Design and Hierarchical Force-Position Control of Redundant Pneumatic Muscles-Cable-Driven Ankle Rehabilitation Robot

Ankle dysfunction is common in the public following injuries, especially for stroke patients. Most of the current robotic ankle rehabilitation devices are driven by rigid actuators and have problems such as limited degrees of freedom, lack of safety and compliance, and poor flexibility. In this letter, we design a new type of compliant ankle rehabilitation robot redundantly driven by pneumatic muscles (PMs) and cables to provide full range of motion and torque ability for the human ankle with enhanced safety and adaptability, attributing to the PM's high power/mass ratio, good flexibility and lightweight advantages. The ankle joint can be compliantly driven by the robot with full three degrees of freedom to perform the dorsiflexion/plantarflexion, inversion/ eversion, and adduction/abduction training. In order to keep all PMs and cables in tension which is essential to ensure the robot's controllability and patient's safety, Karush-Kuhn-Tucker (KKT) theorem and analytic-iterative algorithm are utilized to realize a hierarchical force-position control (HFPC) scheme with optimal force distribution for the redundant compliant robot. Experiment results demonstrate that all PMs are kept in tension during the control while the position tracking accuracy of the robot is acceptable, which ensures controllability and stability throughout the compliant robot-assisted rehabilitation training

A Review Study for Robotic Exoskeletons Rehabilitation Devices

Nowadays, robotic exoskeletons demonstrated great abilities to replace traditional rehabilitation processes for activating neural abilities performed by physiotherapists. The main aim of this review study is to determine a state-of-the-art robotic exoskeleton that can be used for the rehabilitation of the lower limb of people who have mobile disabilities as a result of stroke and musculoskeletal conditions. The study presented the anatomy of the lower limb and the biomechanics of human gait to explain the mechanism of the limb, which helps in constructing a robotic exoskeleton. A state-of-the-art review of more than 100 articles related to robotic exoskeletons and their constructions, functionality, and rehabilitation capabilities are accurately implemented. Moreover, the study included a review of upper limb rehabilitation that has been studied locally and successfully applied to patients who exhibited significant improvements. Results of recent studies herald an abundant future for robotic exoskeletons used in the rehabilitation of the lower extremity. Significant improvement in the mechanism and design, as well as the quality, were observed. Also, impressive results were obtained from the performance when used by patients. This study concludes that working and improving the robotic devices continuously in accordance with the cases are necessary to be treated with the best results and the lowest cost

Structure design, kinematics analysis, and effect evaluation of a novel ankle rehabilitation robot

This paper presents a novel ankle rehabilitation (2-CRS+PU)&R hybrid mechanism, which can meet the size requirements of different adult lower limbs based on the three-movement model of the ankle. This model is related to three types of movement modes of the ankle movement, without axis offset, which can cover the ankle joint movements. The inverse and forward position/kinematics results analysis of the mechanism is established based on the closed-loop vector method and using the optimization of particle groups algorithm. Four groups of position solutions of the mechanism are obtained. The kinematics simulation is analyzed using ADAMS software. The variations of the velocity and acceleration of all limbs are stable, without any sudden changes, which can effectively ensure the safety and comfort of the ankle model end-user. The dexterity of the mechanism is analyzed based on the transport function, and the results indicate that the mechanism has an excellent transfer performance in yielding the structure parameters. Finally, the rehabilitation evaluation is conducted according to the three types of movement modes of the ankle joint. The results show that this ankle rehabilitation mechanism can provide a superior rehabilitation function

Passive Exercise Adaptation for Ankle Rehabilitation Based on Learning Control Framework

[EN] Ankle injuries are among the most common injuries in sport and daily life. However, for their recovery, it is important for patients to perform rehabilitation exercises. These exercises are usually done with a therapist's guidance to help strengthen the patient's ankle joint and restore its range of motion. However, in order to share the load with therapists so that they can offer assistance to more patients, and to provide an efficient and safe way for patients to perform ankle rehabilitation exercises, we propose a framework that integrates learning techniques with a 3-PRS parallel robot, acting together as an ankle rehabilitation device. In this paper, we propose to use passive rehabilitation exercises for dorsiflexion/plantar flexion and inversion/eversion ankle movements. The therapist is needed in the first stage to design the exercise with the patient by teaching the robot intuitively through learning from demonstration. We then propose a learning control scheme based on dynamic movement primitives and iterative learning control, which takes the designed exercise trajectory as a demonstration (an input) together with the recorded forces in order to reproduce the exercise with the patient for a number of repetitions defined by the therapist. During the execution, our approach monitors the sensed forces and adapts the trajectory by adding the necessary offsets to the original trajectory to reduce its range without modifying the original trajectory and subsequently reducing the measured forces. After a predefined number of repetitions, the algorithm restores the range gradually, until the patient is able to perform the originally designed exercise. We validate the proposed framework with both real experiments and simulation using a Simulink model of the rehabilitation parallel robot that has been developed in our lab.This work has been partially funded by the FEDER-CICYT project with reference DPI2017-84201-R (Integracion de modelos biomecanicos en el desarrollo y operacion de robots rehabilitadores reconfigurables) financed by Ministerio de Economia, Industria e Innovacion (Spain).Abu-Dakka, FJ.; Valera Fernández, Á.; Escalera, JA.; Abderrahim, M.; Page Del Pozo, AF.; Mata Amela, V. (2020). Passive Exercise Adaptation for Ankle Rehabilitation Based on Learning Control Framework. Sensors. 20(21):1-23. https://doi.org/10.3390/s20216215S123202

