Disturbance observer enhanced variable gain controller for robot teleoperation with motion capture using wearable armbands

Disturbance observer (DOB) based controller performs well in estimating and compensating for perturbation when the external or internal unknown disturbance is slowly time varying. However, to some extent, robot manipulators usually work in complex environment with high-frequency disturbance. Thereby, to enhance tracking performance in a teleoperation system, only traditional DOB technique is insufficient. In this paper, for the purpose of constructing a feasible teleoperation scheme, we develop a novel controller that contains a variable gain scheme to deal with fast-time varying perturbation, whose gain is adjusted linearly according to human surface electromyographic signals collected from Myo wearable armband. In addition, for tracking the motion of operator’s arm, we derive five-joint-angle data of a moving human arm through two groups of quaternions generated from the armbands. Besides, the radial basis function neural networks and the disturbance observer-based control (DOBC) approaches are fused together into the proposed controller to compensate the unknown dynamics uncertainties of the slave robot as well as environmental perturbation. Experiments and simulations are conducted to demonstrated the effectiveness of the proposed strategy

Cooperative manipulation of deformable objects by single-leader-dual-follower teleoperation

This paper proposes a method for singleleader-dual-follower (SLDF) teleoperation, where one robot (direct-follower robot, DFR) is directly teleoperated and the other robot (assisting-follower robot, AFR) can autonomously cooperate with DFR to hold and move a deformable object, with the contact force regulated to a desired value. Since AFR does not know its partners movement, firstly, it achieves position alignment with DFR by using the contact force. Secondly, we develop an adaptive movement estimation algorithm according to Lyapunov theory, such that DFRs position is estimated in the presence of dynamic uncertainties. Finally, we adopt the impedance control to generate a reference trajectory for AFR to track, in order to maintain the desired contact force. Several simulations are conducted on a platform with two threedegrees-of-freedom (3-DOFs) robots. Experiments are performed with a dual-arm robot (Baxter), results of which demonstrate the feasibility and effectiveness of the proposed method

Trajectory online adaption based on human motion prediction for teleoperation

In this work, a human motion intention prediction method based on an autoregressive (AR) model for teleoperation is developed. Based on this method, the robot's motion trajectory can be updated in real time through updating the parameters of the AR model. In the teleoperated robot's control loop, a virtual force model is defined to describe the interaction profile and to correct the robot's motion trajectory in real time. The proposed human motion prediction algorithm acts as a feedforward model to update the robot's motion and to revise this motion in the process of human-robot interaction (HRI). The convergence of this method is analyzed theoretically. Comparative studies demonstrate the enhanced performance of the proposed approach

Innate Host Response in Primary Human Hepatocytes with Hepatitis C Virus Infection

The interaction between hepatitis C virus (HCV) and innate antiviral defense systems in primary human hepatocytes is not well understood. The objective of this study is to examine how primary human hepatocytes response to HCV infection.An infectious HCV isolate JFH1 was used to infect isolated primary human hepatocytes. HCV RNA or NS5A protein in the cells was detected by real-time PCR or immunofluorescence staining respectively. Apoptosis was examined with flow cytometry. Mechanisms of HCV-induced IFN-β expression and apoptosis were determined.Primary human hepatocytes were susceptible to JFH1 virus and released infectious virus. IFN-α inhibited viral RNA replication in the cells. IFN-β and interferon-stimulated genes were induced in the cells during acute infection. HCV infection induced apoptosis of primary human hepatocytes through the TRAIL-mediated pathway. Silencing RIG-I expression in primary human hepatocytes inhibited IFN-β and TRAIL expression and blocked apoptosis of the cells, which facilitated viral RNA replication in the cells. Moreover, HCV NS34A protein inhibited viral induced IFN-β expression in primary human hepatocytes.Innate host response is intact in HCV-infected primary human hepatocytes. RIG-I plays a key role in the induction of IFN and TRAIL by viruses and apoptosis of primary human hepatocytes via activation of the TRAIL-mediated pathway. HCV NS34A protein appears to be capable of disrupting the innate antiviral host responses in primary human hepatocytes. Our study provides a novel mechanism by which primary human hepatocytes respond to natural HCV infection

Chinese Medicinal Herbs for Childhood Pneumonia: A Systematic Review of Effectiveness and Safety

Objective. To assess the efficacy and safety of Chinese medicinal herbs for Childhood Pneumonia. Methods. We included randomized controlled trials (RCTs). The searched electronic databases included PubMed, the Cochrane Central Register of Controlled Trials, EMBASE, CBM, CNKI, and VIP. All studies included were assessed for quality and risk bias. Review Manager 5.1.6 software was used for data analyses, and the GRADEprofiler software was applied to classify the systematic review results. Results. Fourteen studies were identified (n=1.824). Chinese herbs may increase total effective rate (risk ratio (RR) 1.18; 95% confidence interval (CI), 1.11–1.26) and improve cough (total mean difference (MD), −2.18; 95% CI, (−2.66)–(−1.71)), fever (total MD, −1.85; 95% CI, (−2.29)–(−1.40)), rales (total MD, −1.53; 95% CI, (−1.84)–(−1.23)), and chest films (total MD, −3.10; 95% CI, (−4.11)–(−2.08)) in Childhood Pneumonia. Chinese herbs may shorten the length of hospital stay (total MD, −3.00; 95% CI, (−3.52)–(−2.48)), but no significant difference for adverse effects (RR, 0.39; 95% CI, 0.09–1.72) was identified. Conclusion. Chinese herbs may increase total effective rate and improve symptoms and signs. However, large, properly randomized, placebo-controlled, double-blind studies are required

Occurrence of internally ovipositing non-agaonid wasps and pollination mode of the associated agaonid wasps

Figs (Ficus, Moraceae) and their pollinating fig wasps (Hymenoptera, Agaonidae, Chalcidoidea) are a striking example of obligate mutualism and coevolution. Agaonid females enter the figs to lay their eggs, but also actively or passively transport pollen into the figs at the same time. We examined eight related fig tree species pollinated by host specific Eupristina agaonids to determine the relationships between pollination mode, host pollen, ovule ratios and the ability of the figs to recruit additional non-agaonid pollinators. Uniquely amongst the eight Eupristina species, the pollinator of Ficus curtipes has non-functional pollen pockets and no coxal combs, showing that it pollinates passively. Reflecting this, the anther-to-ovule ratio of F. curtipes is unusually high. In addition to the agaonids, figs support many species of ‘non-pollinating fig wasps’ (NPFW) that are typically ovule gallers or parasitoids. These mainly oviposit from outside the figs but there are a few species of NPFW that are like agaonids and enter the figs to oviposit. Two of the eight Eupristina pollinated fig trees support host specific internally-ovipositing fig wasps belonging to the chalcidoid genera Diaziella (Sycoecinae) and Lipothymus (Otitesellinae). Reflecting the trees' pollination modes, these fig wasps act as supplementary pollinators of F. curtipes, but not of Ficus glaberrima, where agaonid pollination is active