Posts Tagged Functional electrical stimulation

[ARTICLE] Intensity- and Duration-Adaptive Functional Electrical Stimulation Using Fuzzy Logic Control and a Linear Model for Dropfoot Correction – Full Text

Functional electrical stimulation (FES) is important in gait rehabilitation for patients with dropfoot. Since there are time-varying velocities during FES-assisted walking, it is difficult to achieve a good movement performance during walking. To account for the time-varying walking velocities, seven poststroke subjects were recruited and fuzzy logic control and a linear model were applied in FES-assisted walking to enable intensity- and duration-adaptive stimulation (IDAS) for poststroke subjects with dropfoot. In this study, the performance of IDAS was evaluated using kinematic data, and was compared with the performance under no stimulation (NS), FES-assisted walking triggered by heel-off stimulation (HOS), and speed-adaptive stimulation. A larger maximum ankle dorsiflexion angle in the IDAS condition than those in other conditions was observed. The ankle plantar flexion angle in the IDAS condition was similar to that of normal walking. Improvement in the maximum ankle dorsiflexion and plantar flexion angles in the IDAS condition could be attributed to having the appropriate stimulation intensity and duration. In summary, the intensity- and duration-adaptive controller can attain better movement performance and may have great potential in future clinical applications.


Stroke is a leading cause of disability in the lower limb, such as dropfoot (1). A typical cause of dropfoot is muscle weakness, which results in a limited ability to lift the foot voluntarily and an increased risk of falls (24). Great effort is made toward the recovery of walking ability for poststroke patients with dropfoot, such as ankle–foot orthoses (5), physical therapy (6), and rehabilitation robot (7).

Functional electrical stimulation (FES) is a representative intervention to correct dropfoot and to generate foot lift during walking (89). The electrical pulses were implemented via a pair of electrodes to activate the tibialis anterior (TA) muscle and to increase the ankle dorsiflexion angle. The footswitch or manual switch was used to time the FES-assisted hemiplegic walking in previous studies, while they were only based on open-loop architectures. The output parameters of the FES required repeated manual re-setting and could not achieve an adaptive adjustment during walking (1011). Some researchers have found that the maximum ankle dorsiflexion angle by using FES with a certain stimulation intensity had individual differences due to the varying muscle tone and residual voluntary muscle activity and varied during gait cycles (1213). If the stimulation intensity was set to a constant value during the whole gait cycle, the result could be that the muscle fatigues rapidly (14). Another important problem was that the FES using fixed stimulation duration from the heel-off event to the heel-strike event would affect the ankle plantar flexion angle (1516).

Closed-loop control was an effective way to adjust the stimulation parameters automatically, and several control techniques have been proposed (1718). Negård et al. applied a PI controller to regulate the stimulation intensity and obtain the optimal ankle dorsiflexion angle during the swing phase (19). A similar controller was also used in Benedict et al.’s study, and the controller was tested in simulation experiments (20). Cho et al. used a brain–computer interface to detect a patient’s motion imagery in real time and used this information to control the output of the FES (21). Laursen et al. used the electromechanical gait trainer Lokomat combined with FES to correct the foot drop problems for patients, and there were significant improvements in the maximum ankle dorsiflexion angles compared to the pre-training evaluations (22). There were also several studies that used trajectory tracking control to regulate the output and regulate the pulse width and pulse amplitude of the stimulation (23). The module was based on an adaptive fuzzy terminal sliding mode control and fuzzy logic control (FLC) to determine the stimulation output and force the ankle joint to track the reference trajectories. In their study, FES applied to TA was triggered before the heel-off event. Because the TA activation has been proven to occur after the heel-off event and the duration of the TA activation changed with the walking speed (2425), a time interval should be implemented after the heel-off event (26). In Thomas et al.’s study, the ankle angle trajectory of the paretic foot was modulated by an iterative learning control method to achieve the desired foot pitch angles (27). The non-linear relationship between the FES settings and the ankle angle influenced the responses of the ankle motion (28). FLC represents a promising technology to handle the non-linearity and uncertainty without the need for a mathematical model of the plant, which has been widely used in robotic control (29). Ibrahim et al. used FLC to regulate the stimulation intensity of the FES (30), and the same control was used on the regulation of the stimulation duration to obtain a maximum knee extension angle in Watanabe et al.’s study (31). However, most closed-loop controls adjust only one stimulation parameter, and few FES controls considered both varying the stimulation intensity and duration while accounting for the changing walking velocities.

