MSc D.M. van Willigen

1. Measurement of Pipe and Fluid Properties with a Matrix Array-based Ultrasonic Clamp-on Flow Meter
   J. Massaad; P. L. M. J. van Neer; D. M. van Willigen; A. Sabbadini; N. de Jong; M. A. P. Pertijs; M. D. Verweij;
   IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
   Volume 69, Issue 1, pp. 309--322, January 2022. DOI: 10.1109/TUFFC.2021.3111710

2. Design and Proof-of-Concept of a Matrix Transducer Array for Clamp-on Ultrasonic Flow Measurements
   J. Massaad; P. L. M. J. van Neer; D. M. van Willigen; E. C. Noothout; N. de Jong; M. A. P. Pertijs; M. D. Verweij;
   IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control,
   Volume 69, Issue 8, pp. 2555--2568, August 2022. DOI: 10.1109/tuffc.2022.3186170
   
   Abstract: ...

   Common clamp-on ultrasonic flow meters consist of two single-element transducers placed on the pipe wall. Flow speed is measured non-invasively, i.e. without interrupting the flow and without perforating the pipe wall, which also minimizes safety risks and avoids pressure drops inside the pipe. However, before metering, the transducers have to be carefully positioned along the pipe axis to correctly align the acoustic beams and obtain a well-calibrated flow meter. This process is done manually, is dependent on the properties of the pipe and the liquid, does not account for pipe imperfections, and becomes troublesome on pipelines with an intricate shape. Matrix transducer arrays are suitable to dynamically steer acoustic beams and realize self-alignment upon reception, without user input. In this work, the design of a broadband 37x17 matrix array (center frequency of 1 MHz) to perform clamp-on ultrasonic flow measurements over a wide range of liquids (c = 1000 - 2000m/s, α≤1 dB/MHz.cm) and pipe sizes is presented. Three critical aspects were assessed: efficiency, electronic beam steering, and wave mode conversion in the pipe wall. A prototype of a proof-of-concept flow meter consisting of two 36-element linear arrays (center frequency of 1.1 MHz) was fabricated and placed on a 1 mm-thick, 40 mm-inner diameter stainless steel pipe in a custom-made flow loop filled with water. At resonance, simulated and measured efficiencies in water of the linear arrays compared well: 0.88 kPa/V and 0.81 kPa/V, respectively. Mean flow measurements were achieved by electronic beam steering of the acoustic beams and using both compressional and shear waves generated in the pipe wall. Correlation coefficients of R2 > 0.99 between measured and reference flow speeds were obtained, thus showing the operational concept of an array-based clamp-on ultrasonic flow meter.

3. Algorithm to Correct Measurement Offsets Introduced by Inactive Elements of Transducer Arrays in Ultrasonic Flow Metering
   Jack Massaad; Paul L. M. J. van Neer; Douwe M. van Willigen; Michiel A. P. Pertijs; Nicolaas de Jong; Martin D. Verweij;
   Sensors,
   Volume 22, Issue 23, pp. 2--14, November 2022. DOI: 10.3390/s22239317
   
   Abstract: ...

   Ultrasonic flow meters (UFMs) based on transducer arrays offer several advantages. With electronic beam steering, it is possible to tune the steering angle of the beam for optimal signal-tonoise ratio (SNR) upon reception. Moreover, multiple beams can be generated to propagate through different travel paths, covering a wider section of the flow profile. Furthermore, in a clamp-on configuration, UFMs based on transducer arrays can perform self-calibration. In this manner, userinput is minimized and measurement repeatability is increased. In practice, transducer array elements may break down. This could happen due to aging, exposure to rough environments, and/or rough mechanical contact. As a consequence of inactive array elements, the measured transit time difference contains two offsets. One offset originates from non-uniform spatial sampling of the generated wavefield. Another offset originates from the ill-defined beam propagating through a travel path different from the intended one. In this paper, an algorithm is proposed that corrects for both of these offsets. The algorithm also performs a filtering operation in the frequency-wavenumber domain of all spurious (i.e., flow-insensitive) wave modes. The advantage of implementing the proposed algorithm is demonstrated on simulations and measurements, showing improved accuracy and precision of the transit time differences compared to the values obtained when the algorithm is not applied. The proposed algorithm can be implemented in both in-line and clamp-on configuration of UFMs based on transducer arrays.
   
