Robotic ankle-foot prostheses aim to improve the mobility of individuals with belowknee amputations by closely imitating the biomechanical function of the missing biological limb. To accomplish this goal, they must provide biomechanically accurate torque during ambulation. In addition, they must satisfy further requirements such as build height, range of motion (ROM), and weight. These requirements are critical for determining the potential number of users, range of activities that can be performed, and clinical outcomes. Previous studies have proposed addressing this challenge through the use of advanced actuation systems with series and parallel elastic actuators, clutchable leverages, and pneumatic artificial muscles. These ad vanced actuation systems have shown improved mechanical and electrical efficiency compared to conventional servo motors, making powered ankle prostheses possible. However, the improved efficiency comes at the expense of a tall build height, reduced ROM, and significant increase in weight, thus limiting the clinical viability of currently available powered prostheses.

Among wearable robotic devices, hand exoskeletons present an important and persistent challenge due to the compact dimensions and kinematic complexity of the human hand. To address these challenges, this paper introduces HandeXos-Beta (HX-beta), a novel index finger-thumb exoskeleton for hand rehabilitation. The HX-beta system features an innovative kinematic architecture that allows independent actuation of thumb flexion/extension and circumduction (opposition), thus enabling a variety of naturalistic and functional grip configurations. Furthermore, HX-beta features a novel series-elastic actuators (SEA) architecture that directly measures externally transferred torque in real-time, and thus enables both position- and torque-controlled modes of operation, allowing implementation of both robot-in-charge and user-in-charge exercise paradigms. Finally, HX-beta's adjustable orthosis, passive degrees of freedom, and under-actuated control scheme allow for optimal comfort, robot-user joint alignment, and flexible actuation for users of various hand sizes. In addition to the mechatronic design and resulting functional capabilities of HX-beta, this work presents a series of physical performance characterizations, including the position- and torque-control system performance, frequency response, end effector force, and output impedance. By each measure, the HX-beta exhibited performance comparable or superior to previously reported hand exoskeletons, including position and torque step response times on the order of 0.3 s, -3 dB cut-off frequencies ranging from approximately 2.5 to 4 Hz, and fingertip output forces on the order of 4 N. During use by a healthy subject in torque-controlled transparent mode, the HX-beta orthosis joints exhibited appropriately low output impedance, ranging from 0.42 to -0.042 Nm/rad at 1 Hz, over a range of functional grasps performed at real-life speeds. This combination of lab bench characterizations and functional evaluation provides a comprehensive verification of the design and performance of the HandeXos Beta exoskeleton, and its suitability for clinical application in hand rehabilitation.

Robotic ankle prostheses can imitate the biomechanical function of intact legs at the cost of a larger weight and size compared to conventional passive prostheses. Unfortunately, increased weight and size negatively affect comfort and socket stability, ultimately limiting their clinical viability. Alternatively, a nonbackdrivable transmission system can be used to actively regulate the ankle position during nonweight bearing activities only. This semiactive design can be made smaller and lighter as a result of the lower actuation power requirements. However, the transmission system must withstand high loads during stance and standing. Thus, available semiactive prostheses are still significantly heavier and have a larger build height than passive ankle prostheses. In this paper, we present the design, development, and validation of a semiactive ankle prosthesis with a nonbackdrivable cam follower mechanism designed to lower the load on moving components and align with the foot longitudinally as necessary to reduce the prosthesis weight and size. The proposed ankle mechanism is similar to 50% shorter, has similar to 40% wider range of motion (ROM), and is estimated to be similar to 27% lighter than available semiactive prostheses. Experiments with a transtibial subject show that the semiactive prosthesis can increase foot clearance up to 142% and reduce the load on the residual limb as low as 32% compared to passive prostheses.