In the present study, an intensity- and duration-adaptive FES was established, the FLC and a linear model were used to regulate the stimulation intensity and duration, respectively. The performance of the intensity- and duration-adaptive stimulation (IDAS) was compared with those of stimulation triggered by no stimulation (NS), heel-off stimulation (HOS), and speed-adaptive stimulation (SAS) for poststroke patients walking on a treadmill. The objective of this study is to find an appropriate FES control strategy to realize a more adaptive ankle joint motion for poststroke subjects.[…]


Continue —> Frontiers | Intensity- and Duration-Adaptive Functional Electrical Stimulation Using Fuzzy Logic Control and a Linear Model for Dropfoot Correction | Neurology

Figure 4(A) Ankle angles during the gait cycle for one poststroke subject at free speed; (B) knee angles during the gait cycle for the same poststroke subject at free speed.


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[Abstract] Examination of factors related to the effect of improving gait speed with functional electrical stimulation intervention for patients with stroke



Functional electrical stimulation (FES) for patients with stroke and foot drop is an alternative to ankle foot orthoses. Characteristics of FES responders and non-responders have not been clarified.


1. To investigate the effects of treatment with FES on patients with stroke and foot drop. 2. To determine which factors may relate to responders and non-responders.


Multicenter, non-randomized, prospective study.


Multicenter clinical trial.


Participants, who experienced foot drop resulting from stroke, greater than 20 years old, and could provide consent to participate, were enrolled from hospitals between January 2013 and September 2015 and performed rehabilitation with FES.


Stroke Impairment Assessment Set Foot-Pat Test (SIAS-FP), Fugl-Meyer Assessment for Lower Extremity (FMA-LE), modified Ashworth scale (MAS) for ankle joint dorsiflexion and plantar flexion muscles, range of motion (ROM) for ankle joint, 10-m walking test (10mWT), timed up & go test (TUG), and 6-minute walking test (6MWT) were evaluated pre- and post-intervention. Age, sex, type of stroke, onset times of stroke, paretic side, Brunnstrom stage of the lower extremity (Br. stage-LE), functional independent measure (FIM), functional ambulation category (FAC), post-stroke months, number of interventions, total hours of interventions, and whether a brace was used were extracted from patients’ medical records and collected on the physiological examination day.

Main Outcome Measurements

We examined 10mWT and age, sex, type of stroke, onset times of stroke, paretic side, Br. stage-LE, FIM, FAC, post-stroke months, number of interventions, total hours of interventions, whether a brace was used, SIAS-FP, FMA-LE, MAS, ROM, TUG, and 6MWT before intervention. We divided participants into non-responders and responders with a change in 10mWT of <0.1 and ≧0.1 m/s, respectively. Single and multiple regression analyses were used for data analysis. Additionally, we compared the changes between groups.


Fifty-eight responders and 43 non-responders were enrolled. The between-group differences, compared for changes between pre- and post-intervention, were significant in terms of changes in SIAS-FP (P=.02), 10mWT (P<.001), 10-m gait steps (P<.001), TUG (P=.04), and 6MWT (P=.006). In the adjusted regression model, sex (OR, 3.92; 95% CI, 1.426–12.25; P=.007), number of interventions (OR, 1.028; 95% CI, 1.003–1.070; P=.03), and active ankle joint dorsiflexion ROM (OR, 1.047; 95% CI, 1.014–1.088; P=.005) remained significant.


