Fixed-point Digital Signal Processor Research Articles

Practical Considerations for Implementing Adaptive Acoustic Noise Cancellation in Commercial Earbuds

Active noise cancellation has become a prominent feature in contemporary in-ear personal audio devices. However, due to constraints related to component arrangement, power consumption, and manufacturing costs, most commercial products utilize fixed-type controller systems as the basis for their active noise control algorithms. These systems offer robust performance and a straightforward structure, which is achievable with cost-effective digital signal processors. Nonetheless, a major drawback of fixed-type controllers is their inability to adapt to changes in acoustic transfer paths, such as variations in earpiece fitting conditions. Therefore, adaptive-type active noise control systems that employ adaptive digital filters are considered as the alternative. To address the increasing system complexity, design concepts and implementation strategies are discussed with respect to actual hardware limitations. To illustrate these considerations, a case study showcasing the implementation of a filtered-x least mean square-based active noise control algorithm is presented. A commercial evaluation board accommodating a low-cost, fixed-point digital signal processor is used to simplify operation and provide programming access. The earbuds are obtained from a commercial product designed for noise cancellation. This study underscores the importance of addressing hardware constraints when implementing adaptive active noise cancellation, providing valuable insights for real-world applications.

A Passive-Constrained Observer and Controller Applied to an In-Wheel Synchronous Machine Implemented on a Fixed-Point DSP

In this paper, we describe a passivity-based control (PBC) approach for in-wheel permanent magnet synchronous machines that expands on the conventional passivity-based controller. We derive the controller and observer parameter constraints in order to maintain the passivity of the interconnected system and thus improve the control system’s robustness to varying loads and plant parameters. The advantages of the proposed PBC technique are demonstrated in contrast with conventional PBC. The control technique is implemented on an electronic development board equipped with a fixed-point digital signal processor and coupled to a gallium nitride voltage source inverter and 350 W electric machine. Test bench results and numerical simulations in Matlab-Simulink demonstrate the control performance and behaviour under varying loads and parameters.

Single-Phase PLL Based on an Adaptive Notch Filter

Single-Phase Phase-Locked Loops (PLL) have become a crucial component of grid-tied power converters. PLL accuracy and fast response are important for control and protection purposes, especially in the presence of voltage harmonics and frequency variations. In this paper, a new PLL structure based on an Adaptive Notch Filter (ANF) is presented. This ANF, which generates the orthogonal system of the PLL, is implemented with an All-Pass Filter (APF) having inherent advantages, such as low sensitivity to coefficient rounding when implemented in fixed-point microprocessors and easy implementation in a Digital Signal Processing (DSP). Both simulation with MATLAB/Simulink, and experimental results on a fixed-point DSP, are presented and analyzed to evaluate the performance of the introduced PLL and to support the theoretical development. A set of comparative simulations between the proposed PLL and a some single-phase PLL described in the literature are conducted to validate the method.

Current Controller for Multi-level Front-end Converter and Its Digital Implementation Considerations on Three-level Flying Capacitor Topology

This paper presents behaviour analysis and digital implementation of current error space phasor based hysteresis controller applied to three-phase three-level flying capacitor converter as front-end topology. The controller is self-adaptive in nature, and takes the converter from three-level to two-level mode of operation and vice versa, following various trajectories of sector change with the change in reference dc-link voltage demanded by the load. It keeps current error space phasor within the prescribed hexagonal boundary. During the contingencies, the proposed controller takes the converter in over modulation mode to meet the load demand, and once the need is satisfied, controller brings back the converter in normal operating range. Simulation results are presented to validate behaviour of controller to meet the said contingencies. Unity power factor is assured by proposed controller with low current harmonic distortion satisfying limits prescribed in IEEE 519-2014. Proposed controller is implemented using TMS320LF2407 16-bit fixed-point digital signal processor. Detailed analysis of numerical format to avoid overflow of sensed variables in processor, and per-unit model implementation in software are discussed and hardware results are presented at various stages of signal conditioning to validate the experimental setup. Control logic for the generation of reference currents is implemented in TMS320LF2407A using assembly language and experimental results are also presented for the same.