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4. Measurement of pipe and liquid parameters using the beam steering capabilities of array-based clamp-on ultrasonic flow meters
   J. Massaad; P. L. M. J. van Neer; D. M. van Willigen; M. A. P. Pertijs; N. de Jong; M. D. Verweij;
   Sensors,
   Volume 22, Issue 14, pp. 5068, July 2022. DOI: 10.3390/s22145068
   
   Abstract: ...

   Clamp-on ultrasonic flow meters (UFMs) are installed on the outside of the pipe wall. Typically, they consist of two single-element transducers mounted on angled wedges, which are acoustically coupled to the pipe wall. Before flow metering, the transducers are placed at the correct axial position by manually moving one transducer along the pipe wall until the maximum amplitude of the relevant acoustic pulse is obtained. This process is time-consuming and operator-dependent. Next to this, at least five parameters of the pipe and the liquid need to be provided manually to compute the flow speed. In this work, a method is proposed to obtain the five parameters of the pipe and the liquid required to compute the flow speed. The method consists of obtaining the optimal angles for different wave travel paths by varying the steering angle of the emitted acoustic beam systematically. Based on these optimal angles, a system of equations is built and solved to extract the desired parameters. The proposed method was tested experimentally with a custom-made clamp-on UFM consisting of two linear arrays placed on a water-filled stainless steel pipe. The obtained parameters of the pipe and the liquid correspond very well with the expected (nominal) values. Furthermore, the performed experiment also demonstrates that a clamp-on UFM based on transducer arrays can achieve self-alignment without the need to manually move the transducers.

5. A Transceiver ASIC for a Single-Cable 64-Element Intra-Vascular Ultrasound Probe
   D. van Willigen; J. Janjic; E. Kang; Z. Y. Chang; E. Noothout; M. Verweij; N. de Jong; M. Pertijs;
   IEEE Journal of Solid-State Circuits,
   Volume 56, Issue 10, pp. 3157-3166, October 2021. DOI: 10.1109/jssc.2021.3083217
   
   Abstract: ...

   This article presents an application-specific integrated circuit (ASIC) designed for intra-vascular ultrasound imaging that interfaces 64 piezoelectric transducer elements to an imaging system using a single micro-coaxial cable. Thus, it allows a single-element transducer to be replaced by a transducer array to enable 3-D imaging. The 1.5-mm-diameter ASIC is intended to be mounted at the tip of a catheter, directly integrated with a 2-D array of piezoelectric transducer elements. For each of these elements, the ASIC contains a high-voltage (HV) switch, allowing the elements to transmit an acoustic wave in response to an HV pulse generated by the imaging system. A low-noise amplifier then amplifies the resulting echo signals and relays them as a signal current to the imaging system, while the same cable provides a 3-V supply. Element selection and other settings can be programmed by modulating configuration data on the supply, thus enabling full synthetic aperture imaging. An integrated element test mode measures the element capacitance to detect bad connections to the transducer elements. The ASIC has been fabricated in a 0.18-μm HV CMOS technology and consumes only 6 mW in receive. Electrical measurements show correct switching of 30-V transmit pulses and a receive amplification with a 71-dB dynamic range, including 12 dB of programmable gain over a 3-dB bandwidth of 21 MHz. The functionality of the ASIC has been successfully demonstrated in a 3-D imaging experiment.

