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2022 International Conference on Smart Information Systems and Technologies, SIST 2022 -- 28 April 2022 through 30 April 2022 -- 184566, Stability analysis and control of the inverted pendulum on cart system is an important problem that has been investigated by many researchers in recent years. In this study, nonlinear modeling of the inverted pendulum on cart system is derived and free body diagram is explained. Then, the nonlinear model of the system is created in MATLAB program. In order to keep the pendulum on cart in balance, different types of controllers were designed, and stability analysis was performed by drawing root-locus curves for different controllers. The optimum controller design was obtained to keep the pendulum in balance. The impulse response of the system has been simulated and it has been proven that the designed optimum controller keeps the pendulum in balance. © 2022 IEEE.

2022 International Conference on Smart Information Systems and Technologies, SIST 2022 -- 28 April 2022 through 30 April 2022 -- 184566, Stability analysis and control of the inverted pendulum on cart system is an important problem that has been investigated by many researchers in recent years. In this study, nonlinear modeling of the inverted pendulum on cart system is derived and free body diagram is explained. Then, the nonlinear model of the system is created in MATLAB program. In order to keep the pendulum on cart in balance, different types of controllers were designed, and stability analysis was performed by drawing root-locus curves for different controllers. The optimum controller design was obtained to keep the pendulum in balance. The impulse response of the system has been simulated and it has been proven that the designed optimum controller keeps the pendulum in balance. © 2022 IEEE.

A model of the normal-force dependant friction loss between the rotor and pendula is developed for bifilar centrifugal pendulum vibration absorbers (CPVAs). The normal-force is dominantly dependant on the rotor rotational velocity but also dependant on the pendulum path. Simulation results of the pendulum with the proposed normal-force friction model agree well with novel experimental results. Order-response simulations of the rotor-CPVA model with the proposed friction model reveal accuracy improvements on the prediction of the rotor oscillation amplitude at different rotational velocities in comparison to existing friction formulations. Derivation of the equations of motion of the rotor-CPVA is performed by Kane's method and solved numerically. The developed experimental setup is used to validate the model parameters such as friction coefficients, path parameters and relative pendulum rotation without necessitating a special test-apparatus other than standard vibration measurement equipment. CPVAs are commonly used to reduce torsional vibration created by reciprocating engines. To reduce emissions, heavy-duty vehicles manufactures are downsizing and downspeeding the combustion engine while maintaining the power output. Unfortunately, this gives rise to increased torsional vibration in the powertrain. The CPVA is a device that can reduce the torsional vibration and thus help fulfill environmental goals., QC 20210319

Artificial football turf is today an increasingly common playing surface for athletics and kids. Its environmental impact is much debated, which is ranked as the second most common source of micro-plastic migration into nature. There are also concerns regarding the spread of inhalable airborne particles, originating from the wear between the football shoe-artificial turf contact. In this study a British pendulum rig is used to simulate the contact between football shoe stud and the artificial turf. The test rig is placed in a clean room environment, to ascertain if there are measurable levels of airborne particles generated in different sizes. The particle concentration was measured for airborne particles in size between 0.3 to 10 μm. In addition, migration studies of micro-plastics were also performed using the same test set up. Three commonly used rubber granule infill materials are tested in this study: SBR, TPE and EPDM. The results show that EPDM generates more airborne particles than the other two materials. Measurable levels of airborne wear particles were noted in the range from 0.3-10 μm. For the migration studies of micro-plastics, TPE generated the largest number of migrated particles., QC 20200622

In vacuo cryogenic environments are ideal for applications requiring both low temperatures and extremely low particle densities. This enables reaching long storage and coherence times, for example, in ion traps, essential requirements for experiments with highly charged ions, quantum computation, and optical clocks. We have developed a novel cryostat continuously refrigerated with a pulse-tube cryocooler and providing the lowest vibration level reported for such a closed-cycle system with 1 W cooling power for a <5 K experiment. A decoupling system suppresses vibrations from the cryocooler by three orders of magnitude down to a level of 10 nm peak amplitudes in the horizontal plane. Heat loads of about 40 W (at 45 K) and 1 W (at 4 K) are transferred from an experimental chamber, mounted on an optical table, to the cryocooler through a vacuum-insulated massive 120 kg inertial copper pendulum. The 1.4 m long pendulum allows installation of the cryocooler in a separate, acoustically isolated machine room. At the experimental chamber, we measured the residual vibrations using an interferometric setup. The positioning of the 4 K elements is reproduced to better than a few micrometer after a full thermal cycle to room temperature. Extreme high vacuum on the 10−15 mbar level is achieved. In collaboration with the Max-Planck-Institut für Kernphysik, such a setup is now in operation at the Physikalisch-Technische Bundesanstalt for a next-generation optical clock experiment using highly charged ions.

