A Novel Method to Generate Amplitude-Frequency Modulated Vibrotactile Stimulation.

The natural interaction of humans with their environment involves the harmonious coordination of the body, for which multi-modal feedback including vision, proprioception, and tactile perception is essential. Most human-machine interfaces, however, rely on the visual feedback only, and this can lead to considerable cognitive burden. Additional haptic feedback can increase the intuitiveness of the man-machine interaction. Therefore, we propose here a new device able to generate complex vibrotactile stimulation by simultaneously modulating the amplitude and frequency of vibration. Physical measurements were first performed in eight healthy subjects to assess the capability of the device to generate vibrations. The results indicated that the vibration frequency and amplitude can be independently modulated and that the device response to the full-range step-change in the amplitude/frequency commands is almost instantaneous and symmetric. In addition, psychophysical assessments were conducted in four healthy subjects using a standard psychophysical procedure (SIAM). The outcomes indicated that the proposed device can produce approximately 400 vixels (discriminable stimuli), which allow for the generation of a high diversity of vibrotactile patterns. The proposed method allows producing different kinds of stimulation patterns using motor types that are suited for specific applications, with adjustable trade-off between vibration intensity, size, and power consumption.

Angular-velocity control approach for stance-control orthoses.

Currently, stance-control knee orthoses require external control mechanisms to control knee flexion during stance and allow free knee motion during the swing phase of gait. A new angular-velocity control approach that uses a rotary-hydraulic device to resist knee flexion when the knee angular velocity passes a preset threshold is presented. This angular-velocity approach for orthotic stance control is based on the premise that knee-flexion angular velocity during a knee-collapse event, such as a stumble or fall, is greater than that during walking. The new hydraulic knee-flexion control device does not require an external control mechanism to switch from free motion to stance control mode. Functional test results demonstrated that the hydraulic angular-velocity activated knee joint provided free knee motion during walking, engaged upon knee collapse, and supported body weight while the end-user recovered to a safe body position. The joint was tested to 51.6 Nm in single loading tests and passed 200,000 repeated loading cycles with a peak load of 88 Nm per cycle. The hydraulic, angular velocity activation approach has potential to improve safety and security for people with lower extremity weakness or when recovering from joint trauma.

Engineering design review of stance-control knee-ankle-foot orthoses.

Persons with quadriceps muscle weakness are often prescribed a knee-ankle-foot orthosis that locks the knee in full extension during both stance and swing phases of gait. Locking the knee results in abnormal gait patterns characterized by hip hiking and leg circumduction during swing. The stance-control knee-ankle-foot orthosis (SCKAFO), a new type of orthosis, has emerged that permits free knee motion during swing while resisting knee flexion during stance, thereby supporting the limb during weight-bearing. This article examines various SCKAFO designs, discuss the existing design limitations, and identify remaining design challenges. Several commercial SCKAFOs have been released that incorporate different locking mechanisms. Preliminary gait studies have shown some devices to be promising; however, an important functional limitation in some SCKAFOs is dependence on specific joint angles to switch between stance and swing modes. Important design factors such as size, weight, and noise must be considered in new orthosis designs to ensure wide consumer acceptance.

Design and evaluation of a stance-control knee-ankle-foot orthosis knee joint.

Conventional knee-ankle-foot orthoses (KAFOs) are prescribed for people with knee-extensor muscle weakness. However, the orthoses lock the knee in full extension and, therefore, do not permit a natural gait pattern. A new electromechanical stance-control knee-ankle-foot orthosis (SCKAFO) knee joint that employs a novel friction-based belt-clamping mechanism was designed to enable a more natural gait. The SCKAFO knee joint allows free knee motion during swing and other non-weight-bearing activities and inhibits knee flexion while allowing knee extension during weight bearing. A prototype SCKAFO knee joint was mechanically tested to determine the moment at failure, loading behavior, and wear resistance. The mean maximum resisting moment of the SCKAFO knee joint over five loading trials was 69 Nm +/- 4.9 Nm. The SCKAFO knee-joint strength and performance were sufficient to allow testing on a 90 kg subject at normal walking cadence. Proper function of the new electromechanical knee joint was verified in walking trials of an able-bodied subject.

Preliminary kinematic evaluation of a new stance-control knee-ankle-foot orthosis.

