Zhihao Zhou

A proprioceptive neuromuscular facilitation integrated robotic ankle-foot system for post stroke rehabilitation

Ankle joint with spasticity and/or contracture can severely disable the mobility and the independence of stroke survivors. In this paper, we developed a proprioceptive neuromuscular facilitation (PNF) integrated robotic ankle-foot system for post stroke rehabilitation. The system consists of a robotic platform and a control system with graphic user interface. We employ five normal subjects to test the reliability and feasibility of the proposed system. To validate the effectiveness of the PNF integrated robotic system, we recruit five stroke patients and carry out a six-week PNF treatment. Treatment outcome was evaluated quantitatively in passive and active joint properties. The passive hysteresis loop shows that the maximum dorsiflexion angle increases from 32.9 Â? Â? 1.5 Â? to 42.0 Â? Â? 3.2 Â? ( p = 0.014 ) while the resistance torque decreases from 45.6Â?NmÂ?5.8Â?NÂ?m to 29.8Â?NÂ?mÂ?4.4Â?NÂ?m ( p = 0.019 ). The active joint properties are improved significantly with the training score increasing from 5.7 Â? 0.9 to 8.1 Â? 0.6 , and getting close to that of normal subjects ( 9.5 Â? 0.3 ). In addition, muscle strength has a rising trend as time goes on. The results demonstrate that the proposed PNF integrated robotic ankle-foot rehabilitation system is effective in improving ankle spasticity and/or contracture and is a promising solution in clinical rehabilitation. We developed a proprioceptive neuromuscular facilitation (PNF) integrated robotic ankle-foot system for post stroke rehabilitation.It is the first time that PNF method has been used in ankle spasticity/contracture rehabilitation.Five able-bodied subjects participated in the experiments and five stroke patients were recruited with a six-week PNF treatment.The proposed system can offer more effective treatment than passive stretching in improvement of both passive and active joint properties.

BioKEX: A bionic knee exoskeleton with proxy-based sliding mode control

In this paper, we present a powered bionic knee exoskeleton aiming at physical assistance and rehabilitation. The mechanical structure of the knee exoskeleton is based on anthropomorphic design, the tibia rolling or sliding on the femur during joint movements. In addition, a proxy-based sliding mode controller is used to improve the safety of the wearable device. Preliminary experimental results on trajectory tracking and dynamic response verify the feasibility of the proposed knee exoskeleton.

Robot-Assisted Rehabilitation of Ankle Plantar Flexors Spasticity: A 3-Month Study with Proprioceptive Neuromuscular Facilitation

In this paper, we aim to investigate the effect of proprioceptive neuromuscular facilitation (PNF)-based rehabilitation for ankle plantar flexors spasticity by using a Robotic Ankle–foot Rehabilitation System (RARS). A modified robot-assisted system was proposed, and seven poststroke patients with hemiplegic spastic ankles participated in a 3-month robotic PNF training. Their impaired sides were used as the experimental group, while their unimpaired sides as the control group. A robotic intervention for the experimental group started from a 2-min passive stretching to warming-up or relaxing the soleus and gastrocnemius muscles and also ended with the same one. Then a PNF training session including 30 trials was activated between them. The rehabilitation trainings were carried out three times a week as an addition to their regular rehabilitation exercise. Passive range of motion, resistance torque, and stiffness were measured in both ankles before and after the interventions. The changes in Achilles tendon length, walking speed, and lower limb function were also evaluated by the same physician or physiotherapist for each participant. Biomechanical measurements before interventions showed significant difference between the experimental group and the control group due to ankle spasticity. For the control group, there was no significant difference in the 3 months with no robotic intervention. But for the experimental group, passive dorsiflexion range of motion increased (p < 0.01), resistance torque under different dorsiflexion angle levels (0°, 10°, and 20°) decreased (p < 0.05, p < 0.001, and p < 0.001, respectively), and quasi-static stiffness under different dorsiflexion angle levels (0°, 10°, and 20°) also decreased (p < 0.01, p < 0.001, and p < 0.001, respectively). Achilles’s tendon length shortened (p < 0.01), while its thickness showed no significant change (p > 0.05). The robotic rehabilitation also improved the muscle strength (p < 0.01) and muscle control performance (p < 0.001). In addition, improvements were observed in clinical and functional measurements, such as Timed Up-and-Go (p < 0.05), normal walking speed (p > 0.05), and fast walking speed (p < 0.05). These results indicated that the PNF-based robotic intervention could significantly alleviate lower limb spasticity and improve the motor function in chronic stroke participant. The robotic system could potentially be used as an effective tool in poststroke rehabilitation training.

Proxy-based sliding mode control of a robotic ankle-foot system for post-stroke rehabilitation

Robotic platform-based ankle–foot rehabilitation systems have been proved effective in treating joint spasticity and/or contracture of stroke survivors. However, simple force or velocity limiters are not adequate, since they cannot explicitly guarantee slow and overdamped motions without overshoot. In this paper, we propose a proxy-based sliding mode control (PSMC)-based approach, to avoid unsafe behaviors of a robotic ankle–foot rehabilitation system. The proposed method has three advantages: (1) without deteriorating tracking performance during normal operation, it guarantees overdamped, slow, and safe recoveries after abnormal events; (2) it provides a simple and accurate way to confine the output torque exerted on the subject’s ankle; (3) though effective, the control law avoids the necessity to identify the specific system model or build state observer, which is usually difficult for human–robot interaction system. A 71-year-old stroke patient and 10 able-bodied subjects were recruited for the experiments. Preliminary studies comparing PSMC and PID are performed on trajectory tracking, controlled torque output, slow and safe response under disturbance. Additionally, by fulfilling the rehabilitation method and obtaining biomechanical indicators, the proposed controller is proved to be feasible for the system. Graphical Abstract

