Takehiro Iwami

Hybrid Control of Powered Orthosis and Functional Neuromuscular Stimulation for Restoring Gait

The restoration of motor functions of patients with spinal cord injury (SCI) is one of important subjects for study. For this purpose, methods of functional neuromuscular stimulation (FNS) have been investigated in medical science and practice during these three decades. However, we have not achieved complete restoration of motor functions in SCI patients. On the other hand, we have achieved useful devices in human-scaled transportation by using power assist technology. Thus, applying power assist technology to the problem of restoring motor functions is one of possible solutions and sounds practical. In this paper, we propose a new hybrid system to combine power assist technology and FNS for restoring motor functions of lower extremity in SCI patients. Both powered orthosis and FNS are used to generate and control the joints moments of lower extremity in the proposed hybrid system. The main role of powered orthosis Vs is to compensate the joints moments generated by FNS and to enhance the controllability of FNS with the actuators. The proposed hybrid control system has been experimentally evaluated in gait motions by measuring the angle trajectories and generated moments around the knee and hip joints in the cases when only actuators are used and both FNS and actuators of the orthosis are used. The results prove that the control method for the hybrid system is useful to restore motor functions of lower extremity in SCI patients.

Development of a new adaptation system for a manual wheelchair based on human body function

In this paper, we propose a new adaptation system for a manual wheelchair to reduce the load on the upper extremity of the user during wheelchair manipulation and also to increase the efficiency of the wheelchair propulsion. The proposed adaptation system is designed to provide optimal position of the handrim and the desired angular position of seat and backrest of the wheelchair based on the users body function. Electromyogram signals from the user muscles, heart rate signals, oxygen uptake, amount of applied pressure on the seat and backrest, force/moment applied on the handrim, joint force/moment of the upper extremity and analytical results using the dynamic manipulating force ellipsoid and the driving force contribution figure are used as index parameters for the proposed adaptation system.

Development of FES-Rowing Machine

As per present social needs, assisting machines are very much needed for persons of advanced age. We analyzed and developed a fitness apparatus suitable for meeting the requirement of elderly people. The proposed apparatus consists of a rowing machine and Functional Electrical Stimulation (FES), that can be used to exercise every muscle of a person of advanced age. The rowing mechanism was actually developed to train rowers and can train the legs and upper body parts most effectively. Move over FES can assist the exercise of the legs by using surface electrical stimulation. An experiment was conducted and the results prove that the developed apparatus can train the muscles of the person of advanced age effectively and can compensate exercise shortage.

Evaluation of utility of the “Arm-Balancer” arm support system

As modern society becomes increasingly more elderly, developing specialized equipment to help assist this growing population in everyday tasks becomes more and more important. Here we have developed a passive gravity balanced arm support system called the “Arm-Balancer”. It was designed to assist the arm motion of elderly people with disabilities. The objective of this study is to determine the utility of the “Arm-Balancer”. We will evaluate the effect of this device on the arm muscle tension of the user. The “Arm-Balancer” is supported by a gas spring to eliminate gravity and may be attached to a chair, a bed or used on the floor when attached to the “Tatami Mat” seat. The “Arm-Balancer” consists of a two-segment exoskeleton designed for the users upper arm and forearm. The links are made from stainless steel rods whose lengths are designed to parallel the lengths of the users upper arm and forearm. The upper arm segment is telescopic so the length can be adjusted to the size of the users. Driving the evaluation we determined that the “Arm Balancer” had an assistive force of 10N to the arm and 5N to the wrist. Some elderly people with disabilities were receptive to the “Arm Balancer” while others were ambivalent.

A new method for identifying rigid link models of lower limbs

A new method for identifying rigid link models of human lower limbs has been proposed in this paper. The method was motivated by necessity of simulating human body movements for rehabilitation or for design of assistive devices. The method is based on combination of random search and least squares estimation techniques. Simulation and experimental results are given to illustrate the effectiveness of the proposed method.

A new method for identifying rigid link model of lower limb

A new method for identifying rigid link models of human lower limbs has been proposed in this paper. The method was motivated by necessity of simulating human body movements for rehabilitation or for design of assistive devices. The method is based on combination of random search and least squares estimation techniques. Simulation and experimental results are given to illustrate the effectiveness of the proposed method.

Vertex Search Algorithm of Convex Polyhedron Representing Upper Limb Manipulation Ability

In the evaluation of robot manipulator, all possible velocities, accelerations, and forces at the end-effector can be represented as a polyhedra using the concept of manipulability (Yoshikawa, 1990). This evaluation method, which is commonly used in the field of robotics, provides effective knowledge for evaluation of the manipulability of upper and lower limbs considering both the kinematics and dynamics of the system (Sasaki et al., 2008, 2010). The manipulability of the upper and lower limbs in three-dimensional task space is expressed as an invisible six-dimensional polytope. For such evaluation, a slack variable is generally introduced in order to search for the vertex of the polytope (Shim & Yoon, 1997; Chiacchio et al., 1997; Lee, 2001). However, it is extremely difficult to search for the region of a higher-dimensional polytope accurately using conventional methods because of their huge computational complexity, and it is also difficult to formulate an objective function in the case of linear programming. In this chapter, we present a manipulating force polytope reflecting an individual’s joint torque characteristics as a new evaluation method for assessing the manipulability of an upper limb. We also present a visualization algorithm and a vertex search algorithm for a higher-dimensional polytope based on the geometric characteristic of joint torque space. The effectiveness of the method proposed for quantitative evaluation of the individual’s manipulability of the upper limb is confirmed through the presented experimental result.

