Implementation of Adaptive Digital Controllers on Programmable Logic Devices

Abstract Much has been made of the capabilities of Field Programmable Gate Arrays (FPGA's

Programs for Testing an SSME-Monitoring System

A suite of computer programs has been developed for special test equipment (STE) that is used in verification testing of the Health Management Computer Integrated Rack Assembly (HMCIRA), a ground-based system of analog and digital electronic hardware and software for "flight-like" testing for development of components of an advanced health-management system for the space shuttle main engine (SSME). The STE software enables the STE to simulate the analog input and the data flow of an SSME test firing from start to finish

Implementation of Adaptive Digital Controllers on Programmable Logic Devices

Much has been made of the capabilities of FPGA's (Field Programmable Gate Arrays) in the hardware implementation of fast digital signal processing. Such capability also makes an FPGA a suitable platform for the digital implementation of closed loop controllers. Other researchers have implemented a variety of closed-loop digital controllers on FPGA's. Some of these controllers include the widely used proportional-integral-derivative (PID) controller, state space controllers, neural network and fuzzy logic based controllers. There are myriad advantages to utilizing an FPGA for discrete-time control functions which include the capability for reconfiguration when SRAM-based FPGA's are employed, fast parallel implementation of multiple control loops and implementations that can meet space level radiation tolerance requirements in a compact form-factor. Generally, a software implementation on a DSP (Digital Signal Processor) or microcontroller is used to implement digital controllers. At Marshall Space Flight Center, the Control Electronics Group has been studying adaptive discrete-time control of motor driven actuator systems using digital signal processor (DSP) devices. While small form factor, commercial DSP devices are now available with event capture, data conversion, pulse width modulated (PWM) outputs and communication peripherals, these devices are not currently available in designs and packages which meet space level radiation requirements. In general, very few DSP devices are produced that are designed to meet any level of radiation tolerance or hardness. The goal of this effort is to create a fully digital, flight ready controller design that utilizes an FPGA for implementation of signal conditioning for control feedback signals, generation of commands to the controlled system, and hardware insertion of adaptive control algorithm approaches. An alternative is required for compact implementation of such functionality to withstand the harsh environment encountered on spacecraft. Radiation tolerant FPGA's are a feasible option for reaching this goal

Transduction by phage P22 in a recombination-deficient mutant of Salmonella typhimurium

Recombination-deficient (Rec-) mutants of Salmonella typhimurium were used to study special transduction by phage P22 in the absence of the usual background of general transduction. Rec- strains could not be transduced for any marker with a lysate arising by infection. When the same strains were infected with a lysate obtained by induction, low but significant levels of transduction were observed for the pro A and pro B loci (located to one side of the prophage attachment site), but not for pro C (located to the other side of the attachment site), leu, or thy. Integration-deficient (int) phage lysates were unable to transduce the pro A and pro B loci in Rec- cells unless int+ helper phage were present. These results suggest that although Rec- cells cannot undergo general transduction, special transduction (by lysogenization) for the pro A and pro B loci is found. A mixture of int- and int+ phage were unable to transduce the pro C locus despite the large number of pro C-transducing particles present in an int lysate. The inability of the int+ phage genomes to promote successful lysogenization of pro C-transducing particles in Rec- cells may indicate a requirement for a structural element near the left prophage end for integration of phage P22. Alternatively, the deletion of c2, the structural gene for P22 repressor, from most pro C-transducing particles may prevent successful lysogenization by these particles. Finally, the pro C locus may lie too far away from the prophage site to be included in special transducing particles containing any phage DNA.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33102/1/0000488.pd

Disseminated infection due to Nocardia transvalensis coincident with Cryptococcus neoformans variety gattii meningitis.

A case of meningitis due to Cryptococcus neoformans var. gattii coincident with disseminated Nocardia transvalensis infection is reported. Nocardia infection initially progressed despite high-dose antimicrobial therapy. Although a specific immunologic defect could not be defined, in vitro lymphocyte proliferation in response to stimulation with the Nocardia isolate was reduced. It is proposed that coinfection with Cryptococcus neoformans may have contributed to the observed impairment of lymphocyte function, leading to disseminated Nocardia disease and a suboptimal treatment response