Portable robots for upper-limb rehabilitation after stroke: a systematic review and meta-analysis.

BACKGROUND: Robot-assisted upper-limb rehabilitation has been studied for many years, with many randomised controlled trials (RCTs) investigating the effects of robotic-assisted training on affected limbs. The current trend directs towards end-effector devices. However, most studies have focused on the effectiveness of rehabilitation devices, but studies on device sizes are relatively few. GOAL: Systematically review the effect of a portable rehabilitation robot (PRR) on the rehabilitation effectiveness of paralysed upper limbs compared with non-robotic therapy. METHODS: A meta-analysis was conducted on literature that included the Fugl-Meyer Assessment (FMA) obtained from the PubMed and Web of Science (WoS) electronic databases until June 2023. RESULTS: A total of 9 studies, which included RCTs, were completed and a meta-analysis was conducted on 8 of them. The analysis involved 295 patients. The influence on upper-limb function before and after treatment in a clinical environment is analysed by comparing the experimental group using the portable upper-limb rehabilitation robot with the control group using conventional therapy. The result shows that portable robots prove to be effective (FMA: SMD = 0.696, 95% = 0.099 to.293, p < 0.05). DISCUSSION: Both robot-assisted and conventional rehabilitation effects are comparable. In some studies, PRR performs better than conventional rehabilitation, but conventional treatments are still irreplaceable. Smaller size with better portability has its advantages, and portable upper-limb rehabilitation robots are feasible in clinical rehabilitation. CONCLUSION: Although portable upper-limb rehabilitation robots are clinically beneficial, few studies have focused on portability. Further research should focus on modular design so that rehabilitation robots can be decomposed, which benefits remote rehabilitation and household applications.

Design and Evaluation of a Bilateral Semi-Rigid Exoskeleton to Assist Hip Motion.

This study focused on designing and evaluating a bilateral semi-rigid hip exoskeleton. The exoskeleton assisted the hip joint, capitalizing on its proximity to the body's center of mass. Unlike its rigid counterparts, the semi-rigid design permitted greater freedom of movement. A temporal force-tracking controller allowed us to prescribe torque profiles during walking. We ensured high accuracy by tuning control parameters and series elasticity. The evaluation involved experiments with ten participants across ten force profile conditions with different end-timings and peak magnitudes. Our findings revealed a trend of greater reductions in metabolic cost with assistance provided at later timings in stride and at greater magnitudes. Compared to walking with the exoskeleton powered off, the largest reduction in metabolic cost was 9.1%. This was achieved when providing assistance using an end-timing at 44.6% of the stride cycle and a peak magnitude of 0.11 Nm kg-1. None of the tested conditions reduced the metabolic cost compared to walking without the exoskeleton, highlighting the necessity for further enhancements, such as a lighter and more form-fitting design. The optimal end-timing aligns with findings from other soft hip exosuit devices, indicating a comparable interaction with this prototype to that observed in entirely soft exosuit prototypes.

Review of Vision-Based Environmental Perception for Lower-Limb Exoskeleton Robots.

The exoskeleton robot is a wearable electromechanical device inspired by animal exoskeletons. It combines technologies such as sensing, control, information, and mobile computing, enhancing human physical abilities and assisting in rehabilitation training. In recent years, with the development of visual sensors and deep learning, the environmental perception of exoskeletons has drawn widespread attention in the industry. Environmental perception can provide exoskeletons with a certain level of autonomous perception and decision-making ability, enhance their stability and safety in complex environments, and improve the human-machine-environment interaction loop. This paper provides a review of environmental perception and its related technologies of lower-limb exoskeleton robots. First, we briefly introduce the visual sensors and control system. Second, we analyze and summarize the key technologies of environmental perception, including related datasets, detection of critical terrains, and environment-oriented adaptive gait planning. Finally, we analyze the current factors limiting the development of exoskeleton environmental perception and propose future directions.

Can lower-limb exoskeletons support sit-to-stand motions in frail elderly without crutches? A study combining optimal control and motion capture.

