Nurkan Yagiz

Fuzzy Sliding-Mode Control of Active Suspensions

In this paper, a robust fuzzy sliding-mode controller for active suspensions of a nonlinear half-car model is introduced. First, a nonchattering sliding-mode control is presented. Then, this control method is combined with a single-input-single-output fuzzy logic controller to improve its performance. The negative value of the ratio between the derivative of error and error is the input and the slope constant of the sliding surface of the nonchattering sliding-mode controller is the output of the fuzzy logic controller. Afterwards, a four-degree-of-freedom nonlinear half-car model, which allows wheel hops and includes a suspension system with nonlinear spring and piecewise linear damper with dry friction, is presented. The designed controllers are applied to this model in order to evaluate their performances. It has been shown that the designed controller does not cause any problem in suspension working limits. The robustness of the proposed controller is also investigated for different vehicle parameters. The results indicate the success of the proposed fuzzy sliding-mode controller.

MIMO fuzzy sliding mode controlled dual arm robot in load transportation

Abstract The control problem of the cooperative motion of a two-link dual arm robot during handling and transportation of an object was studied in this paper. Since these types of robots are frequently preferred for hazardous applications such as transportation of radioactive materials and disposal of explosives, a robust non-chattering sliding mode controller (SMC) improved by a multiple-input multiple-output (MIMO) fuzzy logic unit was applied to the robot to track the desired trajectory with high accuracy and transport the load safely. In order to assess the performance of the proposed MIMO fuzzy sliding mode controller (MIMO-FSMC) in presence of parameter variations and external disturbances, a sudden load variation and noise were introduced to the robot system. If compared with classical SMC, tracking errors with smaller magnitudes and faster convergence to zero were obtained by using the proposed MIMO-FSMC. Numerical results suggest that this type of control method may safely be used for cooperative motion control of dual arm robots in load handling and transport applications in hazardous environments with high accuracy.

Fuzzy Sliding Modes with Moving Surface for the Robust Control of a Planar Robot

In this paper, we develop a new control method that brings together the advantages of fuzzy logic and sliding mode control. First, we introduce a non-chattering robust sliding mode control. Then, in order to improve the performance of the controller a fuzzy logic algorithm is integrated with the sliding mode controller. This algorithm decides the slope of the sliding surface of the sliding mode controller dynamically. Thus, the system is caught on the sliding surface rapidly and remains over it, more successfully improving the performance of the controller. Afterwards, to test the success of the controller introduced, it is applied to a planar robot, which is to follow a certain trajectory only using the control inputs produced. The results are compared with those of a conventional PID controlled system and a sliding mode controller with constant surface slope. In order to check the robust behavior of the controller designed, an unexpected change in the mass of the second link is introduced and to make the conditions tougher it is assumed that this change is not sensed by the controllers. Noise resistance of the proposed controller is also checked by introducing normally distributed noise components into the equations of motion of the robot model.

Fuzzy logic control of vehicle suspensions with dry friction nonlinearity

We design and investigate the performance of fuzzy logic-controlled (FLC) active suspensions on a nonlinear vehicle model with four degrees of freedom, without causing any degeneration in suspension working limits. Force actuators were mounted parallel to the suspensions. In this new approach, linear combinations of the vertical velocities of the suspension ends and accelerations of the points of connection of the suspension to the body have been used as input variables. The study clearly demonstrates the effectiveness of the fuzzy logic controller for active suspension systems. Suspension working space degeneration is the most important problem in various applications. Decreasing the amplitudes of vehicle body vibrations improves ride comfort. Body bounce and pitch motion of the vehicle are presented both in time domain when travelling over a ramp-step road profile and in frequency domain. The results are compared with those of uncontrolled systems. At the end of this study, the performance and the advantage of the suggested approach and the improvement in ride comfort are discussed.