The factors related to 10mWT showing changes beyond the minimally clinically important difference were found to be patient sex, number of interventions, and active ankle joint dorsiflexion ROM before intervention. When Patients with stroke who are greater active ankle joint ROM in female, use FES positively, they may benefit more from using FES.


via Examination of factors related to the effect of improving gait speed with functional electrical stimulation intervention for patients with stroke – PM&R

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[VIDEO] Rehabilitation centre Reade in Amsterdam on Functional Electrical Stimulation – YouTube

Published on Mar 7, 2018

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[Abstract] Novel multi-pad functional electrical stimulation in stroke patients: A single-blind randomized study

via Novel multi-pad functional electrical stimulation in stroke patients: A single-blind randomized study – IOS Press

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[BOOK Chapter] Functional Electrical Stimulation and Its Use During Cycling for the Rehabilitation of Individuals with Stroke – Abstract+References

Advanced Technologies for the Rehabilitation of Gait and Balance DisordersAbstract

Stroke disease involves an increasing number of subjects due to the aging population. In clinical practice‚ the presence of widely accessible rehabilitative interventions to facilitate the patients’ motor recovery‚ especially in the early stages after injury when wider improvement can be gained‚ is crucial to reduce social and economical costs. The functional electrical stimulation (FES) has been investigated as a tool to promote locomotion ability in stroke patients. Particular attention was given to FES delivered during cycling‚ which is recognized as a safe and widely accessible way to provide a FES-based rehabilitative intervention in the most impaired subjects. In this chapter the neurophysiological basis of FES and its potential correlates to facilitate the long-term reorganization at both cortical and spinal level have been discussed. A discussion on clinical evidence and possible future direction is also proposed.


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[THESIS] A home-based functional electrical stimulation system for upper-limb stroke rehabilitation – Abstract


Due to an increased population of stroke patients and subsequent demand on health providers, there is an urgent need for effective stroke rehabilitation technology that can be used in patients’ own homes. Over recent years, systems employing functional electrical stimulation (FES) have shown the ability to provide effective therapy. However, there is currently no low-cost therapeutic system available which simultaneously supplies FES to muscles in the patient’s shoulder, arm and wrist to provide co-ordinated functional movement. This restricts the effectiveness of treatment, and hence the ability to support activities of daily living.

In this thesis a home-based low cost rehabilitation system is developed which substantially extends the current state of art in terms of sensing and control methodologies. In particular, it embeds novel non-contact sensing approaches; the first use of an electrode array within a closed-loop model based control scheme; an interactive task display system; and an integrated learning-based controller for multiple muscles within the upper-limb (UL), which supports co-ordinated tasks. The thesis then focuses on compacting the prototype by upgrading the depth sensor and using embedded systems to transfer it to the home

Currently available home-based systems employing FES for UL rehabilitation are first reviewed in terms of their underlying technology, operation, scope and clinical evidence. Motivated by this, a detailed examination of a prototype system is carried out that combines low cost non-contact sensors with closed-loop FES controllers. Then potential avenues to extend the technology are highlighted, with specific focus given to low-cost non-contact based sensors for the hand and wrist. Sensing approaches are then reviewed and evaluated in terms of their scope to support the intended system requirements. Electrode array hardware is developed in order to provide accurate movement capability. Biomechanical models of the combined stimulated arm and mechanical support are then formulated. Using these, model-based iterative learning control methodologies are then designed and implemented.
The system is evaluated with both unimpaired participants and stroke patients undergoing a course of treatment. Finally, a home-based prototype is developed which integrates and extends the aforementioned components. Results conrm the system’s scope to provide more effective stroke rehabilitation. Based on the achieved results, courses of future work necessary to continue this development are outlined.

