Table 2.
List of exoskeletons.
| RD name | Known technical characteristics of the RD | Diagnosis | |
|---|---|---|---|
| Rigid exoskeletons | |||
| HAL-Hybrid Assistive Limb (Cyberdyne Inc.) | Hip and knee joints are bilaterally actuated. The HAL has three control systems comprising the Cybernic Voluntary Control (CVC), Cybernic Impedance Control (CIC), and Cybernic Autonomous Control (CAC). The CVC mode assists patients' motion triggered by their EMG in the hip and knee extensor and flexor muscles. An assistive torque was given to each joint according to the detected EMG, with modulation by magnitude, timing of agonist activity, and balance between agonist and antagonist activities. CAC mode provides assistive torque leg trajectories based on postural cues and sensor shoe measurements. CIC mode provides torque to compensate for frictional resistance of the motor based on joint motion. CIC mode does not provide torque assistance for dictating joint trajectories | Multijoint | Chronic diplegic/quadriplegic CP (Ueno et al., 2019; Kuroda et al., 2020) |
| Multijoint | Acute (Nilsson et al., 2014; Taki et al., 2020)/chronic stroke (Kawamoto et al., 2013; Tanaka et al., 2019) | ||
| The single-leg version of the HAL is a wearable robot for patients with hemiplegia that has the cybernic voluntary control mode and the cybernic autonomous control mode. | Multijoint | Acute stroke (Tan et al., 2018; Tanaka et al., 2019)/subacute (Mizukami et al., 2016; Watanabe et al., 2017; Tan et al., 2020)/chronic stroke (Yoshimoto et al., 2015, 2016) | |
| CPWalker | The CPWalker rehabilitation device is composed of an exoskeleton linked to a walker that provides support and balance to the user during over-ground training. There are three training modes: position control mode—the robot guides a prescribed gait pattern to the user's lower limbs; Impedance control modes—in this mode, assistance by the robot is provided as needed by the user to achieve the desired gait pattern; Zero-force control mode—in this mode, the trajectory reference is not given, and the user moves the legs with minimal resistance from the device. It is used with users with enough motor control (acquired with the previous modes) but poor balance, so the device provides stability while the user performs the gait pattern | Multijoint | Chronic, spastic diplegic CP (Bayón et al., 2016, 2018) |
| Novel exoskeleton for crouch gait (Ultraflex Systems) | Wearable robot provides on-demand assistive torque at the knee joint to facilitate knee extension during walking while preserving (or enhancing) muscle activity of the user. Knee angle, FSR, and joint torque signals are input into a feedback control system to control the knee joint torque | Single joint | Chronic, diplegic CP (Lerner et al., 2017a,b; Bulea et al., 2018) |
| Adaptive Ankle | The RD includes a motor assembly, and an ankle pulley mounted in-line with the ankle joint. A proportional joint-moment control scheme, developed to account for stride-to-stride variability, provided plantar-flexor assistance proportional to the real-time biological ankle joint moment using force sensors placed under the forefoot | Single joint | Diplegic CP (Fang et al., 2020) |
| Ekso™ (version 1.1) and Ekso GT™ (version 1.2) (Ekso Bionics) | Hip and knee joints are bilaterally actuated. The software control included ProStep Plus™—each step was triggered by the subject's transfer load from one leg to the other and assistance is provided as needed; Bilateral Max Assist—the amount of power contribution to the legs during walking was totally provided by the robot | Multijoint | Acute (Nolan et al., 2018)/chronic TBI (Karunakaran et al., 2020a,b) |
| Hip and knee were bilaterally actuated. The software control included ProStep Plus™ (each step was triggered by the subject's transfer load from one leg to the other) and Bilateral Max Assist (the amount of power contribution to the legs during walking was totally provided by the robot) | Multijoint | Acute (Pournajaf et al., 2019; Lefeber et al., 2020; Nolan et al., 2020; Swank et al., 2020b; Karunakaran et al., 2021)/subacute (Goffredo et al., 2019; Høyer et al., 2020; Infarinato et al., 2021; Molteni et al., 2021)/chronic stroke (Molteni et al., 2017; Calabrò et al., 2018; Schröder et al., 2019; De Luca et al., 2020; Rojek et al., 2020; Zhu et al., 2021) | |
| BEAR-HI (Shenzhen MileBot Robotics Co., Ltd.) | Hip, knee, and ankle are actuated in the sagittal plane. The RD has a training mode and an intelligent mode. For the training mode, stride frequency could be changed within 3% of the set gait cycle frequency. In the intelligent mode, stride frequency could be adjusted in real-time to achieve synchronization of human-robot interaction. The assistance was provided based on the assist-as-need concept | Multijoint | Subacute stroke (Li et al., 2021) |
| Wearable ankle | Force sensitive resistors (FSR) were used to identify gait phase and the ankle was actuated to provide support for dorsiflexion/plantarflexion | Single joint | Subacute stroke (Yeung et al., 2021) |
| Indego (Parker Hannifin Corp) | Actuated hip and knee. The robot has two modes: Therapy+ and Motion+. In Therapy+, hip flexion initiates steps with trajectory determined by the user with adjustable levels of assist during stance/swing. In Motion+, postural changes triggered the steps with predetermined step and full or variable assist | Multi joint | Subacute and chronic stroke, TBI (Jyräkoski et al., 2021) |
