Human-like bipedal walking is a goal of humanoid robotics. It is especially important to provide a robust falling prevention capability by imitating the human ability to switch between control ...strategies in response to disturbances, e.g., standing balancing and stepping motion. However, the motion control of a humanoid robot is challenging because the contact forces are constrained. This paper proposes a novel framework for control strategy switching based on the maximal output admissible (MOA) set, which is a set of initial states that satisfy the constraints. This makes it possible to determine whether the robot might fall down due to a constraint violation. The MOA set is extended to a trajectory tracking controller with a time-variant reference and constraint. In this extension, the motion of the vertical center of gravity is also considered, which has often been neglected in previous studies. Utilizing the MOA set, an example is shown of the falling prevention control by switching the standing balance control and trajectory tracking control to a stepping and hopping motion. Moreover, a method is presented for applying the MOA set framework to a position-controlled humanoid robot. The validity of the MOA set framework is verified based on simulations and experimental results.
•A novel framework for control strategy switching based on the maximal output admissible set (MOA) set is proposed.•The formulation and computation procedure for the MOA set are presented for trajectory tracking control.•The MOA set was applied to the falling prevention control. By switching between the regulator and trajectory tracking controller based on the MOA set, the robot can avoid falling with the COP constraint satisfied.•An experimental computation method for the MOA set via identification of the macroscopic feedback gain is proposed. The validity of this framework was verified by the results of experiments.
This study presents a resolved viscoelasticity control (RVC) method to handle multiple viscoelasticity in a humanoid system. A previous study proposed an RVC by explicitly considering ...structure-variability and demonstrated biped walking motions on an uneven terrain and a slope. In this study, the RVC is extended to multiple viscoelasticity, namely viscoelasticity on multiple feature points and multiple values in single viscoelasticity. The resolved multiple viscoelasticity control can improve both tracking performance and stability. The results indicate that resolving center of gravity (COG) and swing foot viscoelasticity improves the walking performance and that switching multiple values of the COG viscoelasticity improves the balancing performance. The proposed method is validated by using forward dynamics simulations.
Treatment of pressure ulcers requires removing the cause as well as eliminating factors that interfere with healing. There are no reports on the effect of medications prescribed for underlying ...diseases on pressure ulcers. Accordingly, the aim of this study was to investigate whether medications prescribed to patients with pressure ulcers could be a factor that influences pressure ulcer healing. We retrospectively reviewed the records of patients with pressure ulcer who were admitted to Chiba University Hospital between June 2009 and June 2015. A total of 110 patients were included in this study. In univariate analysis, there were significant differences in corticosteroid use and total caloric intake. Logistic regression analysis was performed for four factors, including corticosteroid use and total caloric intake, which were significant at P < .05, plus the two factors malignancy and body mass index, which were previously reported as factors that may affect pressure ulcer healing. The results showed that corticosteroid use odds ratio (OR) 0.205, 95% confidence interval (CI): 0.046 to 0.911, P = .037 and total caloric intake OR 1.002, 95% CI: 1.000 to 1.003, P = .006 were significant risk factors influencing pressure ulcer healing. This study revealed that use of corticosteroids and total caloric intake could be risk factors affecting pressure ulcer healing. These findings provide useful information for the management of pressure ulcer.
This article discusses a compliance optimization approach that satisfies positive definiteness. Physical human-robot interactions are an important topic in robotics, for which force or compliance ...control is a key technology. Operational space control (OSC) is one of the most common approaches for robot force control with redundant degrees of freedom. By linearizing OSC, we can derive joint stiffness and viscosity matrices equivalent to the OSC. For an appropriate control, it is important that these matrices are positive definite. However, the stiffness matrix equivalent to the OSC is not always positive definite. In this case, a high kinetic energy is required, which is a problem in terms of the control performance. Therefore, the control performance can be improved by explicitly considering the positive definiteness of the stiffness or compliance. In this article, the authors derive a dynamically consistent compliance formulation and propose a compliance optimization that satisfies positive definiteness. The space of the symmetric positive definite matrix is a Riemannian manifold. We show that minimizing the Riemaniann geodesic distance results in a better performance compared with using OSC. The proposed method is validated via forward dynamics simulations and experiments using a hydrostatically driven humanoid Hydra.
Background: There is a scarcity of studies comparing the clinical outcomes after percutaneous coronary intervention (PCI) for women and men stratified by the presentation of acute coronary syndromes ...(ACS) or stable coronary artery disease (CAD).Methods and Results: The study population included 26,316 patients who underwent PCI (ACS: n=11,119, stable CAD: n=15,197) from the CREDO-Kyoto PCI/CABG registry Cohort-2 and Cohort-3. The primary outcome was all-cause death. Among patients with ACS, women as compared with men were much older. Among patients with stable CAD, women were also older than men, but with smaller difference. The cumulative 5-year incidence of all-cause death was significantly higher in women than in men in the ACS group (26.2% and 17.9%, log rank P<0.001). In contrast, it was significantly lower in women than in men in the stable CAD group (14.2% and 15.8%, log rank P=0.005). After adjusting confounders, women as compared with men were associated with significantly lower long-term mortality risk with stable CAD but not with ACS (hazard ratio HR: 0.75, 95% confidence interval CI: 0.69–0.82, P<0.001, and HR: 0.92, 95% CI: 0.84–1.01, P=0.07, respectively). There was a significant interaction between the clinical presentation and the mortality risk of women relative to men (interaction P=0.002).Conclusions: Compared with men, women had significantly lower adjusted mortality risk after PCI among patients with stable CAD, but not among those with ACS.