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[VIDEO] Functional electrical stimulation after stroke – YouTube

Published on Jan 25, 2018

After a stroke, patients may no longer be able to correctly perform simple everyday movements, such as drinking from a glass.
Drinking is still realized as a task, but the impulse sent to the brain is not sufficient to trigger the proper movement.
This process can be practiced with functional electrical stimulation to improve motion sequences on a long-term basis.
The EMG function of the STIWELL electrostimulator measures and enhances the patient’s motion impulse to enable successful movement. Multi-channel electrical impulses support motion control.
For more than 20 years STIWELL has leased and sold electrostimulation devices to provide comprehensive therapy after stroke and other neurological diseases. For more information please visit
This video is for demonstration purposes only. The products, applications and performance characteristics are subject to approval by the responsible national authorities. Not all components may be available in your country or provided by MED-EL for sale in your country.
© MED-EL, technical realization:


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[ARTICLE] Cooperative Control for A Hybrid Rehabilitation System Combining Functional Electrical Stimulation and Robotic Exoskeleton – Full Text

Functional electrical stimulation (FES) and robotic exoskeletons are two important technologies widely used for physical rehabilitation of paraplegic patients. We developed a hybrid rehabilitation system (FEXO Knee) that combined FES and an exoskeleton for swinging movement control of human knee joints. This study proposed a novel cooperative control strategy, which could realize arbitrary distribution of torque generated by FES and exoskeleton, and guarantee harmonic movements. The cooperative control adopted feedfoward control for FES and feedback control for exoskeleton. A parameter regulator was designed to update key parameters in real time to coordinate FES controller and exoskeleton controller. Two muscle groups (quadriceps and hamstrings) were stimulated to generate active torque for knee joint in synchronization with torque compensation from exoskeleton. The knee joint angle and the interactive torque between exoskeleton and shank were used as feedback signals for the control system. Central pattern generator (CPG) was adopted that acted as a phase predictor to deal with phase confliction of motor patterns, and realized synchronization between the two different bodies (shank and exoskeleton). Experimental evaluation of the hybrid FES-exoskeleton system was conducted on five healthy subjects and four paraplegic patients. Experimental results and statistical analysis showed good control performance of the cooperative control on torque distribution, trajectory tracking, and phase synchronization.

1. Introduction

Neurologic injuries such as stroke and spinal cord injury may cause paresis in patients and give rise to movement disability. Physical rehabilitation is highly necessary for paralyzed individuals to restore mobility of extremities. Functional electrical stimulation (FES) and robotic exoskeletons are two important technologies used widely in extremity rehabilitation.

Many FES systems have been developed by using either surface or implanted electrodes in the past decades (Popovic et al., 2001). As a neuro-rehabilitation approach that excites and activates muscles directly, FES can provide not only functional training but also therapeutic benefits to paralyzed patients. Although some advances in closed-loop control and multichannel selection of muscles have achieved complex stimulation, it is still a complicated and tough problem of controlling FES to assist paralyzed individuals to move in a natural manner, mainly due to the nonlinearity and time variability of human musculoskeletal system (Zhang et al., 2007Lynch and Popovic, 2008). The pathological muscle conditions and the poor controllability of FES result in insufficient joint torque to provide limbs movement and body support for patients (del Ama et al., 2012Ha et al., 2012Quintero et al., 2012). In addition, muscle fatigue is often induced under continuous electrical stimulation. In a word, these problems mentioned severely hinder the widespread usage of FES from becoming a popular treatment option.

Robotic exoskeleton is an alternative technology of extremity rehabilitation for paraplegic patients, and lower limb exoskeletons are designed to accomplish neuro-rehabilitation and replace the physical gait training effort of therapists (Dollar and Herr, 2008). The well-known representatives in the application of motor rehabilitation for lower limbs are Lokomat (Hocoma, Switzerland) (Colombo et al., 2000), LOPES (Veneman et al., 2007), POGO and PAM (Reinkensmeyer et al., 2006), ALEX (Banala et al., 2009), etc. The popular exoskeletons usually use electric actuators, hydraulic actuators, or pneumatic actuators (Fan and Yin, 2013Vitiello et al., 2013). In comparison with FES, the therapeutic effect of robotic rehabilitation is limited, because it can merely provide assistive torque to limbs, the muscles are not stimulated actively, which are passively contracted or stretched. Therefore, it is an urgent demand to combine FES with exoskeletons, merging as hybrid rehabilitation systems that bring about not only functional but also physiological benefits to patients.

