A Review of Efforts To Improve Dynamic Environment Testing Practices

Spacecraft must undergo such phase as lift-off, inter-stage separation, fairing jettisoning and spacecraft/launch vehicle separation during the launch. And the dynamic environments of these phases can be divided into vibration, acoustics, shock, etc. To assure its reliability in launch and in-orbit phases, many ground dynamic tests must be carried out in the process of development of the spacecraft, such as vibration test, acoustic test, shock test and so on. In the past few decades, with the successful launch of many spacecrafts and satellites, China has accumulated a lot of test experience and established an effective dynamic environment test specification and standard. But, the dimension and the mass of the Chinese space station have greatly increased compared to the previous satellites. The customary test methods and test facilities cannot satisfy the requirements of the ground dynamic test verification of the large scale spacecraft. For example, the force of vibration table required for vibration test is estimated to far more than the capacity of the largest single electrodynamic vibration shaker. So how to carry out the ground dynamic test for these large scale spacecrafts and ensure their validity is the key technical problem should be solved. This paper mainly introduces the development of the dynamic test verification technology of large scale spacecraft such as “Tianzhou” cargo spacecraft and space station. Firstly, the methods of the vibration test and the acoustic test are presented. Secondly, the static load compensation technology in vibration test, the method of the section test, and the extrapolation technique based on the test data are discussed detailedly, and their merit and shortcoming are summarized respectively. Moreover, the technical difficulties research in the large scale vibration shaker and the reverberation chamber are analyzed, especially in the shaker head expander table and the slip table. The development of VTS-1400 vibration test system and RATF-4000 reverberation chamber at Tianjing AIT Test Center are presented in following. Finally, the prospect of the development of the large scale spacecraft dynamic environment test is proposed.

Study on the establishment of dynamic performance test environment for the digital protective relay using RTDS

New approaches to improve the prediction of failure of long length fibers are presented. They are currently being used in type approval and quality control of optical fibers and cables in Swedish Telecom. One approach is to use the B-parameter. Values on this parameter, usually obtained from testing in liquid nitrogen, high temperature, or under vacuum, are not being considered very useful for lifetime estimation in regular environments. Therefore, a high- speed tensile test has been developed, by which the B-parameter is evaluated, at adequate service conditions. The other approach, to long-term fatigue data, is the expander test by which static and dynamic tests are made on medium length fibers under uniaxial stress. Long- term failure statistics are conveniently accessed by testing a single specimen. Limitations of the techniques are discussed: influence on fatigue parameters of static versus dynamic load and testing environment, and fatigue of high strength versus low strength modes.

Time delay integration (TDI) CCD focal plane assembly is one of the most important components for a space camera, which mainly fulfill photoelectric conversion and output video signal of analog CCD. Due to the hard condition resulted from the transportation and launch of a space camera, it is difficult to keep a TDI CCD with high interleaving precision. Therefore, in this work, we design a TDI CCD focal plane assembly with a good performance based on the optimization both on structural control and thermal control. According to the analysis of the factors that affect the interleaving precision of a TDI CCD focal plane assembly and the maximal error of three axes theoretically, we design an especial structure for a TDI CCD focal plane assembly to keep the high interleaving precision of a TDI CCD which can fit the hard condition for the transportation and launch of a camera and the harsh on-orbit operating temperature. The effectiveness of the modified TDI CCD focal plane assembly is supported by the results obtained from dynamic test and thermal vacuum test. For the dynamic test, the response result shows that the assembly can conquer the interference of dynamic environment and keep a high interleaving precision of TDI CCD. For the thermal vacuum test, thermal balance test indicates that the highest temperature of TDI CCD is 30 in 1.5 min, which can work properly. The interleaving precision of focal plane is done after the dynamic environment and thermal vacuum tests. The linearity error of the TDI CCD is 3.5 m, the interleaving error is 4 m, the parallelism error between two lines of the TDI CCD is 3.5 m, and the coplanar error of 4 TDI CCD is 5 m. These results satisfy the optical design very well. Therefore, the aforementioned course proves that this design is feasible and precise, and it can achieve a high interleaving precision for a TDI CCD.