6. Exploiting nonlinear wave propagation to improve the precision of ultrasonic flow meters
   J. Massaad; P. L. M. J. van Neer; D. M. van Willigen; N. de Jong; M. A. P. Pertijs; M. D. Verweij;
   Ultrasonics,
   Volume 116, pp. 106476, September 2021. DOI: 10.1016/j.ultras.2021.106476

7. Automatic beam alignment in a clamp-on ultrasonic flow meter based on array transducers
   J. Massaad; P. van Neer; D. van Willigen; N. de Jong; M. Pertijs; M. Verweij;
   In Proc. IEEE International Ultrasonics Symposium (IUS),
   September 2021. abstract.

8. Feasibility of measuring flow velocity profiles with array-based clamp-on ultrasonic flow meters
   D. van Willigen; P. van Neer; J. Massaad; N. de Jong; M. Verweij; M. Pertijs;
   In Proc. IEEE International Ultrasonics Symposium (IUS),
   September 2021. abstract.

9. An Algorithm to Minimize the Zero-Flow Error in Transit-Time Ultrasonic Flow Meters
   Douwe M. van Willigen; Paul L.M.J. van Neer; Jack Massaad; Nico de Jong; Martin D. Verweij; Michiel A.P. Pertijs;
   IEEE Transactions on Instrumentation and Measurement,
   2020. DOI: 10.1109/TIM.2020.3007907
   
   Abstract: ...

   Transit-time ultrasonic flow meters are widely used in industry to measure fluid flow. In practice ultrasonic flow meters either show a zero-flow error or suffer from a significant random error due to a limited signal-to-noise ratio, requiring a significant amount of averaging to achieve good precision. This work presents a method that minimizes the zero-flow error whilst keeping the random error low, independent of the hardware used. The proposed algorithm can adjust to changing zero-flow errors while a flow is present. The technique combines the benefits of two common methods of determining the transit-time difference between the upstream and downstream ultrasonic waves: cross-correlation and zero-crossing detection. The algorithm is verified experimentally using a flow-loop. It is shown that the zero-flow error can be greatly reduced without compromising the random error or increasing circuit complexity.

10. Suppression of Lamb wave excitation via aperture control of a transducer array for ultrasonic clamp-on flow metering
    J. Massaad; P. L. M. J. van Neer; D. M. van Willigen; M. A. P. Pertijs; N. de Jong; M. D. Verweij;
    Journal of the Acoustical Society of America,
    Volume 147, Issue 4, pp. 2670-2681, February 2020. DOI: 10.1121/10.0001135
    
    Abstract: ...

    During ultrasonic clamp-on flow metering, Lamb waves propagating in the pipe wall may limit the measurement accuracy by introducing absolute errors in the flow estimates. Upon reception, these waves can interfere with the up and downstream waves refracting from the liquid, and disturb the measurement of the transit time difference that is used to obtain the flow speed. Thus, suppression of the generation of Lamb waves might directly increase the accuracy of a clamp-on flow meter. Existing techniques apply to flow meters with single element transducers. This paper considers the application of transducer arrays and presents a method to achieve a predefined amount of suppression of these spurious Lamb waves based on appropriate amplitude weightings of the transducer elements. Finite element simulations of an ultrasonic clamp-on flow measurement setting will be presented to show the effect of array aperture control on the suppression of the Lamb waves in a 1-mm-thick stainless steel pipe wall. Furthermore, a proof-of-principle experiment will be shown that demonstrates a good agreement with the simulations.

11. Towards a calibration-free ultrasonic clamp-on flow meter: Pipe geometry measurements using matrix arrays
    J. Massaad; P. L. M. J. van Neer; D. M. van Willigen; M. A. P. Pertijs; N. de Jong; M. D. Verweij;
    Proceedings of Meetings on Acoustics,
    Volume 39, Issue 1, February 2020. DOI: 10.1121/2.0001187
    
    Abstract: ...