With the global geriatric population expected to reach 1.5 billion by 2050, different assistive technologies have been developed to tackle age-associated movement impairments. Lower-limb robotic exoskeletons have the potential to support frail older adults while promoting activities of daily living, but the need for crutches may be challenging for this population. Crutches aid safety and stability, but moving in an exoskeleton with them can be unnatural to human movements, and coordination can be difficult. Frail older adults may not have the sufficient arm strength to use them, or prolonged usage can lead to upper limb joint deterioration. The research presented in this paper makes a contribution to a more detailed study of crutch-less exoskeleton use, analyzing in particular the most challenging motion, sit-to-stand (STS). It combines motion capture and optimal control approaches to evaluate and compare the STS dynamics with the TWIN exoskeleton with and without crutches. The results show trajectories that are significantly faster than the exoskeleton's default trajectory, and identify the motor torques needed for full and partial STS assistance. With the TWIN exoskeleton's existing motors being able to support 112 Nm (hips) and 88 Nm (knees) total, assuming an ideal contribution from the device and user, the older adult would need to contribute a total of 8 Nm (hips) and 50 Nm (knees). For TWIN to provide full STS assistance, it would require new motors that can exert at least 121 Nm (hips) and 140 Nm (knees) total. The presented optimal control approaches can be replicated on other exoskeletons to determine the torques required with their mass distributions. Future improvements are discussed and the results presented lay groundwork for eliminating crutches when moving with an exoskeleton.

Effect of an upper body exoskeleton for surgeons on postoperative neck, back and shoulder complaints.

OBJECTIVES: Surgeons are exposed to high levels of physical stress while working in the operating room. In industry, so-called exoskeletons are used to support the back and shoulder area. The aim of this study was to investigate the feasibility and effects of an upper body exoskeleton on postoperative physical complaints of surgeons. METHODS: Surgeons from a university hospital in the fields of orthopaedics, trauma- and visceral surgery performed two operations of the same type and planned length on two different days. The first operation was performed without an exoskeleton, the second with an exoskeleton. The participants completed questionnaires on shoulder pain (SPADI), neck pain (VAS and NDI) and back pain (VAS and ODI) before and after the procedure. RESULTS: A total of 25 participants were included and performed 50 surgeries with a mean surgery duration of 144 min without and 138 min with exoskeleton. Without the exoskeleton, the activity of the operation resulted in a significant increase of the VAS neck by 1.0 points (SD 1.2, p < 0.001), NDI by 4.8 (SD 8.6; p = 0.010), VAS back by 0.7 (SD 1.0, p = 0.002), and ODI by 2.7 (SD 4.1, p = 0.003). With the exoskeleton the the participants reported about significant less complaints after the surgery (VAS neck: p = 0.001, NDI: p = 0.003, VAS back: p = 0.036, ODI: p = 0.036, SPADI: p = 0.016) Conclusion: An upper body exoskeleton can significantly reduce the discomfort in the neck, shoulder and back caused to surgeons by surgery.

Effects of upper-limb exoskeleton on muscle activity in tasks requiring arm elevation: Part II - In-field experiments in construction industry settings.

Background: The body of literature regarding the use of an upper limb exoskeleton during authentic working conditions is sparse. Objective: The aim of this study was to evaluate the effectiveness of an upper limb exoskeleton in reducing muscle strain during authentic industrial construction work. Methods: Fifteen male participants, comprising of roofers, scaffolders, builders, bricklayers, and graders performing overhead work participated in the study. During work without (REF) and with exoskeleton (EXO), muscle activity from 8 muscles, heart rate (HR), metabolic equivalent (MET), and upper arm elevation angles were recorded. Results: When using the exoskeleton, a significant reduction of 20.2% in average muscle activity of 8 muscles was found. The largest effect focused on m. deltoideus, where 46.2 and 32.2% reduction occurred in medial and anterior parts of the muscle, respectively. HR and MET were unaffected. Upper arm elevation angles were similar between REF and EXO, indicating equal biomechanical loading. Conclusions: This study indicates that exoskeletons show great promise in reducing the potential for musculoskeletal strain during authentic overhead construction work.

Human-centered design of a novel soft exosuit for post-stroke gait rehabilitation.