<div class="htmlview paragraph">Dynamic aircraft seat regulations are identified in the Code of Federal Regulations (CFR), 14 CFR Parts § 23.562 [<span class="xref">1</span>] and § 25.562 [<span class="xref">2</span>] for crashworthy evaluation of a seat in dynamic environment. The regulations specify full-scale dynamic testing on production seats. The dynamic tests are designed to demonstrate the structural integrity of the seat to withstand an emergency landing event and occupant safety. SAE standard AS 8049 [<span class="xref">3</span>] supports detailed information on dynamic seat testing procedure and acceptance criteria. Full-scale dynamic testing in support of certification is expensive and repeated testing due to failure drastically increases the expense. Involvement of impact environment, flexibility in interior configuration and complicated nature of seat engineering design makes this problem quite complex, so that classical hand calculations are practically impossible. Efforts have been made to improve the occupant safety and to reduce the testing costs through substantiation via computer modeling analysis techniques.</div> <div class="htmlview paragraph">The goal of the Finite Element Analysis (FEA) in product development is not only to design a seat but to substantiate the certification tests or possibly replace the certification tests. The case of a certification by substantiation tests increases the necessity of validation of the Finite Element (FE) model. Advisory Circular (AC) 20-146 [<span class="xref">4</span>] demonstrates the methodology for dynamic seat “Certification By Analysis” for use in Parts 23, 25, 27 and 29 airplanes and rotorcraft. This AC provides guidance on how to validate the computer model and under what conditions the model may be used in support of certification or Technical Standard Order (TSO) approval/ authorization.</div> <div class="htmlview paragraph">In this study, best FE modeling practices for dynamic aircraft seats are presented using explicit nonlinear FE code such as LS-DYNA [<span class="xref">5</span>, <span class="xref">6</span>] with a brief case study of an aircraft passenger seat. Comparison of FEA results and test results indicate reasonable correlations, establishing confidence in the Dynamic Finite Element Analysis (DFEA) methodology.</div> <div class="htmlview paragraph">Development in DFEA methodology helps aircraft industry in designing and certifying dynamic seats and interior configurations more economically and confidently. Objective of this paper is to provide simple guidelines for the aircraft seating industry in developing simulation techniques for the dynamic environment.</div>

In this paper, the potential field principle is applied to several UAVs (Unmanned Aerial Vehicles) for optimal path planning. Each UAV has its own goals and it is used the attractive potential field to reach the goals. On the contrary, each UAV is considered as obstacle for other UAVs that must be avoided. In this research, there are two types of obstacles, i.e the static and dynamic. The repulsive potential field principle is used to avoid for both static and dynamic obstacles. The whole method is implemented into Parrot AR Drone 2.0 Quadcopter model of UAV and simulated in Gazebo Simulator by Robot Operating System (ROS). The results of this research are to control the thrust of quadcopter so that it is in flying position, the value of value of roll (α) or pitch (β) must set to not equal or approaching 90° or −90° and not between −180° and 180° or between −90° and 90°. Based on the dynamic obstacle performance test with parameter tuning, the optimal avoidance is when the η value is 7.8 while when in static and dynamic test with parameter tuning, the optimal avoidance is when the η value is 7.9 noted by the fastest time and the shortest path.

As part of a larger project aimed at gaining a better understanding of factors that affect the quality of test results using anthropomorphic test devices (ATDs), the FAA tested the effects of dynamic loading of an ATD pelvis. The ATDs required in the aviation regulations were initially developed for the automotive crash environment, which does not include a vertical testing component. One of the two dynamic tests is a vertical impact, with the principal measurement being the compressive load in the lumbar spinal column, with a regulatory limit of 1500 lb. The lumbar load cell is mounted to the pelvis, and data collected could be affected by the performance of the ATD pelvis. The ability to define a vertical calibration test could be used to determine if the pelvis is acceptable for initial use or to monitor in-service degradation. Three ATD pelvises were compressed in a high-rate load frame. The peak load and loading rate of the pelvis compression were selected to simulate conditions achieved in transport category aircraft vertical seat testing. The primary test objective was to measure changes to the rubber and foam cover of the metallic pelvis during high cyclic loading. Each pelvis was subjected to over 100 cycles. Static dimensional measurements, based on a manufacturing tolerance evaluation, were collected during testing. The high-cycle testing did not deform the foam and rubber covers enough to exceed the total dimensional tolerance of the pelvises (± 0.120 in.). The appearance of visual damage was closely monitored throughout the testing. Similar visual damage was seen for each pelvis and occurred at low cycles — 15 to 30. Results suggest the appearance of damage minimally changed the dynamic response of the pelvis. Force-deflection data were also collected from each test series. These data showed minimal change during testing, with the deflection at 2000 lb. changing approximately 0.100 in. across the 105 cycles. This value is similar to the manufacturer’s tolerance for the height of the pelvis. Based on this, the number of vertical sled tests that would precipitate replacement may be over 100 cycles. Due to the harsh environment of dynamic sled testing, other factors, such as cuts in the foam and rubber due to belt loading, may trigger the removal of an ATD pelvis from service prior to the pelvis reaching a defined number of cycles. Future FAA research will evaluate how this change in pelvis force-deflection affects lumbar load.