In vacuo cryogenic environments are ideal for applications requiring both low temperatures and extremely low particle densities. This enables reaching long storage and coherence times, for example, in ion traps, essential requirements for experiments with highly charged ions, quantum computation, and optical clocks. We have developed a novel cryostat continuously refrigerated with a pulse-tube cryocooler and providing the lowest vibration level reported for such a closed-cycle system with 1 W cooling power for a <5 K experiment. A decoupling system suppresses vibrations from the cryocooler by three orders of magnitude down to a level of 10 nm peak amplitudes in the horizontal plane. Heat loads of about 40 W (at 45 K) and 1 W (at 4 K) are transferred from an experimental chamber, mounted on an optical table, to the cryocooler through a vacuum-insulated massive 120 kg inertial copper pendulum. The 1.4 m long pendulum allows installation of the cryocooler in a separate, acoustically isolated machine room. At the experimental chamber, we measured the residual vibrations using an interferometric setup. The positioning of the 4 K elements is reproduced to better than a few micrometer after a full thermal cycle to room temperature. Extreme high vacuum on the 10−15 mbar level is achieved. In collaboration with the Max-Planck-Institut für Kernphysik, such a setup is now in operation at the Physikalisch-Technische Bundesanstalt for a next-generation optical clock experiment using highly charged ions.

The multiple-order response of a rotor equipped with a centrifugal pendulum vibration absorber (CPVA) is investigated in this study. CPVAs have been used in the abatement of torsional vibrations since the 1930s and have been extensively researched but seldom with a focus on the full multiple-harmonic response. Although the firing order in reciprocating engines dominates in amplitude, the higher-order harmonics have impact on driveline-related noise issues. This investigation is conducted in order to understand if an higher-order amplification can stem from the design of the CPVA or if this phenomenon is due an interaction between other powertrain components. Therefore, an isolated rotor-CPVA system is studied. The investigated rotor is subjected to an oscillating torque consisting of single- and multiple-order harmonics. The equations of motion are derived by Kane s method and the multiple-harmonic response of the system is analyzed. The linear steady-state response is compared with numerical time integration of the equations of motion., QC 20190514

The multiple-order response of a rotor equipped with a centrifugal pendulum vibration absorber (CPVA) is investigated in this study. CPVAs have been used in the abatement of torsional vibrations since the 1930s and have been extensively researched but seldom with a focus on the full multiple-harmonic response. Although the firing order in reciprocating engines dominates in amplitude, the higher-order harmonics have impact on driveline-related noise issues. This investigation is conducted in order to understand if an higher-order amplification can stem from the design of the CPVA or if this phenomenon is due an interaction between other powertrain components. Therefore, an isolated rotor-CPVA system is studied. The investigated rotor is subjected to an oscillating torque consisting of single- and multiple-order harmonics. The equations of motion are derived by Kane s method and the multiple-harmonic response of the system is analyzed. The linear steady-state response is compared with numerical time integration of the equations of motion., QC 20211220

The multiple-order response of a rotor equipped with a centrifugal pendulum vibration absorber (CPVA) is investigated in this study. CPVAs have been used in the abatement of torsional vibrations since the 1930s and have been extensively researched but seldom with a focus on the full multiple-harmonic response. Although the firing order in reciprocating engines dominates in amplitude, the higher-order harmonics have impact on driveline-related noise issues. This investigation is conducted in order to understand if an higher-order amplification can stem from the design of the CPVA or if this phenomenon is due an interaction between other powertrain components. Therefore, an isolated rotor-CPVA system is studied. The investigated rotor is subjected to an oscillating torque consisting of single- and multiple-order harmonics. The equations of motion are derived by Kane s method and the multiple-harmonic response of the system is analyzed. The linear steady-state response is compared with numerical time integration of the equations of motion., QC 20211220

The multiple-order response of a rotor equipped with a centrifugal pendulum vibration absorber (CPVA) is investigated in this study. CPVAs have been used in the abatement of torsional vibrations since the 1930s and have been extensively researched but seldom with a focus on the full multiple-harmonic response. Although the firing order in reciprocating engines dominates in amplitude, the higher-order harmonics have impact on driveline-related noise issues. This investigation is conducted in order to understand if an higher-order amplification can stem from the design of the CPVA or if this phenomenon is due an interaction between other powertrain components. Therefore, an isolated rotor-CPVA system is studied. The investigated rotor is subjected to an oscillating torque consisting of single- and multiple-order harmonics. The equations of motion are derived by Kane s method and the multiple-harmonic response of the system is analyzed. The linear steady-state response is compared with numerical time integration of the equations of motion., QC 20211220