Design and Implementation of Embedded Digital Control of Traction Motor in Solar Vehicle

The application of direct torque control with space vector modulation technique (DTCSVM) to induction motor drives has been investigated extensively in the literature. This paper describes its embedded implementation based on 16 bits fixed point digital signal processor (DSP), and compares experimental results with those obtained by simulation using Matlab-Simulink. The result of this work shows the performances obtained using a low cost DSP (dsPIC30F family). The control uses four sensors: a tachymeter sensor for rotor speed capture, two phase motor current sensors and a DC bus voltage sensor. The estimation of electromagnetic torque and stator flux is performed using the open loop method. Simulated and experimental results are presented at the end of this paper.

An AC MPPT with Active/Reactive Power Control Feature for Single-Stage Three-Phase Grid-Connected Photovoltaic VSIs

This article introduces a new AC MPPT (maximum power point tracking) controller for single-stage three-phase grid-connected photovoltaic (PV) voltage source inverters (VSIs) with active/reactive power control capability. Novelty lies in employing the theory of power transfer in short AC transmission lines to achieve MPPT, where two independent control variables exist: load angle and inverter modulation index. Accordingly, the proposed controller maximizes the capabilities of the single-stage VSI and enables it to control either/both active power or/and reactive power, besides achieving MPPT function. Such contribution opens up avenues in MPPTs world in terms of flexibility, fast performance, and low hardware count/cost. AC refers to Alternate Current since the MPPT is managed in AC terms. Theoretical framework of the proposed controller has been addressed. Moreover, the overall system is simulated in MATLAB (The MathWorks, Natick, Massachusetts, USA) environment, and results have been introduced. Design and implementation of proposed algorithms have been carried out using a fixed-point digital signal processor (DSP)TMS320F2812. Furthermore, a breadboard circuit is built up for experimentally investigating the controller's performance using 3-phase VSI that connects PV with the grid. In addition to that, a comprehensive discussion is conducted for demonstrating results. Moreover, a detailed comparison of proposed work with a number of previously published papers in literature is carried out and addressed in this manuscript. Results reveal that introduced controller achieves satisfactory performance.

New parameter for current-sensorless MPPT in grid-connected photovoltaic VSIs

This paper a new quantity for current-sensorless power-angle-based MPPT for single-stage grid-connected photovoltaic voltage-source inverters (VSIs). The proposed tracker eliminates the use of the current sensor by using only the voltage sensor: The current sensor is substituted with a new quantity, which is the sine value of the power-angle (the phase angle between the inverter output voltage and the power grid voltage). A theoretical proof for this quantity is developed and is provided. Then the controller is designed and implemented using a digital signal processor (DSP). Algorithms are configured on a fixed point DSP TMS320F2812. Moreover, a breadboard has been built-up for testing the use of the proposed tracker with a single-stage grid-connected photovoltaic voltage-source inverter. Both of simulation and experimental results show that the proposed tracker attains a satisfactory performance. On the other hand, it requires a good control tool to accurately achieve the arithmetic calculations. A substantial part of the manufacturing cost and complexity burdens of MPPTs involves the use of current sensors. Considering this investigation saves cost, decreases complexity, and therefore increases the power density of the MPPTs.

Comparative study of low-pass filter and phase-locked loop type speed filters for sensorless control of AC drives

High quality speed information is one of the key issues in machine sensorless drives, which often requires proper filtering of the estimated speed. This paper comparatively studies typical low-pass filters (LPF) and phase-locked loop (PLL) type filters with respect to ramp speed reference tracking and steady-state performances, as well as the achievement of adaptive cutoff frequency control. An improved LPF-based filter structure with no ramping and steady-state errors caused by filter parameter quantization effects is proposed, which is suitable for applying LPF for sensorless drives of AC machines, especially when fixed-point digital signal processor is selected e.g. in mass production. Furthermore, the potential of adopting PLL for speed filtering is explored. It is demonstrated that PLL type filters can well maintain the advantages offered by the improved LPF. Moreover, it is found that the PLL type filters exhibit almost linear relationship between the cutoff frequency of the PLL filter and its proportional-integral (PI) gains, which can ease the realization of speed filters with adaptive cutoff frequency for improving the speed transient performance. The proposed filters are verified experimentally. The PLL type filter with adaptive cutoff frequency can provide satisfactory performances under various operating conditions and is therefore recommended.

