Topology Morphing Research Articles

Bilinear stiffness and bimodular Poisson's ratio in cylindrical sinusoidal lattices through topology morphing

Bilinear elastic behaviour allows structural designs to respond in either a stiff or compliant manner depending on the load. Here a cylindrical sinusoidal lattice structure is described that stiffens beyond a certain load. When subjected to axial compression, the lattice can undergo a topological transformation by forming contact connections. This topology change involves a transition from rectangular-like unit cells to kagome-like unit cells, associated with an approximately fourfold increase in stiffness. The lattice exhibits negative Poisson's ratio with a step-change from ≈−0.66 to ≈−0.23 prior to and during contact formation, respectively. After contact formation, it displays a nonlinear Poisson's ratio behaviour. The mechanics underpinning these behaviours are analysed using a combination of experiments and numerical modelling. A comparison with similar planar lattices reveals the effect of the global topology of the lattice (e.g. planar, cylindrical) on the unit cell-level topology morphing. The proposed topology-morphing cylindrical sinusoidal lattice introduces new design possibilities in the application-rich context of tubular structures with nonlinear mechanical properties.

Adaptive stiffness in lattice metastructures through tensile-buckling inspired topology morphing

This paper explores the use of simultaneous tensile buckling of unit cells to induce a transformation in lattice topology. Under tension, unit cells undergo passive transformation from a rectangle-like to a triangle-/pentagon-like topology, with an associated change in the effective stiffness properties. This behaviour is investigated through finite element analysis and experiments, with analytical results providing insights into the observed behaviour. The analysis identifies (i) that the initial unit cell topology (rectangular) is dominated by membrane effects, (ii) the transformation phase is associated with negative stiffness, and (iii) once formed, the new topology (triangular/pentagonal) exhibits increased stiffness in both compression and tension. Finite element analysis confirms that the unit cell behaviour is also preserved in lattices. Under tension, the lattice undergoes a seven-fold increase in stiffness as it transitions from its initial to the new topology, with a regime of negative stiffness during this transformation accounting for approximately 82% of its total elastic deformation. This new approach to elastically tailor the nonlinear response of (meta-)materials/structures has the potential to contribute to the development of novel tensile energy absorbers.

Topology Morphing Insulation: A Review of Technologies and Energy Performance in Dynamic Building Insulation

Topology morphing insulation enables the on-demand switching of thermal properties between insulative and conducting states through shape change. The adaptive nature of these systems allows them to regulate heat transfer by dynamically altering insulation materials or systems in response to changing conditions, including environmental factors, electrical grid dynamics, and occupant requirements. In this article, we highlight the potential of topology morphing insulation for advancing building envelope design, improving energy efficiency, and facilitating on-demand adjustments in effective thermal conductivity. We provide a comprehensive overview of topology morphing insulation, delving into its underlying principles, mechanisms, and potential applications. This review explores cutting-edge research and the potential application of insights from non-building concepts, such as nature, textiles, and origami. Additionally, it examines crucial aspects such as actuation mechanisms, effectiveness, lifecycle considerations, sustainability implications, and manufacturing feasibility. We discuss the potential benefits and challenges associated with implementing topology morphing insulation solutions. Thanks to its transformative capabilities, topology morphing insulation holds tremendous promise for advancing building envelope design, driving energy efficiency improvements, and facilitating responsive changes in effective thermal conductivity.

Stiffness tailoring in sinusoidal lattice structures through passive topology morphing using contact connections

Structures with adaptive stiffness characteristics present an opportunity to meet competing design requirements, thus achieving greater efficiency by the reconfiguration of their topology. Here, the potential of using changes in the topology of planar lattice structures is explored to achieve this desired adaptivity and observe that lattice structures with rectangle-like unit-cells may undergo elastic buckling or bending of cell walls when subject to longitudinal compression. Under sufficient load intensity, cell walls can deform and contact neighbouring cells. This self-contact is harnessed to change the topology of the structure to that of a kagome-like lattice, thereby establishing new load paths, thus enabling enhancement, in a tailored manner, of the effective compressive and shear stiffness of the lattice. Whilst this phenomenon is independent of characteristic length scale, we focus on macroscopic behaviour (lattices of scale ≈ 200 mm). Experimentally observed responses of 3D-printed lattices correlate excellently with finite element analysis and analytical stiffness predictions for pre- and post-contact topologies. The role of key geometric and stiffness parameters in critical regions of the design space is explored through a parametric study. The non-linear responses demonstrated by this topology morphing lattice structure may offer designers a new route to tailor elastic characteristics.