As a consequence of limb loss, trans-femoral amputees exert 60% additional knee extension torque and 50% more plantar flexion torque in the healthy limb compared to non-amputees. In this paper, we developed an active knee-ankle-foot orthosis (KAFO) designed to assist the healthy leg of transfemoral amputees in activities of daily living, such as walking, ascending/descending stairs, and transitioning from sit-to-stand with adequate range of motion, speed, and peak torque. Our KAFO was designed to exceed the performance of similar assistive devices reported in literature in terms of: 1) portability; 2) power; 3) compliance; and 4) versatility. It is based on one-degree-of-freedom active series-elastic actuators in both the knee and ankle, with an additional passive degree of freedom at the ankle level to allow natural inversion/eversion. The knee module consists of a worm-gear surrounded by two pre-compressed springs. The ankle actuator relies on a mechanically adjustable compliance system combined with a 4-bar linkage transmission. The actuators were designed to optimize the torque output at the joints while fulfilling low-power requirements. This novel KAFO is controlled with a three-layer structure. The optimized low level, based on a closed-loop torque controller, has adequate performances for the targeted application. The device is also shown to fulfill the three pre-defined functional requirements for all locomotion modes.

This paper presents the design and experimental characterization of a 4-degree-of-freedom shoulder-elbow exoskeleton, NeuroExos Shoulder-elbow Module (NESM), for upper-limb neurorehabilitation and treatment of spasticity. The NESM employs a self-aligning mechanism based on passive rotational joints to smoothly self-align the robot's rotational axes to the user's ones. Compliant yet high-torque series-elastic actuators allow the NESM to safely interact with the user, particularly in response to sudden unpredicted movements, such as those caused by spastic contractions. The NESM control system provides a variety of rehabilitation exercises, enabling the customization of therapy to patients exhibiting a range of movement capabilities. Available exercises include passive mobilization, active-assisted, active-resisted, and active-disturbed training modes. The experimental characterization of two NESM actuation units demonstrated position and torque control performance suitable for use in neurorehabilitation applications, including up to 7 Hz of bandwidth in torque control. An algorithm for online detection of spastic contractions or sudden object collisions has been implemented and tested as well, with results suggesting that the current system can ensure safe interaction with patients.

Amputation at the above-knee level severely impairs the ability of an individual to ambulate. As ambulation requires power generation and active control of movements, the passive nature of most available leg prostheses is a major cause of the observed deficits. Powered prostheses aim to address this limitation using battery-operated servomotors. However, due to the wide ranges of torque and speed necessary to assistambulation, available powered prostheses are significantly heavier than passive prostheses, which limits their effectiveness and clinical viability. In this letter, we introduce the first fully powered robotic knee prosthesis that matches the weight of state-of-the-art passive prostheses while providing suitable torque and speed to power ambulation on level ground and stairs. Dynamic simulations are shown together with an extended experimental assessment supporting the design of a new actively variable transmission. A preliminary validation is provided by an above-knee amputee subject ambulating on level-ground and stairs.

Recently, the wearable robotic field has become extremely prolific in terms of active devices for human body assistance. Nevertheless, unfortunately, owing to strictly motor and sensor requirements in terms of mechanism, weight, size and dexterous manipulation capabilities, portable hand exoskeletons for rehabilitation and assistance have not been developed as much as the exoskeletons for lower and upper limbs; in fact, only a few of them present an outcome of their use in the clinical practice as positive as expected. This research work aims at designing an aid for the hand function based on exoskeleton technologies for patients who have lost or injured their hand skills. In particular, this paper presents a novel Series Elastic Transmission (SET) used as power transmission on a Hand Exoskeleton System (HES) based on a Series Elastic Actuator (SEA). The elastic element of the transmission has been designed through the innovative topology optimization approach which has led to manufacture a component whose mechanical features strictly replicate the desired ones. The authors have validated the proposed approach by testing a real elastic component. Suitable mechanical tests, whose results are reported in the paper, were executed in order to evaluate the goodness of the design procedure.