BACKGROUND: Stance-control knee-ankle-foot orthoses permit free knee motion in swing while providing knee flexion resistance in stance for individuals with quadriceps muscle weakness. However, some stance-control knee-ankle-foot orthoses require full knee extension to engage the knee-joint lock, thereby not providing knee support when climbing stairs or stepping over curbs. Stance-control knee-ankle-foot orthoses that do support a flexed knee are either heavy, bulky, expensive, offer a limited number of locking positions, or cause noise. This paper presents a preliminary kinematic evaluation of a new stance-control knee-ankle-foot orthosis that was designed to address these limitations. METHODS: Kinematic gait analysis was performed on three male knee-ankle-foot-orthosis users with knee extensor weakness in at least one limb (mean age: 56.3 years (SD 4.0)). Three walking trials were performed with the subjects' current knee-ankle-foot-orthosis and then the new stance-control knee-ankle-foot orthosis (non-randomized before-after trial). Subjects completed a questionnaire about the new stance-control knee-ankle-foot orthosis and current knee-ankle-foot-orthosis. FINDINGS: A mean increase in knee flexion of 21.1 degrees (SD 8.2) during swing and a greater total knee range of motion was found when walking with the new stance-control knee-ankle-foot orthosis. Two knee-ankle-foot-orthosis users experienced a reduction in pelvic obliquity and hip abduction angle abnormalities when walking with the stance-control knee-ankle-foot orthosis. Two out of three subjects preferred walking with the new stance-control knee-ankle-foot orthosis over their prescribed knee-ankle-foot-orthosis. INTERPRETATION: The new stance-control knee-ankle-foot orthosis permitted improved gait kinematics for knee-ankle-foot-orthosis users while providing knee support in stance and free knee motion in swing at appropriate instants in the gait cycle. Overall, the new stance-control knee-ankle-foot orthosis provided more natural gait kinematics for orthosis users compared to conventional knee-ankle-foot-orthoses.

Gait evaluation of a new electromechanical stance-control knee-ankle-foot orthosis.

Commercial versions of a stance-control knee-ankle-foot orthosis (SCKAFO) have emerged to improve gait over conventional knee-ankle-foot orthoses (KAFOs), which lock the knee in full extension in individuals with quadriceps muscle weakness. A new electromechanical SCKAFO was recently designed to address the functional, structural, and cost limitations of these commercial SCKAFOs. This paper presents an evaluation of the new SCKAFO conducted to determine its functional and clinical effectiveness during gait. Three healthy adults (100% male; age, 35.3 +/- 19.7y) and three KAFO users with knee extensor weakness in at least one limb (100% male; mean age, 56.3 +/- 4.0y) participated in the study. The SCKAFO had a minimal effect, as desired, on the kinematics of the able-bodied subjects. KAFO users had a mean increase in knee flexion of 21.1 degrees (sd=8.2) during swing, and a greater total knee range of motion when walking with the new SCKAFO compared to their prescribed KAFO. Two KAFO users experienced a reduction in pelvic obliquity and hip abduction angle abnormalities when walking with the SCKAFO compared to their prescribed KAFO.

Design, construction and evaluation of an electromechanical stance-control knee-ankle-foot orthosis.

A new electromechanical Stance-Control Knee-Ankle-Foot Orthosis (SCKAFO) was designed to provide improved gait for people with knee-extensor weakness. This SCKAFO inhibits knee flexion at any knee angle while allowing knee extension during weight bearing. During swing or other non-weight bearing activities, the SCKAFO allows free knee motion. A prototype joint was mechanically tested to determine the moment at failure, loading behaviour, and device safety. Quantitative kinematic gait analysis of three able-bodied subjects and three knee-anklefoot-orthosis (AFO) users showed that the new SCKAFO had a desired minimal effect on able-bodied walking gait. The SCKAFO permitted a mean increase in sagittal knee motion (488%) during swing for the three KAFO users and a reduction in pelvic obliquity and hip abduction angle abnormalities during terminal stance and swing for two KAFO users.

Design, construction and evaluation of an electromechanical stance-control knee-ankle-foot orthosis.

A new electromechanical Stance-Control Knee-Ankle-Foot Orthosis (SCKAFO) was designed to provide improved gait for people with knee-extensor weakness. This SCKAFO inhibits knee flexion at any knee angle while allowing knee extension during weight bearing. During swing or other non-weight bearing activities, the SCKAFO allows free knee motion. A prototype joint was mechanically tested to determine the moment at failure, loading behaviour, and device safety. Quantitative kinematic gait analysis of three able-bodied subjects and three knee-ankle-foot-orthosis (KAFO) users showed that the new SCKAFO had a desired minimal effect on able-bodied walking gait. The SCKAFO permitted a mean increase in sagittal knee motion (488%) during swing for the three KAFO users and a reduction in pelvic obliquity and hip abduction angle abnormalities during terminal stance and swing for two KAFO users.