Stroke may lead to considerable physical impairment and functional disability, which affects walking ability. As a potential way to assist gaits, lower limb exoskeletons have been developed. To supply appropriate assistive torque, real-time accurate recognition of current gait mode is important. In this article, a hierarchical control system was proposed to recognize locomotion modes in real time for a unilateral knee exoskeleton on different terrains with specific assistive control strategies. Support vector machine classifier was used to recognize the locomotion mode based on two inertia measurement units. The corresponding assistive control strategy was designed according to the recognition result. Real-time recognition experiments under assistive torque control were conducted on five able-bodied subjects and one stroke patient, respectively. For the able-bodied subjects: first, no significance was found on the total recognition accuracies whichever the leading leg was for the five subjects ( p = 0.057 ), which indicated the proposed method in this article was suitable whichever the leading leg was as far as the overall classification accuracy was concerned. Second, transitions occurred in swing phase when the leading leg was the paretic leg and transitions occurred in stance phase when the leading leg was the sound leg. No significance was found on mean delay time for the five subjects ( p = 0.785 ) whichever the leading leg was, which indicated that the proposed method in this article was suitable for these two leading legs as far as the mean delay time were concerned. Third, the method of generating the assistance based on the previous gait cycle time was demonstrated to be reasonable and the tracking performance of the torque could meet the requirement. For the stroke patient, similar experimental results were obtained.

Real-Time Locomotion Mode Recognition and Assistive Torque Control for Unilateral Knee Exoskeleton on Different Terrains

This article introduces a passive four-degree-of-freedom foot interface to control a robotic surgical instrument. This interface is based on a parallel–serial hybrid mechanism with springs and force sensors. In contrast to existing switch-based interfaces that can command a slave robot arm at constant speed in only discrete directions, the novel interface provides an operator with intuitive control in continuous directions and speed with force and position feedback. The output command of the interface was initially derived based on the kinematics and statics of the interface. Since distinct movement patterns among different subjects were observed in a pilot test, a data-driven approach using independent component analysis was developed to convert the foot inputs to the control commands of the user. The capability of this interface in controlling a robotic arm in multiple degrees of freedom was further verified with a teleoperation test.

A Subject-Specific Four-Degree-of-Freedom Foot Interface to Control a Surgical Robot

This study proposes a novel standing mobility device aimed at supporting and assisting people with disabled lower limbs. The developed mobility device is capable of assisting voluntary postural transition between standing and sitting by a passive exoskeleton equipped with gas springs, in addition to providing wheeled locomotion in a standing posture using two in-wheel motors. The device allows voluntary natural assisted sit-to-stand motions. Furthermore, it can be operated in the standing posture without using hands. This paper describes the development and assessment of the standing mobility device as well as a pilot study conducted with a person with spinal cord injury. Then, investigation of the mechanical characteristics of the device is presented for further analysis of sit-to-stand and stand-to-sit transfer assistance.

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Standing Mobility Device With Passive Lower Limb Exoskeleton for Upright Locomotion

In this paper, we propose the design of an exoskeleton with support at the knee joint and lower torso for sit-to-stand and stand-to-sit (STS) posture transitions; devised for users with spinal cord injury and other complete lower-body impairments. The STS transitions assistance is achieved through a power transfer mechanism that synchronizes knees and lumbar motion through a cable-driven pulley system. We analyze the human body dynamics in the posture transition with a rigid link model and the interaction interface with the exoskeleton through an impedance model for producing a passive system voluntarily controlled by natural motions of the upper body. Therefore, allowing the potential users to achieve STS transitions with their body residual capabilities without an external power source. Instead, transferring power from their upper-body to lower-body, herewith, controlling a passive energy storage. A prototype was constructed and evaluated with seven healthy subjects observing the proposed motion and muscle activity during the STS transitions. The results show a significant reduction in the muscle activity evaluated, at the erector spinae, gluteus maximus, and rectus femoris, with reductions between 30% to 50% at the $p level comparing STS transitions with and without the exoskeleton support. Concluding that the STS transitions support is feasible with the passive exoskeleton envisioned for applications in upright locomotion, STS training, and rehabilitation.

Unpowered Lower-Body Exoskeleton with Torso Lifting Mechanism for Supporting Sit-to-Stand Transitions

Robust nonsingular fast terminal sliding-mode control for Sit-to-Stand task using a mobile lower limb exoskeleton

This paper describes a novel stair-climbing wheelchair operated by human upper body using lever propelled rotary-legs with posture transition mechanism. The design principle of this wheelchair is t...

Stair-climbing wheelchair with lever propulsion control of rotary legs

There are a few types of step-climbing wheelchairs in the world, but most of them are large and heavy because they are power-assisted. Therefore, they require large space to maneuver, which is not always feasible with existing house architectures. This study proposes a novel step-climbing wheelchair based on lever propulsion control using human upper limbs. The developed step-climbing wheelchair device consists of manual wheels with casters for moving around and a rotary-legs mechanism that is capable of climbing steps. The wheelchair also has a passive mechanism for posture transition to shift the center of gravity of the person between the desired positions for planar locomotion and step-climbing. The proposed design consists of passive parts, and this leads the wheelchair being compact and lightweight. In this paper, we present the design of this step-climbing wheelchair and some preliminary experiments to test its usability.

Step-climbing wheelchair with lever propelled rotary legs

This study proposes a novel stair-climbing wheelchair based on lever propulsion control using the human upper body. Wheelchairs are widely used as supporting locomotion devices for people with acquired lower limb disabilities. However, steps and stairs are critical obstacles to locomotion, which restrict their activities when using wheelchairs. Previous research focused on power-assisted, stair-climbing wheelchairs, which were large and heavy due to its large actuators and mechanisms. In the previous research, we proposed a wheelchair with lever propulsion mechanism and presented its feasibility of climbing up the stairs. The developed stair-climbing wheelchair consists of manual wheels with casters for planar locomotion and a rotary-leg mechanism based on lever propulsion that is capable of climbing up stairs. The wheelchair also has a passive mechanism powered by gas springs for posture transition to shift the user's center of gravity between the desired positions for planar locomotion and stair-climbing. In this paper, we present an advanced study on both climbing up and going down using lever propulsion control by the user's upper body motion. For climbing down the stairs, we reassembled one-way clutches used for the rotary-leg mechanism to help a user climb down the stairs through lever operation. We also equipped the wheelchair with sufficient torque dampers. The frontal wheels were fixed while climbing down the stairs to ensure safety. Relevant experiments were then performed to investigate its performance and verify that the wheelchair users can operate the proposed lever propulsion mechanism.

A wheelchair with lever propulsion control for climbing up and down stairs

This study proposes a novel personal mobility vehicle for supporting and assisting people with disabled lower limbs. The developed mobile platform is capable of assisting voluntary postural transition between standing and sitting, called the Passively Assistive Limb (PAL) mechanism, in addition to high mobility with upright posture. The device consists of gas-spring-powered passive exoskeleton for postural support and two in-wheel motors for mobility support. The developed robot system allows a user to sit down on chairs and beds, and stand up through easy operations. In addition, a user can move the system in the standing posture without using their hands. In this paper, the development and assessments of the standing mobility vehicle are described.

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Yosuke Eguchi

Papers

Standing Mobility Device With Passive Lower Limb Exoskeleton for Upright Locomotion

Stair-climbing wheelchair with lever propulsion control of rotary legs

Step-climbing wheelchair with lever propelled rotary legs

A wheelchair with lever propulsion control for climbing up and down stairs

Standing mobility vehicle with passive exoskeleton assisting voluntary postural changes