using classical control methods. Therefore, this study suggests a new feedback controller for assignment of eigenvalues, in compliance with Lambert W function. In this regard, an adaptive controller is accurately employed in order to provide the controller with updated predicted time-delay and robust the system against the time-delay. This novel control approach causes the rightmost eigenvalues to locate exactly in desired positions in the stable left hand of the imaginary axis. The simulation results show strong and robust closed-loop performance and better tracking in constant and time-varying delay.