Index to NASA Tech Briefs, 1975

This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs

A comprehensive review of the techniques on regenerative shock absorber systems

In this paper, the current technologies of the regenerative shock absorber systems have been categorized and evaluated. Three drive modes of the regenerative shock absorber systems, namely the direct drive mode, the indirect drive mode and hybrid drive mode are reviewed for their readiness to be implemented. The damping performances of the three different modes are listed and compared. Electrical circuit and control algorithms have also been evaluated to maximize the power output and to deliver the premium ride comfort and handling performance. Different types of parameterized road excitations have been applied to vehicle suspension systems to investigate the performance of the regenerative shock absorbers. The potential of incorporating nonlinearity into the regenerative shock absorber design analysis is discussed. The research gaps for the comparison of the different drive modes and the nonlinearity analysis of the regenerative shock absorbers are identified and, the corresponding research questions have been proposed for future work

A study of vehicle electromagnetic regenerative shock absorber

The technology of energy harvesting from shock absorber has become more promising over the years with a potential for implementation. The aim of the research is to improve the energy harvesting ability of the regenerative shock absorber and evaluate its feasibility operating in the real road condition on the vehicle. This thesis consists of 7 chapters to address the research questions raised from the existing research gaps based on the literature reviews: 1. How can the performance of the electromagnetic energy harvester in 2DOF system be improved? 2. For the direct drive and indirect drive regenerative shock absorbers, which one has better performance? 3. How can the half vehicle model with regenerative shock absorbers be modelled for the premium energy harvesting performance? In order to answer the research questions, firstly a 2 degrees of freedom oscillating system resembling the quarter vehicle suspension system is constructed with the electromagnetic harvester and validated by the simulation model. It is found that the peak power output occurs at natural frequency. Base excitation amplitude and external resistance can also affect the system power output. As for the energy harvester, better energy harvesting performance can be achieved through two factors: coil speed with respect to the magnets and the electro-mechanical coupling constant. The double speed mechanism can increase the coil speed with respect to the magnets and is applied on a design of novel regenerative shock absorber. It is found that increasing the coil speed with respect to the magnets for 2 times can result in increasing the power output by 4 times. A novel indirect drive regenerative shock absorber with the arm-teeth system is also designed and fabricated to answer the second research question. The results show 2 that the power output can be substantially increased compared with the traditional direct drive regenerative shock absorber. It is also found that the arm-teeth system makes the regenerative shock absorber more sensible to parameter optimization and has the potentials to increase the energy harvesting bandwidth. As the response to research question three, a half vehicle suspension system model is established with two indirect drive regenerative shock absorbers. The Taguchi method is unitized for the parameter optimization. With the application of the random road excitation displacement amplitude, the optimized model can harvest more energy than the non-optimized model when the vehicle is driving on the Class A, Class C and Class E road. Lastly a full vehicle suspension system model is developed as an extension to the half vehicle suspension system model. It is found that at high frequency range, the peak power output ratio of full vehicle suspension system is same as that of the half and quarter vehicle suspension system. The advantages of the full vehicle suspension system are more obvious at low frequency range or when the vehicle is driving on the off-road condition

Space programs summary no. 37-63, volume 1 for the period 1 March - 30 April 1970. Flight projects

Mariner Mars 1971, Mariner Venus-Mercury 1973 and Viking Orbiter 1975 status report

Smart materials and vehicle efficiency. Design and experimentation of new devices.

In this dissertation the activities carried out during the PhD are comprehensively described. The research mainly focused on the development of novel smart devices aimed at disengaging auxiliaries in internal combustion engine vehicles. In particular, the activities dealt with modeling, design, manufacturing and testing different fail-safe magnetorheological clutch prototypes, in the framework of a project funded by Regione Toscana, which involved two departments of the University of Pisa and Pierburg Pump Technology - Stabilimento di Livorno. After an extended literature review, several concepts of the clutch were proposed, which led to the design of the first magnetorheological prototype. An intensive experimental campaign was conducted, which involved several prototypes. A particular attention was focused on the measurement and analysis of the torque transmitted by the clutch in different operating conditions and new indices were proposed to objectively analyze the performances of magnetorheological clutches in general. On the basis of the results of the first experimental phase, the limits of the first design were analyzed and a novel prototype was developed, which succeeded in fulfilling all the design specifications. Further analyses were carried out in order to develop a clutch model starting from the experimental results. The effect of clutch heating was considered and a complete model of the clutch based on neural networks was proposed. The model was capable of taking into account the effect of the main parameters influencing the torque characteristic and may be used in a vehicle simulator or in a hardware-in-the-loop bench. Finally, an additional component to be connected to the clutch, which made use of shape memory alloys, was developed and tested during the visiting period at the University of Toledo (OH), USA