BACKGROUND: Stroke remains a major cause of long-term adult disability in the United States, necessitating the need for effective rehabilitation strategies for post-stroke gait impairments. Despite advancements in post-stroke care, existing rehabilitation often falls short, prompting the development of devices like robots and exoskeletons. However, these technologies often lack crucial input from end-users, such as clinicians, patients, and caregivers, hindering their clinical utility. Employing a human-centered design approach can enhance the design process and address user-specific needs. OBJECTIVE: To establish a proof-of-concept of the human-centered design approach by refining the NewGait® exosuit device for post-stroke gait rehabilitation. METHODS: Using iterative design sprints, the research focused on understanding the perspectives of clinicians, stroke survivors, and caregivers. Two design sprints were conducted, including empathy interviews at the beginning of the design sprint to integrate end-users' insights. After each design sprint, the NewGait device underwent refinements based on emerging issues and recommendations. The final prototype underwent mechanical testing for durability, biomechanical simulation testing for clinical feasibility, and a system usability evaluation, where the new stroke-specific NewGait device was compared with the original NewGait device and a commercial product, Theratogs®. RESULTS: Affinity mapping from the design sprints identified crucial categories for stakeholder adoption, including fit for females, ease of donning and doffing, and usability during barefoot walking. To address these issues, a system redesign was implemented within weeks, incorporating features like a loop-backed neoprene, a novel closure mechanism for the shoulder harness, and a hook-and-loop design for the waist belt. Additional improvements included reconstructing anchors with rigid hook materials and replacing latex elastic bands with non-latex silicone-based bands for enhanced durability. Further, changes to the dorsiflexion anchor were made to allow for barefoot walking. Mechanical testing revealed a remarkable 10-fold increase in durability, enduring 500,000 cycles without notable degradation. Biomechanical simulation established the modularity of the NewGait device and indicated that it could be configured to assist or resist different muscles during walking. Usability testing indicated superior performance of the stroke-specific NewGait device, scoring 84.3 on the system usability scale compared to 62.7 for the original NewGait device and 46.9 for Theratogs. CONCLUSION: This study successfully establishes the proof-of-concept for a human-centered design approach using design sprints to rapidly develop a stroke-specific gait rehabilitation system. Future research should focus on evaluating the clinical efficacy and effectiveness of the NewGait device for post-stroke rehabilitation.

Cardioid oscillator-based pattern generator for imitating the time-ratio-asymmetrical behavior of the lower limb exoskeleton.

Introduction: Periodicity, self-excitation, and time ratio asymmetry are the fundamental characteristics of the human gait. In order to imitate these mentioned characteristics, a pattern generator with four degrees of freedom is proposed based on cardioid oscillators developed by the authors. Method: The proposed pattern generator is composed of four coupled cardioid oscillators, which are self-excited and have asymmetric time ratios. These oscillators are connected with other oscillators through coupled factors. The dynamic behaviors of the proposed oscillators, such as phase locking, time ratio, and self-excitation, are analyzed via simulations by employing the harmonic balance method. Moreover, for comparison, the simulated trajectories are compared with the natural joint trajectories measured in experiments. Results and discussion: Simulation and experimental results show that the behaviors of the proposed pattern generator are similar to those of the natural lower limb. It means the simulated trajectories from the generator are self-excited without any additional inputs and have asymmetric time ratios. Their phases are locked with others. Moreover, the proposed pattern generator can be applied as the reference model for the lower limb exoskeleton controlling algorithm to produce self-adjusted reference trajectories.

Innovative Metaheuristic Optimization Approach with a Bi-Triad for Rehabilitation Exoskeletons.

The present work proposes a comprehensive metaheuristic methodology for the development of a medical robot for the upper limb rehabilitation, which includes the topological optimization of the device, kinematic models (5 DOF), human-robot interface, control and experimental tests. This methodology applies two cutting-edge triads: (1) the three points of view in engineering design (client, designer and community) and (2) the triad formed by three pillars of Industry 4.0 (autonomous machines and systems, additive manufacturing and simulation of virtual environments). By applying the proposed procedure, a robotic mechanism was obtained with a reduction of more than 40% of its initial weight and a human-robot interface with three modes of operation and a biomechanically viable kinematic model for humans. The digital twin instance and its evaluation through therapeutic routines with and without disturbances was assessed; the average RMSEs obtained were 0.08 rad and 0.11 rad, respectively. The proposed methodology is applicable to any medical robot, providing a versatile and effective solution for optimizing the design and development of healthcare devices. It adopts an innovative and scalable approach to enhance their processes.