BACKGROUND:Spasticity is a muscle disorder associated with upper motor neuron syndrome occurring in neurological disorders, such as stroke, multiple sclerosis, spinal cord injury and others. It influences the patient's rehabilitation, interfering with function, limiting independence, causing pain and producing secondary impairments, such as contractures or other complications. Due to the heterogeneity of clinical signs of spasticity, there is no agreement on the most appropriate assessment and measurement modality for the evaluation of treatment outcomes.AIM:The aim of this article is to propose the use of new robotic devices for upper-limb spasticity assessment and describe the most relevant measures of spasticity which could be automatically assessed by using a technologically advanced device.DESIGN:Observational pilot study.SETTING:The treatment was provided in a Rehabilitation Centre where the device was located and the subjects were treated in an outpatients setting.POPULATION:Five post-stroke patients, age range 19-79 years (mean age 61, standard deviation [SD]±25) in their chronic phase.METHODS:A new robotic device able to automatically assess upper-limb spasticity during passive and active mobilization has been developed. The elbow spasticity of five post stroke patients has been assessed by using the new device and by means of the Modified Ashworth Scale (MAS). After the first assessment, subjects were treated with botulin toxin injections, and then underwent 10 sessions of robotic treatments. After the treatment, subjects spasticity was assessed by using the robotic device and the MAS Score.RESULTS:In four out of five patients, the botulin toxin injection and robotic treatment resulted in the improvement of the MAS Score; in three patients the robotic measures were able to detect the MAS changes. In one subject botulin toxin was not effective and the robotic device was able to detect the lack of effectiveness.CONCLUSIONS:By using the robotic device some spasticity parameters can be continuously recorded during the rehabilitation treatment in order to objectively measure the effectiveness of the interventions provided.CLINICAL REHABILITATION IMPACT:The standardized evaluation parameters recorded using robotic devices may provide several advantages: 1) the measures for spasticity assessment can be monitored during every rehabilitation session (even during each movement); 2) these measurements are able to highlight even small changes; 3) the recovery plateau can be detected early thus avoiding further rehabilitation sessions; and 4) these measurements can reduce the assessment bias in multicenter studies.

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.

Background: Enabling position/torque control with Series Elastic Actuators (SEAs) is a common trend in modem robotic research. Particularly, in the field of wearable robotics for assistance and rehabilitation, SEAs enable simultaneously torque control rendering a desired impedance, and an intrinsically safe compliance in the user-machine physical interaction. Hence they are usually preferred when deciding over an actuator architecture. However, their implementation is very hard to accomplish, due to the encumbrance, stiffness and torque requirements that these devices should meet. This is a particularly relevant problem for hand exoskeletons. Objectives: This paper presents a novel miniaturized SEA transmission system that can be easily integrated into a hand exoskeleton. The requirements for the elastic element were (i) limited encumbrance (maximum diameter of 18 mm, maximum length of 40 mm), (ii) low stiffness (around 1.6 N m/rad) and (iii) torque up to 0.3 N m. Methods: Two design solutions of miniaturized SEA transmission systems are presented (i.e. a cam-based and a tangential-spring design) along with their experimental validation. Both concepts have been manufactured and tested. The encumbrance, stiffness and maximum torque of the two elements have been quantified. The solution that matched the design specifications has been characterized in position and torque control. Results: The proposed design achieved a resulting equivalent stiffness of 1.985 N m/rad, maximum torque of 0.2 N m, low encumbrance (diameter: 11 mm; length: 37 mm) and parasitic stiffness equal to 0.5 N m/rad with 1.25 Hz movement frequency when controlled in zero-torque modality. Limitations: The miniaturized SEA element should be integrated into a hand exoskeleton to verify its performance in the final application. Conclusions: We present two mechatronic designs of a single-axis torque-sensitive miniaturized compliant element, and their experimental characterizations. One design solution resulted more suitable for being integrated into a hand exoskeleton.

Powered ankle-foot prostheses must provide high power and torque while satisfying stringent size and weight requirements. Previous works have focused on improving the prosthesis torque/weight ratio with novel actuation systems such as series and parallel elastic actuators, clutchable leverages, and pneumatic artificial muscles. In this paper, we propose an alternative design approach to minimize the prosthesis size and weight, while improving torque generation and electrical efficiency, based on a polycentric kinematic chain. The proposed approach is implemented on a novel powered polycentric ankle prosthesis (p(2)Ankle). Kinematics and mechatronic design are presented together with bench-top testing. Preliminary validation in standing and walking is conducted with an able-bodied user using a bypass orthosis.

This paper presents a novel methodology for estimating the gait phase of human walking through a simple sensory apparatus. Three subsystems are combined: a primary phase estimator based on adaptive oscillators, a desired gait event detector and a phase error compensator. The estimated gait phase is expected to linearly increase from 0 to 2\(\pi \) rad in one stride and remain continuous also when transiting to the next stride. We designed two experimental scenarios to validate this gait phase estimator, namely treadmill walking at different speeds and free walking. In the case of treadmill walking, the maximum phase error at the desired gait events was found to be 0.155 rad, and the maximum phase difference between the end of the previous stride and beginning of the current stride was 0.020 rad. In the free walking trials, phase error at the desired gait event was never larger than 0.278 rad. Our algorithm outperformed against two other benchmarked methods. The good performance of our gait phase estimator could provide consistent and finely tuned assistance for an exoskeleton designed to augment the mobility of patients.

