The Journal of the Acoustical Society of Korea (한국음향학회지)

The Acoustical Society of Korea (한국음향학회)
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The efficient implementation of the multi-channel active noise controller using a low-cost microcontroller unit

저가 microcontoller unit을 이용한 효율적인 다채널 능동 소음 제어기 구현

  • Chung, Ik Joo (Department of Electrical & Electronics Engineering, Kangwon National University)
  • Received : 2018.10.04
  • Accepted : 2019.01.25
  • Published : 2019.01.31
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Abstract

In this paper, we propose a method that can be applied to the efficient implementation of multi-channel active noise controller. Since the normalized MFxLMS (Modified Filtered-x Least Mean Square) algorithm for the multi-channel active noise control requires a large amount of computation, the difficulty has lied in implementing the algorithm using a low-cost MCU (Microcontoller Unit). We implement the multi-channel active noise controller efficiently by optimizing the software based on the features of the MCU. By maximizing the usage of single-cycle MAC (Multiply- Accumulate) operations and minimizing move operations of the delay memory, we can achieve more than 3 times the performance in the aspect of computational optimization, and by parellel processing using the auxillary processor included in the MCU, we can also obtain more than 4 times the performance. In addition, the usage of additional parts can be minimized by maximizing the usage of the peripherals embedded in the MCU.

본 논문에서는 저가 MCU(Microcontoller Unit)를 이용하여 다채널 능동 소음 제어기를 효율적으로 구현할 수 있는 방안을 제안하였다. 다채널 능동 소음 제어 알고리즘으로 사용된 정규화된 MFxLMS(Modified Filtered-x Least Mean Square) 알고리즘은 많은 연산량을 요구하며, 저가 MCU로 구현하기에는 어려움이 있었다. 본 연구에서는 MCU의 특성을 잘 활용하여 소프트웨어를 최적화함으로써 효율적으로 다채널 능동 소음 제어기를 구현할 수 있었다. CPU(Central Processing Unit)가 지원하는 단일 싸이클 MAC(Multiply- Accumulate) 연산을 극대화하고, 지연 메모리 연산을 최소화함으로써 3배 이상의 연산 최적화를 달성하였다. 또한 MCU가 지원하는 보조 프로세서를 이용하여 병렬 처리함으로써 4배 이상의 연산 최적화를 이루었다. 더불어 MCU에 내장된 주변 장치를 최대한 활용함으써, 추가적인 부품의 사용을 최소화하였다.

Keywords

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Fig. 1. The block diagram of the MFxLMS algorithm.

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Fig. 2. The block diagram of TMS320F280049 MCU.

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Fig. 3. Analog front-end for anti-aliasing and amplification.

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Fig. 4. Frequency response of the analog front-end.

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Fig. 5. Adaptation of adaptive filter coefficients with delay memory move.

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Fig. 6. Adaptation of adaptive filter coefficients without delay memory move.

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Fig. 7. Level one of parallel processing using CLA.

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Fig. 8. Level two of parallel processing using CLA.

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Fig. 9. Comparison of the excution times between CPU and CLA with C code.

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Fig. 10. Comparison of the excution times between CPU and CLA with assembly code.

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Fig. 11. Hardware for the active noise controller using TMS320F280049 MCU module and analog front-end and back-end.

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Fig. 12. System setup for multi-channel acitve noise controller.

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Fig. 13. Comparison of the error signals with different convergence factors.

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Fig. 14. Convergence behavior of the multi-sinusoidal noise.

Table1. The number of multiplications of the multi-channel MFxLMS algorithm.

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Table 2. The maximum number of filter taps for real-time operation at each optimization stage.

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