Prosthetic Hand Finger Control Using Fuzzy Sliding Modes

In order to improve the life quality of amputees, providing approximate manipulation ability of a human hand to that of a prosthetic hand is considered by many researchers. In this study, a biomechanical model of the index finger of the human hand is developed based on the human anatomy. Since the activation of finger bones are carried out by tendons, a tendon configuration of the index finger is introduced and used in the model to imitate the human hand characteristics and functionality. Then, fuzzy sliding mode control where the slope of the sliding surface is tuned by a fuzzy logic unit is proposed and applied to have the finger model to follow a certain trajectory. The trajectory of the finger model, which mimics the motion characteristics of the human hand, is pre-determined from the camera images of a real hand during closing and opening motion. Also, in order to check the robust behaviour of the controller, an unexpected joint friction is induced on the prosthetic finger on its way. Finally, the resultant prosthetic finger motion and the tendon forces produced are given and results are discussed.

Adaptive backstepping control with estimation for the vibration isolation of buildings

A new adaptive backstepping controller with estimation for uncertain systems is presented in this study. The uncertainties are due to an unknown control coefficient and unknown or uncertain terms included in the system equations. The backstepping control technique is preferred because it has a systematic design procedure and guarantees the stability of the system, since it is based on Lyapunov’s direct method. The proposed controller is used for the vibration isolation of a nine-story building model with an active tuned mass damper installed on the top floor. The results indicate that the proposed controller effectively suppresses the vibrations of the building.

Sliding Mode Control of a Finger for a Prosthetic Hand

A prosthetic finger model, intended to imitate a real human hand and for use in replacing the real index finger of an amputee, is designed using tendons instead of joint motors. A dynamic model of the prosthetic finger model is developed, and a non-chattering robust sliding mode control is applied to make the model follow a certain trajectory. Trajectory planning of the finger model is based on images of the closing motion of a human hand, and time varying reference joint angles are obtained using these images. The robustness of the controller is confirmed by introducing an unexpected sudden joint friction induced in the prosthetic finger.

Improving the ride comfort of vehicle passenger using fuzzy sliding mode controller

Attenuation of the adverse effects of vehicle vibrations on human health is a challenging problem. One common approach to solve this problem is to use various types of controllers in vehicle suspensions. In this study, in order to decrease the vehicle vibrations and hence improve the ride comfort, a fuzzy logic integrated sliding mode controller was designed. The performance of the controller was tested in a biodynamic human-vehicle combined model. The human body was considered as a lumped parameter model and incorporated into a full vehicle model. The biodynamic responses of a human body to vehicle vibrations were analyzed. Performances of the conventional sliding mode and fuzzy integrated sliding mode controllers were compared with those of a passive control strategy. According to the numerical results, the fuzzy sliding mode controller overcame both classic sliding mode and passive control approaches and decreased vehicle vibrations considerably. It can be deduced from the study that active suspension systems would play a key role in decreasing the negative effects of vehicle vibrations on human health, such as motion sickness, discomfort and spine injuries.

Vibrations of a Rectangular Bridge as an Isotropic Plate under a Traveling Full Vehicle Model

In this paper we analyze the vibrations of a bridge modeled as an isotropic plate with all sides simply supported under the effect of a moving load due to a full vehicle having seven degrees of freedom. A mathematical model of the bridge is obtained by applying Lagrange’s formulation to orthogonal mode shapes and the non-conservative moving forces. The modern materials used in the construction of the bridges satisfy isotropic conditions mostly, and they can be modeled as rectangular plates with four sides simply supported. The time responses of the mid-span and quarter-span of the bridge are obtained. The transverse vibration of the bridge and the body bounce, pitch, and roll of the vehicle are presented for different vehicle speeds. Finally, the bending moment at the mid-span is presented for different vehicle speeds to aid in the structural design of the bridge.

High order sliding mode control with estimation for vehicle active suspensions

In this study, a new high order sliding mode controller (HOSMC), based on super twisting algorithm (STA), is proposed for vehicle active suspensions. It is well known that first order sliding mode controller (SMC) is insensitive to parameter variations and external disturbances. On the other hand, it suffers from chattering present in control signal that may harm the mechanical components of the system. Therefore, HOSMC is preferred in this study that attenuates chattering effectively while preserving its robustness. Proposed HOSMC uses an estimation for the equivalent part of the control signal and uses the STA for the discontinuous part of the control law. Additionally, the controller gains are obtained by offline multi-objective genetic algorithm search. Extensive simulations and experimental results are presented to reveal the performance of the proposed controller. First order SMC is also designed and used for comparison. The results indicate the superior performance of the proposed HOSMC.