Application of Analog Adaptive Filters for Dynamic Sensor Compensation

Abstract

Abstract-This paper investigates the application of analog adaptive techniques to the area of dynamic sensor compensation, of which there is little reported work in the literature. The case is illustrated by showing how the response of a load cell can be improved to speed up the process of measurement. The load cell is a sensor with an oscillatory response in which the measurand contributes to the response parameters. Thus, a compensation filter needs to track variation in measurand, whereas a simple fixed filter is only valid at one specific load value. To facilitate this investigation, computer models for the load cell and the adaptive compensation filter have been developed. To allow a practical implementation of the adaptive techniques, a novel piecewise linearization technique is proposed in order to vary a floating voltage-controlled resistor in a linear manner over a wide range. Simulation and practical results are presented, thus, demonstrating the effectiveness of the proposed techniques.

Dynamic sensor compensation using analogue adaptive filter compatible with digital technology

“…The values of these poles can be determined practically. These poles are selected as shown in [5] so that the output of the filter quickly reaches its steady-state value with minimum oscillation. The transfer function of the compensation filter is…”

“…Hence, the aspect ratio of the memory transistors is considered to be W L = 30µm 3µm and for the NMOS To test the compensation filter, the output signal of the load cell is needed. In [4], we developed computer models for the load cell and the adaptive compensation filter and they have been implemented in PSpice, and also validated by practical discrete circuit [5]. However, for CMOS transistor level simulation with Cadence, a VerilogA behavioral modelling facility has been used, which can produce load cell oscillatory current.…”

“…These include digital adaptive techniques [1], artificial neural network [2] and estimation with recursive least square procedure [3], which basically employ digital signal processing (DSP) chips or microcontrollers to implement the required filtering algorithms. Recently, analogue adaptive techniques [4,5] have been used to perform effective sensor response compensation, with the main benefits being smaller size, lower complexity and lower power consumption compared to digital techniques. The sensor compensation analogue technique employs an adaptive biquadratic filter to track the variations in the measurand by changing the position of the filter zeroes.…”

“…The sensor compensation analogue technique employs an adaptive biquadratic filter to track the variations in the measurand by changing the position of the filter zeroes. In [5], a discrete adaptive filter prototype consisting of op-amps, resistors and capacitors was produced to validate the compensation analogue technique in practice.…”

“…In the sensor research community, efforts have focused on making silicon-based sensors and circuit designers investigate techniques to develop CMOS compatible analogue electronic circuits [6,7,8,9,10] because this is dominant processing technology used for integrated circuits and systems. Despite the effectiveness of the op-amp based compensation filter reported in [5], the filter is not compatible with digital CMOS technology since it contains resistors and capacitors. This limits its applications in SoCs, and therefore, the motivation of this research is to develop and implement an analogue filter for sensor compensation, which is compatible with CMOS technology.…”