The multiple-order response of a rotor equipped with a centrifugal pendulum vibration absorber (CPVA) is investigated in this study. CPVAs have been used in the abatement of torsional vibrations since the 1930s and have been extensively researched but seldom with a focus on the full multiple-harmonic response. Although the firing order in reciprocating engines dominates in amplitude, the higher-order harmonics have impact on driveline-related noise issues. This investigation is conducted in order to understand if an higher-order amplification can stem from the design of the CPVA or if this phenomenon is due an interaction between other powertrain components. Therefore, an isolated rotor-CPVA system is studied. The investigated rotor is subjected to an oscillating torque consisting of single- and multiple-order harmonics. The equations of motion are derived by Kane s method and the multiple-harmonic response of the system is analyzed. The linear steady-state response is compared with numerical time integration of the equations of motion., QC 20211220

The multiple-order response of a rotor equipped with a centrifugal pendulum vibration absorber (CPVA) is investigated in this study. CPVAs have been used in the abatement of torsional vibrations since the 1930s and have been extensively researched but seldom with a focus on the full multiple-harmonic response. Although the firing order in reciprocating engines dominates in amplitude, the higher-order harmonics have impact on driveline-related noise issues. This investigation is conducted in order to understand if an higher-order amplification can stem from the design of the CPVA or if this phenomenon is due an interaction between other powertrain components. Therefore, an isolated rotor-CPVA system is studied. The investigated rotor is subjected to an oscillating torque consisting of single- and multiple-order harmonics. The equations of motion are derived by Kane s method and the multiple-harmonic response of the system is analyzed. The linear steady-state response is compared with numerical time integration of the equations of motion., QC 20211220

The paper investigates the conditional stability of the basic steady motions of the spatial model of an isolated system, consisting of a rotating lifting body, a particle, creating its static unbalance and two identical mathematical pendulums, mounted on a longitudinal axis of the lifting body and moving in the plane of the static unbalance, the relative motion of which is hindered by the viscous resistance forces. It is found that in the case where unbalance is present and pendulums can correct it with a certain margin, there is one basic motion. In the absence of unbalance, there is a one-parameter family of basic motions. In the case of maximum unbalance, which can be corrected by pendulums, there is one basic motion, but it generates a pseudo family of basic motions. Also, it is revealed that some basic motions, if isolated, or a family or a pseudo family of basic motions is conditionally asymptotically stable. In the absence of unbalance, the presence of a single zero root of the characteristic equation does not affect the stability of a one-parameter family of basic motions and is responsible for the transition from one steady motion of a family to another. In the case of maximum unbalance, the presence of a single zero root of the characteristic equation does not affect the stability of the basic motion and is responsible for the transition from one steady motion of a pseudo family to another. Transition processes are oscillatory-damped.

The paper investigates the conditional stability of steady motions of a flat model of an isolated system consisting of a rotating LB, material point, which creates its static imbalance, and two identical mathematical pendulums, mounted on the longitudinal axis of the LB and moving in the plane of the static imbalance, the relative motion of which is prevented by the viscous resistance. It was found that in the case where there is imbalance and pendulums can eliminate it with a certain reserve, there is one basic motion; in the absence of imbalance, there is a one-parameter family of basic motions; in the case of maximum imbalance, which can be eliminated by pendulums, there is one basic motion, but it generates pseudo-family of basic motions. Also, it was found that some basic motions are conditionally asymptotically stable, if they, or family, or pseudo-family of basic motions are isolated. In the absence of imbalance, the presence of a single zero root of the characteristic equation does not affect the stability of the one-parameter family of basic motions, and is responsible for the transition from one to another steady motion of the family. In the case of maximum imbalance, the presence of a single zero root of the characteristic equation does not affect the stability of the basic motion, and is responsible for the transition from one to another steady motion of pseudo-family. Transients, depending on the system parameters can be aperiodic or oscillatory-damped. It was found that the side motions are unstable.

A derivation of a non-dimensionalized math model was presented for predicting oscillation frequencies of a submerged tethered buoy. The model included a prediction of the buoy excitation frequencies due to vortex shedding. To match this excitation frequency with buoy natural frequencies, this model included coupling effects of an internal pendulum and added mass of the buoy, but excluded viscous damping. This model did not include coupling of the buoy motion on the vortex shedding frequencies. This report also presents a linear generator system that could be used internally in an upright buoy to produce power. Simple power tests were conducted using machine and manual actuation of the magnets. Future work on this project will include (1) laboratory and field testing to validate the VIV oscillation model, (2) a possible adjustment of the model to include a coupling effect of buoy motion with vortex shedding as well as viscous damping, and (3) incorporation of a generator into a buoy design to validate power output predictions. The effects of the generator on the model will the then be included., The original document contains color images.

