Synchronized Tactile Stimulation on Upper Limbs Using a Wearable Robot for Gait Assistance in Patients With Parkinson's Disease.

This study aimed to investigate whether using a wearable robot applying interactive rhythmic stimulation on the upper limbs of patients with Parkinson's disease (PD) could affect their gait. The wearable robot presented tactile stimuli on the patients' upper limbs, which was mutually synchronized with the swing of their upper limbs. We conducted an evaluation experiment with PD patients (n = 30, Modified Hoehn-Yahr = 1-3, on-state) to investigate the assistance effect by the robot and the immediate after-effect of intervention. The participants were instructed to walk 30 m under four different conditions: (1) not wearing the robot before the intervention (Pre-condition), (2) wearing the robot without the rhythm assistance (RwoA condition), (3) wearing the robot with rhythm assistance (RwA condition), and (4) not wearing the robot immediately after the intervention (Post-condition). These conditions were conducted in this order over a single day. The third condition was performed three times and the others, once. The arm swing amplitude, stride length, and velocity were increased in the RwA condition compared to the RwoA condition. The coefficient of variance (CV) of the stride duration was decreased in the RwA condition compared to the RwoA condition. These results revealed that the assistance by the robot increased the gait performance of PD patients. In addition, the stride length and velocity were increased and the stride duration CV was decreased in the Post-condition compared to the Pre-condition. These results show that the effect of robot assistance on the patient's gait remained immediately after the intervention. These findings suggest that synchronized rhythmic stimulation on the upper limbs could influence the gait of PD patients and that the robot may assist with gait rehabilitation in these patients.

Gait-Assist Wearable Robot Using Interactive Rhythmic Stimulation to the Upper Limbs.

Many power-assist wearable exoskeletons have been developed to provide walking support and gait rehabilitation for elderly subjects and gait-disorder patients. Most designers have focused on a direct power-assist to the wearer's lower limbs. However, gait is a coordinated rhythmic movement of four limbs controlled intrinsically by central pattern generators, with the upper limbs playing an important role in walking. Maintaining a normal gait can become difficult as a person ages, because of decreases in limb coordination, stride length, and gait speed. It is known that coordination mechanisms can be governed by the principle of mutual entrainment, in which synchronization develops through the interaction between nonlinear phase oscillators in biological systems. This principle led us to hypothesize that interactive rhythmic stimulation to upper-limb movements might compensate for the age-related decline in coordination, thereby improving the gait in the elderly. To investigate this hypothesis, we developed a gait-assist wearable exoskeleton that employs interactive rhythmic stimulation to the upper limbs. In particular, we investigated the effects on spatial (i.e., hip-swing amplitude) and temporal (i.e., hip-swing period) gait parameters by conducting walking experiments with 12 healthy elderly subjects under one control condition and five upper-limb-assist conditions, where the output motor torque was applied at five different upper-limb swing positions. The results showed a statistically significant increase in the mean hip-swing amplitude, with a mean increment of about 7% between the control and upper-limb-assist conditions. They also showed a statistically significant decrease in the mean hip-swing period, with a mean decrement of about 2.3% between the control and one of the upper-limb-assist conditions. Although the increase in the hip-swing amplitude and the decrease in the hip-swing period were both small, the results indicate the possibility that interactive rhythmic stimulation to the upper limbs might have a positive effect on the gait of the elderly.

Intuitive operability evaluation of surgical robot using brain activity measurement to determine immersive reality.

Surgical robots have improved considerably in recent years, but intuitive operability, which represents user inter-operability, has not been quantitatively evaluated. Therefore, for design of a robot with intuitive operability, we propose a method to measure brain activity to determine intuitive operability. The objective of this paper is to determine the master configuration against the monitor that allows users to perceive the manipulator as part of their own body. We assume that the master configuration produces an immersive reality experience for the user of putting his own arm into the monitor. In our experiments, as subjects controlled the hand controller to position the tip of the virtual slave manipulator on a target in a surgical simulator, we measured brain activity through brain-imaging devices. We performed our experiments for a variety of master manipulator configurations with the monitor position fixed. For all test subjects, we found that brain activity was stimulated significantly when the master manipulator was located behind the monitor. We conclude that this master configuration produces immersive reality through the body image, which is related to visual and somatic sense feedback.

