Mustafa Sinasi Ayas

Fractional order control of conducting polymer artificial muscles

Fractional order control has been designed for conducting polymer artificial muscle actuator.The Cuckoo search algorithm has been used for controller optimization.A specific cost function considering control signal and maximum overshoot has been used in optimization. This paper proposes a fractional order PID (FOPID) controller to improve the positioning ability of conducting polymer actuators (CPAs), a novel class of smart material based actuators. In the controller design process, the performance requirements and constraints which are crucial in precise positioning of CPAs such as fast settling time, low steady-state error, overshoot and control voltage are considered. In order to obtain the optimal controller parameters, cuckoo search (CS) and particle swarm optimization (PSO) meta-heuristic search methods which utilize a fractional order model of the CPA and a specifically defined fitness function, are used. Both of the algorithms are compared in terms of convergence rate and success of converging to an optimal solution. In order to test the performance of the FOPID controller, a PID controller is also tuned with both algorithms and all controllers are implemented experimentally on the CPA. The results show that the FOPID controller tuned with CSA has provided less overshoot, settling and rise-time than that tuned with PSO. The performance of the PID control is slightly worse than the FOPID controllers in terms of transient and steady-state response. Although both search algorithms have satisfied the control input constraint in FOPID and PID controllers, CSA tuned PID controller has required smallest control signal.

Fractional order based trajectory tracking control of an ankle rehabilitation robot

Human–robot interaction is inherently available and used actively in ankle rehabilitation robots. This interaction causes disturbances to be counteracted on the rehabilitation robots in order to reduce the side effects. This paper presents a fractional order proportional–integral–derivative controller to improve the trajectory tracking ability of a developed 2-degree of freedom parallel ankle rehabilitation robot subject to external disturbances. The parameters of the controller are optimally tuned by using both the cuckoo search algorithm and the particle swarm optimization algorithm. A traditional proportional–integral–derivative controller, which is also tuned using both of the algorithms, is designed to test the performance of the fractional order proportional–integral–derivative controller. The experimental results show that the optimally tuned FOPID controller improves the tracking performance of the ankle rehabilitation robot subject to external disturbances significantly and decreases the steady-state tracking errors compared to the optimally tuned PID controller.

A PSO optimized fractional-order PID controller for a PV system with DC-DC boost converter

In this study, a fractional-order PID (FOPID) controller is designed to control a DC-DC boost converter in a PV-system. Because of the nonlinear V-I characteristic of a PV-panel, a power electronic interface is required to obtain a desired and fixed voltage level. In order to obtain the best system performance, parameters of the proposed controller are tuned by using Particle Swarm Optimization (PSO) algorithm. Both of the system responses with the FOPID and classical PID are tested under various power conditions by changing the load resistor and solar irradiation values. The simulation results are compared in terms of integral of time weighted squared error (ITSE) criterion, percentage overshoot (Mp) and rising time (Tr). The results show that the FOPID controller performs better performance than the classical PID controller.

An optimized fuzzy logic controller for a parallel mechanism rehabilitation robot

This paper focuses on the trajectory tracking control of the two-degree-of-freedom parallel manipulator. In order to have a robust tracking a fuzzy logic controller of which the boundary scales of the membership functions are optimized is developed. The performance of the developed optimized fuzzy logic controller is compared to the optimized proportional-integral-derivative controller. Particle swarm optimization algorithm is used with a fitness function, integral of time weighted absolute error (ITAE) performance index, during the optimization process. The performances of both controllers are measured using the ITAE performance index. In addition, other error-based objective functions called integral of squared error (ISE), integral of absolute error (IAE) and integral of time weighted squared error (ITSE) are calculated for a better comparison of the controllers. The results of the simulations show that the developed optimized fuzzy logic controller has better tracking performance compared to optimized proportional-integral-derivative controller.

