Theoretical development of minimum effort active noise control with feedback inclusion architecture.

This paper presents the development of minimum effort active noise control theory for feedforward single-input single output (SISO) architecture, which includes the feedback acoustic path in the controller formulation. The theoretical range of effective minimum effort parameter with respect to level of point cancellation at the observer and the interference pattern generated around the observer for periodic noise control in free-field are investigated. It is found that for a minimum of 6 dB cancellation which corresponds to cancellation factor of 0.75 at the observer, the effort parameter must be specified as less than unity. It is also found that the cancellation pattern characterised by 20 dB, 10 dB and 6 dB zones reduces significantly in terms of size with an increase in the value of the effort term

Performance comparison of THF-NLFXLMS and VFXLMS algorithms for Hammerstein NANC

Recently, THF-NLFXLMS algorithm was developed to compensate the nonlinearity encountered in nonlinear active noise control systems. Despite similar performance, this algorithm is more advantageous than the Nonlinear Filtered-X Least Mean Square (NLFXLMS) due to the use of tangential hyperbolic function (THF) instead of scaled error function (SEF) which allows the degree of nonlinearity to be modeled. In addition, the computational complexity is relatively small compared to other direct nonlinear adaptive algorithm like the Volterra filter. In this paper, the performance of THF-NLFXLMS algorithm for Hammerstein secondary path structure is quantified and compared with NLFXLMS and the Volterra Filtered-x Least Mean Squares (VFXLMS) algorithm of similar computational complexity. The results show that the THF-NLFXLMS algorithm has similar performance as NLFXLMS algorithm and outperforms 2nd order VFXLMS algorithm

Performance comparison of LFXLMS, MOVFXLMS and THF-NLFXLMS algorithms for Hammerstein NANC

Filtered-X least mean square (FXLMS) algorithm is widely used in active noise control (ANC) systems when the secondary path is linear. However, the performance of FXLMS reduces when nonlinearity is present. Leaky FXLMS (LFXLMS) and minimum output variance FXLMS (MOVFXLMS) algorithms are effective in compensating the nonlinearity effects in nonlinear ANC (NANC). When using optimum leakage factors, these algorithms show close performance with benchmark nonlinear FXLMS (NLFXLMS) algorithm. In all three algorithms, the degree of nonlinearity must be known in advance and are usually assumed. In previous works, Tangential Hyperbolic Function NLFXLMS (THF-NLFXLMS) algorithm has been developed whereby the degree of nonlinearity is estimated using tangential hyperbolic function (THF). In this work, the performance of LFXLMS and MOVFXLMS based on optimum leakage factors calculated using the estimated degree of nonlinearity is compared with THF-NLFXLMS for Hammerstein structure. The results show that optimum MOVFXLMS performs similarly to optimum LFXLMS and THF-NLFXLMS

Analysis of geometry related constraints of minimum effort active noise control system

This paper presents an analysis of the geometry-related constraints of a single-input single output (SISO) minimum effort active noise control system with feedback inclusion architecture which includes the feedback path in the controller formulation. Realisation of this type of minimum effort controller imposes an infinite gain control (IGC) requirement for certain geometrical arrangements. In the investigation into these geometrical arrangements with fixed primary and secondary source locations, the IGC locus is found to be two circles occupied by the detector and observer respectively in three dimensions. Varying the minimum effort parameter term has the effect of moving these two circles closer or away from each other, hence varying their location and radii. As a result, the minimum effort parameter, apart from constraining the control signal has a potential of overcoming the IGC constraints for a fixed geometrical arrangement

Design of self-tuning minimum effort active noise control with feedback inclusion architecture

This paper presents the development of a self-tuning controller design of minimum effort active noise control (ANC) for feedforward single-input single-output (SISO) architecture which includes the feedback acoustic path in the controller formulation. The controller design law is derived for suitable self-tuning implementation and the self-tuning controller is evaluated in a realistically constructed ANC simulation environment. The self-tuning controller design involves a two-stage identification process where the controller is replaced by a switch. This switch is closed and opened in sequence generating two transfer functions which are then used in constructing the controller specified by a minimum effort control law. The implementation requires an estimate of the secondary path transfer function which can be identified either online or offline. The controller design and implementation are evaluated in terms of the level of cancellation at the observer through simulation studies for various values of modified effort weighting parameter in the range ⩽0γ⩽1. It was found that the optimal controller designed using this technique which is constrained only by the accuracy of the two models identified using recursive least squares algorithm, yields good cancellation level