We present a novel powered knee prosthesis with an active variable transmission (AVT) that adapts motor torque and speed output based on the requirements of different ambulation activities. The AVT works in combination with a spring/damper system to allow for both active and passive operation modes. Preliminary tests performed by an able-bodied subject wearing a bypass orthosis show that the proposed knee can support walking on level ground in passive mode, as well as ambulating on stairs with a reciprocal gait pattern in active mode.

Lower-limb amputation affects the ambulation ability and quality of life of about 600,000 individuals in the United States alone1. Individuals with transfemoral amputation typically walk slower, expend more energy, and have a higher risk of falls than able-bodied individuals2. Ambulation activities such as climbing ramps or stairs or standing up from a seated position are much more difficult than for able-bodied persons. Advances in prosthetic technologies are needed to improve the ambulation ability of above-knee amputees. Passive knee prostheses are lightweight, robust, and quiet, but can only perform activities with dissipative dynamics. Powered prostheses3 overcome this limitation by motorizing the prosthetic joints throughout the entire day, thus enabling the achievement of more activities. However, the prosthesis actuator must then accommodate a wide range of speed and torque to support the various activities, plus provide power over the course of the entire day. Consequently, powered prostheses provide the ability to perform more tasks at the expense of substantial weight, noise, and battery life, which in turn affect their acceptability and clinical viability. To address these shortcomings, we propose a hybrid actuation design for prosthetic knees. The proposed hybrid actuation system uses a motor, transmission, and control only for those activities requiring net-positive mechanical energy, such as climbing on stairs and ramps or performing sit-to-stand transfers. For non-positive mechanical energy tasks, such as standing and walking, the motor and transmission are mechanically disconnected, and passive knee components are used alone, thus achieving improved joint dynamics, and avoiding any electrical energy consumption.

Background: In human-centered robotics, exoskeletons are becoming relevant for addressing needs in the healthcare and industrial domains. Owing to their close interaction with the user, the safety and ergonomics of these systems are critical design features that require systematic evaluation methodologies. Proper transfer of mechanical power requires optimal tuning of the kinematic coupling between the robotic and anatomical joint rotation axes. We present the methods and results of an experimental evaluation of the physical interaction with an active pelvis orthosis (APO). This device was designed to effectively assist in hip flexion-extension during locomotion with a minimum impact on the physiological human kinematics, owing to a set of passive degrees of freedom for self-alignment of the human and robotic hip flexion-extension axes.Methods: Five healthy volunteers walked on a treadmill at different speeds without and with the APO under different levels of assistance. The user-APO physical interaction was evaluated in terms of: (i) the deviation of human lower-limb joint kinematics when wearing the APO with respect to the physiological behavior (i.e., without the APO); (ii) relative displacements between the APO orthotic shells and the corresponding body segments; and (iii) the discrepancy between the kinematics of the APO and the wearer's hip joints.Results: The results show: (i) negligible interference of the APO in human kinematics under all the experimented conditions; (ii) small (i.e., < 1 cm) relative displacements between the APO cuffs and the corresponding body segments (called stability); and (iii) significant increment in the human-robot kinematics discrepancy at the hip flexion-extension joint associated with speed and assistance level increase.Conclusions: APO mechanics and actuation have negligible interference in human locomotion. Human kinematics was not affected by the APO under all tested conditions. In addition, under all tested conditions, there was no relevant relative displacement between the orthotic cuffs and the corresponding anatomical segments. Hence, the physical human-robot coupling is reliable. These facts prove that the adopted mechanical design of passive degrees of freedom allows an effective human-robot kinematic coupling. We believe that this analysis may be useful for the definition of evaluation metrics for the ergonomics assessment of wearable robots.

