Programmable Coefficients Research Articles

3D bi-directional auxetic square metastructure with programmable thermal expansion and Poisson's ratio

Multifunctional integration research on metastructures has become the current development trend and hotspot, especially satellite platforms and hypersonic aircraft in the aerospace field. A 3D bi-directional auxetic square metastructure (BASM) with the programmable coefficient of thermal expansion (CTE) and Poisson's ratio (PR) is designed through the combination of re-entrant hexagonal structures and bi-material triangles. Specimens in the form of the 1*2 array are designed and fabricated through 3D printing. The correctness of the results of finite element analysis (FEA) of the BASM is verified by uniaxial compression experiments. Additionally, FEA is adopted to investigate the effective mechanical properties of the BASM with the form of the 2*3 array, and deformation mechanisms are further explored. Results indicate that the CTE, PR, and stiffness of the BASM depend on material combinations and geometric parameters. Under thermal and mechanical loads, the BASM achieves bi-directional regulation of the CTE and PR, encompassing both axial and circumferential deformations. Notably, the deformation mechanisms and critical conditions of the BASM are explored under the thermo-mechanical load. A novel strategy for programming the PR of the BASM is proposed in addition to changing the geometric parameters and the material combinations.

Machine learning-accelerated inverse design of programmable bi-functional metamaterials

Bi-functional metamaterials with programmable coefficients of thermal expansion (CTEs) and Poisson’s ratios (PRs) have garnered significant attention among researchers due to the ability to manifest desired deformations under thermal and mechanical loads. Nevertheless, a current challenge lies in efficiently achieving the inverse design of these metamaterials to meet diverse application requirements. This paper presents a machine learning (ML) model that can establish a logical mapping relationship between geometric/material parameters and mechanical properties, and it is applied to the inverse design of bi-functional metamaterials with desired CTEs and PRs. Furthermore, the inverse design capability of the ML model was validated by the finite element analysis and experimental test. The results demonstrate that the geometric models obtained from the inverse prediction can effectively exhibit the desired deformation behavior under thermal and mechanical loads. And the ML model proves to be a valuable tool, offering effective guidance for the design of bi-functional metamaterials with specific CTEs and PRs.

Controllable design of bi-material metamaterials with programmable thermal expansion and Poisson's ratio

Metamaterials possess superior acoustic, thermal, and mechanical properties, making them potential candidates for scientific and engineering applications. Previous studies were mainly limited to single counterintuitive property, while current applications of high-precision machines often necessitate a combination of advanced properties, such as negative thermal expansion (NTE), light-weight and negative Poisson's ratio (NPR). In this work, two bi-material missing rib-type anti-chiral metamaterials were devised and analyzed to integrate the programmable coefficient of thermal expansion (CTE), Poisson’s ratios (PR) and light-weight. The analytical solutions for the proposed metamaterials were then derived to provide guidelines for determining the geometries with targeted mechanical properties. It is shown that the proposed designs exhibit a range of special properties, including light-weight, widely programmable CTE with isotropy and stable PR performance. The analytic solutions of the CTE were further validated by numerical simulations and experimental tests. Finally, the coupling relationships among the CTE, PR and relative density were elucidated. Such an analysis of the coupled relationships is anticipated to have profound implications for the engineering community, where there is a pressing demand for materials that can meet stringent requirements of light-weight and programmable properties.

Synergistically program thermal expansional and mechanical performances in 3D metamaterials: Design-Architecture-Performance

Metamaterials, incorporating specific micro-architectures, could be purposely customized to export the programmability in both thermal expansional and mechanical performances, which are beneficial to obtain the thermal and structural stabilities in engineering devices. Here, by focusing on developing an original design strategy, multiple classes of metamaterials were devised and analyzed to integrate the programmable coefficient of thermal expansion (CTE) and mechanical performances (relative density, stiffness and strength). In detail, firstly, a series of the bi-material metaunits was devised, and a vector analysis method was proposed to analytically identify the CTE tensors. Then, an original design strategy, i.e., matrix transformation method, was developed to systematically devise multiple classes of 3D metamaterials with the unidirectional, transversal isotropic and isotropic CTEs. Besides, the mechanical performances, including the relative density, stiffness and strength, were theoretically established. It was identified that these metamaterials well balanced the directionality and programmability of the CTEs. Most importantly, by modulating the geometrical parameters, the desirable CTEs, light weight, high stiffness and strength could be synergistically achieved in these metamaterials. Eventually, a principle was established to guide the development of metamaterials. That was the original design strategy acted as the underlying foundation to map the specific architectures in metamaterials, correspondingly, to build the ability to synergistically program or customize the thermal expansional and mechanical performances.

