Active orthosis is one of the main research topics in the field of motor recovery. This paper deals with the design and control of an active knee orthosis driven by a customized rotary Series Elastic ...Actuator (SEA). The proposed actuator includes a DC motor, a worm gear and a customized torsion spring. Since the elastic element is the most important component in SEA design, a finite element analysis of the spring is performed to meet the specific requirements for knee assistance. Torque and impedance control are implemented to ensure secure interaction with the patient and to enable new strategies for rehabilitation. The torque controller, cascaded with an inner motor velocity control loop, is based on H∞ criterion to achieve good system performance with relation to parametric uncertainties and external disturbances. The impedance control is implemented using a PD position controller in cascade with the torque controller, where the outer position controller determines the desired torque according to position and velocity errors and impedance parameters. A variable impedance control strategy is then implemented to show the possibility to regulate the impedance of the knee joint during walking. Experiments considering the interaction between the subject and the active orthosis are performed to evaluate the proposed controllers.
•Design of a knee active orthosis driven by a rotary Series Elastic Actuator (SEA).•Robust H-infinity torque and impedance control of the SEA.•Experimental characterization of the torque and impedance controllers.•Evaluation of a variable impedance control strategy for the knee active orthosis interacting with a healthy subject walking on a treadmill.
Robotic rehabilitation of the upper limb following neurological injury is most successful when subjects are engaged in the rehabilitation protocol. Developing assistive control strategies that ...maximize subject participation is accordingly an active area of research, with aims to promote neural plasticity and, in turn, increase the potential for recovery of motor coordination. Unfortunately, state-of-the-art control strategies either ignore more complex subject capabilities or assume underlying patterns govern subject behavior and may therefore intervene suboptimally. In this paper, we present a minimal assist-as-needed (mAAN) controller for upper limb rehabilitation robots. The controller employs sensorless force estimation to dynamically determine subject inputs without any underlying assumptions as to the nature of subject capabilities and computes a corresponding assistance torque with adjustable ultimate bounds on position error. Our adaptive input estimation scheme is shown to yield fast, stable, and accurate measurements regardless of subject interaction and exceeds the performance of current approaches that estimate only position-dependent force inputs from the user. Two additional algorithms are introduced in this paper to further promote active participation of subjects with varying degrees of impairment. First, a bound modification algorithm is described, which alters allowable error. Second, a decayed disturbance rejection algorithm is presented, which encourages subjects who are capable of leading the reference trajectory. The mAAN controller and accompanying algorithms are demonstrated experimentally with healthy subjects in the RiceWrist-S exoskeleton.
•A novel hybrid soft-rigid hand exoskeleton (HSRexo) for rehabilitation is proposed.•The simplified three-layered sliding spring (sTLSS) mechanism is designed to achieve compliance.•Pseudo-rigid-body ...model (PRBM) method is used to achieve comprehensible kinematics.•The simulation and preliminary prototyping are conducted to verify the design and model.
Poststroke patients’ need for hand rehabilitation is urgent since hand plays a significant role in people's activities of daily life (ADLs). Contrast to traditional rigid devices with excessive stiffness and soft devices lacking well-understood models, we present a hybrid soft-rigid exoskeleton (HSRexo) for poststroke hand rehabilitation adopting the simplified three-layered sliding spring (sTLSS) mechanism that combines the intrinsic compliance and comprehensible kinematics. The compliant spring blades in the sTLSS mechanism make it possible to compactly actuate three natural flexion/extension of finger joints by only 1 ° of freedom (DOF). To deal with the nonlinear deformation of soft elastic elements, the modeling of the sTLSS mechanism is proposed by the pseudo-rigid-body model (PRBM) method to achieve comprehensible kinematics and optimize design parameters. Finally, the simulation and preliminary prototyping demonstrate the accuracy of the model and the compliant natural flexion/extension joint angle of the HSRexo design due to the modeling and optimization of the sTLSS mechanism.
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•Rehabilitation robots need to mimic the real three-dimensional motion of humans.•The position and attitude of the limb end-effector are controlled for 3D gait.•Exponential mapping in SO(3) and the ...properties of the tangent vector are used.•Newton method based on geodesic distance is applied to obtain the closest attitude.•Moment field generates the adjusting torque along tangential and normal directions.