For the layer rubber spring of a high-speed bogie, lab tests were conducted to obtain the dynamic parameters under extremely high and low temperatures (-60°C∼60°C) to obtain the nonlinear stiffness and damping parameters relevant to the frequency, amplitude and temperature changes. It starts from introducing the rubber element dynamic parameter test equipment, test plan and test methods. The applied loads and the temperatures are discussed. Then both the static and dynamic tests were performed for the layer spring of axle box, along the axial and radial directions. It shows that the common results can only reflect frequency- and amplitude-dependent characteristics of rubber, but the corresponding parameter change associated with each frequency and amplitude is highly dependent on the temperature. This phenomenon is quite severe in the low and extremely low temperature cases. Therefore, it is essential and necessary to carry out environmental temperature tests as well as basic theory study and simulations on all rubber components in order to know the parameter variation domain of the suspension system of a railway vehicle.

In the last two decades, dynamic optimization problems (DOPs) have drawn a lot of research studies from the evolutionary computation (EC) community due to the importance in real-world applications. A variety of evolutionary computation approaches have been developed to address DOPs. In parallel with developing new approaches, many benchmark and real-world DOPs have been constructed and used to compare them under different performance measures. In this chapter, we describe the concept of DOPs and review existing dynamic test problems that are commonly used by researchers to investigate their EC approaches in the literature. Some discussions regarding the major features of existing dynamic test environments are presented. Typical dynamic benchmark problems and real-world DOPs are described in detail. We also review the performance measures that are widely used by researchers to evaluate and compare their developed EC approaches for DOPs. Suggestions are also given for potential improvement regarding dynamic test and evaluation environments for the EC community.

Simulating animal movement in spatially-explicit individual-based models (IBMs) is both challenging and critically important to accurately estimating population dynamics. I compared four distinct movement approaches or sub-models (restricted-area search, kinesis, event-based, and run and tumble) in a series of simulation experiments. I used an IBM loosely based on a small pelagic fish that simulated growth, mortality, and movement of a cohort on a 2-dimensional grid. First, I tested the sub-models calibrated (i.e., trained) with a genetic algorithm in one set of environmental conditions in three other novel environments. The sub-models performed well, except restricted-area search and event-based that needed to be trained in environments with gradients similar to the test environment. Also, run and tumble only trained in steep habitat quality gradients. The sub-models were then trained and tested across a range of spatio-temporal resolutions (cell size and time step). The sub-models generally performed well across resolutions, but the sub-models did not perform equally well at all resolutions. Kinesis and run and tumble performed better at coarser resolutions, and restricted-area and event-based performed better at finer resolutions. I attributed the trends across resolution to differences in how the habitat quality individuals experienced changed at each time step. Finally, I trained and tested the sub-models in an IBM with dynamic prey and predator fields. I trained and tested the sub-models in dynamic and static versions of the environment. Sub-models trained in the dynamic environment performed well in both dynamic and static test environments; however, sub-models trained in static environment did not perform consistently well in dynamic test environment. Overall, restricted-area search, kinesis, and event-based were robust across the range of conditions in which I tested them, but run and tumble only performed well in environments with very steep habitat quality gradients. In selecting a movement sub-model, researchers should consider the assumptions of potential sub-models, the observed movement patterns of the species of interest, the shape and steepness of the underlying habitat quality gradient, and the spatio-temporal resolution of the model. Sub-models that will be applied in dynamic conditions should be calibrated in comparable dynamic conditions.

