Yunus Ziya Arslan

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.

Prediction of externally applied forces to human hands using frequency content of surface EMG signals

In this work, a new signal processing method was proposed in order to predict externally applied forces to human hands by deriving a relationship between the surface electromyographic (SEMG) signals and experimentally known forces. This relationship was investigated by analyzing the spectral features of the SEMG signals. SEMG signals were recorded from three subjects during isometric contraction and from another three subjects during anisometric contraction. In order to determine force-SEMG signal relationship, higher order frequency moments (HOFMs) of the signals were calculated and used as characterizing features of SEMG signals. Subsequently, artificial neural networks (ANN) with backpropagation algorithm were trained by using the HOFMs. Root mean square difference (RMSD) between the actual and predicted forces was calculated to evaluate force prediction performance of the ANN. In addition to RMSD, cross-correlation coefficients between actual and predicted force time histories were also calculated for anisometric experiment results. The RMSD values ranged from 0.34 and 0.02 in the isometric contraction experiments. In the anisometric contraction tests, RMSD results were between 0.23 and 0.09 and cross-correlation coefficients ranged from 0.91 to 0.98. In order to compare the performance of the HOFMs with a widely used EMG signal processing technique, root-mean-squared (RMS) values of the EMG signals were also calculated and used to train the ANN as another characterizing feature of the signal. Predicted forces using HOFMs technique were in general closer to the actual forces than those of obtained by using RMS values. The results indicated that the proposed signal processing method showed an encouraging performance for predicting the forces applied to the human hands, and the spectral features of the EMG signal might be used as input parameter for the myoelectric controlled prostheses.

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.

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.

EXPERIMENTAL ASSESSMENT OF LUMPED-PARAMETER HUMAN BODY MODELS EXPOSED TO WHOLE BODY VIBRATION

Whole body vibration (WBV) is uncontrolled vibrations in occupational settings such as vehicle driving or hand tool operating. Chronic occupational WBV exposure may cause many health problems such as fatigue, lower back pain, spinal degenerations, vision problems and so on. In order to simulate and observe the adverse effects of WBV on the human body, many lumped-parameter human body models were proposed. The objective of this study is to provide quantified assessments of human body biodynamic models which were designed to characterize the response of real human body exposed to WBV. To do so, direct measurements of vibration accelerations obtained from different segments of human body and vehicle seat were carried out during riding on roads with different unevenness levels. Recorded experimental acceleration data were compared with those obtained from simulations of different human body models. Root mean square difference and correlation coefficient values were calculated between theoretical and experimen...

A quantitative skin impedance test to diagnose spinal cord injury

The purpose of this study was to develop a quantitative skin impedance test that could be used to diagnose spinal cord injury (SCI) if any, especially in unconscious and/or non-cooperative SCI patients. To achieve this goal, initially skin impedance of the sensory key points of the dermatomes (between C3 and S1 bilaterally) was measured in 15 traumatic SCI patients (13 paraplegics and 2 tetraplegics) and 15 control subjects. In order to classify impedance values and to observe whether there would be a significant difference between patient and subject impedances, an artificial neural network (ANN) with back-propagation algorithm was employed. Validation results of the ANN showed promising performance. It could classify traumatic SCI patients with a success rate of 73%. By assessing the experimental protocols and the validation results, the proposed method seemed to be a simple, objective, quantitative, non-invasive and non-expensive way of assessing SCI in such patients.

PREDICTION OF MUSCLE FORCES USING STATIC OPTIMIZATION FOR DIFFERENT CONTRACTILE CONDITIONS

In this study, we introduced a novel cost function for the prediction of individual muscle forces for a one degree-of-freedom musculoskeletal system. Unlike previous models, the new approach incorporates the instantaneous contractile conditions represented by the force-length and force-velocity relationships and accounts for physiological properties such as fiber type distribution and physiological cross-sectional area (PCSA) in the cost function. Using this cost function, it is possible to predict experimentally observed features of force-sharing among synergistic muscles that cannot be predicted using the classical approaches. Specifically, the new approach allows for predictions of force-sharing loops of agonistic muscles in one degree-of-freedom systems and for simultaneous increases in force in one muscle and decreases in a corresponding agonist. We concluded that the incorporation of the contractile conditions in the weighting of cost functions provides a natural way to incorporate observed force-sharing features in synergistic muscles that have eluded satisfactory description.

Fuzzy sliding mode control of a finger of a humanoid robot hand

: The motion control problem for the finger of a humanoid robot hand is investigated. First, the index finger of the human hand is dynamically modelled as a kinematic chain of cylindrical links. During construction of the model, special attention is given to determining bone dimensions and masses that are similar to the real human hand. After the kinematic and dynamic analysis of the model, in order to ensure that the finger model tracks its desired trajectory during a closing motion, a fuzzy sliding mode controller is applied to the finger model. In this controller, a fuzzy logic algorithm is used in order to tune the control gain of the sliding mode controller; thus, an adaptive controller is obtained. Finally, numerical results, which include a performance comparison of the proposed fuzzy sliding mode controller and a conventional sliding mode controller, are presented. The results demonstrate that the proposed control method can be used to perform the desired motion task for humanoid robot hands efficiently.

COMPARATIVE EVALUATION OF THE MECHANICAL PROPERTIES OF RESORBABLE AND TITANIUM MINIPLATES USED FOR FIXATION OF MANDIBULAR CONDYLE FRACTURES

In this paper, comparative evaluation of the mechanical properties of resorbable and titanium miniplates, which are used for the fixation of the mandibular condyle fractures, was carried out using finite element analysis (FEA). To do so, first two-dimensional (2D) computed tomography (CT) images of mandibles recorded from 10 adult patients were converted into three-dimensional (3D) solid body models. Then these models were transferred to the finite element software. In the finite element stage of the study, a condyle fracture was created onto the mandible and double-titanium and double-resorbable miniplates were separately fixed to the mandible surface such that the fractured sites to be firmly attached. Stress distribution over the plates and interfragmentary displacements between adjacent surfaces, which stem from the clenching force applying to the mandible, were calculated using FEA. It was observed from the results that maximum tensile stresses occurred in the titanium miniplates were significantly higher than those obtained from resorbable miniplates (p < 0.01). Higher maximum displacements between fractured surfaces were observed in the case of resorbable plate systems (p < 0.01). Maximum stress and displacement values obtained from both titanium and resorbable plate systems were under clinically acceptable limits. According to results, resorbable plates showed a similar reliability with titanium miniplates in terms of withstanding various stress and strain deformations.