Muscle overactivity (spasticity, dystonia or spasm) seen in certain neuromuscular disorders has been effectively treated with intramuscular injection of botulinum neurotoxins (BoTXs). Since they act in the nerve terminals, the toxin must be transported to the neuromuscular junctions which are generally clustered in one or more restricted areas (innervations zone(s)) in a skeletal muscle. The innervation zone targeted BoTX injections using guidance is highly recommended to achieve an optimal therapeutic goal with lower doses and fewer side effects. Hence, detection of the injection sites should be based on the knowledge about the localization of the innervation zone and the transport mechanism of BoTX in skeletal muscle. In this paper, we discuss the relevant muscle architecture and physical principles as regards BoTX distribution during muscle overactivity management.

Below-knee level amputation significantly impacts the ability of an individual to ambulate. Transtibial amputees are typically prescribed energetically passive ankle-foot prostheses that behave as a spring or controlled damper, and therefore cannot fully replace the function of the missing limb. More recently, fully-powered devices have been proposed to more closely match the power generation ability of intact limbs. However, these fully-powered devices are significantly heavier than passive devices, thus increasing the stress on the socket-residual limb interface. An alternative solution consists of using a motorized mechanism to actively reposition the foot during non-weight-bearing phases. By using this approach, the Össur© PROPRIO FOOT® showed promising outcomes such as improved gait energetics at self-selected speed, symmetry, and comfort. However, this device cannot be used by many transtibial amputees due to large build height (180 mm). Moreover, its weight has been shown critical for socket suspension. To address these limitations, we propose a novel non-backdrivable cam-based transmission. Based on this novel transmission, we developed a compact, lightweight ankle foot prosthesis. Bench-top testing and preliminary experiments with an able-bodied subject show that the proposed design can actively reposition the foot in swing as necessary to increase foot clearance, while adapting the ankle position to the ground inclination in stance.

Introduction : Spasticity is a typical motor disorder in patients affected by stroke. Typically post-stroke rehabilitation consists of repetition of mobilization exercises on impaired limbs, aimed to reduce muscle hypertonia and mitigate spastic reflexes. It is currently strongly debated if the treatment's effectiveness improves with the timeliness of its adoption; in particular, starting intensive rehabilitation as close as possible to the stroke event may counteract the growth and postpone the onset of spasticity. In this paper we present a phase-II clinical validation of a robotic exoskeleton in treating subacute post-stroke patients.Methods : Seventeen post-stroke patients participated in 10 daily rehabilitation sessions using the NEUROExos Elbow Module exoskeleton, each one lasting 45 min: the exercises consisted of isokinetic passive mobilization of the elbow, with torque threshold to detect excessive user's resistance to the movement. We investigated the safety by reporting possible adverse events, such as mechanical, electrical or software failures of the device or injuries or pain experienced by the patient. As regards the efficacy, the Modified Ashworth Scale, was identified as primary outcome measure and the NEEM metrics describing elbow joint resistance to passive extension (i.e., maximum extension torque and zero-torque angle) as secondary outcomes.Results : During the entire duration of the treatments no failures or adverse events for the patients were reported. No statistically significant differences were found in the Modified Ashworth Scale scores, between pre-treatment and post-treatment and between post-treatment and follow-up sessions, indicating the absence of spasticity increase throughout (14 days) and after (3-4months follow-up) the treatment. Exoskeleton metrics confirmed the absence of significant difference in between pre-and post-treatment data, whereas intra-session data highlighted significant differences in the secondary outcomes, toward a decrease of the subject's joint resistance.Conclusions : The results show that our robotic exoskeleton can be safely used for prolonged sessions in post-stroke and suggest that intensive early rehabilitation treatment may prevent the occurrence of spasticity at a later stage. Moreover, the NEEM metrics were found to be reliable compared to the Modified Ashworth Scale and sensitive to revealing intra-session changes of elbow resistance to passive extension, in agreement with clinical evidences.

This paper presents the design and preliminary evaluation of a novel version of the robotic elbow exoskeleton NEUROExos, designed for the in-clinic treatment of stroke survivors in acute and subacute phases. The robotic design implements a novel series elastic actuation system, a 4-degree-of-freedom (DoFs) passive mechanism for the anatomical axis alignment, and one active DoF with remote cable-driven actuation. The low-level control system allows two working modalities: a torque control and a joint position control. The high-level control system employs a finite-state machine that allows the setting and execution of these modalities during rehabilitation exercises. Preliminary pilot tests based on passive exercises, with three chronic post-stroke patients, demonstrated the effectiveness of the proposed approach in assessing joint rigidity and its usability within a rehabilitation clinic.