Vibration Damping for Highly Compliant Robots

In order to guarantee save interaction of robots with the environment and to ensure mechanical robustness, one of the key technical properties of robotic systems is physical compliance of the actuation systems. This is mostly achieved by a highly elastic element decoupling the link from the motor. The flexible elements cause a partially undesired vibration dynamics in the robotic structure when excited with harmonic torque on the link sides. The aim of this thesis is to analyze and to reduce oscillations through optimally chosen settings of the controller. To achieve that, we focus on two control approaches, namely Elastic Structure Preserving Impedance (ESpi) and Visco-Elastic Structure Preserving Impedance (VESpi) controller developed by Keppler et al. in [Kep+18a] and [Kep+18b]. To analyze the closed loop system, we focus on a non-tracking case, one joint and linear spring characteristic. As the aim is to absorb the introduced energy as efficiently as possible, we investigate the effect on certain tuning par meters. The physically motivated design approach of ESpi and VESpi controllers enables us to represent the closed-loop system as a nonconservative multispring-damper two-mass oscillator. Taking the concept of a tuned mass damper (TMD) into account, we extend the existing rule of how to choose the impedance of the absorber presented in for use in the VESpi and ESpi system. This is achieved in two steps: Firstly, we derive an analytical model of the closed-loop system and find parameters for the minimax amplitude in the frequency response. Secondly, we run a Monte Carlo simulation using a visco-elastic two-mass-system controlled by ESpi and VESpi. We want to obtain cost values for vibration and power efficiency that represent vibration efficiency and control effort. The results provide a guideline to determine the parameters for either minimum amplitude at link-side or best power efficiency. One of the most interesting contributions is that the VESpi controller - in contrast to ESpi - features optimal damping characteristic for all excitation frequencies given the optimal setting. On the other hand, the control approach ESpi cannot be used as a TMD due to the placement of the damper. Nevertheless, an optimal setting for a wide range of frequencies can be found

A Gravity Compensation Strategy for On-ground Validation of Orbital Manipulators

The on-ground validation of orbital manipulators is a challenging task because the robot is designed for a gravity-free operational environment, but it is validated under the effect of gravity. As a consequence, joint torque limits can be easily reached in certain configurations when gravity is actively compensated by the joints. Hence, the workspace for on-ground testing is restricted. In this paper, an optimal strategy is proposed for achieving gravity compensation of an orbital manipulator arm on ground. The strategy minimizes the joint torques acting on the manipulator by solving an optimization problem and it computes the necessary forces to be tracked by an external carrier. Hence, full gravity compensation is achieved for the orbital manipulator. Experimental results validate the effectiveness of the method on the DLR CAESAR space robot, which uses a cable suspended system as external carrier to track the desired gravity compensation force, resulting from the proposed method

Integrating the UB-Tree into a Database System Kernel

Multidimensional access methods have shown high potential for significant performance improvements in various application domains

Palifermin for oral mucositis after intensive therapy for hematologic cancers

BACKGROUND: Oral mucositis is a complication of intensive chemotherapy and radiotherapy with no effective treatment. We tested the ability of palifermin (recombinant human keratinocyte growth factor) to decrease oral mucosal injury induced by cytotoxic therapy. METHODS: This double-blind study compared the effect of palifermin with that of a placebo on the development of oral mucositis in 212 patients with hematologic cancers; 106 patients received palifermin (60 microg per kilogram of body weight per day) and 106 received a placebo intravenously for three consecutive days immediately before the initiation of conditioning therapy (fractionated total-body irradiation plus high-dose chemotherapy) and after autologous hematopoietic stem-cell transplantation. Oral mucositis was evaluated daily for 28 days after transplantation. RESULTS: The incidence of oral mucositis of World Health Organization (WHO) grade 3 or 4 was 63 percent in the palifermin group and 98 percent in the placebo group (P\u3c0.001). Among patients with this degree of mucositis, the median duration of mucositis was 6 days (range, 1 to 22) in the palifermin group and 9 days (range, 1 to 27) in the placebo group. Among all patients, regardless of the occurrence of mucositis, the median duration of oral mucositis of WHO grade 3 or 4 was 3 days (range, 0 to 22) in the palifermin group and 9 days (range, 0 to 27) in the placebo group (P\u3c0.001). As compared with placebo, palifermin was associated with significant reductions in the incidence of grade 4 oral mucositis (20 percent vs. 62 percent, P\u3c0.001), patient-reported soreness of the mouth and throat (area-under-the-curve score, 29.0 [range, 0 to 98] vs. 46.8 [range, 0 to 110]; P\u3c0.001), the use of opioid analgesics (median, 212 mg of morphine equivalents [range, 0 to 9418] vs. 535 mg of morphine equivalents [range, 0 to 9418], P\u3c0.001), and the incidence of use of total parenteral nutrition (31 percent vs. 55 percent, P\u3c0.001). Adverse events, mainly rash, pruritus, erythema, mouth and tongue disorders, and taste alteration, were mild to moderate in severity and were transient. CONCLUSIONS: Palifermin reduced the duration and severity of oral mucositis after intensive chemotherapy and radiotherapy for hematologic cancers