Program multi-directional thermal expansion in a series of bending dominated mechanical metamaterials

Most metamaterials based on the bi-material curved beam (BC) were designed through hinge joints and presented only a unidirectional programmable coefficient of thermal expansion (CTE). Here, by contrast, a series of mechanical metamaterials based on the beam BC are originally devised with fixed joints. Moreover, by integrating the triangular, quadrilateral and hexagon configurations with rotational symmetry, these metamaterials could exclusively program the CTE in multiple directions. The explicit expressions of the relative densities are theoretically established. It is shown that increasing the parameter L1/h and reduction of the angle θ is beneficial to achieve light weight performance in these metamaterials. Besides, the closed-form expressions of the CTE are also theoretically derived and verified through numerical modeling. The analysis confirms that the CTE of the metamaterial in multiple directions can be well programmed to be either positive or negative values by rationally selecting the material combination and geometrical parameters. The CTEs vary linearly with the parameters L1 and θ, while show the parabolic variation with parameter m. In addition, the coupling relationships between the CTE and relative density are revealed and provide a guideline to achieve the large positive or large negative CTEs as well as light weight simultaneously. This work originally devises and analyzes a series of metamaterials of light weight and multi-directional customized CTE for engineering applications.

Three-dimensional hierarchical metamaterials incorporating multi-directional programmable thermal expansion

The dimensional stability under the temperature variation is of great significance for the temperature-sensitive structures, motivating the development of metamaterials with the programmable coefficient of thermal expansion (CTE). Here, all the configurations, totally including 51 types for the bi-material pyramid unit cells, were comprehensively devised to attain the widely programmable CTE in single direction. Furthermore, by using an originally developed matrix transformation method, multiple classes of the pyramid-based hierarchical metamaterials were systematically devised. These hierarchical metamaterials incorporated the unidirectional, transversal and isotropic CTEs in the multiple directions. The closed-form expressions of the CTE and relative density for the devised pyramid unit cells and hierarchical metamaterials were analytically established. The theoretical analysis was well verified by the performed numerical modeling, and confirmed that the large ranges of the programmable CTEs could be obtained by rationally adjusting the material and geometry parameters. Besides, the comprehensive comparison of the specific CTE identified that the programmable CTE and low relative density could be well balanced through the devised hierarchical metamaterials. The coupling effect of both material and geometrical parameters on the programmable CTE was figured out, providing a proper guideline to design the metamaterials with both light weight and desirable CTE.

Large programmable coefficient of thermal expansion in additively manufactured bi-material mechanical metamaterial

ABSTRACT The current metamaterials with the programmable coefficient of thermal expansion (CTE) usually present the unexpected anisotropy, and the experimentally measured CTEs are quite narrower. Here, a bi-material metamaterial was constructed. The material extrusion process was established to fabricate the metamaterial. The measured CTEs in various in-plane directions are in good consistency to each other, experimentally verifying the identical CTE in various in-plane directions. The relative deviation between the experimental measurements and theoretical predictions is within −13.0% to +11.0%. The positive programmable CTEs are as high as 204 and 258 ppm/°C, which are larger than those of the basic polymers nylon and polyvinyl alcohol (PVA). Otherwise, the negative CTEs of −25 and −77 ppm/°C are obtained, even though both the nylon and PVA have positive CTEs. The programmable CTEs are expanded to be [−77, +258] ppm/°C, far beyond the literature results, supplementing the additive manufacturing and experimental basis to the engineering applications.

Simultaneously program thermal expansion and Poisson’s ratio in three dimensional mechanical metamaterial

The engineering materials and structures, which usually suffer both temperature variation and mechanical loading, motivate the urgent need of the multifunctional metamaterials with simultaneously programmable coefficient of thermal expansion (CTE) and Poisson’s ratio (PR). Whereas, the current 3D metamaterials can not continuously program the CTE and PR. Herein, a class of 3D metamaterial is originally devised by an exclusive geometrical methodology. The explicit expressions of the CTE and PR are theoretically established and are also verified by the numerical modeling. The analysis confirms that the CTE can be widely tailored by varying the geometrical parameters and selection of the constituents. Besides, the controllable PR can be also easily obtained by adjusting the geometrical parameters. Moreover, the devised 3D metamaterial gives paired tailorable CTE and controllable PR, including especially negative CTE + negative PR. An arrangement rule is developed to construct a series of hierarchical cells which can program CTE and PR in multi principle axes and can be periodically arrayed for obtaining the 3D cellular metamaterials. The devised 3D metamaterials are capable of realizing the widely coupled programmability of both CTE and PR and provide a strategy of shape morphing stimulated both by temperature variation and mechanical loading.

