Search

A novel method is presented for producing dead-bea response in a lightly-damped oscillatory feedback system. Complete transient response times of the order of a fraction of the natural oscillatory period can be obtained. Excellent waveshape reproduction is achieved through a linear phase lag with frequency. The method consists of exciting several transient oscillations, at closely spaced times, with magnitudes and phases so adjusted that the resultant sum of the transient oscillation phasors is zero. The steady-state output is the arithmetic sum of the excitation magnitudes. When a step input transient is divided into two spaced excitations, one-half cycle response is obtainable. When the input transient is divided into three excitations, one-fourth period or faster transient times are realizable, depending upon the available dynamic range or signal-to-noise ratio. The principle of design is to adjust a system to the maximum possible resonant frequency, independent of the damping factor, but stable, and then to apply the Posicast control to completely remove the oscillatory component in the output. In an electrical feedback control system, the additional hardware consists of one or two artificial transmission lines.

An instrument is described that converts signals from photomultipliers into pulses of standard amplitude (10 mA) and adjustable width (2.5–100 ns). It consists of an input shaping network, of which two versions are given, and a tunnel diode cascade trigger circuit. An attempt has been made to reduce the time slewing to a minimum: with input pulses ranging from 10–160 mA, from a 56 AVP photomultiplier, it remains within ±0.25 ns. The instrument is capable of working up to frequencies of 150 Mc/sec.

The circuit described in this paper can accurately define the time at leading-edge of pulses from radiation detectors. The basic circuit consists of two input shaping networks and an amplitude comparator generating output pulse having a fixed time almost independent of input pulse height. The output pulse shifts only ±0.5 ns when the input having risetime range of 0.1 to 0.5 μs is varied from 0.25 to 10 V in amplitude.

Within the Environmental Restoration and Waste Management Program of the US Department of Energy, the remediation of single-shell radioactive waste storage tanks is one of the areas that challenge state-of-the-art equipment and methods. Concepts that utilize long-reach manipulators are being seriously considered for this task. Due to high payload capacity and high length-to-cross-section ratio requirements, these long-reach manipulator systems are expected to exhibit significant structural flexibility. To avoid structural vibrations during operation, various types of shaping filter methods have been investigated. A robust notch filtering method and an impulse shaping method were used as simulation benchmarks. In addition to that, two very different approaches have been developed and compared. One new approach, referred to as a ``feedforward simulation filter,`` uses imbedded simulation with complete knowledge of the system dynamics. The other approach, ``fuzzy shaping method,`` employs a fuzzy logic method to modify the joint trajectory from the desired end-position trajectory without precise knowledge of the system dynamics.