Narrow Results

Both selectivity and sensitivity of chemical sensors can be significantly improved by exploiting the information contained in microfluctuations present in the sensor system. We call our collection of methods to extract information from these microfluctuations Fluctuation-Enhanced Sensing (FES). In this review paper we discuss general FES principles and two types of applications; gas sensing with commercial solid state sensors and the Sensing of Phage-Triggered Ion Cascde (SEPTIC) technique to detect and identify bacteria.

To regain mobility, stroke patients need to receive repetitive and intensive therapy. Robot-assisted rehabilitation is an active area of research. Cheap robotic leg rehabilitation devices should be developed to meet the demands and assist most patients. A low cost hip-knee exoskeleton prototype powered by pneumatic muscles was developed. On this basis, Functional Electrical Stimulation (FES) induced paralyzed muscles to realize ankle joint rehabilitation training. These three ankle muscles: the tibialis anterior, the soleus, and the gastrocnemius under electrical stimulation cooperated together to realize optimally coordinated control of dorsiflexion and plantar-flexion movement. As both of pneumatic muscle and FES induced muscle possess highly nonlinear characteristics, a sliding control algorithm called Chattering mitigation Robust Variable Control (CRVC) was applied to leg hybrid rehabilitation. The combination of exoskeleton and FES is a promising way to reduce the cost and the complexity of designing hip-knee-ankle exoskeleton. The proposed hybrid method was verified by treadmill-based gait training experiments.

Hemiplegia means paralysis of half of the body. It commonly occurs following "stroke", which is due to impedance of blood supply to the brain, hence also termed as "cerebrovascular accident" (CVA). As a consequence of this, the brain tissues suffer from ischemic damage resulting in several symptoms, such as mere weakness, numbness to complete loss of power (paralysis). In order to restore or improve the lost functional movement of the body of the stroke-affected and hemiplegic subjects, a method called functional electrical stimulation (FES) has often been employed as the measure of rehabilitation. FES makes use of low levels of electrical current to activate the nerves and then the muscles, affected. The response of the body to this electrically triggered nervous stimulation could be recorded through different bio-signals. In our work, we measured the accelerometers of hemiplegic patient in two states; with FES and without FES. The nonlinear and nonstationary walking-function-related accelerometers are analyzed using recurrence plots (RP), which helps to visualize the dynamic behavior of the signals. The RPs of electromyography (EMG) signals with stimulation showed distinct periodicity and rhythm when compared to that without stimulation. In addition, we extracted recurrence quantification analysis (RQA) parameters from RP to quantify the obtained information from the RP. Lower values were observed for most of the RQA parameters with FES than obtained without FES. This also confirmed the fact that FES is very useful in bringing more order, rhythm and better control in the physical activities of hemiplegic people.

The non-idealities resulting from the excitation of the paraplegic quadriceps muscle by the functional electrical stimulation (FES) make the control problem challenging. Few works addressed the control of this highly non-linear behavior where the elaborated controllers are useless in the real world. To improve the controllers’ metrics available in the literature, we test others controllers which are the Double PID, the backstepping, the backstepping with an integral action and the super-twisting. For that, we first propose an in-depth study of the knee’s dynamic through which we explain the poorness of the paraplegic quadriceps response to the FES. As a result, we propose to control using derivative way instead of de-convolving approaches as proposed in the literature. Second, we implement the different controllers cited earlier. Finally, we compare the resulting metrics of each controller with those of literature and we conclude by identifying the best controller among the ones chosen in this study which presents a considerable improvement and advantages.

In this paper, we develop a control law for Functional Electrical Stimulation (FES) application fields. This work aims to command the knee joint movement of patients in the seated position suffering from neurological disorders that lead to a partial or total paralysis of the limb. For this purpose, we propose the synthesis of an adaptive continuous control that permits to the knee joint the tracking of a time-varying desired angle. The knee movement is represented by the dynamical model of the lower limb. The designed control ensures an asymptotic stability while considering constraints such as unknown model parameters, unknown perturbation effects and unknown spasticity and fatigue parameters. The applicability and the effectiveness of the designed control law are shown through the simulation results.

Functional electrical stimulation (FES) is a method for restoring the functional movements of paraplegic or patients with spinal cord injuries. However, the selection of parameters that control the restoration of standing up and sitting functions has not been extensively investigated.

This work provides a method for choosing the four main items involved in evaluating the strategies for sit-stand-sit movements with the aid of a modified walker. The control method uses the arm-supported force and the angles of the legs as feedback signals to change the intensity of the electrical stimulation of the leg muscles. The control parameters, Ki and Kp, are vary for different control strategies. Four items are collected through questionnaires and used for evaluation. They are the maximum reactions of the two hands, the average reaction of the two hands, largest absolute angular velocity of the knee joints, and the sit-stand-sit duration time. The experimental data are normalized to facilitate comparison. Weighting factors are obtained and analyzed from questionnaires answered by experts and are added to evaluation process for manipulation. The results show that the best strategy is the closed-loop control with parameters Ki=0.5 and Kp=0.

Both selectivity and sensitivity of chemical sensors can be significantly improved by exploiting the information contained in microfluctuations present in the sensor system. We call our collection of methods to extract information from these microfluctuations Fluctuation-Enhanced Sensing (FES). In this review paper we discuss general FES principles and two types of applications; gas sensing with commercial solid state sensors and the Sensing of Phage-Triggered Ion Cascde (SEPTIC) technique to detect and identify bacteria.

Achieving automated control of FES induced walking had been a challenge for control system engineers. This work examines control efforts in FES aided movement applications with the aim of identifying a gap in knowledge that would create an impact towards solving or getting closer to total approval for clinical usage, easy to understand and use, simple, faster implementation and with high regards to safety. Effort was made to use all available means within reach and are close to works on restoration of gait control with emphasis on the lower limbs. FES can be applied alone (pure), but for walking or other active exercise it is usually combined with orthosis (hybrid). Nature of the plant which is a combination of the nervous, muscular and skeletal (neural-muscular-skeletal) systems as well as of limitations in sensor availability made the linear approach not favorable to such systems. Intelligent strategies most likely could provide clinically acceptable solutions, but are likely to face stability issues which are serious concern in this scenario, other shortcomings include longer tuning duration, re-tuning for different subjects and involvement of high computation. Stability issues can be dealt with directly when nonlinear techniques are used and also periodic utterances can be handled with relative ease. Nonlinear control techniques share the shortcoming of high computational requirement and at times complexity problems with the intelligent schemes, but kudos to achievements in microprocessor technologies that always yields higher capability processors which could eradicate issue. Hence, exploring the nonlinear technique could provide solution which could pave way for making countless things easy. That is; more impact could be made by understanding fundamentals or revisiting fundamental studies on nonlinear control for this application.