System Requirements Elicitation and Conceptualization for a Novel Space Robot Suspension System

Robotic manipulators play a pivotal role in space exploration and pave the way for satellite lifetime extensions, orbital asset inspections, and deorbiting. However, space robots are tested under Earth's gravity despite being designed for zero gravity. Most space robots are constructed such that they cannot bear the Earth's gravitational loads, necessitating an external support system for on-ground tests. Conventional test facilities, however, face significant limitations including workspace constraints and influence of the dynamics. Against this background, a novel suspension system for non-gravity-bearing space robots is planned. To address this challenge, the paper reviews mechanical suspension systems for space robot test setups and outlines essential requirements for the novel suspension system. A comparative analysis of concepts that fulfill the stated requirements complements the literature. The findings highlight the cable-driven parallel robot as an optimal trade-off solution

Palifermin for Oral Mucositis after Intensive Therapy for Hematologic Cancers

BACKGROUND Oral mucositis is a complication of intensive chemotherapy and radiotherapy with no effective treatment. We tested the ability ofpalifermin (recombinant human keratinocyte growth factor) to decrease oral mucosal injury induced by cytotoxic therapy. METHODS This double-blind study compared the effect ofpalifermin with that of a placebo on the development of oral mucositis in 212 patients with hematologic cancers; 106 patients received palifermin (60 μg per kilogram ofbody weight per day) and 106 received a placebo intravenously for three consecutive days immediately before the initiation of conditioning therapy (fractionated total-body irradiation plus high-dose chemotherapy) and after autologous hematopoietic stem-cell transplantation. Oral mucositis was evaluated daily for 28 days after transplantation. RESULTS The incidence oforal mucositis of World Health Organization (WHO) grade 3 or 4 was 63 percent in the palifermin group and 98 percent in the placebo group (P<0.001). Among patients with this degree of mucositis, the median duration of mucositis was 6 days (range, 1 to 22) in the palifermin group and 9 days (range, 1 to 27) in the placebo group. Among all patients, regardless ofthe occurrence of mucositis, the median duration of oral mucositis of WHO grade 3 or 4 was 3 days (range, 0 to 22) in the palifermin group and 9 days (range, 0 to 27) in the placebo group (P<0.001). As compared with placebo, palifermin was associated with significant reductions in the incidence of grade 4 oral mucositis (20 percent vs. 62 percent, P<0.001), patient-reported soreness of the mouth and throat (area-under-the-curve score, 29.0 [range, 0 to 98] vs. 46.8 [range, 0 to 110]; P<0.001), the use ofopioid analgesics (median, 212 mg ofmorphine equivalents [range, 0 to 9418] vs. 535 mg of morphine equivalents [range, 0 to 9418], P<0.001), and the incidence of use of total parenteral nutrition (31 percent vs. 55 percent, P<0.001). Adverse events, mainly rash, pruritus, erythema, mouth and tongue disorders, and taste alteration, were mild to moderate in severity and were transient CONCLUSIONS Palifermin reduced the duration and severity oforal mucositis after intensive chemotherapy and radiotherapy for hematologic cancers

Das Datenbank-Cache Entwurfsprinzipien, Algorithmen, Eigenschaften

TIB: RN 7878 (8208) + DO 1128 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Progressive Drug Policies and the Impacts of Supply-Side Control

For over a century the international community has widely accepted a policy of universal drug prohibition. However, an increasing number of countries have been willing to experiment with progressive drug policies as the shortcomings of strict prohibition become more clear. This thesis is a study of the structures of drug laws in four countries – the Netherlands, Portugal, the United States, and Mexico – and their economic, public health, and human rights outcomes. The policies range in restrictiveness from the decriminalization of all drugs in Portugal to complete criminalization in Mexico. This thesis focuses on cannabis and heroin, two drugs which differ markedly in their risk for addiction and acute harm. A wide range of sources in the drug policy literature was analyzed. Evidence suggests that progressive policies in Portugal and the Netherlands have not significantly increased drug use and have led to numerous favorable public health outcomes. States in America that have legalized marijuana face many legal and economic challenges, and they should be observed closely as their policies develop further. Strict supply-control enforcement in Mexico has, on the other hand, led to an extreme upsurge in violent crime. These results suggest that in the future policymakers should drastically reallocate resources from ineffective supply-side strategies and pursue proven policies centered on public health and the protection of human rights