Bit-Width Optimization by Divide-and-Conquer for Fixed-Point Digital Signal Processing Systems

This paper presents a novel approach to fractional bit-width optimization of fixed-point designs. We first propose a divide-and-conquer algorithm that can assign optimal fractional bit-widths to a special class of designs that does not have re-convergent paths starting from an internal signal. General designs are partitioned into designs of that special class and our algorithm is applied to each design. The algorithm recursively breaks down a given design into sub-designs and finds Pareto optimal solutions to each sub-design. Those solutions are merged to form Pareto optimal solutions to a larger design. In addition, two pruning methods based on area and error, respectively, are proposed, speeding up the algorithm. The optimization process is guided by static maximum absolute error analysis, and functional correctness is guaranteed for all possible input stimuli. Our approach is demonstrated in five case studies including polynomial approximation and RGB-to-YCbCr conversion, for which the divide-and-conquer algorithm produces the optimal solutions.

Optimized Speech Compression Algorithm Based on Wavelets Techniques and its Real Time Implementation on DSP

This paper presents an optimized speech compression algorithm using discrete wavelet transform, and its real time implementation on fixed-point digital signal processor (DSP). The optimized speech compression algorithm presents the advantages to ensure low complexity, low bit rate and achieve high speech coding efficiency, and this by adding a voice activity detector (VAD) module before the application of the discrete wavelet transform. The VAD module avoids the computation of the discrete wavelet coefficients during the inactive voice signal. In addition, a real-time implementation of the optimized speech compression algorithm is performed using fixed-point processor. The optimized and the original algorithms are evaluated and compared in terms of CPU time (sec), Cycle count (MCPS), Memory consumption (Ko), Compression Ratio (CR), Signal to Noise Ratio (SNR), Peak Signal to Noise Ratio (PSNR) and Normalized Root Mean Square Error (NRMSE).

Sensorless Sliding-Mode Rotor Speed Observer of Induction Machines Based on Magnetizing Current Estimation

This paper presents a rotor speed observer for induction-machine drives based on a sliding-mode approach and magnetizing current estimation. The back electromotive force (EMF) is calculated from the stator current and the stator voltage signals. The magnetizing currents are obtained from the back EMF. A theorem which gives the rotor speed estimate in the continuous-time domain is formulated using the magnetizing current estimation. The stability analysis is achieved based on the Lyapunov approach. Moreover, the discrete-time approach of the method is discussed, and a theorem for the discrete-time implementation is proposed. The limits that ensure the system stability for the switching gains and for the observer gain are discussed. This paper shows that the limits for the gains of the discrete-time algorithm are different from the limits for the gains of the continuous-time algorithm. Simulation results are presented to validate the theoretical analysis. In addition, experimental results based on a fixed-point digital signal processor (DSP) platform (DSP TMS320F2812) demonstrate the performance of the proposed scheme.

A reliable low cost power electronics interface for photovoltaic energy systems

Performance, efficiency, cost of the power converters and their associated control, are important considerations for the commercialization of renewable power sources. In view of this, this paper proposes a reliable and low cost power electronics interface for photovoltaic energy systems, using a single DSP controller. The proposed approach will achieve the following: (a) integrate the DC–DC converter control and inverter control by utilizing a single, low cost, fixed point Digital Signal Processor (DSP controller), (b) implement a fast converging MPP tracking method in the DC–DC converter stage and (c) reduce the size of the DC-link capacitor by using a modified pulse width modulation (PWM) technique for single phase inverter control.

DSP implementation of a novel envelope analysis approach for the diagnosis of broken rotor bar in induction motor

Design and implementation of a novel technique for the detection of broken rotor bar of the induction motor is presented. At first, the discrete wavelet transform (DWT) is performed on the windowed steady state stator currents and then discrete Hilbert transform is utilised to obtain envelopes of the detailed coefficients at higher wavelet level. It has been observed that the faulty motor produces higher statistical parameters – mean, rms, standard deviation and median of the envelopes than those for the healthy one. The method is implemented in real time by means of low cost TMS320VC5416 fixed point digital signal processor (DSP). A framework of assembly language program for the calculation of the DWT is given and the problems which should be paid attention during real time implementation are discussed. Illustrative laboratory test results confirm the validity and accurate performance of the proposed method.

Digital Single-Side Band Modulation Using Digital Signal Processor

Abstract In this paper, we describe the design of a digital single-side band amplitude modulator with 40 kHz output using high-performance digital signal processor for ultrasonic transmitters. The baseband signal is converted to zero-IF signal by using quadrature frequency converter. Then zero-IF signal is filtered by two low-pass filter and converted to output frequency by frequency quadrature up-conversion. It is implemented by using single fixed-point digital signal processor. Experimental result shows that the digital modulation function is well operated, and performance of side-band rejection is better than 50 dB isolation.