Feasibility study and model development for a ferrofluid viscous damper Final report, 8 Nov. 1966 - 8 Mar. 1967

Development of magnetic fluid viscous oscillation damper for scientific satellite

A novel Active Control of Trolleybus Current Collection System (ACTCCS)

The trolleybus has been a popular public transport vehicle for more than a hundred years across the world. However, the typical features of double passive pantograph-booms with two-wire overhead line often creates complicated catenary webs (particularly at crossroads) and can result in easily de-wiring and arcing issues. In this thesis, a novel concept of Active Control of Trolleybus Current Collection System (ACTCCS) is introduced with actuator-controlled solo-pantograph and single overhead line (catenary formed by two wires fitted on a frame with enough electric clearance and creep) as well as electric (traction)-electric (battery or supercapacitor backup) hybrid (E-E hybrid) propulsion. [Continues.

Quarter and Full Car Models Optimisation of Passive and Active Suspension System Using Genetic Algorithm

© The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/This study evaluates a suspension design of a passenger car to obtain maximum rider's comfort when the vehicle is subjected to different road profile or road surface condition. The challenge will be on finding a balance between the rider's comfort and vehicle handling to optimize design parameters. The study uses a simple passive suspension system and an active suspension model integrated with a pneumatic actuator controlled by proportional integral derivative (PID) controller in both quarter car and full car models having a different degree of freedoms (DOF) and increasing degrees of complexities. The quarter car considered as a 2-DOF model, while the full car model is a 7-DOF model. The design process set to optimise the spring stiffnesses, damping coefficients and actuator PID controller gains. For optimisation, the research featured genetic algorithm optimisation technique to obtain a balanced response of the vehicle as evaluated from the displacement, velocity and acceleration of sprung and unsprung masses along with different human comfort and vehicle performance criteria. The results revealed that the active suspension system with optimised spring stiffness, damping coefficients and PID gains demonstrated the superior riding comfort and road holding compared to a passive suspension system.Peer reviewe

The Convergence of Parametric Resonance and Vibration Energy Harvesting

Energy harvesting is an emerging technology that derives electricity from the ambient environment in a decentralised and self-contained fashion. Applications include self-powered medical implants, wearable electronics and wireless sensors for structural health monitoring. Amongst the vast options of ambient sources, vibration energy harvesting (VEH) has attracted by far the most research attention. Two of the key persisting issues of VEH are the limited power density compared to conventional power supplies and confined operational frequency bandwidth in light of the random, broadband and fast-varying nature of real vibration. The convention has relied on directly excited resonance to maximise the mechanical-to-electrical energy conversion efficiency. This thesis takes a fundamentally different approach by employing parametric resonance, which, unlike the former, its resonant amplitude growth does not saturate due to linear damping. Therefore, parametric resonance, when activated, has the potential to accumulate much more energy than direct resonance. The vibrational nonlinearities that are almost always associated with parametric resonance can offer a modest frequency widening. Despite its promising theoretical potentials, there is an intrinsic damping dependent initiation threshold amplitude, which must be attained prior to its onset. The relatively low amplitude of real vibration and the unavoidable presence of electrical damping to extract the energy render the onset of parametric resonance practically elusive. Design approaches have been devised to passively minimise this initiation threshold. Simulation and experimental results of various design iterations have demonstrated favourable results for parametric resonance as well as the various threshold-reduction mechanisms. For instance, one of the macro-scale electromagnetic prototypes (∼1800 cm3) when parametrically driven, has demonstrated around 50% increase in half power band and an order of magnitude higher peak power (171.5 mW at 0.57 ms−2) in contrast to the same prototype directly driven at fundamental resonance (27.75 mW at 0.65 ms−2). A MEMS (micro-electromechanical system) prototype with the additional threshold-reduction design needed 1 ms−2 excitation to activate parametric resonance while a comparable device without the threshold-reduction mechanism required in excess of 30 ms−2. One of the macro-scale piezoelectric prototypes operated into auto-parametric resonance has demon-strated notable further reduction to the initiation threshold. A vacuum packaged MEMS prototype demonstrated broadening of the frequency bandwidth along with higher power peak (324 nW and 160 Hz) for the parametric regime compared to when operated in room pressure (166 nW and 80 Hz), unlike the higher but narrower direct resonant peak (60.9 nW and 11 Hz in vacuum and 20.8 nW and 40 Hz in room pressure). The simultaneous incorporation of direct resonance and bi-stability have been investigated to realise multi-regime VEH. The potential to integrate parametric resonance in the electrical domains have also been numerically explored. The ultimate aim is not to replace direct resonance but rather for the various resonant phenomena to complement each other and together harness a larger region of the available power spectrum