An adaptive controller for current-fed induction motor

A model reference speed adaptive controller for a current-fed induction motor drive is proposed. It uses a proportional-plus-integral (PI) adaptation to satisfy the hyperstability condition for taking care of the load and machine parameter changes of the drive. The available information on the states and output of the reference model as well as the plant output are all that are required for the control; no explicit parameter identification is needed. The controller can be designed by using a reduced reference model to simplify the design without much degradation of the performance, so that it is relatively easy to implement practically     

Digital control algorithms for multi-degree-of-freedom microgravity isolation systems

Two general methodologies have been developed to design digital controllers for multi-degree-of-freedom microgravity isolation systems such that the desired transmissibility matrix is achieved. The absolute accelerations and relative displacements are used as feedback signals. Absolute acceleration signals are used to provide proportional damping in the system whereas relative displacement signals are used to achieve the desired transmissibility. In the first method, the closed-form expression of the controller transfer function metrix for the relative displacement feedback is obtained directly in the Z-domain. The controller transfer function matrix is first obtained in the S-domain and then discretized in the second method. The discrete-time controller transfer function matrices and numerical results are presented for a three-degree-of-freedom system with attractive electromagnetic actuators.     

Missile Guidance Based on Kalman Filter Estimation of Target Maneuver

A fourth-order extended Kalman filter is developed to estimate target maneuvers, and a guidance law using these estimates is implemented.     

Plasma effects in the formation,evolution and present configuration of the Saturnian ring system

The Voyager 1 and 2 observations of the fine structure of the Saturnian ring system demonstrate the importance of electric forces in controlling the dynamics of fine (charged) dust in the rings. A new theory (“gravito-electrodynamics”) which combines the electric and the gravitational forces on these grains leads to natural explanations of a number of observed ring phenomena. If plasma processes play a significant role in the dynamics of the ring system at the present time, it is difficult to avoid the conclusion that they also played an important and perhaps crucial role at cosmogonic times during the emplacement and subsequent condensation of the initial dusty plasma. We believe that the Saturnian ring system represents a “time-capsule” containing vital clues about the physical processes operating during the early stages of its formation. We will show that both its overall structure as well as its fine structure, as determined by Voyagers 1 and 2, indicate the crucial importance of plasma processes in its formation and subsequent evolution.     

Highlights of the 1975 URSI/COSPAR workshop on the IRI

Some of the presentations made at the IRI Workshop held at Louvain in 1985 have not appeared in the Proceedings. Some discussions which took place during the workshop could be of interest in future work. This article tries to highlight the IRI modelling aspects in the four principal height regions of the ionosphere.     

The influence of pressure on combustion intensity

The influence of pressure in the range of 3–15 kgf/cm² on combustion intensity is studied experimentally in a medium-sized rig. The apparatus is described and temperature measurements by different thermocouple techniques are discussed; gas composition was monitored by gas chromatography. The experiments were performed at different cross sections allowing to map temperatures and gas concentrations. The results show that temperature and carbon dioxide concentration increase more rapidly as the pressure is raised. Carbon monoxide appears as an intermediate and is concentrated near the combustion axis. The combustion zone becomes shorter with increasing pressure and the combustion intensity increases correspondingly.     

The composition of heavy ions in solar energetic particle events

We review recent advances in determining the elemental, charge-state, and isotopic composition of 1 to 20 MeV per nucleon ions in solar energetic particle (SEP) events and outline our current understanding of the nature of solar and interplanetary processes which may explain the observations.The composition within individual SEP events may vary both with time and energy, and will in general be different from that in other SEP events. Average values of relative abundances measured in a large number of SEP events, however, are found to be roughly energy independent in the 1 to 20 MeV per nucleon range, and show a systematic deviation from photospheric abundances which seems to be organized in terms of the first ionization potential of the ion.Direct measurements of the charge states of SEPs have revealed the surprisingly common presence of energetic He⁺ along with heavy ions with typically coronal ionization states. High-resolution measurements of isotopic abundance ratios in a small number of SEP events show these to be consistent with the universal composition except for the puzzling overabundance of the SEP ²²Ne/²⁰Ne relative to this isotopes ratio in the solar wind. The broad spectrum of observed elemental abundance variations, which in their extreme result in composition anomalies characteristic of ³He-rich, heavy-ion rich and carbon-poor SEP events, along with direct measurements of the ionization states of SEPs provide essential information on the physical characteristics of, and conditions in the source regions, as well as important constraints to possible models for SEP production.It is concluded that SEP acceleration is a two-step process, beginning with plasma-wave heating of the ambient plasma in the lower corona, which may include pockets of cold material, and followed by acceleration to the observed energies by either flare-generated coronal shocks or Fermi-type processes in the corona. Interplanetary propagation as well as acceleration by interplanetary propagating shock will often further modify the composition of SEP events, especially at lower energies.     

Power Converter Design Optimization

Utilizing the demonstrated capability of nonlinear programming algorithms, a practical design optimization approach for power converters is established which allows conception of a design to meet all power-circuit performance requirements and concurrently optimize a defined quantity such as weight or losses. In addition to facilitating a costeffective design, the computer-aided approach provides a means to readily assess 1) the weight-efficiency tradeoff, 2) impacts of converter requirements and component characteristics on a given design, and 3) optimum powersystem configurations.     

Microgravity experiment system utilizing a balloon

A system for microgravity experiments by using a stratospheric balloon has been planned and developed in ISAS since 1978. A rocket-shaped chamber mounting the experiment apparatus is released from the balloon around 30 km altitude. The microgravity duration is from the release to opening of parachute, controlled by an on-board sequential timer. Test flights were performed in 1980 and in 1981. In September 1983 the first scientific experiment, observing behaviors and brain activities of fishes in the microgravity circumstance, have been successfully carried out. The chamber is specially equipped with movie cameras and subtransmitters, and its release altitude is about 32 km. The microgravity observed inside the chamber is less than 2.9 × 10^?3 G during 10 sec. Engineering aspects of the system used in the 1983 experiment are presented.