| H2 | Hip, knee, and ankle joints are actuated. Foot switches, potentiometers, hall effect sensors, and strain gauges were used to detect different phases of gait. An assistive gait control algorithm was developed to create a force field along a desired trajectory, only applying torque when patients deviate from the prescribed movement pattern | Multi joint | Chronic stroke (Bortole et al., 2015) |
| Robot-assisted ankle-foot-orthosis | Ankle was actuated. FSR and inertial measurement unit (IMU) were used to detect gait phases to provide dorsiflexion assistance | Single joint | Chronic stroke (Yeung et al., 2018) |
| Exoband | Exoband is a passive hip assistive device. The device includes three main components: a waist belt and two thigh parts connected to the waist belt by means of two elastic elements, one for each leg. When the hip extends the elastic element stretches, thus storing elastic mechanical energy. When the leg starts to accelerate forward the elastic element initiates to shorten and applies a force in parallel with the hip flexor muscles, ultimately assisting the user's gait. The amount of force applied to the user can be changed by varying the length of the ratchet strap | Single joint | Chronic stroke (Panizzolo et al., 2021) |
| ExoAtlet (Exoatlet Global S.A.) | ExoAtlet is actuated at the hip and the knee joints. Patients can control the level of support they receive from the exoskeleton through various types of control systems. These include tablets, buttons on the control handles or smart crutches | Multi joint | Subacute (Kotov et al., 2021) and chronic stroke (Kotov et al., 2021; Kovalenko et al., 2021) |
| Vanderbilt | The exoskeleton incorporates four control actuators that provide sagittal-plane torques bilaterally at hip and knee joints. IMU's are used to detect step initiation and assistance is provided as needed. | Multi joint | Subacute/chronic stroke (Murray et al., 2014) |
| Stride Management Assist (SMAS) system (Honda R&D Corporation®) | This device provides independent assistance with hip flexion and extension for each leg to increase step length. The SMAS control architecture uses a mutual rhythm scheme to influence the user's walking patterns. The SMAS control law uses neural oscillators in conjunction with the user's CPG to synchronize itself with user input. Angle sensors embedded in the SMAS actuators detect the user's hip joint angles throughout the gait cycle. These angles are input to the SMAS controller, which calculates hip joint angle symmetry. The SMAS then generates assist torques at specific instances during the gait cycle to regulate these walking patterns | Single joint | Chronic stroke (Buesing et al., 2015; Jayaraman et al., 2019) |
| UG0210 (Hangzhou RoboCT Technology Development Co., Ltd) | Hip, and knee are actuated | Multi joint | Acute and subacute stroke (Zhang et al., 2020) |
| GEMS-Gait Enhancing and Motivating System (Samsung Advanced Institute of Technology) | The GEMS torque assistance units consist of angular sensors and actuators that work on bilateral hip joints. The GEMS can provide assist torque and power around the bilateral hip joints for both extension and flexion during walking | Single joint | Chronic stroke (Lee et al., 2019) |
| RLO, (Tibion Corporation) | The RLO activated and provided forward propulsion when the participants generated enough force on their paretic knee. The device had an internal sensor that detected the wearer's foot pressure. The RLO provided assistance with extension, controlled flexion, and free movement. Device settings includes changing threshold (the minimum force to activate the device), assistance (the percentage of body weight provided through the limb during extension in the stance phase of the gait cycle), and resistance (level of resistance during flexion on the stance phase of the gait cycle) | Single joint | Chronic stroke (Li et al., 2015) |
| Soft exoskeletons | |||
| ReWalk ReStore™ (ReWalk Robotics, Inc.) | The device consists of motors worn at the waist that generate mechanical forces that are transmitted by cables to attachment points located proximally on a functional textile worn around the calf and distally on a shoe insole to provide dorsiflexion assistance to the ankle | Single Joint | Chronic stroke (Awad et al., 2020) |
| Myosuit (MyoSwiss AG) | Two adjustable polymer springs cross the hip joints to passively assist hip and actuated knee help with knee movements during gait. Gait events and joint angles were estimated from IMU data. Assistance during gait can be customized to the participant deficits and gait phases as needed | Multi joint | Chronic stroke (Haufe et al., 2020) |
| Regent | The Regent Suit consists of supporting elements (vest, shorts, knee caps, and foot straps) made of synthetic materials, and a set of elastic loading elements equipped with located fixtures (metal spring hooks) and regulating and locking buckles. There are three sizes of the suit and, for each size, the volume of the vest and shorts can be further adjusted by means of zips sewn on the supporting elements. The elastic elements are fastened to the outer surface of the supporting elements along the patient's body and lower limbs, and not only create a central load on the body and leg muscles, but also allow postural corrections as well as providing for body rotation, stoop, and stretch, which helps to reduce pathological muscular synergisms | Multi joint | Subacute and chronic stroke (Monticone et al., 2013; Poydasheva et al., 2016; Saenko et al., 2016) |