Trunk Balance Evaluation in Adolescent Athletes and Gender Difference using the Dynamic Sitting Balance Device

Objective: The purpose of this study was to quantitatively measure the trunk stability of adolescent athletes using a recently developed, plane-specific, dynamic trunk stability measuring device and to examine gender differences. Methods: This was a cross-sectional study to confirm the difference in dynamic trunk stability between male and female adolescent athletes ranging in age from 12 to 15 years. 15 adolescent athlete cohort was divided into 2 groups by gender. In the dynamic trunk balance evaluator that we developed, the seating surface can be vibrated at a constant cycle (0.2 Hz, 0.4 Hz, 0.6 Hz), the pressure of the seating surface under vibration is detected by three small force sensors installed under the seating surface, and the center of pressure (COP) can be calculated. Measurements were performed for 30 s by one examiner, and each participant was measured three times after two practice attempts. While the seating surface was swaying, the participants gaze was fixed to a mark about 1 cm in diameter set at a position 2 m in front of the participant at eye height, and the participant was asked to maintain the position of the head constant. The fluctuation of the center of gravity on the seat surface over time was measured, and the total trajectory length of the COP was used as the evaluation item. Results: There were no adverse events during measurement. The results for the total COP trajectory length of male was 2365 ± 176 mm, and that of female was 2674 ± 293 mm. There were significant differences between the male and female groups. In particular, Adolescent female athletes had less dynamic trunk stability in the coronal plane. Conclusion: Adolescent female athletes had less dynamic trunk stability in the coronal plane than their male counterparts. The recently developed device may be a useful tool for assessing the effects of prevention programs on dynamic core stability.

Measurement of Immediate Effect by Therapeutic Electrical Stimulation Using a New Desktop Rehabilitation Robot

Objective: More frequent use of robot technology in the field of rehabilitation is driving the need for smaller, less cumbersome devices. The objectives of the present study were to evaluate and compare quantitatively the upper limb function of chronic stroke patients before and after therapeutic electrical stimulation using a newly developed rehabilitation robot. Methods: Five stroke patients (3 men, 2 women; mean age: 66.4 ± 9.6 years; time since stroke: 36.0 ± 52.9 months) in the sub-acute and chronic phase of stroke-induced hemiplegia (induced by cerebral hemorrhage in four and by cerebral infarction in one; Brunnstrom stages III-V) participated in the study. None of them had any secondary motor neuron dysfunction or unstable disease control. Before and after 15 min of therapeutic electrical stimulation for repeated finger flexion and extension, participants performed reaching movements while moving the rehabilitation robot with their affected hand. Assessment parameters included Maximum swerve, Average speed, and smoothness of movements, as calculated by Jerk cost X (right-left direction) and Jerk cost Y (forward-backward direction). Results: All patients were able to use the rehabilitation robot to perform the reaching movements. Clear differences were observed before and after therapeutic electrical stimulation for Maximum swerve and Average speed in the X direction, and there was a tendency for Jerk cost X to differ before and after therapeutic electrical stimulation. In contrast, there were no significant differences in either Jerk cost Y or Average speed in the Y direction before and after the stimulation. Conclusion: The immediate effects of therapeutic electrical stimulation in chronic stroke patients can be quantified using our newly developed rehabilitation robot. Successful quantification of the effects of therapeutic electrical stimulation in stroke patients using smaller robotic systems could revolutionize the rehabilitation of these and other patients suffering from motor dysfunction or paralysis.

A Study of the Reliability of a New Dynamic Trunk Balance Measuring Device

Objective: A new method of evaluating sitting balance that improved on a previous device was developed. However, the reliability of body trunk balance measured by this device is unknown. The purpose of this study was to verify its reliability within and between examiners. Methods: This was a cross-sectional study involving healthy adult males (age 20 to 45 years) who were able to walk. The seating surface could be vibrated at a constant cycle (0.2 Hz, 0.4 Hz, 0.6 Hz), the pressure of the seating surface under vibration was detected by three small force sensors installed under the seating surface, and the center of pressure (COP) could be calculated. Measurements were performed by two examiners, and each participant was measured three times in a sitting position. The platform was tilted to the left and right at a front face inclination angle ± 7°, with two cycles in 10 s (0.2 Hz), while the participant’s gaze was fixed to a mark 2 m in front of the participant at eye height, and the participant was asked to maintain the position of the head constant. Measurement was then performed for 30 s. The fluctuation of the center of gravity on the seat surface over time was measured, and the total trajectory length of the COP was used as the evaluation item. To examine the reliability of the measuring instrument, ICC (1.3) was obtained as the intra-class correlation coefficient for intra-examiner reliability, and ICC (2.1) was obtained for inter-examiner reliability. Results: The ICC for intra-examiner reliability was 0.815, and that for inter-examiner reliability was 0.789. No adverse events occurred during balance evaluation. Conclusion: This device could be used to evaluate dynamic trunk balance with relatively high reliability. Thus, the present device appears to be useful for quantitatively evaluating dynamic trunk balance conveniently and safely.