<div class="htmlview paragraph">Dynamic tests were conducted in 1986 with airline passenger triple-seat assemblies. The goal was to gain experience in testing methods and gather data on airline seat performance in the dynamic environment of an emergency landing. The test series investigated acceleration levels, impact velocity, longitudinal and vertical impacts, multiple-row effects, and floor deformation. The test conditions remained below the point of total seat assembly failure so that the performance of the seat assemblies could be evaluated for structural integrity, reaction loads of the seat legs with the floor structure, and the loads experienced by the instrumented dummy occupant.</div>

Military specifications contain numerous requirements for qualification of equipment for dynamic environments. Cost and schedule effective application of these specifications require tailoring of these test requirements. This paper presents a technique for tailoring dynamic environment tests based on equipment response characteristics. The dynamic response theory is explained and applied to a procedure for comparing the relative severity of dynamic environmental tests. The procedure is shown using the example of an electronic assembly.

We have developed a centralized application for acquiring images from multiple picture archiving and communication systems (PACS) and distributing images to a clinical image web server and other repositories. Our flexible strategy addresses a number of administrative challenges associated with delivering images into clinical, research, and test environments. DICOM images flow from PACSs and modalities to a UNIX-based "distributor" application, which relays them to one or more destinations. Image volume and transmission times were collected and analyzed. Three distributors receive an average of 34 gigabytes of image data per day. Images are sent concurrently to two web-based image servers, one used clinically by physicians and one used for testing. Transmission of certain classes of studies is prioritized for key physician groups. Delivery to research systems is also supported. Acquiring images from multi-vendor PACS for distribution to a web server for clinical image viewing is a challenging task. Centralizing the acquisition and distribution process reduces both the administrative effort and the impact on clinical operations associated with maintaining dynamic clinical, testing, and research environments.

The NASA Jet Propulsion Laboratory (JPL) successfully landed the Mars 2020 Perseverance Rover at Jezero Crater on the Martian surface. Perseverance's main mission objective is to cache Martian rock and regolith samples in hermetically sealed tubes to be brought back to Earth by future missions. To achieve this goal the rover is equipped with a 2-meter-long Robotic Arm (RA) which manipulates the Turret to interact with the surface. The Turret is comprised of science instruments and tools that enable surface sampling and science. The backbone of the Turret hardware is the Rotary Percussive Coring Drill. The science instruments, which are directly mounted to the structural housing of this drill, must be able to withstand not only the launch and entry, descent and landing (EDL) loads of the vehicle but also the dynamic percussive environment, induced by the drill throughout surface operations. This paper discusses the technical hardware design, development and testing of a vibration isolation system to protect the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) Instrument from these dynamic environments. The hardware design aspect of this problem was limited by both size and mass constraints. The Turret is tightly configured and the physical space in which hardware can reside is restricted due to multiple axes of surface interaction points. Another driving requirement is the extreme range of thermal non-operational environment from -135C to +90C. This, in addition to SHERLOC being a heavier instrument than previously integrated on a turret, made the use of isolation systems employed on previous rover missions problematic. The final design incorporates custom wire mesh springs preloaded within titanium hexapod struts equipped with flexure ends. Custom versions of commercially available wire mesh springs were designed and tested. These custom springs differed in dimension, density and stiffness from the off the shelf options. The newly designed springs went through various stages of flight acceptance testing. Detailed physics-based modeling to understand what loads the isolation system would experience was used to define the test conditions for the springs and entire isolation subsystem. The testing program developed around this was extensive to fully characterize the isolation performance over cleanliness levels, temperature and life. Another major aspect of this work was developing a method of replicating the drill's percussive environment for performance and life testing of Turret mounted hardware. Attaching the instrument to an operating drill for testing was not a viable option. A method of using a Highly Accelerated Life Test (HALT) table was developed and applied across the project as the most representative and tunable option to physically simulate this new environment. This method, along with launch environment random vibration testing, was used to build an entire dynamic qualification and flight hardware test program. The results of the design, modeling, testing and analysis of the SHERLOC Isolation System is described throughout the following paper.

Multi-factor mining and corrosion rate prediction model construction of carbon steel under dynamic atmospheric corrosion environment