On the design of a robot-assisted rehabilitation system for ankle joint with contracture and/or spasticity based on proprioceptive neuromuscular facilitation

Ankle joint with contracture and/or spasticity can severely disable the mobility and the independence of stroke survivors. Robot-assisted rehabilitation has been proposed to support physicians in providing effective therapies. In this paper, we propose a robot-assisted ankle rehabilitation system integrated with human-computer interaction interface and acquisition of Electromyography signals, joint torque and joint angle. Furthermore, we investigate the effects of proprioceptive neuromuscular facilitation (PNF) rehabilitation method applied in our robotic system. The proposed robot-assisted system has been used in real experiments and provides PNF rehabilitation to five stroke patients for six weeks. Preliminary experimental results suggest that PNF is effective in increasing ankle range of motion(ROM), decreasing ankle resistance torque, and alleviating joint stiffness.

Changes of Achilles tendon properties via 12-week PNF based robotic rehabilitation of ankle joints with spasticity and/or contracture

Ankle joint with spasticity and/or contracture can severely affect mobility and independence of stroke survivors. Due to that, the Achilles tendon(AT) is affected. In this paper, we aim to study changes of AT properties via proprioceptive neuromuscular facilitation (PNF) treatment. A robotic ankle-foot rehabilitation system has been proposed, which consists of a robotic ankle-foot platform and a graphic user interface. In this pilot study, two post-stroke patients participated and carried out a 12-week PNF treatment with the robotic system. The treatment is evaluated quantitatively in AT properties. The evaluation shows that after the PNF treatment, the average decrease of AT length is 4.1 mm (6.5%) and the recovery ratio is 30.4%, while the thickness has no change. The results indicate that the PNF based robotic rehabilitation for ankle joints with spasticity and/or contracture is effective to improve the ankle spasticity/contracture.

Multi-class SVM Based Real-Time Recognition of Sit-to-Stand and Stand-to-Sit Transitions for a Bionic Knee Exoskeleton in Transparent Mode

Real-time locomotion intent recognition is a challenge in lower-limb exoskeletons. In this paper, we present a multi-sensor based locomotion intent prediction system for sit-to-stand and stand-to-sit transition recognition the subject wears a knee exoskeleton in transparent mode. The desired reference torque for movement control is obtained from a direct torque control loop. The feedback torque is estimated by an inner current control loop. Five able-bodied subjects were recruited in experiments. The classifier is based on multi-class Support Vector Machine. Four kinds of modes and four kinds of transitions are tested in this study. Recognition accuracy during steady periods is 99.68% ± 0.07% for five able-bodied subjects. And during transition periods, all the transitions are correctly detected and no missed detections was observed for all the trials of the five subjects. Preliminary experimental results show that the proposed method is capable of performing real-time intent recognition and consequently reduces the interaction force between human body and the exoskeleton.

Range-of-motion measurement with therapist-joined method for robot-assisted ankle stretching

Abstract The range of motion (ROM) measurement is an important issue in a robot-assisted ankle–foot rehabilitation. This study presents a therapist-joined method to improve the ROM measurement accuracy of a robotic ankle–foot rehabilitation system by combining therapist-joined zero-torque control and proxy-based sliding mode control. The zero-torque control is applied when measuring the subject’s range of motion to obtain its extreme joint angle and largest resistance torque. Moreover, a controller switch is applied to ensure that the extreme joint angle is appropriate. Comparative studies between the ROM measurement using a protractor and the proposed method are then performed, comparing the ankle resistance torque variations during stretching under different ROM-measuring results. Ten able-bodied subjects are recruited for this experiment. The results show that the proposed method is feasible in improving the measured ROM accuracy. In addition, a more accurate ROM leads to a larger improvement of the ankle stiffness.

Recognizing Sit-Stand and Stand-Sit Transitions for a Bionic Knee Exoskeleton

Sit-to-stand and stand-to-sit transitions (STS), as one of the most demanding functional task in daily life, are affected by aging or stroke and other neurological injuries. Lower-limb exoskeletons can provide extra assistance for affected limbs to recover functional activities [1]. Several studies presented locomotion mode recognition of sitting, standing and STS, or only STS, or static modes [2–6]. They are based on fusing information of the mechanical sensors worn on the human body, e.g. inertial measurement unit (IMU) [2–4], plantar pressure force [5], barometric pressure[2], EMG [6]. However, most of them put sensors on the human body and did not show experiments integrated with exoskeletons. Since the physical interaction between the exoskeleton and human body, the recognition method might be different when wearing a real exoskeleton.To deal with these problems, in this study we proposed a recognition method about STS based on the multi-sensor fusion information of interior sensors of a light-weight bionic knee exoskeleton (BioKEX). A simple classifier based on Support Vector Machine (SVM) was used considering the computational cost of the processing unit in exoskeleton.Copyright

Improving the safety of ankle-foot rehabilitation system with hybrid control

The safety is an important issue in robot-assisted rehabilitation systems. In this paper, we present a therapist-joined hybrid control method to improve the safety of a robotic ankle-foot system for post stroke rehabilitation, combining therapist-joined zero torque control and proxy-based sliding mode control in the continuous passive motion based rehabilitation. The zero torque control is applied when measuring the range of motion of the subject to obtain its extreme joint angle and largest resistance torque. According to these data, a subject-suited position controller of proxy-based sliding mode control can be specified to implement passive stretching, with desired trajectory designed and torque output limited for the subject individually. Experiments were performed to demonstrate the feasibility of the proposed method on improving safety.