Brain-machine interface based on deep learning to control asynchronously a lower-limb robotic exoskeleton: a case-of-study.

BACKGROUND: This research focused on the development of a motor imagery (MI) based brain-machine interface (BMI) using deep learning algorithms to control a lower-limb robotic exoskeleton. The study aimed to overcome the limitations of traditional BMI approaches by leveraging the advantages of deep learning, such as automated feature extraction and transfer learning. The experimental protocol to evaluate the BMI was designed as asynchronous, allowing subjects to perform mental tasks at their own will. METHODS: A total of five healthy able-bodied subjects were enrolled in this study to participate in a series of experimental sessions. The brain signals from two of these sessions were used to develop a generic deep learning model through transfer learning. Subsequently, this model was fine-tuned during the remaining sessions and subjected to evaluation. Three distinct deep learning approaches were compared: one that did not undergo fine-tuning, another that fine-tuned all layers of the model, and a third one that fine-tuned only the last three layers. The evaluation phase involved the exclusive closed-loop control of the exoskeleton device by the participants' neural activity using the second deep learning approach for the decoding. RESULTS: The three deep learning approaches were assessed in comparison to an approach based on spatial features that was trained for each subject and experimental session, demonstrating their superior performance. Interestingly, the deep learning approach without fine-tuning achieved comparable performance to the features-based approach, indicating that a generic model trained on data from different individuals and previous sessions can yield similar efficacy. Among the three deep learning approaches compared, fine-tuning all layer weights demonstrated the highest performance. CONCLUSION: This research represents an initial stride toward future calibration-free methods. Despite the efforts to diminish calibration time by leveraging data from other subjects, complete elimination proved unattainable. The study's discoveries hold notable significance for advancing calibration-free approaches, offering the promise of minimizing the need for training trials. Furthermore, the experimental evaluation protocol employed in this study aimed to replicate real-life scenarios, granting participants a higher degree of autonomy in decision-making regarding actions such as walking or stopping gait.

Robotic assisted and exoskeleton gait training effect in mental health and fatigue of multiple sclerosis patients. A systematic review and a meta-analysis.

PURPOSE: Robotic and Exoskeleton Assisted Gait Training (REAGT) has become the mainstream gait training module. Studies are investigating the psychosocial effects of REAGT mostly as secondary outcomes. Our systematic review and meta-analysis aims to investigate the effects of REAGT in MS patients' mental health and fatigue. MATERIALS AND METHODS: We searched the electronic databases (Scopus, PubMed, Pedro, Cochrane Trials, Dare) for RCT studies fulfilling our inclusion criteria. A meta-analysis of available assessment tools was conducted calculating the summary mean differences in two different timepoints, before and after the intervention using random-effects models. RESULTS: The systematic search of the electronic databases identified 302 studies. Seven RCT studies were considered eligible for data extraction and meta-analysis, according to our eligibility criteria. We were able to obtain adequate data to proceed with a quantitative synthesis for QoL SF36-MC (Mental Component), QoL SF-36 mental and psychosocial subscales, Multiple Sclerosis Quality of Life-54-Mental Health Composite (MSQoL-54-MHC), Patient's Health Questionnaire (PHQ-9) and Fatigue Severity Scale (FSS). CONCLUSIONS: Overall, REAGT seems to have a positive effect to Quality of Life, especially in MS patients' perspective of General and Mental Health and a slight positive effect in depression as measured by PHQ-9.Implications for rehabilitationMultiple Sclerosis (MS) decreases physical and non-physical aspects of patients' quality of life perspective.Rehabilitation strategy must take into consideration the non-physical effects of a training intervention.Robotic and Exoskeleton Gait Training has a positive effect in MS patients' non-physical quality of life and a slight positive effect in depression.

Wearing a back-support exoskeleton alters lower-limb joint kinetics during single-step recovery following a forward loss of balance.