Light load analysis and topology morphing between full-/half-bridge DC-to-DC converter

ABSTRACT To retain high efficiency in a wide output voltage range and reduce the conduction and switching losses for a DC power supply, this work makes use of topology morphing between full- and half-bridge converters. The operation of the converter is better as a phase-shift modulated (PSM) full-bridge converter for a high output voltage and as the asymmetrical pulse-width modulated (APWM) half-bridge counterpart for a low output voltage. The light load operations of PSM full-bridge and APWM half-bridge DC converter are analysed in detail to account for the voltage gain variation as well as the switching and conduction losses. A suitable control algorithm is also proposed to facilitate smooth morphing transitions and eliminates the unwanted voltage and current overshoot. A laboratory converter circuit rated at outputs up to 60 V, 1.8 kW with 180 V input voltage is designed and built to verify the operation with topology morphing. The experimental results have demonstrated by adapting the PSM full-bridge DC converter to the APWM half-bridge DC converter at the low voltage range that the circuit efficiency can be effectively improved and enhanced 6% for the best.

High-Efficiency Quad-Mode Parallel PV Power Optimizer for DC Microgrids

The paper introduces a new parallel photovoltaic (PV) power optimizer intended for direct integration of PV modules into a dc bus or microgrid. The topology is derived from a typical galvanically isolated buck series resonant dc-dc converter (SRC) to the buck-boost SRC recently proven as a parallel PV power optimizer (PO). By applying the topology morphing control, this two-mode converter is extended to the quad-mode parallel PV PO. Its operation modes defined by changing modulation of switches are detailed, and gain expressions are provided. The proposed concept provides enhanced performance in the region where global power maximum could occur due to partial shading. Accordingly, a significant efficiency improvement is achieved at voltages below the nominal value that targets the most probable PV module operating point without shading. An experimental prototype was built to demonstrate the benefits of the proposed quad-mode PV PO and compare it to the existing two-mode buck-boost SRC. Thermal stress analysis is supported with power loss breakdown calculations to demonstrate component thermal stresses in critical operating points.

Novel Universal Power Electronic Interface for Integration of PV Modules and Battery Energy Storages in Residential DC Microgrids

This paper introduces the novel concept of a highly versatile smart power electronic interface for fast deployment of residential dc microgrids. The proposed approach has bidirectional power flow control capabilities, wide operating voltage range, and high efficiency resulting from the topology morphing control utilization. This enables universal compatibility with the majority of the commercial 60- and 72-cell photovoltaic modules, as well as the efficient charge/discharge control of the 24 V and 48 V battery energy storages using the same hardware platform. The proposed concept features fully autonomous operation where switching between the photovoltaic and battery interfacing modes is automatically done using the input source identification algorithm. Moreover, the proposed universal interface converter employs droop control and solid-state protection, making it fully compatible with the emerging standards and requirements for power electronic systems used in dc microgrid environments. A 350 W prototype was developed and tested in the residential 350 V dc microgrid with droop control to validate the proposed concept experimentally.

Bidirectional Isolated Hexamode DC–DC Converter

The proposed isolated buck-boost series resonant dc dc converter contains two full-bridge hybrid switching cells capable of half-bridge operation. This feature is regarded as topology morphing control. The voltage buck regulation requires special modulations applied to the primary-side hybrid switching cell. In contrast, the voltage boost regulation requires special modulations for the secondary-side hybrid switching cell. Combining the topology morphing control with the buck-boost regulation capability a novel dc-dc converter operating in six different modes is derived. Moreover, the proposed converter is capable of bidirectional operation. This paper describes how the topology morphing control influences the converter dc voltage gain, which results in three boost and three buck modes. The obtained six modes are described and equations for the converter dc voltage gain are provided. Selected design guidelines for the power part and control system are presented. Using those, a 350 W prototype was designed and built. Experimental results confirm the theoretical expressions for the converter dc voltage gain. Experimental efficiency is provided in a wide input voltage range for both energy transfer directions. Analysis of operating points with the highest thermal stress of components is presented with corresponding power loss breakdown calculations confirming measured thermal results.

