Recent advances in wearable actuated ankle-foot orthoses: Medical effects, design, and control

This paper presents a survey on recent advances of wearable actuated ankle-foot orthoses (AAFOs). First of all, their medical functions are investigated. From the short-term aspect, they lead to rectification of pathological gaits, reduction of metabolic cost, and improvement of gait performance. After AAFO-based walking training with sufficient time, free walking performance can be enhanced. Then, key design factors are studied. First, primary design parameters are investigated. Second, common actuators are analysed. Third, human-robot interaction (HRI), ergonomics, safety, and application places, are considered. In the following section, control technologies are reviewed from the aspects of rehabilitation stages, gait feature quantities, and controller characteristics. Finally, existing problems are discussed; development trends are prospected.

Mechanism and Effect of Tread Swing for Lower Limbs Strength Training Device

The aim of this study was to propose a tread swing mechanism for lower-limb strength training devices and to confirm its effects. In the standing position and for training the lower limbs, if the tread-surface angle is inappropriate, the posture of the knee joints gets affected, and knee adduction/valgus moments, which result in knee stress, get generated. The target training exercises are the front-back leg scissors and open-close leg triangle exercises. With regard to the swing of the tread, it is necessary to realize a pitch/yaw rotation and a roll/yaw rotation for the former and the latter exercises, respectively. As a result, knee joint stress can be reduced by moving the center of pressure (COP). The proposed mechanism has a further differential mechanism that utilizes the difference between the pulley diameters. The translational movement force of the tread is transmitted as the torque of the swing motion for the pitch, roll, and yaw through the effects of a differential mechanism. The rate of the swing angle can be changed by adjusting the pulley diameter. As a result of evaluating the effect of exercises using a manufactured device, it was confirmed that the tread performed a predetermined swing motion. It was also confirmed that the COP position changed. Therefore, it is expected that knee joint stress will reduce. Rehabilitation and strength training that result in small knee joint stresses and generate large muscle load are in great demand for people experiencing knee joint failure.

Training to Improve the Landing of an Uninjured Leg in Crutch Walk Using AR Technology to Present an Obstacle

A patient who unexpectedly sustains a lower leg injury often uses crutches for walking, to both assist the patient and prevent further injury until a full recovery is made. In this study, a novel crutch walk training system was developed; a head-mounted display (HMD) was introduced to present a virtual obstacle for trainees using crutches. Through repetitions of the training, it was expected that the trainees would improve their overall body stability. Healthy subjects participated in experimental training exercises using the developed training system. As a result, the participants acquired the skill of walking well with crutches without losing their body balance significantly, even in the event of facing a virtual obstacle, during the five training sessions.

Ankle Joint Stretching Device Using Tension Rod for Self Rehabilitation

This paper proposed an ankle joint stretching device that is intended for self-rehabilitation by using a tension rod structure. Physical therapists treat their patients to prevent a subject ankle joint’s contracture and improve walking function. Still a sufficient rehabilitation therapy cannot be done due to demand for a labor-task of the ankle joint rehabilitation. There is a demand for the self-rehabilitation system long time to reduce the labor task, and especially it can be installed easily in a chair or bed in a patient home. By using a pantograph jack and spring casters, the developed device does not depend on installation location. It does not need a transfer assist process to the rehabilitation machine, which causes back pain of caregivers, and it allows for a self-rehabilitation of an ankle joint stretching. The experiment confirmed that the positional relationship was stabilized between the rotation axis of the device and the ankle joint position within (σx,σy)=(2.4, 2.5) mm during ankle dorsiflexion stretching in a fixed state of the device, which was realized by the pantograph jack and spring casters. Our proposed system that does not need transfer assistance before/after treatment will lead to self-rehabilitation for the ankle joint.