Passive exercise adaptation for ankle rehabilitation based on learning control framework

This article belongs to the Special Issue Human-Robot Interaction.Ankle injuries are among the most common injuries in sport and daily life. However, for their recovery, it is important for patients to perform rehabilitation exercises. These exercises are usually done with a therapist's guidance to help strengthen the patient's ankle joint and restore its range of motion. However, in order to share the load with therapists so that they can offer assistance to more patients, and to provide an efficient and safe way for patients to perform ankle rehabilitation exercises, we propose a framework that integrates learning techniques with a 3-PRS parallel robot, acting together as an ankle rehabilitation device. In this paper, we propose to use passive rehabilitation exercises for dorsiflexion/plantar flexion and inversion/eversion ankle movements. The therapist is needed in the first stage to design the exercise with the patient by teaching the robot intuitively through learning from demonstration. We then propose a learning control scheme based on dynamic movement primitives and iterative learning control, which takes the designed exercise trajectory as a demonstration (an input) together with the recorded forces in order to reproduce the exercise with the patient for a number of repetitions defined by the therapist. During the execution, our approach monitors the sensed forces and adapts the trajectory by adding the necessary offsets to the original trajectory to reduce its range without modifying the original trajectory and subsequently reducing the measured forces. After a predefined number of repetitions, the algorithm restores the range gradually, until the patient is able to perform the originally designed exercise. We validate the proposed framework with both real experiments and simulation using a Simulink model of the rehabilitation parallel robot that has been developed in our lab

Stiffness evaluation of a novel ankle rehabilitation exoskeleton with a type-variable constraint

This paper presents a novel ankle rehabilitation exoskeleton with two rotational degrees of freedom, which is suitable for dynamical rehabilitation for patients with neurological impairments. Its stiffness performance is assessed in consideration that the interaction between the footplate and the ground may deflect the mechanism away from the desired/predefined motion patterns. The novel design employs a universal-prismatic-universal (U-P-U) joint link, whose constraint type changes between a couple and a line vector during manipulation of the exoskeleton. To conduct a stiffness analysis of such a mechanism with a type-variable constraint – for the first time – a modified screw-based method (SBM) is proposed. Comparisons with the results obtained from finite element analysis verified that, the modified SBM provides reliable estimates of the exoskeleton's stiffness within the complete workspace (covering the constraint-type transition configurations). The stiffness of the exoskeleton is further evaluated by acquiring the minimum/maximum stiffness values, after computing the distribution of the most crucial linear and angular stiffness parameters within the workspace. Moreover, the influence of the architectural parameters on the stiffness properties is considered for further design optimization

A 7R Spatial Linkage for Ankle Rehabilitation with an Arbitrary Ankle Rotation Axis

In this paper, a 7R spatial linkage for ankle rehabilitation was proposed. Thanks to its kinematic geometry, the output joint, which is accommodated by the patient\u27s ankle, of the linkage can possess an arbitrary joint axis at any configuration. This advantage allows the patient achieving a flexible ankle motion in 3-D space while performing the rehabilitation exercise. The design concept of the 7R linkage is explained, and the displacement and force relationships between the input and output joints (i.e., the motor and patient\u27s ankle) are analyzed through an equivalent RSSR linkage. A prototype is built to validate the proposed design concept

Robot-assisted ankle rehabilitation for the treatment of drop foot: A case study

This paper involves the use of an intrinsically-compliant ankle rehabilitation robot for the treatment of drop foot. The robot has a bio-inspired design by employing four Festo fluidic actuators that mimic skeletal muscles to actuate three rotational degrees of freedom (DOFs). A position controller in task space was developed to track the predefined trajectory of the end effector. The position tracking was achieved by the length tracking of each actuator in joint space by inverse kinematics. A stroke patient with drop foot participated in the trial as a case study to evaluate the potential of this robot for clinical applications. The patient gave positive feedback in using the ankle robot for the treatment of drop foot, although some limitations exist. The trajectory tracking showed satisfactory accuracy throughout the whole training with varying ranges of motion, with the root mean square deviation (RMSD) value being 0.0408 rad and the normalized root mean square deviation (NRMSD) value being 8.16%. To summarize, preliminary findings support the potential of the ankle rehabilitation robot for clinical applications. Future work will investigate the effectiveness of the robot for treating drop foot on a large sample of subjects

A Preliminary Study on Robot-Assisted Ankle Rehabilitation for the Treatment of Drop Foot

This paper involves the use of a compliant ankle rehabilitation robot (CARR) for the treatment of drop foot. The robot has a bio-inspired design by employing four Festo Fluidic muscles (FFMs) that mimic skeletal muscles actuating three rotational degrees of freedom (DOFs). A trajectory tracking controller was developed in joint task space to track the predefined trajectory of the end effector. This controller was achieved by controlling individual FFM length based on inverse kinematics. Three patients with drop foot participated in a preliminary study to evaluate the potential of the CARR for clinical applications. Ankle stretching exercises along ankle dorsiflexion and plantarflexion (DP) were delivered for treating drop foot. All patients gave positive feedback in using this ankle robot for the treatment of drop foot, although some limitations exist. The proposed controller showed satisfactory accuracy in trajectory tracking, with all root mean square deviation (RMSD) values no greater than 0.0335 rad and normalized root mean square deviation (NRMSD) values less than 6.7%. These preliminary findings support the potentials of the CARR for clinical applications. Future work will investigate the effectiveness of the robot for treating drop foot on a large sample of subjects