Knee-ankle-foot orthosis with powered knee for support in the elderly

Abstract

A prototype of a powered knee orthotic device was developed to determine whether fractional external torque and power support to the knee relieves the biomechanical loads and reduces the muscular demand for a subject performing sit-to-stand movements. With this demonstrator, consisting of the subsystems actuation, kinematics, sensors, and control, all relevant sensor data can be acquired and full control is maintained over actuator parameters. A series-elastic actuator based on a direct current motor provides up to 30 Nm torque to the knee via a hinge joint with an additional sliding degree of freedom. For reasons of feasibility under everyday conditions, user intention is monitored by employing a noninvasive, nonsticking muscle activity sensor to replace electromyographic sensors, which require skin preparation. Furthermore, foot plates with force sensors have been developed and included to derive ground reaction forces. The actual knee torque needed to provide the desired support is based on an inverse dynamics model using ground reaction forces signals and leg kinematics. A control algorithm including disturbance feed forward has been implemented. A demonstration experiment with two subjects showed that 23 % of moment support in fact leads to a similar reduction in activation of the main knee extensor muscle.

A Review on the Control of the Mechanical Properties of Ankle Foot Orthosis for Gait Assistance

“…It could be clearly observed that the fixed output reference worked with a flexible rigid AFO [18,64] and an AFO with only mechanical actuators, such as an oil damper [69] and a spring [32,73]. The adaptive output reference could be observed from those works that utilized electrical actuators such as an MR device [41,49,56], SEA [54,75], and a pneumatic system [53]. The adaptive output reference was not adapted to all types of disturbances, but some of them, such as the gait phase [41] and GRF were adaptive output references [75].…”

“…The estimation of the damping stiffness reference in real time was presented in the Knee AFO (KAFO) by Pete et al [75]. The estimation is needed because the actual knee joint torque could be measured directly.…”

“…The adaptive output reference could be observed from those works that utilized electrical actuators such as an MR device [41,49,56], SEA [54,75], and a pneumatic system [53]. The adaptive output reference was not adapted to all types of disturbances, but some of them, such as the gait phase [41] and GRF were adaptive output references [75]. The previous works also showed that when the EMG model was used in the control system, the output reference was able to adapt to more types of environmental disturbances.…”

“…Both sensors can give information about foot contact. However, a force sensor offers additional information such as the GRF, which can be used to estimate the desired joint torque [75,77]. When using a GRF sensor, the position of the sensor should be especially considered for obtaining the reading from the heel contact force [12].…”

Biomechanic and Energetic Effects of a Quasi-Passive Artificial Gastrocnemius on Transtibial Amputee Gait

“…A variety of robotic orthoses have been developed to assist human knee joints for locomotion. Many of these devices utilize active components such as electric motors [20][21][22] or pneumatic actuators [23][24][25][26], but these elements tend to require a large power source or otherwise require off-board tethered actuation, limiting the scope of their applicability. Alternatively, some researchers have developed quasi-passive knee exoskeletons that do not provide net mechanical power to the wearer but instead require at most the minimal input power to operate the electronics and mechanical components [27][28][29][30].…”