    Current ultrasonic clamp-on flow meters are manually calibrated. This process is based on manual placement of two single-element transducers along a pipe wall. Due to the usually unknown pipe properties and inhomogeneities in the pipe geometry, the axial distance of the transducers needs to be manually calibrated to align the location of the emitted beam on the receiver. In this work it is presented an automatic calibration procedure, based on matrix transducer arrays, to provide calibration information that would normally be entered into the instrument manually prior to ultrasonic clamp-on flow measurements. The calibration consists of two steps: First, along the axial direction of the pipe, Lamb waves are excited and recorded. Then, the measured time signals are combined with the Rayleigh-Lamb dispersion equation to extract pipe wall thickness and bulk wave sound speeds. Second, along the circumferential direction of the pipe, a specific Lamb wave mode is excited and recorded, from which the pipe diameter is estimated. The potential of both calibration procedures is shown, and the necessity of a matrix transducer array (i.e. small elements) is highlighted.

12. An Algorithm to Minimize the Zero-Flow Error in Transit-Time Ultrasonic Flow Meters
    D. M. van Willigen; P. L. M. J. van Neer; J. Massaad; N. de Jong; M. D. Verweij; M. A. P. Pertijs;
    IEEE Transactions on Instrumentation and Measurement,
    Volume 70, pp. 1-9, July 2020. DOI: 10.1109/TIM.2020.3007907
    
    Abstract: ...

    Transit-time ultrasonic flowmeters are widely used in industry to measure fluid flow. In practice, ultrasonic flowmeters either show a zero-flow error or suffer from a significant random error due to a limited signal-to-noise ratio, requiring a significant amount of averaging to achieve good precision. This work presents a method that minimizes the zero-flow error while keeping the random error low, independent of the hardware used. The proposed algorithm can adjust to changing zero-flow errors, while a flow is present. The technique combines the benefits of two common methods of determining the transit time difference between the upstream and downstream ultrasonic waves: cross correlation and zero-crossing detection. The algorithm is verified experimentally using a flow loop. It is shown that the zero-flow error can be greatly reduced without compromising the random error or increasing circuit complexity.

13. Experimental Characterization of a Linear Transducer Array Prototype for Ultrasonic Clamp-on Flow Metering
    J. Massaad; D. van Willigen; P. van Neer; E. Noothout; N. de Jong; M. Pertijs; M. Verweij;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    September 2020. abstract.

14. Fabrication and characterization of a prototype forward-looking single-cable 64-element intra-vascular ultrasound probe
    D. van Willigen; M. Mozaffarzadeh; E. Noothout; M. Verweij; N. de Jong; M. Pertijs; V. Daeichin;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, pp. 1-4, October 2019.

15. A 1.54mW/Element 150μm-Pitch-Matched Receiver ASIC with Element-Level SAR/Shared-Single-Slope Hybrid ADCs for Miniature 3D Ultrasound Probes
    J. Li; Z. Chen; M. Tan; D. van Willigen; C. Chen; Z. Y. Chang; E. Noothout; N. de Jong; M. D. Verweij; M. A. P. Pertijs;
    In Dig. Techn. Paper IEEE Symposium on VLSI Circuits (VLSI),
    IEEE, pp. 1-2, June 2019.

16. Acoustic Stack Design of a Transducer Array for Ultrasonic Clamp-on Flow Metering
    J. Massaad; D. van Willigen; P. van Neer; N. de Jong; M. Pertijs; M. Verweij;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, pp. 1-4, October 2019.

17. Pipe geometry calibration measurements for the improvement of ultrasonic clamp-on flow meters
    J. Massaad; D. van Willigen; P. van Neer; N. de Jong; M. Pertijs; M. Verweij;
    In Meeting of the Acoustical Society of America,
    November 2019. (abstract),. DOI: 10.1121/1.5136993

18. Clamp-on Ultrasonic Flow-metering via Matrix Transducers
    J. Massaad; P. van Neer; D. van Willigen; N. de Jong; M. Pertijs; Martin Verweij;
    In Proc. Int. Conf. on Ultrasonic-based Applications,
    June 2018.