Existing rehabilitation robots focus on mimicking sagittal motion alone; however, sagittal motion is only a subset of actual human motions in three-dimensional space. Thus, the positions and attitudes of limb end-effectors should be controlled. The attitudes are expressed by rotation matrices, which belong to a special orthogonal group SO(3). As they lie in manifold and not in Euclidean space as is the case with the positions, it is difficult to achieve assist-as-needed control. Herein, the moment field control for robotic rehabilitation is studied. First, the error matrix and its exponential coordinate describe the attitude error. Geodesic distance-based Newton method is applied to obtain the closest attitude to the actual attitude in the desired trajectory. Thus, the tangential and normal directions are determined and the moment field is established to generate sufficient torque to adjust the attitude. Using the robotic exoskeleton for hip rehabilitation, the algorithm is simulated, and its effectiveness is verified. The proposed control method achieves adequate attitude control of joints with three degrees of freedom or pose control of limb end-effectors, providing a reference for controlling rehabilitation robots.
Due to the complexity of the human musculoskeletal system and intra/intersubjects variability, powered exoskeletons are prone to human-robot misalignments. These induce undesired interaction forces ...that may jeopardize safe operation. Uncompensated inertia of the robotic links also generates spurious interaction forces. Current design approaches to compensate for misalignments rely on the use of auxiliary passive degrees of freedom that unavoidably increase robot inertia, which potentially affects their effectiveness in reducing undesired interaction forces. Assessing the relative impact of misalignment and robot inertia on the wearer can, therefore, provide useful insights on how to improve the effectiveness of such approaches, especially in those situations where the dynamics of the movement are quasi-periodic and, therefore, predictable such as in gait. In this paper, we studied the effects of knee joint misalignments on the wearer's gait, by using a treadmill-based exoskeleton developed by our group, the ALEX II. Knee joint misalignments were purposely introduced by adjusting the mismatch between the length of the robot thigh and that of the human thigh. The amount of robot inertia reflected to the user was adjusted through control. Results evidenced that knee misalignment significantly changes human-robot interaction forces, especially at the thigh interface, and this effect can be attenuated by actively compensating for robot inertia. Misalignments caused by an excessively long robot thigh are less critical than misalignments of equal magnitude deriving from an excessively short robot thigh.
We present a lightweight robotic knee prosthesis with a novel hybrid actuation system that enables passive and active operation modes. The proposed hybrid knee uses a spring-damper system in ...combination with an electric motor and transmission system, which can be engaged to provide a stair ambulation capability. In comparison to fully powered prostheses that power all ambulation activities, a hybrid knee prosthesis can achieve significant weight reduction by focusing the design of the actuator on a subset of activities without losing the ability to produce equivalent torque and mechanical power in the active mode. The hybrid knee prototype weighs 1.7 kg, including battery and control, and can provide up to 125 Nm of repetitive torque. Experiments with two transfemoral amputee subjects show that the proposed hybrid knee prosthesis can support walking on level ground in the passive mode, as well as stair ambulation with a reciprocal gait pattern in the active mode.
Upper limb exoskeletons have drawn significant attention in neurorehabilitation because of the anthropomorphic mechanical structure analogous to human anatomy. Whereas, the training movements are ...typically unorganized because most exoskeletons ignore the natural movement characteristic of human upper limbs, particularly inter-joint postural synergy. This paper introduces a newly developed exoskeleton (Armule) for upper limb rehabilitation with a postural synergy design concept, which can reproduce activities of daily living (ADL) motion with the characteristics of human natural movements. The semitransparent active control strategy with the interactive force guidance and visual feedback ensured the active participation of users. Eight participants with hemiplegia due to a first-ever, unilateral stroke were recruited and included. They participated in exoskeleton therapy sessions for 4 weeks, with passive/active training under trajectories and postures with the characteristics of human natural movements. The primary outcome was the Fugl-Meyer Assessment for Upper Extremities (FMA-UE). The secondary outcomes were the Action Research Arm Test(ARAT), modified Barthel Index (mBI), and metric measured with the exoskeleton After the 4-weeks intervention, all subjects showed significant improvements in the following clinical measures: the FMA-UE (difference, 11.50 points, p = 0.002), the ARAT (difference, 7.75 points <inline-formula> <tex-math notation="LaTeX">{p} < 0.001 </tex-math></inline-formula>), and the mBI (difference, 17.50 points, <inline-formula> <tex-math notation="LaTeX">{p} = 0.003 </tex-math></inline-formula>) score. Besides, all subjects showed significant improvements in kinematic and interaction force metrics measured with the exoskeleton. These preliminary results demonstrate that the Armule exoskeleton could improve individuals' motor control and ADL function after stroke, which might be associated with kinematic and interaction force optimization and postural synergy modification during functional tasks.