Loudspeaker nonlinearity compensation with inverse tangent hyperbolic function-based predistorter for active noise control

In active noise control (ANC), the performance of the filtered-x least mean squares (FXLMS) algorithm is degraded by the saturation of the loudspeaker in the secondary path. Predistortion is a linearization technique commonly used in signal processing applications to compensate for saturation nonlinearity. The design of the predistorter (PD) requires the use of direct measurement from the output of the nonlinear element. However, in ANC applications, direct measurement from the loudspeaker output is not available. Therefore, a conventional PD design approach cannot be directly applied. In this paper, a new PD-based compensation technique based on the inverse model of the loudspeaker nonlinearity is proposed. The PD is represented by an approximated memory-less inverse tangent hyperbolic function (ITHF). The approximated ITHF is scaled by a pre-identified parameter, which represents the loudspeaker nonlinearity strength. This parameter can be obtained by modelling the secondary path using a proposed block-oriented Hammerstein structure in which the nonlinear part is represented by a memory-less tangent hyperbolic function (THF). Simulation results show that using the proposed PD along with the FXLMS algorithm increase the noise reduction performance significantly

Automation of anaesthesia: a review on multivariable control

Anaesthesia is a multivariable problem where a combination of drugs are used to induce desired hypnotic, analgesia and immobility states. The automation of anaesthesia may improve the safety and cost-effectiveness of anaesthesia. However, the realization of a safe and reliable multivariable closed-loop control of anaesthesia is yet to be achieved due to a manifold of challenges. In this paper, several significant challenges in automation of anaesthesia are discussed, namely model uncertainty, controlled variables, closed-loop application and dependability. The increasingly reliable measurement device, robust and adaptive controller, and better fault tolerance strategy are paving the way for automation of anaesthesia

Evolution Architectural Heritage Through Typology Of Negeri Sembilan Traditional Houses

The architecture of traditional house is a regional architectural heritage assets which are valuable, inherited and built in various customs and cultures of each country. It has the characteristics of the different designs and concepts that shape its own identity. The uniqueness design of the Negeri Sembilan traditional house is influenced by the Minangkabau, West Sumatra, Indonesia, which is the symbol of the community. Minangkabau house is a house occupied by the customary rules of practice matrilineal kinship system and the tendency of the people to go abroad for the purpose of exploration. The study was made on the basis of these factors, the occurrence of evolution, the changes that occurred since the 14th century AD, which started from Minangkabau to Negeri Sembilan, Malaysia. Additionally, the study proves that the customs, culture and regionalism have established the typology of Negeri Sembilan traditional houses. The study involves several locations starting from West Sumatra, Indonesia such as Padang, Bukit Tinggi and Kampar to Negeri Sembilan, Malaysia such as Rembau, Tampin and Kuala Pilah. The data were obtained through a process of observation, sketches, interviews, questionnaires and related photos. The identity and uniqueness of Negeri Sembilan traditional house is the architectural heritage that will bring awareness and references to future generations which are increasingly difficult to sustain and lost in their own countr

Design and Calibration of Pinch Force Measurement Using Strain Gauge for Post-Stroke Patients

Two fingers strength is an indicative measurement of pinch impairment. Conventionally, Fugl Meyer Upper Extremity Assessment (FMA-UE) is the primary standard to measure pinch strength of post-stroke survivors. In literature, the evaluation method performed by the therapist is subjective and exposed to inter-rater and intra-rater reliabilities. Recently, force-sensing resistors were implemented to measure two fingers force, but these sensors are subjected to nonlinearity, high hysteresis, and voltage drift. This paper presents a design of pinch force measurement based on the strain gauge. The pinch sensor was calibrated within a range of between 0 N to 50 N over a pinching length of 20 mm with a linearity error of 0.0123% and hysteresis of 0.513% during the loading and unloading process. The voltage drift has an average of 0.24% over 20 minutes. The pinch force measurement system reveals an objective pinch force measurements in evaluating the rehabilitation progress of post-stroke patients

Characterization and Application of Molten Slag as Catalyst in Pyrolysis of Waste Cooking Oil

Chemical and physical analysis was performed to identify the molten slag composition and its ability to be used as alternative catalyst in pyrolysis of waste cooking oil. The implementation such type of catalytic material could be useful in reducing the process cost. To increase the efficiency (increase the active site) of molten slag, it was modified by acid washing that resulted in an increase in the acidity from 159 to 1224 µmol/g. The results showed that the yield of bio-fuel was increased and the product selective to n-C15 upon the modification of molten slag by acid treatment. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).