Flexible dynamic modeling and control for the Remote Manipulator System

This thesis focuses on modeling and controller design for the Space Shuttle Remote Manipulator System (RMS). A dynamic model of the RMS is derived using Book's recursive Lagrangian method. This model has six degree-of-freedom rigid dynamics, joint flexibility dynamics, link transverse elastic dynamics and torsional elastic dynamics. A computationally efficient control approach for addressing joint and boom flexibility of the RMS is investigated. The control strategy consists essentially of four parts. The first part involves pre-shaping the joint trajectories in order to reduce the excitation of link flexibility. The second part is a rigid model based inverse dynamics control which is used to obtain the desired joint torque. The third part is a flexible-joint control loop which is based on a perturbation technique. The last part is a pulse active damping (PAD) control loop which is applied to damp out the system residual vibrations in a fast manner. The integrated control strategy leads to fast end-effector trajectory tracking with less end-effector vibration and fast damping of residual vibrations

Online Bus Speed Prediction With Spatiotemporal Interaction: A Laplace Approximation-Based Bayesian Approach

This study proposes a novel Bayesian hierarchical approach for online bus speed prediction by explicitly accounting for the spatiotemporal interaction (STI) of speed observations. The use of Laplace approximation can expedite the estimation of Bayesian models and enable the implementation of online prediction. Large numbers of trials are carried out to identify significant predictors and the optimal length of the look-back time window to achieve the highest prediction accuracy. The spatiotemporal interacting patterns are also explored, and results show that the Type IV model assuming the structured spatial effect interacts with the structured temporal effect can best accommodate the bus speed data. Besides, prediction errors of the Type IV model randomly distribute over time and space. The proposed model can achieve high prediction accuracy and computational efficiency without compromising the interpretability of the contributing factors and the unobserved spatiotemporal heterogeneity. The proposed model can be used to assist public transit operation and management, such as bus scheduling, congestion warning, and the development of proactive measures to mitigate bus delays

Improving Strength and Microstructure of SiC Reticulated Porous Ceramic through In-Situ Generation of SiC Whiskers within Hollow Voids

SiC Reticulated Porous Ceramic with Excellent Strength and High-Density Ceramic Struts Was Successfully Prepared using the Polymer Replica Method, Followed by Pressureless Sintering under a Buried Charcoal Atmosphere. First, a Polyurethane (PU) Template Was Coated with a Si Slurry and Then a SiC-Containing Slurry, and Subsequently Heated under the Buried Charcoal Atmosphere. to Ensure Excellent Coating Ability of the Slurries, the Viscosity, Thixotropy, and Yield Stresses of the Si Slurry Were Optimized by Adjusting the Content of the Thickening Agent. during Heating, Si in the Coating Layer Reacted with the Residual C and CO Gas from the PU Template and Buried Charcoal, Forming SiC Whiskers that Filled Hollow Voids within the SiC Struts. Additionally, Catalyst Ferric Nitrate Was Added to the Si Slurry to Promote the Generation and Growth of SiC Whiskers. as a Result, When Compared to the Untreated SiC Reticulated Porous Ceramic, the SiC Reticulated Porous Ceramic Pre-Coated with Si Layers Exhibited Significant Improvements in Mechanical Strength and Thermal Shock Resistance, Despite Minor Differences in Porosity. Furthermore, an Industrial Test Conducted in the Copper Smelting Industry Showed that the Structure of SiC Reticulated Porous Ceramic, Prepared in This Study and Used as Filters, Remained Intact Even after 7 Days of Continuous Use. Meanwhile, a Significant Number of Inclusions Was Adhered to the Surfaces of the Filters. Therefore, the Processes Combined with In-Situ Generation of SiC Whiskers is an Ideal and Low-Cost Method for Fabricating SiC Filters with Excellent Properties

Analysis of the Clinical Characteristics of Malignant Tumor Patients with Rheumatic Symptoms and Rheumatic Disease Combined with Malignant Tumor Patients

