Jorge Landeck

Dissolved oxygen control of the activated sludge wastewater treatment process using stable adaptive fuzzy control

Abstract In the operation of wastewater treatment plants a key variable is dissolved oxygen (DO) content in the bioreactors. The paper describes the development of an adaptive fuzzy control strategy for tracking the DO reference trajectory applied to the Benchmark Simulation Model n.1. The design methodology of this data-driven controller uses the Lyapunov synthesis approach with a parameter projection algorithm to construct an adaptive fuzzy controller (AFC), and guarantees the global stability of the resulting closed-loop system. To work in parallel with the AFC it is proposed a new easy to design supervisory fuzzy control with a smooth switching scheme between supervisory and nonsupervisory modes. Both controllers assume no mathematical model of the plant and may integrate human knowledge. The results of simulations show that this combined controller can learn and improve control rules resulting in accurate DO control.

A pulse processing station

This is the first of two papers concerning the architecture, circuitry design and performance of a pulse processing system based on a digital signal processor. This multifunction system, implemented as a single PC module, incorporates a high performance 16-bit Pulse Height Analyser (PHA) a Multichannel Scaler (MCS), a Digital Oscilloscope (DSO) and also a Digital Pulse Processor (DPP). This paper presents the PHA architecture with emphasis on the baseline restorer and peak stretcher circuits. Differential nonlinearities (DNL) are corrected by a new implementation of the sliding scale technique and performance ranges from better than 2% (at 16-bit resolution) up to less than 0.2% for 12-bit operation. The DNL correction technique is assessed for different sliding-scale ranges.

Testing high-resolution digitizers using conventional signal sources

This paper presents a method to evaluate the performance of high-resolution digitizers using signal sources that may be of lower specification than the device under test. The method is based on the best fitting of a straight line to a set of measures of the signal to noise ratio, excluding the harmonic distortion, obtained for several amplitudes of the test signal. Theoretical derivations and both computer simulated and experimental data are included. It is shown that the effective number of bits estimated using this method is not affected by the leakage effects that occur when other frequency domain tests are used and the input signal is sampled along a non-integer number of cycles.

On-line trigger processing for a small animal RPC-Pet camera

A complex task for pet cameras is the design of an appropriate coincidence-detection trigger system as it usually encompasses coincidences in a large number of channels and tight time specifications. Those requirements are even greater for a resistive plate chamber (RPC)-based detector technology as the time window specification is quite small (in the order of a few hundred picoseconds) and the number of coincidence-channels can be quite large.

Sensor-fault tolerance in a wastewater treatment plant by means of ANFIS-based soft sensor and control reconfiguration

Abstract This work presents a sensor-fault-tolerant design applied to a decentralized dissolved oxygen control in an activated sludge process subject to sensor faults such as bias and slow drifts. The core idea is to use a data-driven soft sensor based on adaptive neuro-fuzzy inference system to act as a backup of the joint sensor and controller block, and to exploit the data/analytical correlations existing in the system. After fault detection and isolation, a control reconfiguration technique takes action in order to surmount/counteract the effect of the fault until the faulty sensor is repaired. The approach presented here was applied to the Benchmark Simulation Model n.1 and was able to demonstrate the improvements on the control system dependability.

Adaptive fuzzy control of the dissolved oxygen concentration in an activated sludge process

In this paper an adaptive fuzzy control strategy for dissolved oxygen concentration (DO) control of an activated sludge process is proposed and evaluated in a benchmark simulation model. The controller uses DO concentration error feedback and manipulates the flow control valves supplying air to the bioreactor cells. The results of simulation shows that this adaptive controller can optimize control rules resulting in an accurate controls of dissolved oxygen.

A fast, high-throughput digital coincidence detection system for a large RPC-PET camera

Current work aiming at studying the feasibility of a resistive plate chamber (RPC)-PET camera for human whole-body screening indicates that a very cost-effective and high-sensitivity camera can be built. Such a camera will use the high intrinsic time resolution (better than 300 ps full width at half maximum (FWHM) of the RPC technology to implement a time of flight (TOF)-PET camera that, along with its very large field of view, can reach a sensitivity exceeding the present crystal-based PET technology by a factor up to 20 with a spatial resolution near 2 mm. Due to the large number of RPC plates forming such a system (in the order of 100 RPC plates, or even more) and to the large amount of data generated it is essential to have an effective on-line trigger that helps reducing the pressure on the data saving and processing system. In this work we present simulation results of an all-digital coincidence-detection system implemented in a Field Programmable Gate Array (FPGA) that can cope with the task of generating the high speed trigger for such a camera. The method implemented for coincidence detection is virtually dead-time free and very fast. It is shown the trigger system can process all the events inside the RPC-PET camera in real-time. This will allow a better understanding of the camera and will contribute to its optimization, simplifying significantly the design of its data acquisition system.

Determining the effective number of bits of high resolution digitizers

A new testing method has been used to evaluate the dynamic performance of several digitizing systems used in nuclear physics experiments. This method is useful for characterizing high resolution analog to digital converters when a pure enough signal source is not available. The signal to noise ratio of the digitizer, excluding the harmonic components from the noise, is the computed parameter. The use of this method to estimate jitter errors is also studied.