Control Design for CABLEankle, a Cable Driven Manipulator for Ankle Motion Assistance

A control design is presented for a cable driven parallel manipulator for performing a controlled motion assistance of a human ankle. Requirements are discussed for a portable, comfortable, and light-weight solution of a wearable device with an overall design with low-cost features and user-oriented operation. The control system utilizes various operational and monitoring sensors to drive the system and also obtain continuous feedback during motion to ensure an effective recovery. This control system for CABLEankle device is designed for both active and passive rehabilitation to facilitate the improvement in both joint mobility and surrounding muscle strength.

Analysis of a Wearable Robotic System for Ankle Rehabilitation

As one of the most commonly injured joints of the human body, the ankle is often subject to sprains or fractures that require motion assistance to recover mobility. Whereas physiotherapists usually perform rehabilitation in one-on-one sessions with patients, several successful robotic rehabilitation solutions have been proposed in the last years. However, their design is usually bulky and requires the patient to sit or stand in a static position. A lightweight wearable device for ankle motion assistance, the CABLEankle, is here proposed for motion ankle exercising in rehabilitation and training. The CABLEankle is based on a cable-driven S-4SPS parallel architecture, which enables motion assistance over the large motion range of the human ankle in a walking gait. The proposed mechanism design is analyzed with kinematic and static models, and the force closure workspace of the mechanism is discussed with analytical results. Finally, the feasibility of the proposed design is investigated through numerical simulations over the ankle motion range as a characterization of the peculiar motion.

Robot-assisted ankle rehabilitation: a review

Aim: The aim of this review paper is to summarize recent developments and research in robotics, relevant to the field of ankle rehabilitation, to overview new findings and determine the actual state of the art.Method: The literature search was performed using scientific and medical databases (Scopus, PubMed and Web of Science) and other websites related to robots used in the area of ankle rehabilitation, analysing studies from 1950s to present. Information about the mechanical and kinematic specifications, actuation and stage of development was extracted from the selected literature.Results: Several types of rehabilitation robots have been considered, and they were classified depending on their architecture and design features. We we found that, regardless of the differences in architectures, only a few of them have been commercialized. The majority of rehabilitation robots designs allows plantarflexion-dorsiflexion movements. Unless some exceptions, most of the wearable robots do not allow the adduction-abduction movement. Neither the physical appearance of the robot nor the user's perception towards it has not regularly been taken into account in the design stage. This limits the possibility of successful commercialization.Conclusions: Up to the present moment, the main challenges in the field of robot rehabilitation are the lack of unique rehabilitation protocols capable to fulfil the needs of all types of patients and the additional resources to measure the effectiveness of proposals that have not yet been commercialized. Nonetheless, we have mentioned above three areas were the challenges in design are more pressing. The first one is the robot architecture, which still presents some incommodities nowadays to emulate the ankle joint movement in a natural way. Thus, the displacements experienced by the axes in the joint must be adaptable to each patient and a wide range of pathologies. Moreover, many proposals are not been conceived to the purpose of commercialization, and even less to become an object of personal use.Implications for rehabilitationThis review states that the use of robotic devices for ankle rehabilitation is a consolidated paradigm in the ankle's rehabilitation.Platform-based robots allow to do complex and specialized spatial movements and these architectures endow the device with high stiffness, a balanced force distribution and better adaptability to the mechanical properties of human ankle joints. Unless some exceptions, most of the wearable robots do not allow the adduction-abduction movement.For a full integration of these technologies in the ankle's rehabilitation field, more clinical evaluations are needed.Regardless of the potential of robotic devices in rehabilitation, only a few of them have been commercialized.

Design and kinematic analysis of redundantly actuated parallel mechanisms for ankle rehabilitation

In this paper, we present the design of two serial spherical mechanisms to substitute for a single spherical joint that is usually used to connect the platform with the base in three degrees of freedom parallel mechanisms. According to the principle derived from the conceptual design, through using the two serial spherical mechanisms as the constraint limb, several redundantly actuated parallel mechanisms are proposed for ankle rehabilitation. The proposed parallel mechanisms all can perform the rotational movements of the ankle in three directions while at the same time the mechanism center of rotations can match the ankle axes of rotations compared with other multi-degree-of-freedom devices, due to the structural characteristics of the special constraint limb and platform. Two special parallel mechanisms are selected to analyze their kinematical performances, such as workspace, dexterity, singularity, and stiffness, based on the computed Jacobian. The results show that the proposed scheme of actuator redundancy can guarantee that the redundantly actuated parallel mechanisms have no singularity, better dexterity, and stiffness within the prescribed workspace in comparison with the corresponding non-redundant parallel mechanisms. In addition, the proposed mechanisms possess certain reconfigurable capacity based on control strategies or rehabilitation modes to obtain sound performance for completing ankle rehabilitation exercise.

Spinal Implant Development, Modeling, and Testing to Achieve Customizable and Nonlinear Stiffness

The spine naturally has a nonlinear force-deflection characteristic which facilitates passive stability, and thus there is a need for spinal implants that duplicate this behavior to provide stabilization when the spine loses stiffness through injury, degeneration, or surgery. Additionally, due to the complexity and variability in the mechanics of spinal dysfunction, implants could potentially benefit from incorporating a customizable stiffness into their design. This paper presents a spinal implant with contact-aided inserts that provide a customizable nonlinear stiffness. An analytical model was utilized to optimize the device design, and the model was then verified using a finite element model. Validation was performed on physical prototypes, first in isolation using a tensile tester and then using cadaveric testing on an in-house spine tester. Testing confirmed the performance of the implant and it was observed that the device increased mechanical stability to the spinal segment in flexion-extension and lateral-bending.