Development of a Rehabilitation and Training Device Considering the Ankle Degree of Freedom

While the number of people who need rehabilitation has been increasing because of the aging population, there are only a limited number of physical therapists engaged in rehabilitation, making it difficult to perform rehabilitation at a sufficient level. In this situation, various devices have been developed to replace physical therapists. However, no rehabilitation devices that can respond to the complicated degrees of freedom of an ankle joint complex (AJC) are commercially available. In the present study, we developed an AJC rehabilitation device using a Stewart platform parallel link mechanism. Using the device, we aim to measure and control the AJC with six degrees of freedom so that complicated composite motions of the AJC can be realized. To evaluate the device’s usefulness, we investigated how the composite motion generated by moving the AJC along the trajectory the device reproduced could influence a crural muscle. Muscular activities of the anterior tibial, soleus, and gastrocnemius muscles, generated by a composite motion of plantar flexion and inversion, had a similar feature to those generated by plantar flexion. However, the muscular activity of the peroneus longus muscle generated in the composite motion was significantly different from that generated only in plantar flexion. In the composite motion of plantar flexion and inversion, based on the knowledge that activity to develop only back muscles while suppressing muscular activities of the anterior tibial and peroneus longus muscles is possible. Based on the knowledge, the device was used to perform isokinetic contraction for evaluating the device’s usefulness for muscular training. We found a difference between the combination of active muscles during the composite motion and that during plantar flexion. A load can be applied to different muscles depending on the composite motion, which indicates that the device can be suitable for rehabilitation or training with high degrees of freedom.

One-DOF Wire-Driven Robot Assisting Both Hip and Knee Flexion Motion

Gait assistance robots are used to improve gait performance ability or perform gait motion with an assistance for several articular motions. The sparing use of a gait assistance robot to decrease the duration of the robot’s assistance is important for keeping the ability to perform a movement when the robot assists walking. In previous research, methods of ensuring a compliance mechanism and control method have been studied, and assistance for articular motions has been conducted independently using actuators corresponding to each articular motion. In this paper, we propose a wire-driven gait assistance robot to aid both hip and knee articular flexion motions by applying just one force to assist motion in the swing phase. We focused on a force that assists hip and knee flexion motion, and designed a robot with a compensation mechanism for the wire length. We used an assistance timing detection method for the robot, conducting tensile force control based on information from the hip, knee, and ankle angles. We carried out an experiment to investigate the controlled performance of the proposed robot and the effect on hip and knee angular velocity. We confirmed that the proposed robotic system can aid both hip and knee articular motion with just one force application.

Development of Upper-Limb Power Assist Machine Using Linkage Mechanism – Drive Mechanism and its Applications –

This paper proposes an upper-limb power assist machine driven by a single actuator to reduce the weight and cost. This assist machine is used to support the shoulder and elbow movements for viticulture operations, and upper-limb holding for load transport tasks. This assist machine consists of an arm part and a mounting part. The arm part is composed of a parallel link mechanism, which is driven by an actuator and a trapezoidal feed screw. To realize a natural upper-limb motion, the length of the arm part was designed based on the human upper-limb motion. The assist machine is controlled based on the user’s intention by applying bend sensors attached to the input device. By measuring the electromyography signal of five muscles, the effectiveness of the proposed upper-limb power assist machine was verified experimentally.

Experimental Study of Ankle Joint Pushing Mechanism Concerning About the Horizontal Movement of Talus

[abstFig src='/00290002/03.jpg' width='300' text='Proposed ankle joint pushing mechanism for the movement of the talus' ] An ankle joint pushing system that absorbs the horizontal movement of the talus is proposed, and the effects of the horizontal movement absorbing mechanism in the system are examined. The bending of the ankle joint is an important medical treatment that physical therapists (PTs) utilize to help their patients recover their ability to walk and to prevent contracture. However, since the ankle treatment requires a large amount of force (nearly equal to the subject’s weight) plus precise angle and power control, manual treatment by PTs has not been replaced by mechanical treatment systems. In order to realize the mechanization of the ankle joint pushing treatment, the system developed here uses two features. (1) The proposed device fixes the ankle joint position correctly by making contact with the Achilles tendon, the back of the calf, and the hip. (2) The bucket rotation center shifts its position horizontally with the movement of the talus when the foot is pushed back. This mechanism can push the toes or any part of the foot strongly and stably without causing the patient any pain. It can also stretch the biceps femoris and gastrocnemius muscles simultaneously, which could previously only be done by a physical therapist. During 73 N stretching treatment tests done on four subjects, 22.2 mm (S.D. 6.4 mm) horizontal (ventral direction) movements of the ankle joint were observed due to the movement of the talus, and our proposed device mechanism successfully suppressed the movement to a 1.8 mm (S.D. 1.3 mm) horizontal (ventral) movement in the same 73 N stretching treatment.