Patient-driven loop control for hand function restoration in a non-invasive functional electrical stimulation system.

PURPOSE: In this study, a patient-driven loop control in a non-invasive functional electrical stimulation (FES) system was designed to restore hand function of stroke patients with their residual capabilities. METHOD: With this patient-driven loop control, patients use the electromyographic (EMG) signals from their voluntary controlled muscles in affected limbs to adjust stimulus parameters of the system. A special designed FES system generated electrical stimuli to excite the paralyzed muscles through surface electrodes on the basis of the control command from the residual myoelectric signals. EMG signals were also served as the trigger and the adjustment of stimulus parameters and thereby adding versatility of the FES system. Four stroke patients were recruited in the experiment to validate our system. RESULTS: The experimental results showed that hemiplegics could successfully control the system to restore their lost hand functions with the strategy of patient-driven loop control (the average estimated success rate was 77.5% with the tasks of cylindrical grasp and lateral pinch); and further, they would benefit by using the residual capabilities to regain their hand functions from the viewpoints of rehabilitation and psychology. CONCLUSION: According to the experiment results, this patient-driven loop control can be beneficial for hemiplegics to restore their hand functions such as cylindrical grasp and lateral pinch. The control strategy of this study has the potential to be employed not only in the FES system but also in other assistive devices.

Safety assurance of assistive devices based on a two-level checking scheme.

The increasing number of physically challenged individuals has boosted the demand of powered wheelchairs. This paper is on the subject of a DSP (Digital Signal Processors) based assistive system, which is associated with a two-level checking scheme. The assistive system takes on the M3S (Multiple Master Multiple Slave) regulation for the assurance of safety. The CAN (Control Area Networks) embedded module in the DSP provides robust transmission of information within the system. The hardware interfaces based on the two-level checking scheme is implemented in input devices (e.g. joystick, head control apparatus) and in output devices (e.g. manipulator, prime mover motors).

The comparison of electromyographic pattern classifications with active and passive electrodes.

Electromyographic (EMG) signals are usually acquired using surface electrodes, and they commonly serve as the control sources of myoelectric prosthetic limbs. The use of passive electrodes and amplifiers with adjustable gain is very popular in laboratories for the development of new control strategies. However, active electrodes without conductive jelly are used in most clinical applications of myoelectric hand control. There remains an important question: Are there any differences between using active and passive electrodes in EMG pattern classifications? Autoregressive and cepstral coefficients were used to evaluate recognition rates via both types of electrodes. The results showed that the estimated recognition rates in the passive electrodes were comparable to those in the active ones (averaged recognition rate, 88.5 vs. 85.84% in the autoregressive coefficients, and 84.84 vs. 83.5%, in the cepstral coefficients, respectively). Aside from the lack of significant statistical differences between them, the results imply that the differences between the recognition rates via these electrodes could be negligible. This would be helpful for the myoelectric control of assistive devices.

A noninvasive functional electrical stimulation system with patient-driven loop for hand function restoration.

In this study, a noninvasive functional electrical stimulation (FES) system is proposed to restore hand functions. The control strategy of this system is based on the patient-driven control loop. The patient can use his sound extremity to control FES system to generate the electrical stimulation so that the paralyzed muscles will be excited. In addition, electromyographic (EMG) signals, which are recorded by the sensors in the electrical stimulator, can serve as the trigger for the initialization of the system and the adjustment of the electrical stimulation parameters. From the preliminary results, they show that the subjects can successfully control the proposed system. We hope that patients will benefit a lot from this kind of FES system with patient-driven control loop.