OPTIMIZED CONTROL OF A PARALLEL MECHANISM REHABILITATION ROBOT

This paper presents an optimized PID control approach for trajectory tracking of a parallel ankle rehabilitation robot which is a two degrees of freedom parallel manipulator. In order to have a robust tracking a PID controller of which the parameters are tuned by using particle swarm optimization algorithm is developed. The performances of the optimized controller is measured using Integral Squared Error performance measure method which is a version of the integral-error based performance measure methods. A white noise is introduced as an external disturbance to examine the robustness of the controller. The results of the simulations given in Section 5 show that the optimized PID controller has excellent tracking performance. In brief, the simulation results confirm the effectiveness of the developed controller.

Trajectory tracking control of a stewart platform

This paper presents a fuzzy logic control approach for trajectory tracking of Stewart platform which is a six degrees of freedom parallel manipulator. In order to have a robust tracking a fuzzy logic controller, convenient for nonlinear complex systems, is developed. The performance of the developed FLC is compared with classical PID controller. The performances of both controllers are measured using Integral Squared Error performance measure method which is a version of the integral-error based performance measure methods. The results of the simulations given in Section IV show that the developed fuzzy logic controller has excellent tracking performance. In brief, the simulation results confirm the effectiveness of the developed controller.

Designing and implementing a plug-in type repetitive controller for a redundantly actuated ankle rehabilitation robot:

This article is focused on increasing the tracking performance of a developed ankle rehabilitation robot subject to external disturbance. A plug-in-type repetitive controller cascaded to a proportional–integral–derivative controller is designed and implemented in order to make improvement in the tracking ability of the parallel mechanism while performing the common range of motion exercises which are intensive training exercises in ankle rehabilitation. First, the trajectory tracking control is simply implemented by the PID controllers, the parameters of which are optimally tuned using Cuckoo search algorithm. Then, the designed RC is plugged into the system and trajectory tracking control is carried out. Performance measurements of the PID controller and plug-in RC controller are estimated using error-based performance methods and considerable improvements are observed in attenuating the external disturbance and decreasing the tracking error when the plug-in RC is implemented.

Design of a fuzzy logic controller for a 2-DOF robot manipulator

In this study, a 2-DOF robot manipulator is designed and controlled by modified fuzzy logic controller. In order to have a good position tracking a fuzzy logic controller, which is convenient for nonlinear complex systems, is developed by modifying the ones from previous works. The performance of the developed FLC is compared with the classical PID controller of which the parameters are tuned by means of Integral Squared Error (ISE) performance measure. The optimum results for both developed FLC and classical PID controller are given in the result section.

A redundantly actuated ankle rehabilitation robot and its control strategies

Robotic-based rehabilitation has attracted great attention since it provides various advantages from the viewpoint of patients, therapists and rehabilitation process. This paper presents a redundantly actuated ankle rehabilitation robot, its control schemes for the common rehabilitation exercises, and experimental results indicating the effectiveness of the control schemes and the performance of the controllers. In order to analyze the effect of external disturbance in position control scheme, the related experiments are performed with and without artificial disturbance required for making a fair performance comparison of the optimized controllers. The effectiveness of admittance control scheme is analyzed utilizing a healthy subject. The performance of the developed controllers are calculated using common performance indexes.

Undetectable sensor and actuator attacks for observer based controlled Cyber-Physical Systems

Cyber-Physical Systems (CPSs) have vital importance because of their applications in many different areas. Attacks on these CPSs can cause considerable impact on public safety in addition to economic losses. Although studies on increasing the protection and reliability of CPSs against random malfunction are available, protection of CPSs against malignant attacks is needed. In particular, wireless sensor and actuator networks increase the attack risk. Even when a CPS functions properly, there can be undetectable attacks increasing costs or waiting for the right time to attack and destroy the CPS. In this paper, undetectable sensor and actuator attacks on observer-based controlled systems are theoretically analyzed. Explicit equations of both undetectable sensor and actuator signal attacks are derived. In addition, it is proved that the actuator signal attack is optimal in the sense of minimal energy attack signal. Numerical experiments are provided to validate the theoretical analyses and illustrate the effect of the undetectable attack signals.