There is an increasing interest in developing hybrid rehabilitation systems, taking the advantages of FES and exoskeleton, and overcoming the limitations in separate application (To et al., 2008del Ama et al., 2012). In general, there are two kinds of such hybrid rehabilitation systems, i.e., combination of FES and powerless (passive) orthoses, or combination of FES and powered (active) exoskeletons. The controlled-brake orthosis (CBO) developed by Goldfarb and Durfee (1996) used joint brakes to control the body movement generated by FES. An obvious deficiency of orthoses is the inability to generate active torque for joints. Compared with orthoses, powered exoskeletons using mechanical actuators can compensate insufficient torque generated by FES. Recently, some achievements in hybrid FES-exoskeleton systems have been made, such as WalkTrainer (Stauffer et al., 2009), Vanderbilt Exoskeleton (Ha et al., 2012), Kinesis (del Ama et al., 2014), iLeg (Chen et al., 2014) and so on. In WalkTrainer system, Stauffer et al. (2009) developed closed-loop control of FES that modulated muscle stimulation to minimize the interaction force between the wearer and the exoskeleton, or modulated the desired torques as a function of the gait cycle. That system did not take account for muscle fatigue compensation as the exoskeleton was not actively involved. In order to accomplish cooperative control of FES with the Vanderbilt Exoskeleton during walking, Ha et al. (2016) proposed a two-loop controller, where motor control loop and muscle control loop co-existed. In that manner, the motor control loop used joint angle feedback to control the output of the joint motor to track the desired joint trajectories, while the muscle control loop utilized joint torque profiles from previous steps to regulate the muscle stimulation for the subsequent step to minimize the motor torque contribution required for joint angle trajectory tracking. del Ama et al. (2014)proposed cooperative control to balance the effort between muscle stimulation and exoskeleton in hybrid system (Kinesis), which sought to minimize the interaction torque and realized hybrid ambulatory gait rehabilitation. The torque-time integral generated by FES was measured to estimate muscle fatigue and a learning method was used to modulate the stimulation strength so as to compensate the torque loss. Alibeji N. A. et al. (2015) and Alibeji et al. (2017) developed an adaptive control method inspired by muscle synergy to compensate for actuator redundancy and FES-induced muscle fatigue in a hybrid FES-exoskeleton system, which showed ability to coordinate FES of quadriceps and hamstrings muscles and electric motors at the hip joint and knee joint of the exoskeleton. Chen et al. (2014) designed an FES-assisted control strategy for a hybrid lower-limb rehabilitation system (iLeg), where active FES control was achieved via a combination of neural network based feedforward control and PD feedback control to realize torque control, and meanwhile impedance control was adopted for exoskeleton control. Tu et al. (2017) combined FES with exoskeleton to accomplish gait rehabilitation in a different way, where FES and exoskeleton made effect on different joints separately, i.e., exoskeleton was applied on hip and knee joints, and FES was applied on ankle joint. A sliding control algorithm called chattering mitigation robust variable control (CRVC) was used for cooperative control in that hybrid system.

This study aims to accomplish harmonic and elegant control between FES and exoskeleton and explore their combined function on single-joint movement. Different from previous works, the active roles of FES and exoskeleton can be set freely here, i.e., the contribution of FES and exoskeleton can be distributed arbitrarily under different circumstances with specified requirements. Meanwhile, the synchronization problem of different drivers (motor vs. muscle) is well solved. It is well known knee joints play very important roles in lower limb locomotion, and knee joint control is a benchmark in previous literature (Chang et al., 1997Ferrarin et al., 2001Hunt et al., 2004Sharma et al., 2009Alibeji N. et al., 2015). Therefore, a hybrid rehabilitation system called FEXO Knee is developed in this work, which combines FES with a knee exoskeleton. A novelty of the system is the interactive force can be measured, which can help realize the better cooperative control. Moreover, it is very interesting and challenging to synchronize the human leg (driven by biological muscles) and exoskeleton (driven by artificial motor) to accomplish one task together, which is particularly solved in this work. A new cooperative control scheme is proposed, which can achieve shank swing motion under the harmonized and synchronized action of FES and exoskeleton, and realize different contribution of FES and exoskeleton. In such a scheme, a biologically-inspired control method, central pattern generator (CPG), is adopted because CPG has some favorable properties in synchronization, entrainment, and robustness against disturbance in general (Ijspeert, 2008). A combination of feedforward control and feedback control is used for FES and exoskeleton. A parameter regulator based on policy gradient method is designed to coordinate FES controller and exoskeleton controller adaptively. Five healthy subjects and four hemiplegic patients have participated in a series of experiments to test the cooperative control performance of FEXO Knee.