Cut-to-length logging (CTL) is a mechanized harvesting process where trees are delimbed and cut to length directly at the stump. CTL is typically a two-machine operation with a harvester felling, delimbing, and bucking trees, and a forwarder transporting the cut logs from the felling area to a landing area that is accessible by trucks, or trains. A major challenge for the manufacturers of forestry machines for CTL logging is to (1) further increase the harvesting and log transportation productivity, e.g. by enabling operation with higher transportation speed and on eco-soils, (2) reduce the damage to the soil, e.g. by controlling the rut depth and preserving the root layer, and (3) reduce the daily vibration dosage for the machine operators, e.g. by active chassis and cabin suspensions. This paper presents a study of a novel all-wheel-drive pendulum-arm suspended medium-sized forestry machine, with several upgrade performance steps, e.g. passive and active chassis suspensions. The dynamic performance of the new concept are quantified with simulations and compared with a present bogie solution. The simulations show an 80% reduction of whole body vibrations with an active suspension system compared to present passive bogie solutions when operating on a standardized test ground., QC 20150610

The preventive warning systems are seen as an alternative to rider assistance and risk reduction for Powered Two Wheeled (PTW) vehicles. In this work we propose an analysis of the critical lean dynamics of motorcycle based on a model of double inverted pendulum (DIP). The choice of this structure is motivated by its simplicity and that the model contains the main parts which contribute principally in the PTW vehicle tilt dynamics. The analysis will be focused on the effect of the tire-road adhesion, the longitudinal speed and its dynamics, the road curvature, the road bank angle and the tilt of the rider's upper body.

Accurate, direct measurement of thrust or impulse is one of the most critical elements of electric thruster characterization, and one of the most difficult measurements to make. The American Institute of Aeronautics and Astronautics has started an initiative to develop standards for many important measurement processes in electric propulsion, including thrust measurements. This paper summarizes recommended practices for the design, calibration, and operation of pendulum thrust stands, which are widely recognized as the best approach for measuring microN- to mN-level thrust and microNs-level impulse bits. The fundamentals of pendulum thrust stand operation are reviewed, along with its implementation in hanging pendulum, inverted pendulum, and torsional balance configurations. Methods of calibration and recommendations for calibration processes are presented. Sources of error are identified and methods for data processing and uncertainty analysis are discussed. This review is intended to be the first step toward a recommended practices document to help the community produce high quality thrust measurements., Presented at the 33rd International Electric Propulsion Conference, Washington, DC, October 6-10, 2013.

In this paper, smartphone acceleration sensors were used to perform a quantitative analysis of mechanical coupled oscillations. Symmetric and asymmetric normal modes were studied separately in the first two experiments. In the third, a coupled oscillation was studied as a combination of the normal modes. Results indicate that acceleration sensors of smartphones, which are very familiar to students, represent valuable measurement instruments for introductory and first-year physics courses.

In this paper, smartphone acceleration sensors were used to perform a quantitative analysis of mechanical coupled oscillations. Symmetric and asymmetric normal modes were studied separately in the first two experiments. In the third, a coupled oscillation was studied as a combination of the normal modes. Results indicate that acceleration sensors of smartphones, which are very familiar to students, represent valuable measurement instruments for introductory and first-year physics courses.

Waltz is a typical example of physical human-human interaction (pHHI) in a well-structured environment. Waltz involves two dancers. The goal is to reproduce the female dancer's abilities with a robot in pHRI. The project focused on the lower level interaction in pHRI, i.e., coupled dynamics, and proposed a framework which covers modeling, analysis, human state sensing and robot control in developing a cooperative female robot dancer. The two dancers' coupled dynamics was modeled as two physically connected inverted pendulums. Stability of this two pendulum system was analyzed. The human state was measured by two laser range sensors, while the measurement noise and bias were corrected by a Kalman filter. Several candidate robot controllers were discussed and evaluated in experiments.

[EN] This paper presents the potential of open source software for designing educational tools in the automatization field. In particular, this paper presents a complete tool that students can use for studying and testing nonlinear control algorithms. The system has three different parts that students can evaluate and modify. Firstly, a virtual model represents the physical model and, in this case, an inverted pendulum is used. Secondly, the controller is implemented by a real-time distributed control system. Finally, the system can be managed with a JAVA application. Therefore, students have all the necessary elements to practice using nonlinear and complex systems. The main tools applied in the design are open source software and the developed platform is Generalized Public License(GPL). © 2009 Wiley Periodicals, Inc.