Among past years interest in robot-assisted rehabilitation arose significantly; thus, constructions such as exoskeletons are involved in this process much more often. As a patient's bio-signals may ...be included in a control loop of these devices, they may be also used to support the motion of extremities in an everyday life. Therefore, a field of control over them stays a popular research topic. For this reason, an exoskeleton described in a paper was designed. The most important aim of a project was to enable all anatomical movements within ranges required for the lifting of an object while minimising the mass of the device; to enable everyday support within a wide range of motions. The following paper contains a concept of such a device with the description of a whole designing proces. It consists of antropomethric modelling, FEM simulations and topology optimisation applied to decrease the amount of material needed, and the analysis of considered manufacturing methods. As the exoskeleton was designed to be built with FDM 3-D printing technology, created parts were modelled orthotopically based on nominal mechanical parameters of filaments and directions of their beams. The design is complemented with a short description of control with EMG signals and analysis of load on a user's musculoskeletal system.
Individuals with chronic hemiparesis post-stroke exhibit gait impairments that require functional rehabilitation through training. Exoskeletal robotic assistive devices can provide a user with ...continuous assistance but impose movement restrictions. There are currently devices that allow unrestricted movement but provide assistance only intermittently at specific points of the gait cycle. Our design, a cable-driven active leg exoskeleton (C-ALEX), allows the user both unrestricted movement and continuous force assistance throughout the gait cycle to assist the user in new walking patterns. In this study, we assessed the ability of C-ALEX to induce a change in the walking patterns of ten post-stroke participants using a single-session training protocol. The ability of C-ALEX to accurately provide forces and torques in the desired directions was also evaluated to compare its design performance to traditional rigid-link designs. Participants were able to reach 91% ± 12% of their target step length and 89% ± 13% of their target step height. The achieved step parameters differed significantly from participant baselines (p <; 0.05). To quantify the performance, the forces in each cable's out of the plane movements were evaluated relative to the in-plane desired cable tension magnitudes. This corresponded to an error of under 2Nm in the desired controlled joint torques. This error magnitude is low compared to the system command torques and typical adult biological torques during walking (2-4%). These results point to the utility of using non-restrictive cable-driven architectures in gait retraining, in which future focus can be on rehabilitating gait pathologies seen in stroke survivors.
This paper presents the design and experimental testing of the robotic elbow exoskeleton NEUROBOTICS Elbow Exoskeleton (NEUROExos). The design of NEUROExos focused on three solutions that enable its ...use for poststroke physical rehabilitation. First, double-shelled links allow an ergonomic physical human-robot interface and, consequently, a comfortable interaction. Second, a four-degree-of-freedom passive mechanism, embedded in the link, allows the user's elbow and robot axes to be constantly aligned during movement. The robot axis can passively rotate on the frontal and horizontal planes 30° and 40°, respectively, and translate on the horizontal plane 30 mm. Finally, a variable impedance antagonistic actuation system allows NEUROExos to be controlled with two alternative strategies: independent control of the joint position and stiffness, for robot-in-charge rehabilitation mode, and near-zero impedance torque control, for patient-in-charge rehabilitation mode. In robot-in-charge mode, the passive joint stiffness can be changed in the range of 24-56 N·m/rad. In patient-in-charge mode, NEUROExos output impedance ranges from 1 N·m/rad, for 0.3 Hz motion, to 10 N·m/rad, for 3.2 Hz motion.
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