Analysis of EMG signals of patients with essential tremor focusing on the change of tremor frequency.

Essential tremor is a disorder that causes involuntary oscillations in patients while engaging in actions or while maintaining a posture. ET patients have serious difficulties in performing activities of daily living such as eating food, drinking water, and writing. We have thus been developing an EMG-controlled exoskeletal robot to suppress tremors. The EMG signal of ET patients involves a mix of voluntary movement and tremor signals. To control the exoskeletal robot accurately, tremor signals must be removed from the patient's EMG signal. To date, we have been developing a filter to remove tremor signals from the patient's EMG. The design of this filter was based on the hypothesis that the rectified tremor signals are able to be approximated by a powered sine wave. This filter was found to have a large effect on removing tremor signals. However, tremor signals are generated both while performing voluntary movement and while maintaining a posture, and the filter was attenuating both signals. To control this robot accurately, the signal generated while performing voluntary movement is expected not to be attenuated. To accomplish this, we try to use a parameter that reflects a state of the patient's movement, performing a voluntary movement or maintaining a posture, as a switch to activate the powered sine filter. This paper provides an analysis of the favorable parameters. We focus on two parameters: the peak-to-peak interval of the rectified EMG signal, and the interval of the flat and low amplitude area of the rectified EMG signal. Through evaluation, it is affirmed that both parameters change with the state of the patient's movement. However, the latter parameter is superior to the former in terms of variability, which indicates that the interval of the flat and low amplitude area of the rectified EMG signal is a more favorable parameter to promote control of the exoskeletal robot. As a future work, we will mount the parameter to the algorithm and evaluate the robotic system.

Filtering essential tremor noise on surface EMG based on squared sine wave approximation.

Essential Tremor (ET) refers to involuntary movements of a part of the body. ET patients have serious difficulties in performing daily living activities. Our ultimate goal is to develop a system that can enable ET patients to perform daily living activities. We have been developing an exoskeleton robot for ET patients. We make use of the electromyogram (EMG) signal to control this robot. However, the EMG signal of ET patients contains not only signals from voluntary movements but also noise from involuntary tremors. In this paper, we focus on developing a signal processing method to suppress tremor noise present in the surface EMG signal. The proposed filter detected attenuation ratio by the correlation between the last EMG data and one period squared sine wave. The filtered EMG signals indicated that essential tremor noise of the elbow flexed posture while holding a water-filled bottle was suppressed. In addition, voluntary information was less affected by the filter. Welch's t-value test confirmed that ease of extraction of voluntary movement was increased by the proposed filter.

Subtle grip force estimation from EMG and muscle stiffness--relationship between muscle character frequency and grip force.

A number of upper limb amputees experience difficulty in picking up a food bowl during a meal, because grip force estimation using EMG currently does not provide sufficient accuracy for this task. In this paper, we propose a grip force estimation system that allows amputees to pick up a bowl with a prosthetic hand by using the properties of muscle stiffness in addition to EMG. We have chosen a tray holding task to evaluate the proposed system. A weight is dropped on the tray and the subjects are expected to control the tray's attitude during the task. Actual grip force, EMG, and muscle stiffness are measured, and the actual measured grip force is compared with the estimated grip force for evaluation. As a result, the proposed algorithm is found to be able to estimate grip force with an error of just 18[N], which is 30% smaller than in the method that uses only EMG. From the result that the response time estimated by proposed system is even less than a human's mechanical reaction time, the effectiveness of the proposed method has been validated.

Modeling the internal pressure dependence of thermal conductivity and in vitro temperature measurement for lung RFA.

Radio frequency ablation (RFA) for lung cancer has increasingly been used over the past few years because RFA is minimally invasive treatment for patients. As a feature of RFA for the lung cancer, lung has the air having low thermal conductivity. Therefore, RFA for lung has the advantage that only the tumor is coagulated because heating area is confined to the immediate vicinity of the heating point. However, it is difficult for operators to control the precise formation of coagulation zones due to inadequate imaging modalities. We propose a method using numerical simulation to analyze the temperature distribution of the organ in order to overcome the current deficiencies. Creating an accurate thermophysical model was a challenging problem because of the complexities of the thermophysical properties of the organ. In this work, as the processes in the development of ablation simulator, measurement of the pressure dependence of lung thermal conductivity and in vitro estimation of the temperature distribution during RFA is presented.