An electro-hydrostatic actuator (EHA) has high backdrivability and is suitable for robots that interact with the environment, including human. However, the challenging problem in its mechanical ...design is that it is difficult to achieve compact size and high power transmission efficiency, compared with standard gear reducers. To tackle this problem, this study presents the design method by macro- and micro-scale designs. A linear-type EHA consists of a cylinder and a hydraulic pump. The former includes cylinder parameters that are dominant in the total size, and the latter includes gap width in the gear pump that is important for reducing power loss. We propose the hierarchical design to determine these parameters. In the macro-scale design, we determine the cylinder radius and differential pressure to maximize the efficiency-to-volume ratio. Based on the result of the macro-scale design, the micro-scale design determines the width of internal gaps to minimize the power loss in the gear pump. We derive mathematical formulations for the designs and develop the EHA by utilizing modular design and 3D printing. Moreover, we evaluate the fundamental properties of the developed EHA module, focusing on its power transmission efficiency and backdrivability.
A computational knee model facilitates efficient component design evaluations and preclinical testing under various dynamic loadings. However, the development of a highly mimicked dynamic whole knee ...model with specified ligament constraints that provides high predictive accuracy with in-vivo experiments remains a challenge.
In the present study, a musculoskeletal integrated force-driven explicit finite-element knee model with tibiofemoral and patellofemoral joints constrained with detailed soft tissue was developed. A proportional-integral-derivative controller was concurrently added to the knee model to track the boundary conditions. The actuations of the quadriceps and hamstrings were predicted via a subject-specific musculoskeletal model and matched with electromyography results.
Compared to in-vivo fluoroscopic results in a gait cycle, the predicted results of the kinematics of the tibiofemoral joint exhibited an agreement in terms of tendency and magnitude (anterior–posterior translation: RMSE = 1.1 mm, r2 = 0.87; inferior–superior translation: RMSE = 0.83 mm, r2 = 0.84; medial–lateral translation: RMSE = 0.82 mm, r2 = 0.05; flexion–extension rotation: RMSE = 0.23°, r2 = 1; internal-external rotation: RMSE = 1.85°, r2 = 0.65; varus–valgus rotation: RMSE = 1.39°, r2 = 0.08). Contact mechanics, including the contact area, pressure, and stress, were synchronously simulated on the tibiofemoral and patellofemoral joints.
The study provides a calibrated knee model and a kinematical validation approach that can be widely used in preclinical testing and knee prosthesis design.
•A musculoskeletal integrated force-driven finite element knee model was developed and verified by experiments.•The predicted results of kinematics of the tibiofemoral joint exhibited an agreement with in-vivo fluoroscopic results.•Contact mechanics including the contact area, pressure, and stress can be synchronously simulated by the proposed knee model.
This study investigates the compatibility between the soft deformation and high stiffness through the development of a soft robotic gripper for a human-scale payload. Softness is important for ...robotic systems that physically interact with the environments, especially for adaptive grasping or manipulation of unknown objects. Pursuing only softness would not achieve them either, and creating a certain stiffness is also an essential function in many human-scale applications. Soft robotics is unique in that it employs soft materials for the structure, and will find a lot more applications if it gains the human-scale specifications of force or the equivalent stiffness. We discuss the compatibility of the soft deformation and high stiffness based on a numerical analysis, and then present the design of a soft robotic gripper actuated by high oil-pressure, reporting its experimental validations.
Background: There is a scarcity of data evaluating contemporary real-world dual antiplatelet therapy (DAPT) strategies after percutaneous coronary intervention (PCI).Methods and Results: In the ...OPTIVUS-Complex PCI study multivessel cohort enrolling 982 patients undergoing multivessel PCI, including left anterior descending coronary artery using intravascular ultrasound (IVUS), we conducted 90-day landmark analyses to compare shorter and longer DAPT. DAPT discontinuation was defined as withdrawal of P2Y12inhibitors or aspirin for at least 2 months. The prevalence of acute coronary syndrome and high bleeding risk by the Bleeding Academic Research Consortium were 14.2% and 52.5%, respectively. The cumulative incidence of DAPT discontinuation was 22.6% at 90 days, and 68.8% at 1 year. In the 90-day landmark analyses, there were no differences in the incidences of a composite of death, myocardial infarction, stroke, or any coronary revascularization (5.9% vs. 9.2%, log-rank P=0.12; adjusted hazard ratio, 0.59; 95% confidence interval, 0.32–1.08; P=0.09) and BARC type 3 or 5 bleeding (1.4% vs. 1.9%, log-rank P=0.62) between the off- and on-DAPT groups at 90 days.Conclusions: The adoption of short DAPT duration was still low in this trial conducted after the release of the STOPDAPT-2 trial results. The 1-year incidence of cardiovascular events was not different between the shorter and longer DAPT groups, suggesting no apparent benefit of prolonged DAPT in reducing cardiovascular events even in patients who undergo multivessel PCI.
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