Takagi–Sugeno–Kang type probabilistic fuzzy neural network control for grid‐connected LiFePO 4 battery storage system

A Takagi-Sugeno-Kang type probabilistic fuzzy neural network (TSKPFNN) control is proposed to control a grid-connected LiFePO 4 battery storage system in this study. First, the modelling of the battery and bidirectional AC-DC converter are described in detail. Then, the active and reactive power controls using phase-lock loop are briefly introduced. Moreover, to improve the control performance of the grid-connected LiFePO 4 battery storage system, the TSKPFNN control, which combines the advantages of Takagi-Sugeno-Kang type fuzzy logic system and three-dimensional membership function, is developed. The network structure, online learning algorithm using delta adaptation law and convergence analysis of the TSKPFNN are described in detail. Furthermore, a 32-bit fixed-point digital signal processor, TMS320F28035, is adopted for the implementation of the proposed intelligent controlled battery storage system. Finally, some experimental results are illustrated to show the validity of the proposed TSKPFNN control for the grid-connected LiFePO 4 battery storage system.

An Iterative Fourier Transform Algorithm for digital hologram generation using phase-only information and its implementation in a fixed-point digital signal processor

An Iterative Fourier Transform Algorithm (IFTA) for digital hologram generation from a digital image using phase-only information is described in this paper. The algorithm is implemented in a Texas Instruments TMS320C64x fixed point digital signal processor (DSP). The holograms are reconstructed in real time using a liquid crystal display system and a He–Ne laser. The ideas described in this paper can be extended to digital hologram generation of three-dimensional objects and their reconstruction in real time using liquid crystal spatial light modulators, which could be a way for 3D-display systems.

Research on Driver Design for CMOS Image Sensor Based on DM642

This paper mainly researches on the TI company fixed-point digital signal processor TMS320DM642 video capture technology for CMOS image sensors, sensor interface and video mini-driver carried out a detailed analysis, established different levels of peripheral structures under different CMOS Sensor, the research in this field has flexible characteristics and high practical value.

An Adaptive Digital Control Technique for Improved Performance of Grid Connected Inverters

Grid connected voltage source inverters may be controlled in the stationary reference frame by means of the infinite impulse response (IIR) P+Resonat regulator. This regulator is able to correctly track fixed frequency sinusoidal references, but does not perform well if the frequency of the electric grid voltage is varied. In order to avoid the lack of precision to track variable frequency sinusoidal references, an adaptive IIR filter structure is proposed which offers good tracking properties even if the frequency of the grid voltage varies. This filter adapts its coefficients in real time and is inherently stable no matter the adaptation process, thus overcoming one of the most important drawbacks of the IIR filter structure. Furthermore, this structure is perfectly suited to be programmed in fixed point digital signal processors (DSPs) because of some important numeric properties, i.e., it has a high mapping precision and a low round-off accumulation, and it avoids quantization limit cycle oscillations. The proposed adaptive controller has been tested by means of the TI TMS320F2812 DSP. The obtained experimental results show up that this controller allows the correct tracking of a sinusoidal reference, even if this reference is time variant.

A fast algorithm for color space conversion and rounding error analysis based on fixed-point digital signal processors

The YCbCr (luminance, chrominance-blue, and chrominance-red) color space is adopted in video codecs or transmission, while the HSV (hue, saturation and value) color space is used in some video analysis algorithms. In this paper, a fast algorithm based on fixed-point digital signal processors (DSPs) is proposed for YCbCr to HSV conversion. Floating-point multiplications are replaced with fixed-point shifts, 16-bit fixed-point multiplications, and additions. To compensate for rounding error and convert floating-point multiplication into 16-bit fixed-point multiplication in the calculation, tables occupying 225bytes and 256bytes are established, respectively. According to the experimental results, the error caused by the proposal is within the acceptable range. At the same time, the proposed algorithm is about 10 times faster than traditional YCbCr to HSV conversion algorithm on a fixed-point digital signal processor (DSP) platform and about 1.41 times faster on a personal computer (PC) platform.

Frequency and Total Harmonic Distortion Estimation Based on Adaptive Filters

In this paper, a low computacional cost total harmonic distortion and frecuency estimation method is proposed. This method is based on adaptive digital filters allowing tracking the fundamental frequency variations. Real time experimental results obtained using a fixed point digital signal processor development kit are presented. They show an acceptable performance and have a robust behavior to signal distortions such as frequency fluctuations, high harmonic content, subharmonic and interharmonics.