Simulation and Investigation of the Positional System of an Electric Drive with Nonlinear Correction

The design principle, structure, and synthesis of parameters of a positional electric-drive system with a nonlinear correction providing a high level of performance when working out a given motion are considered. The structure of the positional system is created on the basis of the standard electric drive with a thyratron (brushless) motor and microprocessor module, in which the program of nonlinear correction switches the feedbacks in the function of error of a given motion. The algorithm of nonlinear correction operates in real time and provides the working out of a given motion in two stages. At the first stage, a positive feedback by the motor-rotation speed is introduced to the speed-regulator input, which provides the system movement with an acceleration limit. As soon as the mismatch error reaches a predetermined value, the algorithm of the second stage begins to operate. Instead of positive feedback to the speed-regulator input, a negative feedback by the motor speed with programmable coefficient is introduced that makes it possible to provide effective braking of the electric drive and generate a transition process with given quality indicators. A comparative analysis is carried out of the operation of the system with the standard electric drive, in which the control is constructed on the basis of the principle of subordinate regulation of coordinates. In addition, it was revealed that introducing into the regulating system of nonlinear corrector makes it possible to reduce the working out time of given motion by 2.4 times. This is because the motion speed in the system with nonlinear correction varies by a triangular law that makes it possible in to fully use the overload capacity of the thyratron motor, while, in the electric-drive system without nonlinear correction, the motion speed varies by a trapezoidal law. The obtained results make it possible to draw a conclusion about the effectiveness of application of a nonlinear correction in positional electrical drives with subordinate regulation of coordinates.

A Programmable 0.7–2.7 GHz Direct $\Delta \Sigma$ Receiver in 40 nm CMOS

This paper presents a wideband direct ΔΣ receiver for the 0.7-2.7 GHz frequency range. The architecture embeds a wideband direct-conversion RF front-end into a continuous-time feedback ΔΣ modulator, which initiates the analog-to-digital conversion of the selected channel already at the RF nodes. A feedback-type architecture enables simultaneous filtering of nearby interfering signals. The inductorless 40 nm CMOS receiver supports programmable ΔΣ modulator coefficients and RF channel bandwidths up to 20 MHz. The receiver consumes 90 mW from a 1.1 V supply, and it provides a peak SNDR of 46 dB, NF of 5.9-8.8 dB, and an IIP3 of -2 dBm.

A single source microwave photonic filter using a novel single-mode fiber to multimode fiber coupling technique

In this paper we present a fully tunable and reconfigurable single-laser multi-tap microwave photonic FIR filter that utilizes a special SM-to-MM combiner to sum the taps. The filter requires only a single laser source for all the taps and a passive component, a SM-to-MM combiner, for incoherent summing of signal. The SM-to-MM combiner does not produce optical interference during signal merging and is phase-insensitive. We experimentally demonstrate an eight-tap filter with both positive and negative programmable coefficients with excellent correspondence between predicted and measured values. The magnitude response shows a clean and accurate function across the entire bandwidth, and proves successful operation of the FIR filter using a SM-to-MM combiner.

Implementing Concurrent Error Detection in Infinite-Impulse-Response Filters

Advanced electronic circuits suffer errors caused by multiple sources. For example, radiation can induce transient errors, and manufacturing variations can cause some devices to sporadically suffer errors. Fault tolerance is therefore an important issue in advanced electronic circuits. Digital filters are commonly used in many applications, and therefore, their protection against errors has been widely studied. However, infinite-impulse-response (IIR) filters have received little attention as most of the existing works focus on finite-impulse-response filters. In this brief, a technique to implement concurrent error detection in IIR filters with programmable coefficients is proposed and evaluated. The protection effectiveness is assessed through fault injection experiments that show that it can efficiently detect errors. The cost is estimated using the synthesis results for a 45-nm library. The results show that the area overhead is much lower than that of a duplicated system that can also detect errors.

Research and Application of a FPGA-Based Dynamic Distributed Algorithm

A dynamic distributed algorithm (DDA) with a look-up dynamic table instead of ROM was put forward based on the theory of signed distributed algorithm, in order to improve processing speed and flexibility of product sum on FPGA. Since the DDA occupies few hardware resources, performs fast operation and realizes programmable coefficient, the limitation of digital signal processing speed on fixed data bus width and sequential operation was avoided by using the algorithm. At the same time, an effective solution to realizing coefficient programmable FIR filter was presented.