[EN] This paper presents the potential of open source software for designing educational tools in the automatization field. In particular, this paper presents a complete tool that students can use for studying and testing nonlinear control algorithms. The system has three different parts that students can evaluate and modify. Firstly, a virtual model represents the physical model and, in this case, an inverted pendulum is used. Secondly, the controller is implemented by a real-time distributed control system. Finally, the system can be managed with a JAVA application. Therefore, students have all the necessary elements to practice using nonlinear and complex systems. The main tools applied in the design are open source software and the developed platform is Generalized Public License(GPL). © 2009 Wiley Periodicals, Inc.

The use of krypton as an alternative to xenon for Hall thruster propellant is an interesting option for satellite system designers due to its lower cost. However, this cost-savings comes at the expense of thrust efficiency. Reduction in efficiency can be caused by energy losses from Joule heating, radiation, and the ionization process as well as degradation of plume quality from an increase in velocity distribution spread (most often from an increase in multiply charged ion populations) and geometric beam divergence.1 In order to quantify this performance reduction for the case of the flight model SPT-100 HET (1.35 kW), an ongoing series of experimental measurements is being conducted to measure how various thruster efficiency terms change with propellant and operating condition. This study will combine thrust measurements with plume data from electrostatic probes. This paper presents the results of performance measurements made using an inverted pendulum thrust stand. Krypton operating conditions were tested over a large range of operating powers from 800 W to 3.9 kW. Analysis of how performance is impacted by propellant and operating condition is presented. A simple mission analysis was done based on these measurements to evaluate the practicality of krypton propellant for an SPT-100 subsystem using krypton propellant for north-south station keeping (NSSK) for a typical communications spacecraft in geosynchronous orbit., Presented at the International Electric Propulsion Conference (32nd) Weisbaden, Germany on 11-15 September 2011.

A child takes a running start, grabs hold of the free-hanging end of a rope at the edge of a water hole at x = 0, swings upward, and lets go of the rope at some point, flying freely through the air until he lands in the water at x = R . For small initial speeds, the maximum range R is obtained by releasing the rope just short of its turning point and dropping almost straight down into the water from rest. On the other hand, as a child's running speed gets larger and larger (compared to the square root of the product of the length of the rope and earth's gravitational field), the rope should be released at an angle of about pie / 4 to maximize the range. That is, the optimum trajectory of a child is dominated by pendulum motion at low running speeds and by projectile motion at high initial speeds., Published in Lat. Am. J. Phys. Educ., v5 n2 p335-337, June 2011.

Milliken contracted Southwest Research Institute (SwRI) to conduct blast pendulum tests on various panels. The blast pendulum allows one to investigate a material's capability of mitigating sample deformation and bulk structural loading that result from "close-in" blast loading. The methodology is based upon placing a sample in a semi-rigid frame. The frame is supported by large supports that are free to rotate about a fixed position. Based upon the angular motion, the momentum transferred into the sample can be determined. The pendulum is most useful for looking at plate coatings which hopefully can reduce the plate deformation and the overall momentum transferred into a structure. SwRI conducted a total of four tests on September 5, 2007, using the blast pendulum at its remote site near Yancey, Texas. A representative from Milliken witnessed each test. None of the tests resulted in perforation of the target assembly, and their swing angles and deflections were considerably less than those of a baseline 3/8-inch mild steel target performed the next day (47.2-degree maximum swing with 4.53-inch maximum plate deflection) versus the best Milliken combination that showed a 41.8-degree maximum swing with 2.64-inch maximum plate deflection., Prepared in cooperation with Milliken & Company, Spartanburg, SC. The original document contains color images.

Motivated by recent efforts to mitigate blast loading using energy-absorbing materials, this report uses analytical and computational modeling to investigate the influence of mass distribution on the uniaxial crushing of cellular sandwich plates under air blast loading. In the analytical model, the cellular core is represented using a rigid, perfectly-plastic, locking idealization, as in previous studies, and the front and back faces are modeled as rigid, with pressure loading applied to the front face and the back-face unrestrained. This model is also applicable to the crushing of cellular media in blast pendulum experiments. Fluid structure interaction effects are treated using a recent result that accounts for nonlinear compressibility effects for intense air blasts. Predictions of the analytical model show excellent agreement with explicit finite element computations, and the model is used to investigate the response of the system for all possible distributions of mass between the front and back faces and the cellular core. Increasing the mass fraction in the front face is found to increase the impulse required for complete crushing of the cellular core but also to produce undesirable increases in back-face accelerations. Optimal mass distributions for mitigating shock transmission through the sandwich plate are investigated by maximizing the impulse capacity while limiting the back-face accelerations to a specified level., Pub. in the International Journal of Solids and Structures, v45, p2297-2321, 2008. Prepared in cooperation with National Institute of Standards and Technology, Gaithersburg, MD.