Objective: We study the relationship between rheumatic immune disease and malignant tumor to provide the basis for clinical diagnosis and treatment. Methods: We selected 53 patients who were hospitalized in our department from January 2013 to February 2020, including 26 patients with rheumatic immune disease combined with malignant tumor and 27 patients with malignant tumor with rheumatic symptoms. We retrospectively analyzed the relationship between gender, age, main clinical manifestations, tumor system distribution, metastasis rate, rheumatic immune disease type and tumor type. Results: Among the patients with rheumatic immune disease complicated with tumor, 26.1% were male and 66.7% were female. Among the tumor patients with rheumatic symptoms, 73.9% were male and 33.3% were female. There was a significant difference in gender composition between the two groups. Among the patients with rheumatic immune disease complicated with tumor, respiratory system tumor was the highest. Among the tumor patients with rheumatic symptoms, the incidence of hematological tumors was the highest. The distribution of tumor system was different between the two groups. The proportion of metastatic tumor in patients with rheumatic symptoms is higher than that in patients with rheumatic immune disease combined with malignant tumor. The percentage of concurrent tumor in three diseases in the same period was 0.363% for rheumatoid arthritis, 2.02% for polymyositis/ dermatomyositis and 0.24% for Sjogren's syndrome. This study shows that patients with polymyositis/ dermatomyositis are more likely to develop malignant tumors. Conclusion: There were significant differences in gender composition, distribution of tumor system and the proportion of metastatic tumor between patients with rheumatic immune disease complicated with malignant tumor and patients with rheumatic symptoms, and malignant tumor was more common in patients with polymyositis/ dermatomyositis

Reconfigurable Fabry-Pérot Cavity Antenna Basing on Phase Controllable Metasurfaces

Fabry-Pérot cavity (FPC) antenna is a kind of high-gain antenna. Compared with other high-gain antennas, such as array antenna and reflector antenna, the FPC antenna enjoys the advantages of simple structure and high efficiency. So it has attracts many attention since proposed. However, it also suffers the disadvantages of narrow band and fixed radiation patterns, due to its resonance structure. In order to overcome these disadvantages, we proposed novel strategies to realize reconfigurable FPC antennas using the phase controllable metasurfaces (MSs). Through adding PIN diodes into every unit cell of the MS, the reflection phase of the MS can be controlled by tuning the states of the diodes. Then the designed phase controllable MSs are used as the partially reflection surfaces (PRS) to realize frequency or radiation pattern reconfigurable FPC antennas. In this chapter, we analyze the basic theory of the FPC antenna and describe its radiation principle firstly. Then, reflection phase controllable MSs are designed and applied to the FPC antennas. Thus frequency and radiation pattern reconfigurable FPC antennas are formed. The design processes are described in details, and the proposed antennas are fabricated and measured. The measured results verify the correctness of the designs. Through this chapter, the readers can form a comprehensive understanding of reconfigurable FPC antenna design

Interfacial electronic structure at the CH3NH3PbI3/MoOx interface

Interfacial electronic properties of the CH3NH3PbI3 (MAPbI3)/MoOx interface are investigated using ultraviolet photoemission spectroscopy and X-ray photoemission spectroscopy. It is found that the pristine MAPbI3 film coated onto the substrate of poly (3,4-ethylenedioxythiophene) poly(styrenesulfonate)/indium tin oxide by two-step method behaves as an n-type semiconductor, with a band gap of ~1.7 eV and a valence band edge of 1.40 eV below the Fermi energy (EF). With the MoOx deposition of 64A ° upon MAPbI3, the energy levels of MAPbI3 shift toward higher binding energy by 0.25 eV due to electron transfer from MAPbI3 to MoOx. Its conduction band edge is observed to almost pin to the EF, indicating a significant enhancement of conductivity. Meanwhile, the energy levels of MoOx shift toward lower binding energy by ~0.30 eV, and an interface dipole of 2.13 eV is observed at the interface of MAPbI3/MoOx. Most importantly, the chemical reaction taking place at this interface results in unfavorable interface energy level alignment for hole extraction. A potential barrier of ~1.36 eV observed for hole transport will impede the hole extraction from MAPbI3 to MoOx. On the other hand, a potential barrier of ~0.14 eV for electron extraction is too small to efficiently suppress electrons extracted from MAPbI3 to MoOx. Therefore, such an interface is not an ideal choice for hole extraction in organic photovoltaic devices