We assessed the effects of a passive, back-support exoskeleton (BSE) on lower-limb joint kinetics during the initiation and swing phases of recovery from a forward loss of balance. Sixteen (8M, 8F) young, healthy participants were released from static forward-leaning postures and attempted to recover their balance with a single-step while wearing a BSE (backXTM) with different levels of support torque and in a control condition. The BSE provided âˆ¼ 15-20 Nm of external hip extension torque on the stepping leg at the end of initiation and beginning of swing phases. Participants were unable to generate sufficient hip flexion torque, power, and work to counteract this external torque, although they sustained hip flexion torque for a more prolonged period, resulting in slightly increased hip contribution to positive leg work (compared to control). However, net positive leg work, and the net contribution of hip joint (human + BSE) to total leg work decreased with BSE use. While all participants had changes in hip joint kinetics, a significant compensatory increase in ankle contribution to positive leg work was observed only among females. Our results suggest that BSE use adversely affects reactive stepping by decreasing the stepping leg kinetic energy for forward propulsion, and that the relative contributions of lower-limb joints to total mechanical work done during balance recovery are altered by BSE use. BSEs may thus need to be implemented with caution for dynamic tasks in occupational settings, as they may impair balance recovery following a forward loss of balance.

A novel exoskeletal-derived C-type lectin facilitates phagocytosis of hemocytes in the oriental river prawn Macrobrachium nipponense.

C-type lectins (CTLs) execute critical functions in multiple immune responses of crustaceans as a member of pattern recognition receptors (PRRs) family. In this study, a novel CTL was identified from the exoskeleton of the oriental river prawn Macrobrachium nipponense (MnLec3). The full-length cDNA of MnLec3 was 1150 bp with an open reading frame of 723 bp, encoding 240 amino acids. MnLec3 protein contained a signal peptide and one single carbohydrate-recognition domain (CRD). MnLec3 transcripts were widely distributed at the exoskeleton all over the body. Significant up-regulation of MnLec3 in exoskeleton after Aeromonas hydrophila challenged suggested the involvement of MnLec3 as well as the possible function of the exoskeleton in immune response. In vitro tests with recombinant MnLec3 protein (rMnLec3) manifested that it had polysaccharide binding activity, a wide spectrum of bacterial binding activity and agglutination activity only for tested Gram-negative bacteria (Escherichia coli, Vibrio anguillarum and A. hydrophila). Moreover, rMnLec3 significantly promoted phagocytic ability of hemocytes against A. hydrophila in vivo. What's more, MnLec3 interference remarkably impaired the survivability of the prawns when infected with A. hydrophila. Collectively, these results ascertained that MnLec3 derived from exoskeleton took an essential part in immune defense of the prawns against invading bacteria as a PRR.

Clinical Delivery of Overground Exoskeleton Gait Training in Persons With Spinal Cord Injury Across the Continuum of Care: A Retrospective Analysis.

Background: After spinal cord injury (SCI), inpatient rehabilitation begins and continues through outpatient therapy. Overground exoskeleton gait training (OEGT) has been shown to be feasible in both settings, yet its use as an intervention across the continuum has not yet been reported. Objectives: This study describes OEGT for patients with SCI across the continuum and its effects on clinical outcomes. Methods: Medical records of patients with SCI who completed at least one OEGT session during inpatient and outpatient rehabilitation from 2018 to 2021 were retrospectively reviewed. Demographic data, Walking Index for Spinal Cord Injury-II (WISCI-II) scores, and OEGT session details (frequency, "walk" time, "up" time, and step count) were extracted. Results: Eighteen patients [male (83%), White (61%), aged 37.4 ± 15 years, with tetraplegia (50%), American Spinal Injury Association Impairment Scale A (28%), B (22%), C (39%), D (11%)] completed OEGT sessions (motor complete, 18.2 ± 10.3; motor incomplete, 16.7 ± 7.7) over approximately 18 weeks (motor complete, 15.1 ± 6.4; motor incomplete, 19.0 ± 8.2). Patients demonstrated improved OEGT session tolerance on device metrics including "walk" time (motor complete, 7:51 ± 4:42 to 24:50 ± 9:35 minutes; motor incomplete, 12:16 ± 6:01 to 20:01 ± 08:05 minutes), "up" time (motor complete, 16:03 ± 7:41 to 29:49 ± 12:44 minutes; motor incomplete, 16:38 ± 4:51 to 23:06 ± 08:50 minutes), and step count (motor complete, 340 ± 295.9 to 840.2 ± 379.4; motor incomplete, 372.3 ± 225.2 to 713.2 ± 272). Across therapy settings, patients with motor complete SCI experienced improvement in WISCI-II scores from 0 ± 0 at inpatient admission to 3 ± 4.6 by outpatient discharge, whereas the motor incomplete group demonstrated a change of 0.2 ± 0.4 to 9.0 ± 6.4. Conclusion: Patients completed OEGT across the therapy continuum. Patients with motor incomplete SCI experienced clinically meaningful improvements in walking function.