2. Method

2.1. FEXO Knee

The cooperative control of FES and exoskeleton is accomplished on our available prototype, FEXO Knee, which has two parts: a self-designed knee exoskeleton and a commercial FES device (RehaStim 2, Hasomed, Germany). The exoskeleton is composed of mechanical parts, electric motor, elastic actuator, sensors, and accessories. The function of exoskeleton is to generate assistive torque for rhythmic swing of human shank. It is designed for subjects with sitting posture, so it has a base bench that may be fixed on a table to hold the whole structure. The preliminary version (FEXO Knee I) has been reported in Ren and Zhang (2014). The new version (FEXO Knee II) is shown in Figure 1.

Figure 1. Structure of exoskeleton in FEXO Knee: (1) base bench, (2) electric motor (AC servo motor), (3) reducer, (4) shank wrap, (5) silicone board, (6) interactive force sensors, (7) outer shell, (8) signal amplification circuit, (9) encoder, (10) linear springs.

Continue —>  Frontiers | Cooperative Control for A Hybrid Rehabilitation System Combining Functional Electrical Stimulation and Robotic Exoskeleton | Neuroscience

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[ARTICLE] The immediate effect of FES and TENS on gait parameters in patients after stroke – Full Text PDF


[Purpose] This study was conducted to compare the immediate effects of different electrotherapies on the gait parameters for stroke patients.

[Subjects and Methods] Thirty patients with stroke were randomly assigned either to the functional electrical stimulation group or the transcutaneous electrical nerve stimulation group, with 15 patients in each group. Each electrotherapy was performed for 30 minutes simultaneously with the therapeutic exercise, and the changes in the spatial and temporal parameters of gait were measured.

[Results] After the intervention, a significant, immediate improvement in cadence and speed was observed only in the functional electrical stimulation group.

[Conclusion] Based on this study, functional electrical stimulation that stimulates motor nerves of the dorsiflexor muscles on the paretic side is recommended to achieve immediate improvement in the gait ability of stroke patients.[…]

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[Abstract] Sensing motion and muscle activity for feedback control of functional electrical stimulation: Ten years of experience in Berlin


After complete or partial paralysis due to stroke or spinal cord injury, electrical nerve stimulation can be used to artificially generate functional muscle contractions. This technique is known as Functional Electrical Stimulation (FES). In combination with appropriate sensor technology and feedback control, FES can be empowered to elicit also complex functional movements of everyday relevance. Depending on the degree and phase of impairment, the goal may be temporary support in a rehabilitation phase, e.g. during re-learning of gait after a stroke, or permanent replacement/support of lost motor functions in form of assistive devices often referred to as neuro-prostheses.

In this contribution a number of real-time capable and portable approaches for sensing muscle contractions and motions are reviewed that enable the realization of feedback control schemes. These include inertial measurement units (IMUs), electromyography (EMG), and bioimpedance (BI). This contribution further outlines recent concepts for movement control, which include e.g. cascaded control schemes. A fast inner control loop based on the FES-evoked EMG directly controls the amount of recruited motor units. The design and validation of various novel FES systems are then described that support cycling, walking, reaching, and swallowing. All methods and systems have been developed at the Technische Universität Berlin by the Control Systems Group within the last 10 years in close cooperation with clinical and industrial partners.

Source: Sensing motion and muscle activity for feedback control of functional electrical stimulation: Ten years of experience in Berlin – ScienceDirect

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