The ability of three mathematical human body models to predict previously published human responses in two different side impact loading configurations was evaluated using an objective rating method. In particular the kinematics of the shoulder, T1 and head were evaluated. The human body models evaluated were THUMS, HUMOS 2 and the GM model. The impact loading configurations used were pendulum impact tests and sled tests. In the pendulum configurations, the closest correlation to the published responses was shown by THUMS followed by the GM model. In the sled configuration, closest correlation to the published responses was shown by HUMOS 2 followed by THUMS. According to the objective rating method the published responses in the pendulum configuration were predicted by all human body models. The published responses in the sled configuration were predicted by HUMOS 2 and THUMS., QC 20141017

The mathematical pendulum is one of the most widely studied problem in engineering physics. This is, however, primarily limited to the classical pendulum with a single bar and mass configuration. Extensions to this include multi-degree of freedom systems, but many of the classical assumptions, such as a single bar per mass, are preserved. Several designs used in practice utilize multiple or trapezoidal configurations in order to enhance stability. Such designs have not been studies in great detail and there is a need for additional work in order to fully analyze their response characteristics. The two-string pendulum design characteristics are initially investigated, both in terms of oscillation characteristics and string tension. Analytical and numerical methodologies are applied in order to predict the response of the two-string pendulum in free and forced oscillations. Validation of the results is performed by comparisons to simulations conducted with a standard commercial software package. A preliminary optimization study is conducted for a driven two-string pendulum. Finally, it is shown how to apply the results of the analysis and optimization studies developed in this work in a typical design case., The original document contains color images.

The mathematical pendulum is one of the most widely studied problems in engineering physics. This is, however, primarily limited to the classical pendulum with a single bar and mass configuration. Extensions to this include multi-degree of freedom systems, but many of the classical assumptions, such as a single bar per mass, are preserved. Several designs used in practice utilize multiple or trapezoidal configurations to enhance stability. Such designs have not been studied in great detail and there is a need for additional work to fully analyze their response characteristics. The two-string pendulum design characteristics are initially investigated, both in terms of oscillation characteristics and string tension. Analytical and numerical methodologies are applied to predict the response of the two-string pendulum in free and forced oscillations. Validation of the results is performed by comparisons to simulations conducted with a standard commercial software package. A preliminary optimization study is conducted for a driven two-string pendulum. Finally, it is shown how to apply the results of the analysis and optimization studies developed in this work in a typical design case., The original document contains color images.

We consider the problem of creating oscillations with respect to a part of state variables in underactuated mechanical systems. The main contribution is a modification of a recently proposed control strategy, exploiting passivity to shape the energy of the system with respect to a subset of the state variables and neglecting the dynamics of the other ones. We propose a way to design an additional control action, which guarantees boundedness of the motion of these other degrees of freedom, which otherwise almost always evolve without any bound. The idea is presented on the well-known two-degrees-of-freedom benchmark example of inverted pendulum on a cart.

An impulse pendulum with significantly increased sensitivity compared to its predecessor is described. The problems associated with its predecessor are discussed and other pendulum designs are also presented. The design approach for the new pendulum is then presented along with the current mechanical design and photographs of the finished pendulum. The pendulum's performance is presented compared to its predecessor. Finally, other embodiments of the approach are presented., Prepared in collaboration with Polaris Sensor Technologies, Huntsville, AL.

Dynamics starts with fundamentals of Newtonian mechanics. Further topics include kinematics, particle dynamics, motion relative to accelerated reference frames, work and energy, impulse and momentum, systems of particles and rigid body dynamics. Applications to aerospace engineering are discussed, including introductory topics in orbital mechanics, flight dynamics, inertial navigation and attitude dynamics.

Dynamics starts with fundamentals of Newtonian mechanics. Further topics include kinematics, particle dynamics, motion relative to accelerated reference frames, work and energy, impulse and momentum, systems of particles and rigid body dynamics. Applications to aerospace engineering are discussed, including introductory topics in orbital mechanics, flight dynamics, inertial navigation and attitude dynamics.

Dynamics starts with fundamentals of Newtonian mechanics. Further topics include kinematics, particle dynamics, motion relative to accelerated reference frames, work and energy, impulse and momentum, systems of particles and rigid body dynamics. Applications to aerospace engineering are discussed, including introductory topics in orbital mechanics, flight dynamics, inertial navigation and attitude dynamics.

A study to investigate the mode-cleaning and injection optics of the gravitational-wave detector GEO600 was presented. The instrument uses two high-finesse triangular ring cavities of 8 m optical wavelength each, as an optical mode-cleaning system. The duty cycle of the system was measured to be 99.7%. It was found that the throughput of the whole modecleaner system is about 50%.