Determinants of wearer satisfaction factors for harnesses in upper-limb assistive wearable robots.

Wearable robots are increasingly being deployed for use in industrial fields. However, only a few studies have focused on the usability of wearable robots. The present study evaluated the factors affecting the usability of a harness in securing a wearable robot to the body because the harness directly affects the work efficiency, and thus its design and use require careful consideration. A comparative evaluation of the arrangement of the Vest Exoskeleton before and after improvements was conducted, in which participants performed a benchmark assembly task while wearing the robot. Results showed that wearability decreased after the improvements due to the additional straps and buckles used, but the overall wearing satisfaction improved as a result of increased stability. Stability and convenience were the main factors affecting the overall wearing satisfaction, while sub-indicators included wearing comfort and tactile sensation. Therefore, improvements in stability, such as those related to fixation strength and tactile sensation, had a direct positive impact on the overall wearing satisfaction.

Modularity Implications of an Overground Exoskeleton on Plantar Pressures, Strength, and Spasticity in Persons with Acquired Brain Injury.

This study explored the effects of a modular overground exoskeleton on plantar pressure distribution in healthy individuals and individuals with Acquired Brain Injury (ABI). The research involved 21 participants, including ABI patients and healthy controls, who used a unique exoskeleton with adaptable modular configurations. The primary objective was to assess how these configurations, along with factors such as muscle strength and spasticity, influenced plantar pressure distribution. The results revealed significant differences in plantar pressures among participants, strongly influenced by the exoskeleton's modularity. Notably, significant distinctions were found between ABI patients and healthy individuals. Configurations with two modules led to increased pressure in the heel and central metatarsus regions, whereas configurations with four modules exhibited higher pressures in the metatarsus and hallux regions. Future research should focus on refining and customizing rehabilitation technologies to meet the diverse needs of ABI patients, enhancing their potential for functional recovery.

Biomechanical Effects of Using a Passive Exoskeleton for the Upper Limb in Industrial Manufacturing Activities: A Pilot Study.

This study investigates the biomechanical impact of a passive Arm-Support Exoskeleton (ASE) on workers in wool textile processing. Eight workers, equipped with surface electrodes for electromyography (EMG) recording, performed three industrial tasks, with and without the exoskeleton. All tasks were performed in an upright stance involving repetitive upper limbs actions and overhead work, each presenting different physical demands in terms of cycle duration, load handling and percentage of cycle time with shoulder flexion over 80°. The use of ASE consistently lowered muscle activity in the anterior and medial deltoid compared to the free condition (reduction in signal Root Mean Square (RMS) -21.6% and -13.6%, respectively), while no difference was found for the Erector Spinae Longissimus (ESL) muscle. All workers reported complete satisfaction with the ASE effectiveness as rated on Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST), and 62% of the subjects rated the usability score as very high (>80 System Usability Scale (SUS)). The reduction in shoulder flexor muscle activity during the performance of industrial tasks is not correlated to the level of ergonomic risk involved. This preliminary study affirms the potential adoption of ASE as support for repetitive activities in wool textile processing, emphasizing its efficacy in reducing shoulder muscle activity. Positive worker acceptance and intention to use ASE supports its broader adoption as a preventive tool in the occupational sector.

Optimization of Torque-Control Model for Quasi-Direct-Drive Knee Exoskeleton Robots Based on Regression Forecasting.