Survey of Topology Morphing Control Techniques for Performance Enhancement of Galvanically Isolated DC-DC Converters

This paper provides a systematic survey on the topology morphing control techniques used in the galvanically isolated dc-dc converters. Existing techniques are broadly categorized based on the part where a converter changes its topology: at the input side, at the output side, and the advanced techniques that cannot be categorized in the first two groups. The techniques span from the simple reconfiguration between the full- and half-bridge switching cells similar to the conventional power supplies with universal ac input to the advanced multi-track topology and reconfigurable resonant tanks. In addition, the described variety of application examples proves the wide application range and versatility of the topology morphing control. These include fault tolerance, efficiency curve flattening, input voltage range extension, and other properties. Hence, this article provides a single comprehensive source for researchers and engineers willing to enter the topic of topology morphing control.

Bidirectional Resonant Converter for DC Microgrid Applications

A bidirectional resonant converter is presented and verified in this paper for an electric vehicle battery charger/discharger system. The presented circuit can achieve forward and backward power operation, low switching losses on active devices, and wide output voltage operation. The circuit structure of the presented converter includes two resonant circuits on the primary and secondary sides of an isolated transformer. The frequency modulation approach is adopted to control the studied circuit. Owing to the resonant circuit characteristic, active devices for both forward (battery charge) and backward (battery discharge) power operation can be turned on at zero voltage switching. In order to implement a universal battery charger for different kinds of electric vehicle applications, the DC converter is demanded to have a wide output voltage range capability. The topology morphing between a full bridge resonant circuit and half bridge resonant circuit is selected to obtain high- and low-output voltage range operations so that the 200–500 V output voltage range is realized in the presented resonant converter. Compared to the conventional bidirectional converters, the proposed can be operated under a wide voltage range operation. In the end, a 1 kW laboratory prototype circuit is built, and experiments are provided to demonstrate the validity and performance of the presented bidirectional resonant converter.

Implementation of a Resonant Converter with Topology Morphing to Achieve Bidirectional Power Flow

A DC converter with the benefits of reverse power capability, less switching loss and wide voltage operation is presented and implemented for wide input voltage applications such as fuel cell energy, photovoltaic (PV) system and DC wind power. Two full bridge resonant circuits are used in the presented converter to achieve bidirectional power flow capability and reduce switching losses on active devices. To overcome the wide input DC voltage variation problem for fuel cell energy and PV solar panel, the topology morphing between the half bridge circuit and full bridge circuit is adopted on the primary side to obtain low (or high) voltage gain under a high (or low) input voltage condition. Therefore, the stable DC voltage is controlled at the load side by using the variable switching frequency modulation. The studied hybrid CLLC converter is tested by a 1 kW prototype and the performance is verified and confirmed by experiments.

A variable-topology morphing composite cylindrical lattice

Morphing composite structures are of significant interest due to the fact that they exhibit superior mass-to-stiffness ratios and a large degree of tailorability in comparison to traditional materials and structures. One such morphing composite structure is the multistable composite cylindrical lattice. Current work introduces a novel variable-topology morphing mechanism to it through the use of both permanent magnets and electromagnets. By replacing a set of mechanical fasteners from the central intersection of the lattice strips with a bespoke variable-topology mechanism introduces a controllable and replicable semi-autonomous means for topology morphing. The variable-topology mechanism allows the structure to transition from being a linear deployment actuator to one that deploys along a curved path, without need for external mechanical input. The behaviour of both the variable-topology mechanism and the topology-changing cylindrical lattice are thoroughly characterised through a combination of mechanical and virtual tests.

A Novel LLC Converter With Topology Morphing Control for Wide Input Voltage Range Application

Wide voltage gain range applications are challenging for dc/dc converters, and the system efficiency would be degraded in order to satisfy the voltage gain requirement. Inductor–inductor–capacitor ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> ) resonant converters have gained popularity owning to its high efficiency feature. However, wide voltage gain range applications also challenge the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> converters from the following three aspects: 1) large switching frequency operating range is required to meet the voltage gain requirement, which degrades the converter electromagnetic interference (EMI) performance and challenges the optimization of magnetic components; 2) small inductor ratio is required to boost the voltage gain, which increases the resonant tank root-mean-square (rms) current and conduction loss; and 3) control instability issues may occur at both maximum voltage gain and minimum voltage gain, which reduce the converter reliability. To address these issues, in this article, a novel <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> converter with topology morphing control is proposed for wide voltage gain range applications. Three operation modes, dual full-bridge (DFB), hybrid full-bridge and half-bridge (HFBHB), and dual half-bridge (DHB), can be achieved by adopting the topology morphing control, which can cover a wide voltage gain operation range. Operational principles, design considerations, and experimental validations of the proposed converter are presented.