In this paper, we report on a new stability analysis for hybrid legged locomotion systems based on factorization of return maps. We apply this analysis to a family of models of the Spring Loaded Inverted Pendulum (SLIP) with different leg recirculation strategies. We obtain a necessary condition for the asymptotic stability of those models, which is formulated as an exact algebraic expression despite the non-integrability of the SLIP dynamics. We outline the application of this analysis to other models of legged locomotion and its importance for the stability of legged robots and animals.

Two fundamental mechanisms underlie walking and running. walking involves an inverted pendulum-like exchange of kinetic and gravitational potential energy. Running involves spring-like exchange between kinetic and gravitational potential energy with elastic energy stored in the tendons. People are better able to utilize the inverted pendulum mechanism when loads are carried on the head and this method allows small loads to be carried for free. However, there is not a clear link between the mechanical work performed in walking and the metabolic cost. Rhinoceros beetles are able to carry enormous loads very cheaply but how they do so is not clear. People can use external springs to carry loads more comfortably, but not more cheaply. But kangaroos and wallabies can use internal springs to save energy during their bopping gait and to carry loads in their pouches. These examples can inspire novel means of improved human load carriage., The original document contains color images. Pres: RTO Human Factors and Medicine Panel (HFM) Specialists' Meeting, Kingston, Canada, KN2-1/KN2-8, 27-29 Jun 2000. This article is from ADA394945 Soldier Mobility: Innovations in Load Carriage System Design and Evaluation (la Mobilite du combattant: innovations dans la conception et l'evaluation des gilets d'intervention)

Bifurcation to high dimensional hyperchaos is observed in a driven coupled pendulum-flexible rod system. When the rod is in resonance with the pendulum, the system changes from a low dimensional attractor to a high dimensional attractor abruptly. It is shown that high dimensional chaotic dynamics is hysteretic, and exhibits extreme sensitivity with respect to small parameter changes. Such sensitivity poses a problem in obstructing predictability in mechanics. A brief discussion of sustaining chaos to prevent resonance is included., Prepared in cooperation with Princeton Univ, Princeton, NJ, and the National Technical Univ of Athens, Greece.

An inverted pendulum has been used as the controlled device in a prototype real-time control system employing the Simplex (trademark) architecture. In this report, we address the control issues of such a system in an analytic way. In particular, an analytic model of the system is derived; control algorithms are designed for the baseline control, experimental control and safety control based on the concept of analytic redundancy; the safety region is obtained as the stability region of the system under the safety control; and the control switching logic is established to provide fault tolerant functionality. Finally, the results obtained and the lessons learned are summarized, and future work is discussed.

Reciprocity calibration of electromechanical transducers is carried out with three transducers, which are secured to a mass mounted for oscillation as a pendulum. A first transducer is driven and the electrical output of a second transducer is measured. A third transducer, which must be a linear, reciprocal device, is driven and the electrical output of the second transducer is measured. The first transducer is driven while the electrical output of the third transducer is measured. The sensitivities of the transducers can be deduced from the electrical inputs and the measured electrical outputs by taking advantage of reciprocity. The transducers may be mounted to the pendulum mass two at a time, or alternatively, all three transducers may be fixed to the pendulum mass.

Reciprocity calibration of electromechanical transducers is carried out with three transducers, which are secured to a mass mounted for oscillation as a pendulum. A first transducer is driven and the electrical output of a second transducer is measured. A third transducer, which must be a linear, reciprocal device, is driven and the electrical output of the second transducer is measured. The first transducer is driven while the electrical output of the third transducer is measured. The sensitivities of the transducers can be deduced from the electrical inputs and the measured electrical outputs by taking advantage of reciprocity. The transducers may be mounted to the pendulum mass two at a time, or alternatively, all three transducers may be fixed to the pendulum mass., Supersedes PAT-APPL-682 033-96.

In severe helicopter accidents, flight helmets rotate or sometimes come off the head, triggering wearer injury. This study evaluates rotation potential for new flight helmets. Current and prototype flight helmets (SPH-4B and two versions of the HGU-56) were subjected to three tests. First, rotation was measured with up to a 50-pound upward pull at the rear edge of the helmet on a medium-size headform. Second, angular displacement was measured with a 30-pound force at the side of the helmet. Third, the helmet was placed on a Hybrid II headform and Hybrid III neck, then mounted on a pendulum test device. The freefalling pendulum was decelerated to produce 16 to 20 G peak acceleration at the neck. Angular displacement of the helmet versus time was measured with high-speed video. The upward pull tests produced 18 to 33 degrees of helmet rotation. Sideward loads produced 13 to 21 degrees of rotation. The pendulum test produced up to 45 degrees forward and up to 25 degrees rearward displacement.