19. ASIC design for a single-cable 64-element ultrasound probe
    D. van Willigen; J. Janjic; E. Kang; Z. Y. Chang; E. Noothout; M. Verweij; N. de Jong; M. Pertijs;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, pp. 1-4, October 2018.
    
    Abstract: ...

    This paper presents an ASIC (Application Specific Integrated Circuit) design for a catheter probe that interfaces 64 piezoelectric elements directly integrated on top of the ASIC to an imaging system using a single micro-coaxial cable. Each of the piezo elements can be used for both transmit (TX) and receive (RX), enabling full synthetic aperture imaging. A prototype has been realized with a 1.5mm diameter circular layout, intended for 3D intra-vascular ultrasound imaging. The functionality of this ASIC has been successfully demonstrated in a 3D imaging experiment. The design allows a single-element transducer to be replaced by a transdcuer array while using the same cable, making it a promising solution for 3D imaging with size constrained probes.

20. Feasibility of ultrasound flow measurements via non-linear wave propagation
    J. Massaad; P. L. M. J. van Neer; D. M. van Willigen; N. de Jong; M. A. P. Pertijs; M. D. Verweij;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, pp. 1-4, October 2018. DOI: 10.1109/ULTSYM.2018.8579943
    
    Abstract: ...

    Typically, ultrasonic flow meters assume linear wave propagation. Nevertheless, if the transducers of an ultrasonic flow sensor excite a pressure wave with a high amplitude, nonlinear wave propagation effects become significant. The appearance of higher harmonics increases the bandwidth of the received signal, which may potentially lead to a more precise flow measurement. However, the question arises whether the increased bandwidth can be used in practice, since the intensity of the 2nd harmonic can be 25 dB below the fundamental. One exploit of the increased bandwidth is to filter the received signals and to obtain two components: the fundamental and the 2nd harmonic. Differences between the upstream and downstream transit times are directly related to the flow speed, and these can be computed for each component of the received signals. This paper shows that averaging the transit time differences of the fundamental signals and the 2nd harmonic signals results in a lower standard deviation compared to the standard deviation of the transit time differences of the fundamental or the 2nd harmonic signal alone. This demonstrates the feasibility of using non-linear wave propagation to improve the precision of flow measurements using ultrasound.

21. Minimizing the zero-flow error in transit time ultrasonic flow meters
    D. van Willigen; P. van Neer; J. Massaad; N. de Jong; M. Verweij; M. Pertijs;
    In Proc. IEEE International Ultrasonics Symposium (IUS),
    IEEE, pp. 1-4, October 2018. DOI: 10.1109/ULTSYM.2018.8579771
    
    Abstract: ...

    Transit-time ultrasonic flow meters are based on the fundamental idea that the flow is the only non-reciprocal effect between an upstream and downstream measurement. Non-identical transducers can be used in a reciprocal manner if the circuit is made reciprocal. In this paper we analyze the effect of driver- and readout electronics on the zero-flow error in transit-time ultrasonic flow meters by simulation and measurement. Using the frequency characteristic of two nonidentical transducers, the cause of the zero-flow error in nonreciprocal circuits is evaluated. Both simulation and measurement results show that the lowest zero-flow error can be obtained by using circuits that have an impedance significantly higher or lower than the impedance of the transducers.

22. Data collection system, in particular suitable for imaging of a distant object
    D. M. van Willigen; M. A. P. Pertijs;
    Patent, Dutch NL2020426B1, February 2018.

23. A Transceiver ASIC for a Single-Cable 64-Element Intra-Vascular Ultrasound Probe
    Douwe {van Willigen};
    MSc thesis, Delft University of Technology, July 2017.
    document

24. In-air ultrasonic gesture sensing with MEMS microphones
    D. M. van Willigen; E. Mostert; M. A. P. Pertijs;
    In Proc. IEEE Sensors Conference,
    IEEE, pp. 90‒93, October 2014. DOI: 10.1109/icsens.2014.6984940

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