Microwave photonic filters with programmable bipolar coefficients based on -phase inversion of DSB sidebands

A new technique to realise dynamic negative coefficients for microwave photonic signal processors is presented. It is based on π-phase inversion of two sidebands in double-sideband (DSB) modulation, through spectral-line phase manipulation. The all-optical technique has advantages of enabling scaling to multiple-taps, and is highly versatile because it is programmable and enables dynamic reconfiguration of all the taps using only software. Experimental results demonstrate a programmable bipolar photonic signal processor with operation to high frequencies.

Charge-domain FIR sampler with programmable filtering coefficients

A charge-domain sampling technique for realization of mixed-mode finite-impulse response (FIR) filters is presented. The method is based on weighting signal current samples integrated into a sampling capacitor with a set of parallel digitally controlled current-mode switches each carrying a unit current element. The fine achievable resolution and digital controllability of the filter tap coefficients allows realization of advanced programmable FIR filtering functions embedded into high-frequency signal sampling. Circuit-level simulation results of an example 50-MHz IF-sampler with a built-in 22-tap complex bandpass sinc/sup 3/ FIR function in 0.35-/spl mu/m CMOS are shown, demonstrating the feasibility of the presented method.

Hardware-efficient pipelined programmable FIR filter design

With the increasing demand for video-signal processing and transmission, high-speed programmable FIR filters are required for real-time processing. This paper presents a hardware-efficient pipelined FIR architecture with programmable coefficients. FIR operations are first reformulated into multi-bit DA form at an algorithm level. Then, at the architecture level, the ( p, q) compressor, instead of Booth encoding or RAM implementation, is used for high-speed operation. Due to the simple architecture, we can easily pipeline the proposed FIR filter to the adder level and save up to half of the cost of previous designs without sacrificing performance. The presented design is useful for bit-parallel input design, which can save 36.7% of the area cost compared with previous approaches.

A low V/sub t/ CMOS implementation of an LPLV digital filter core for portable audio applications

A low power 32nd-order digital filter for portable audio applications has been designed and implemented in a single threshold 1-V 0.5-/spl mu/m CMOS process. The design is full custom, using a combination of conventional CMOS and pass-transistor circuits, optimized for low energy consumption and small area. The filter features up to 16 biquad sections with programmable coefficients and performs fixed-point computations with 16-bit resolution. The measured average energy consumption of 330 pJ per biquad computation indicates that the implementation of complex digital signal processing in a single-threshold low-voltage process is a viable alternative to implementations in multiple threshold processes.

A new hardware-efficient architecture for programmable FIR filters

Although much research has been done on efficient high-speed filter architectures, much of this work has focused on filters with fixed coefficients, such as Canonical Signed Digit coefficient filter architectures, multiplierless designs, or memory-based designs. In this paper, we focus on digit-serial, high-speed architectures with programmable coefficients. To achieve high performance goals, we consider both of algorithm level and architecture implementation level of FIR filters. In algorithm level, we reformulate the FIR formulation in bit-level and take the associative property of the addition in both the digit-serial multiplications and filter formulations. In architecture level, we considered issues to implement the reformulated results efficiently. The issues include addition implementation, data flow arrangements, and treatment of sign-extensions. Based on the above considerations, we can obtain a filter architecture with accumulation-free tap structure and properties of short latency, flexible pipelinability and high speed. Comparing the cost and performance with previous designs, we find that the proposed architecture reduces the hardware cost of a programmable FIR filter to only half that of previous designs without sacrificing performance.

Application-specific integrated circuit based image processor and its simulated results

A real-time image processing system is presented. The system consists, mainly, of a 2-D convolver appilcation-specific integrated circuit (ASIC) that performs 2-D convolution, and a pixel image sensor capable of capturing an image of 256x 256 resolution. The ASIC can convolve the pixel image data (8 bit/pixel) present within a video window with a set of programmable coefficients that can be loaded by the microprocessor, which is responsible for the proper flow of image information within the system. The image simulated results by the system are presented for a number of convolution masks.

Intelligent digital filter synthesis system

Abstract This paper presents an intelligent digital filter synthesis system which consists of a user‐friendly graphic I/O interface, a synthesis program designing filter coefficients, an intelligent hardware generation system and a simulator including time and frequency domain simulation. Users need only to specify the filter type, filter specifications, sampling rate requirement and some parameters through the graphic interface. The filter response and the simulation results can be immediately shown on the screen. The graphic interface is based on the X Window System and therefore provides a network‐transparent and vendor‐independent operating environment for the system. The synthesis system is targeted for two main types of digital filter: FIR and IIR. An automatic partition algorithm on FIR is developed to meet the user's sampling rate requirement. The optimal cascade architecture of biquad‐based IIR with programmable coefficients is also derived. The final circuit designs under economic bitwidth are generated by the GDT system and further layouts can be generated.