The choice of torque curve in lower-limb enhanced exoskeleton robots is a key problem in the control of lower-limb exoskeleton robots. As a human-machine coupled system, mapping from sensor data to joint torque is complex and non-linear, making it difficult to accurately model using mathematical tools. In this research study, the knee torque data of an exoskeleton robot climbing up stairs were obtained using an optical motion-capture system and three-dimensional force-measuring tables, and the inertial measurement unit (IMU) data of the lower limbs of the exoskeleton robot were simultaneously collected. Nonlinear approximations can be learned using machine learning methods. In this research study, a multivariate network model combining CNN and LSTM was used for nonlinear regression forecasting, and a knee joint torque-control model was obtained. Due to delays in mechanical transmission, communication, and the bottom controller, the actual torque curve will lag behind the theoretical curve. In order to compensate for these delays, different time shifts of the torque curve were carried out in the model-training stage to produce different control models. The above model was applied to a lightweight knee exoskeleton robot. The performance of the exoskeleton robot was evaluated using surface electromyography (sEMG) experiments, and the effects of different time-shifting parameters on the performance were compared. During testing, the sEMG activity of the rectus femoris (RF) decreased by 20.87%, while the sEMG activity of the vastus medialis (VM) increased by 17.45%. The experimental results verify the effectiveness of this control model in assisting knee joints in climbing up stairs.

A transporter that allows phosphate ions to control the polymorph of exoskeletal calcium carbonate biomineralization.

The SLC20A2 transporter supplies phosphate ions (Pi) for diverse biological functions in vertebrates, yet has not been studied in crustaceans. Unlike vertebrates, whose skeletons are mineralized mainly by calcium phosphate, only minute amounts of Pi are found in the CaCO3-mineralized exoskeletons of invertebrates. In this study, a crustacean SLC20A2 transporter was discovered and Pi transport to exoskeletal elements was studied with respect to the role of Pi in invertebrate exoskeleton biomineralization, revealing an evolutionarily conserved mechanism for Pi transport in both vertebrates and invertebrates. Freshwater crayfish, including the study animal Cherax quadricarinatus, require repeated molt cycles for their growth. During the molt cycle, crayfish form transient exoskeletal mineral storage organs named gastroliths, which mostly contain amorphous calcium carbonate (ACC), an unstable polymorph long-thought to be stabilized by Pi. RNA interference experiments via CqSLC20A2 dsRNA injections reduced Pi content in C. quadricarinatus gastroliths, resulting in increased calcium carbonate (CaCO3) crystallinity and grain size. The discovery of a SLC20A2 transporter in crustaceans and the demonstration that knocking down its mRNA reduced Pi content in exoskeletal elements offers the first direct proof of a long-hypothesized mechanism by which Pi affects CaCO3 biomineralization in the crustacean exoskeleton. This research thus demonstrated the distinct role of Pi as an amorphous mineral polymorph stabilizer in vivo, suggesting further avenues for amorphous biomaterial studies. STATEMENT OF SIGNIFICANCE: • Crustaceans exoskeletons are hardened mainly by CaCO3, with Pi in minute amounts • Pi was hypothesized to stabilize exoskeletal amorphous mineral forms in vivo • For the first time, transport protein for Pi was discovered in crayfish • Transport knock-down resulted in exoskeletal CaCO3 crystallization and reduced Pi.

Gait Recognition and Assistance Parameter Prediction Determination Based on Kinematic Information Measured by Inertial Measurement Units.

The gait recognition of exoskeletons includes motion recognition and gait phase recognition under various road conditions. The recognition of gait phase is a prerequisite for predicting exoskeleton assistance time. The estimation of real-time assistance time is crucial for the safety and accurate control of lower-limb exoskeletons. To solve the problem of predicting exoskeleton assistance time, this paper proposes a gait recognition model based on inertial measurement units that combines the real-time motion state recognition of support vector machines and phase recognition of long short-term memory networks. A recognition validation experiment was conducted on 30 subjects to determine the reliability of the gait recognition model. The results showed that the accuracy of motion state and gait phase were 99.98% and 98.26%, respectively. Based on the proposed SVM-LSTM gait model, exoskeleton assistance time was predicted. A test was conducted on 10 subjects, and the results showed that using assistive therapy based on exercise status and gait stage can significantly improve gait movement and reduce metabolic costs by an average of more than 10%.