The Mechanics of Vibration By Prof R E D Bishop and Prof D C Johnson Pp xii + 592 (Cambridge: At the University Press, 1960) 120s net

The Mechanics of Vibration

The U.S. Air Force Research Laboratory developed the deployable optical telescope testbed as part of the large deployable optics research program. The goal of this programwas to investigate the feasibility of a deployable space telescope concept and to mature critical enabling technologies to provide risk reduction for the general mission concept. This paper discusses many of the challenges encountered in laboratory testing of complex, sensitive, deployable systems. Implementation of a white-light interferometer for initialization and calibration, a pencil beam or single-pixel heterodyne interferometer for measuring primary mirror motion, and a Twyman–Green interferometer system for wave-front monitoring are discussed. Development of integrated system models and system identification methods for controller design are discussed. Active structural control was demonstrated to maintain optical alignment of the telescope while subjected to simulated reaction wheel disturbances, ambient vibration and atmospheric beam steering. Wave-front sensing and interferogram analysis were used to quantitatively assess optical performance, but wave-front error was not fed back to the controller.

Active Vibration Control of a Deployable Optical Telescope

A neural network controller (NNC) whose parameters are adjusted online is presented to control a class of multivariable linear systems. The plant to be controlled is assumed to be square (p inputs, p outputs) and almost strictly positive real (ASPR). The NNC is applied to a linear model of a large segmented space reflector and simulation results are presented. The ASPR condition is a strong condition, in general, but for the specific application of interest, i.e. control of flexible structures, the ASPR condition can be satisfied by an appropriate combination of the output variables (positions and velocities). As compared to other adaptive NNC reported in the literature, the proposed NNC is simpler and more suitable for real time applications.

Adjustable neural network controller: application to a large segmented reflector

Nowadays the percentage of power electronic devices, which use shunts for sensing of electrical signals, is increasing significantly. This method of measurements is simple, reliable and low-cost, however it requires careful elaboration of schematics and meticulous design of printed circuit boards. The author provides a detailed insight into the design of power converter Printed Circuit Boards (PCBs) with shunt-based sensing circuits and provides recommendations on improvement of signal measurements. He analyses the most popular design mistakes and illustrates their impact on measuring signals, which can be used for mistake localization. This paper demonstrates that the properly designed schematic can be turned into poorly operating PCB and recommends measures to avoid it. The author shares his more than 20-years experience and illustrates his statements with examples from real life. Although this paper is mainly addressed to young engineers, it could also be useful for experienced researchers, who work in neighboring areas and do not gain experience in PCB design.

Recommendations and Typical Errors in Design of Power Converter PCBs With Shunt Sensors

This paper presents the research conducted at the Structures, Pointing and Control Engineering (SPACE) laboratory in achieving precision pointing of segmented reflector testbed. The system's top-level requirements include figure maintenance of the primary mirror to hold within 1 micron RMS distortion and precision pointing with accuracy of 2 are seconds. The paper focuses on the integrated analysis of the different control challenges that such advanced system would face. The objective of this research is broader in the sense that the methods and tools developed in this study shall be useful for and applicable to a broad variety of pointing control applications

Pointing Control Testbed for Segmented Reflectors

The 3-dimensional model for a segmented reflector telescope is developed using finite element techniques. The structure is decomposed into six subsystems. System control design using neural networks is performed. Performance evaluation is demonstrated via simulation using PRO-MATLAB and SIMULINK.

/pdf/the-use-of-decentralized-control-in-the-design-of-a-large-33vzww6pgb.pdf

The Use of Decentralized Control in the Design of a Large Segmented Space Reflector

The next generation space telescope (NGST) is expected to produce a vast amount of raw images, which need to be stored and disseminated efficiently for astronomical research and education. Therefore, effective compression and transmission methods are very important. This paper proposes a joint compression and transmission scheme for efficient streaming of astronomical images based on their special characteristics. The objective of the joint approach is to maximize the recognition of the astronomical entities presented in the image under the same rate constraint and channel loss behavior. In the compression stage, each astronomical entities is segmented and coded independently using zero-tree based wavelet codec, and robust packetization scheme is employed to prevent error propagation; in the transmission stage, content information of the image is utilized to maximize the perceptual quality of the entities at the presence of packet loss. Experiment results are presented to demonstrate the effectiveness of the proposed approach.

Content-based compression and transmission of astronomical Images

The results presented in this paper prove the viability of developing a robotic network for search and rescue operations. With the capability of peer-to-peer communication, such robots form an ad-hoc network called Cooperative Mobile Network CMN. All robots in the CMN are semi-autonomous in that each operates in three modes: 1 fully controlled by a human commander; 2 controlled by a human commander for critical operations only; and 3 fully relying on its own intelligence to make decisions for cooperative operations. Due to the constraints of weight and processing power, diverse CMN operations utilize multiple robots with complementing functionalities. This work was performed at the Structures Propulsion And Control Engineering SPACE NASA sponsored University Research Center URC of excellence at the California State University, Los Angeles.

/pdf/cooperative-semi-autonomous-robotic-network-for-search-and-3q0saz9i6a.pdf

Cooperative Semi-autonomous Robotic Network for Search and Rescue Operations

Previously, Hybrid-Routing Algorithm Model was proposed by the Structures, Pointing, and Control Engineering (SPACE) University Research Center 1 at California State University of Los Angeles (CSULA). The Hybrid-Routing Algorithm Model utilizes semi-autonomous control during robotic operations in unknown, remote, hazardous, or otherwise inaccessible terrains. In order to observe and monitor mobile robot's surroundings, an onboard virtual reality system has been designed and implemented. It operates by remotely following the commanded movement of the robotic mission operator's headset. The proposed design features the Inertial Measurement Unit (IMU) chip secured to the center of the iTV-goggles unit., which is worn by the robotic mission operator. Direction cosine matrix algorithm is used to update the body coordinates of the IMU chip to the global reference system. Euler angles are computed based on the angular orientation of the mission operator's headset and are transmitted to the mobile robot. The observation system contains multiple servo motors that rotate onboard camera based on the received pitch roll, and yaw information. The observation system transmits compressed visual information of robot's surroundings to the Host Computing Station. This video is rendered via iTV-goggles display to the mission operator.

Virtual reality head-tracking observation system for mobile robot

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