The purpose of this work was to develop a controller that could perform the highly discontinuous and nonlinear task of balancing the inverted pendulum from an arbitrary set of initial conditions. Fuzzy logic was chosen as the control technique because of its ability to deal with nonlinear systems, as well as its intuitive nature. The rule base depends on intuition and logic, rather than an exact mathematical model. This makes it more robust to changes in the model, and also gets rid of the need to solve nonlinear differential equations or optimality conditions. Using a set of fuzzy logic controllers, linked in the right way, the primary research objectives were accomplished. In addition, the adjustable desired energy allows for different tip masses and arm lengths to be controlled equally as well with a simple number adjustment on the interactive animation window. This makes the controller very robust. There are many options for future research on the inverted pendulum using fuzzy logic. The current controller could be improved by further adjustment of the membership functions. This adjustment could be performed manually by experimenting and checking the results. An optimization routine using Genetic Algorithms could also be used. This would involve letting the computer run simulations and compare results automatically. (KAR) p. 47

Several spin-stabilized communication satellites with liquid stores on board have exhibited unstable nutational motion. Liquid sloshing is suspected as the cause of this undesirable behavior. During an initial three year grant period, a test rig was built and instrumented, a rigid body computer model was developed using a pendulum analogy to simulate the sloshing liquid, and computational fluid dynamic (CFD) methods were used to develop a primitive variable numerical algorithm to describe two and three dimensional liquid sloshing. During the current three year grant period, the test rig and rigid body computer model have been used to study the effect of various physical parameter values on the motion, and stability conditions have been determined. The structural mathematical model has been improved by introduction of finite element techniques to account for elastic deformation of the test rig, and an implicit-explicit numerical approach has been implemented to solve the coupled, nonlinear equations of motion.

The Lorentz force equation governing the interaction between radiation and charged particles in the presence of a static magnetic field can be reduced to the form of the simple pendulum equation, when applied to the Free Electron Laser (FEL) and to the amplification of whistler waves in the magnetosphere. The first topic in this thesis is the start-up of an FEL with a compact design having a small, spatial undulator period, many periods, and a small undulator field strength. Under these conditions, the number of photons spontaneously emitted into the resonator mode each pass is so small that a classical field cannot be established. Quantum fluctuations affect the wave- particle interaction and therefore diminish weak field gain. An FEL start-up condition, several orders of magnitude more restrictive than determined by quantum recoil alone, is derived from the photon rate equation. The next topic is the evolution of a weak, classical radiation field driven by a long electron pulse.

At the request of the Carderock Division, Naval Surface Warfare Center, Bethesda, MD, the Air Force Packaging Evaluation Activity evaluated a modular collapsible aluminum container developed under contract with a commercial vendor by the Navy. The container configuration evaluated consisted of two aluminum end caps serving as top and bottom and two 18 inch collars and is secured to a 40 X 48 inch wood shipping pallet to an overall height of 41 inches by steel strapping. The advantage of the CECON container is that it can be disassembled, collapsed, and stacked for return shipment with greatly reduced volume. With a 1000 pound net weight load, the CECON container was subjected to a rough handling test series consisting of superimposed load, mechanical handling, repetitive shock vibration, 20 inch edgewise and cornerwise drop, 18 inch flat bottom drop, 10 feet per second pendulum impact, and blowing rain tests

A field coil stator of an electrical generator is fixed to the fuse body of an explosive projectile within which the rotor of the generator is supported for limited rotation dampened by a pendulum to effectively induce an electrical output from the stator field coils during and after launch of the projectile from an internally rifled gun barrel. The rotor is rotationally isolated from the stator during launch by shock absorbing means to avoid defeat of the pendulum dampening action on the rotor

A field coil stator of an electrical generator is fixed to the fuse body of an explosive projectile within which the rotor of the generator is supported for limited rotation dampened by a pendulum to effectively induce an electrical output from the stator field cods during and after launch of the projectile from an internally rifled gun barrel. The rotor is rotationally isolated from the stator during launch by shock absorbing means to avoid defeat of the pendulum dampening action on the rotor.

Several propellant charges using heterogeneous configurations of JA2 sticks and ball powder were evaluated with respect to their response to a shaped charge jet direct impact. Vulnerability tests were performed on the JA2 and ball powder propellants separately and together. The test results show that the JA2+ball powder configurations gave a response no better than the JA2 alone. Separate tests of loose and compressed powder showed that the compressed sample gave a 37% increased response over the loose sample.... Ban powder propellants, Shock velocity tests, Impulse pendulum tests, Consolidated ball powder, Propelling charges