Design of an exoskeleton ankle robot for robot-assisted gait training of stroke patients

Abstract

Lower Limb Exoskeleton robot that can facilitate stair walking is a big challenge, most systems could only provide level ground walking. In this study, a lightweight (0.5kg at ankle, 0.5kg at waist for control box) and autonomous exoskeleton Ankle Robot was proposed to provide power assistance for gait training of chronic stroke patients and it can facilitate three walking conditions in real-time: (1) level walking, (2) stair ascending, and (3) stair descending. Chronic stroke patients (n=3) with drop foot gait deficit and moderate motor impairment were recruited to evaluate the system under different walking conditions (Functional Ambulatory Category: FAC=4.7±0.5 and Fugl-Meyer Assessment for lower-extremity: FMA-LE=13.7±2.9). The system consisted of a specially designed carbon fiber AFO, servomotor, gear transmission system, IMU and force sensors, and control box. The IMU sensors embedded in the shank measured acceleration and angular velocity to identify distinct features in leg tilting angle and leg angular velocity between the three walking conditions. The results showed the powered ankle dorsiflexion assistance could reduce dropped foot of the stroke patients in swing phase and provide better gait pattern. A demo of the ankle robot will be conducted in the conference.

Randomized controlled trial of robot-assisted gait training with dorsiflexion assistance on chronic stroke patients wearing ankle-foot-orthosis

“…Researchers found positive results in SMWT with longer walking distance and stair climbed when subjects were walking in the exoskeleton robots [ 20 , 39 ]. Although these two clinical studies did not have controls and had smaller sample size, results of the current pilot trial agrees with the previous studies [ 32 ].…”

“…The current study show robot assistance could improve gait independency, motor recovery, and walking speed of chronic stroke patients. Noting that both robot and FES assistance could lead to immediate improvement of walking endurance and functional ambulation [ 13 , 14 , 32 ], indicating these devices are good candidates of walking aids.…”

“…Detailed description of the robot-assisted AFO is presented elsewhere [ 32 ]. The robot-assisted AFO was developed by our research team, and was designed for long-distance walking to be portable without tethered external power source to facilitate casual walking in indoor environment with stairs (Fig.…”

Actuation system of the ankle exoskeleton T-FLEX: first use experimental validation in people with stroke

“…In general terms, the kinematic results during the first use of the T-FLEX actuation system showed improvements in some participants (i.e., increase foot clearance, and early push-off), which are similar to a robust AAFO based on pneumatic actuation [31]. Additionally, these results are comparable to devices controlled by Force Sensitive Resistor (FSR) for gait detection [32,33] that is the most common detection strategy used in wearable robotic orthoses. Nevertheless, those previous studies enrolled a smaller sample of subjects reducing the probability of poor-performance in the participants.…”

Effects of Wearable Ankle Robotics for Stair and Over-ground Training on Sub-acute Stroke: A Randomized Controlled Trial

“…The robot can identify changes in gait phases using embedded force sensitive resistors (FSR-402, Interlink Electronics, USA) placed under heel and forefoot. An inertial measurement unit (MPU6050, 6-axis MotionTracking, InvenSense, USA) mounted on the shank can measure leg tilting angle for classifying user walking intention on level and stair walking [25]. The robot weighted 0.5 kg (including AFO and motor) on the leg, with the control box (0.5 kg) held by the trainer.…”