3-Bridge LLC resonant converter for achieving wide output voltage control range based on topology morphing

In this paper, a control method for a 3-bridge LLC resonant converter operating with a wide output voltage control range is described. Duty changes that stem from switching devices cause topology transitions that allow the converter to shift sequentially across four operating modes, where the primary resonant tank circuits and the secondary terminals can be connected in parallel or in series making it possible to achieve a wide controllable output voltage (7.5–120 VDC). During topology mode transitions, morphing control within narrow hysteresis bands, which is achieved by varying the switching frequency and duty of the switching devices, maintains a tight regulation without noticeable output voltage transients. To verify the performance of the proposed converter, a 5-kW 700 VDC input prototype with an output voltage ranging from 7.5 to 120 VDC is built and tested.

A Structure-Reconfigurable Soft-Switching DC-DC Converter for Wide-Range Applications

In this paper, a structure-reconfigurable resonant DC-DC (direct current – direct current) converter is presented. By controlling the state of the auxiliary switch, the converter could change the resonant structure to acquire a high efficiency and wide voltage gain range simultaneously. The characteristics of the LLC (inductor-inductor-capacitor) resonant converter are firstly analyzed. Based on this, through introducing additional resonant elements and adopting the topology morphing method, the proposed converter can be formed. Moreover, a novel parameter selection method is discussed to satisfy both working states. Then, a detailed loss analysis calculation is conducted to determine the optimal switching point. In addition, an extra resonant zero point is generated by the topology itself, and the inherent over-current protection is guaranteed. Finally, a 500 W prototype is built to demonstrate the theoretical rationality. The output voltage is constant at 400 V even if the input voltage varies from 160 to 400 V. A peak efficiency of 97.2% is achieved.

Power Density and Efficiency Enhancement in ICN DC–DC Converters Using Topology Morphing Control

This paper introduces a new approach for output voltage regulation in impedance control network (ICN) resonant dc–dc converters, in which the rectifier of the ICN converter alternates between full-bridge and half-bridge topologies. This approach, termed topology morphing control, allows the ICN converter to maintain soft switching across power levels while substantially reducing the output capacitance requirement and improving partial-power efficiencies compared to the conventional burst mode ( on/off ) control. A closed-loop control architecture for the ICN converter is also introduced, which regulates the converter's output voltage under input voltage and load variations while ensuring smooth transitions between the multiple operating modes of the proposed topology morphing control. A prototype 1-MHz, 120-W step-down ICN resonant converter designed for an input voltage range of 18–36 V, an output voltage of 12 V, and a 10:1 output power range has been built and tested with both burst mode control and the proposed topology morphing control. The topology morphing control reduces the output capacitance requirement in the prototype ICN converter by 57% and reduces converter losses at partial power levels by up to 46.5%. The prototype ICN converter is also tested under closed-loop control and is shown to successfully regulate its output voltage in the face of input voltage and load variations.

On-the-Fly Topology-Morphing Control—Efficiency Optimization Method for LLC Resonant Converters Operating in Wide Input- and/or Output-Voltage Range

This paper presents a control method for efficiency improvement of the LLC resonant converter operating with a wide input-voltage and/or output-voltage range by means of topology morphing, i.e., changing of power converter's topology to that which is the most optimal for given input-voltage and/or output-voltage conditions. The proposed on-the-fly topology-morphing control maintains a tight regulation of the output during the topology transitions so that topology transitions are made without noticeable output-voltage transients. The performance of the proposed topology morphing method is verified experimentally on an 800-W LLC dc/dc converter prototype designed for a 100-V to 400-V input-voltage range.

Module-based method for design and analysis of reconfigurable parallel robots

This paper presents a method for the design and analysis of reconfigurable parallel robots. The inherent modularity in a parallel robot lends itself as a natural candidate for reconfiguration. By taking the branches as building blocks, many modular parallel robots can be constructed, from which a reconfigurable parallel robot can be realized. Among three types of reconfigurations, namely, geometry morphing, topology morphing, and group morphing, the method presented here is for the last two reconfigurations, thereby advancing the current research that is mainly limited to geometry morphing. It is shown that the module-based method not only provides a systematic way of designing a reconfigurable parallel robot, but also offers a unified modeling for robot analysis. Two examples are provided, one showing the topology morphing and the other showing the group morphing.