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A demand-customized selective wireless power transfer system is proposed in this article. Multiple receivers can be recognized based on their positions and the magnetic field in the powering area can be controlled and regulated accordingly. For authorized receivers, the system can simultaneously deliver power to meet different output requirements for different electrical appliances, while for unauthorized ones, they can be shut down independently for energy security, even when they are also in the powering area. Compared to the traditional calculation models for multi-input multi-output systems, the proposed current control algorithm uses a piecewise optimization procedure to simplify the iteration and improve control flexibility. Hybrid-frequency pacing is adopted as the control strategy to further reduce the output fluctuation and raise the system efficiency. An experimental prototype with a 3 × 3 transmitter matrix is established. The system can successfully power two receivers with the same sizes for four different power requirement scenarios, which validates the selectivity and the controllability of the proposed system. [ABSTRACT FROM AUTHOR]

This article proposes and implements an advanced pulse frequency modulation (PFM) scheme to adjust the output power of the parity-time (PT) symmetric wireless power transfer (WPT) system. The key is to utilize PFM to adjust the duty ratio of the self-excited oscillating inverter for the PT-symmetric WPT system, hence transferring more power than that of the conventional forced oscillating inverter under the same input voltage and duty ratio. Besides, the transmission efficiency can maintain high when the coupling coefficient is larger than the critical value. With a proper signal processing circuit, the phase of the inverter output voltage can lead to that of the primary-side current, which can help reduce the switching loss. Therefore, the system efficiency of this self-excited oscillation scheme for WPT can keep high, while the output power can be larger than that of using the conventional forced oscillation scheme. Theoretical analysis and simulation results are given to verify the feasibility of the proposed scheme. [ABSTRACT FROM AUTHOR]

This article proposes and implements an output-controllable efficiency-optimized wireless power transfer scheme using hybrid modulation. The key is to combine pulse frequency modulation (PFM) and on-off keying (OOK) modulation and to utilize feedback control. Among them, PFM is used for the output voltage regulation of the inverter to adjust the rectified output voltage on the receiver side, while OOK modulation is adopted to convert the load resistance to be close to the optimal resistance value so that the system efficiency can be effectively optimized. When the relationship between the input and output voltages reaches a ratio related to system parameters, it can be considered that the load resistance has reached the optimal state. Hence, the feedback output voltage is utilized to help convert the load resistance into an optimal value and only one voltage acquisition circuit is needed. In this article, theoretical analysis and practical experimentation (using the LED lamp as a nonlinear load and the 102-Ω resistance as a linear load) are both given to verify that the proposed scheme can help to maintain high system efficiency during the output voltage regulation process. [ABSTRACT FROM AUTHOR]

This article proposes and implements an integrated wireless motor system using the laminated magnetic coupler (LMC) and commutative-resonant control (CRC). Prominently, a unique wireless power transfer system is developed to directly drive the switched reluctance motor (SRM) over an extendable distance with all controls centralizing in the transmitter. Differing from the multifrequency wireless motor system, the proposed system first employs the single resonant frequency to wirelessly drive a multiphase SRM through the single power transfer channel. Particularly, two orthogonal bipolar coils and one unipolar coil are skillfully integrated and naturally decoupled to form an LMC which acts as the transmitter, intermediate, and receiver coils, respectively. By utilizing the CRC to sequentially energize coils in the transmitter, the SRM phase windings can be properly excited by relevant coils in the receiver, which takes the distinct advantages of balanced phase currents, flexible transfer distance, high integration, and free maintenance. A prototype is constructed with the system efficiency of 89.14% and motor speed of 1500 rpm under the distance of 200 mm. Both theoretical and experimental results are provided to validate the feasibility of the proposed system. [ABSTRACT FROM AUTHOR]

This article proposes and implements a novel wireless power and drive transfer system using orthogonal bipolar couplers and separately excited modulation (SEM). Specifically, two bipolar coils are orthogonally integrated and naturally decoupled to form a compact magnetic coupler which will be utilized in the transmitter and receiver, respectively. The key is to employ the SEM to alternatively energize bipolar coils in the transmitter while self-driven circuits in the receiver can directly extract the drive information to control receiver-side switches. Consequently, the concurrent wireless power transfer and wireless drive transfer can be skillfully realized via the shared transfer channel at the single resonant frequency. Moreover, the proposed system can effortlessly achieve the wireless dc motor drive with the capability of bidirectional motion, or the wireless ac motor drive with the variable-voltage variable-frequency control. Besides driving the dc and ac motors, a 200-W prototype is constructed with the transmission efficiency of 89.5% over the transfer distance of 100 mm for a resistive load of 40 Ω. Both theoretical and experimental results are provided to validate the feasibility and flexibility of the proposed system. [ABSTRACT FROM AUTHOR]

The code base of system software is growing fast, which results in a large number of vulnerabilities: for example, 296 CVEs have been found in Xen hypervisor and 2195 CVEs in Linux kernel. To reduce the reliance on the trust of system software, many researchers try to provide trusted execution environments (TEEs), which can be categorized into two types: non-privileged TEEs and privileged TEEs. Non-privileged TEEs (e.g., Intel SGX) are extensible, but cannot protect security services like virtual machine introspection (VMI) due to the lack of system-level semantics. On the contrary, privileged TEEs (e.g., the secure world of ARM TrustZone) have system-level semantics, but any additional service implemented in the privileged TEE directly increases the TCB of the entire system. In this article, we propose a new design of TEE to support system-level security services and achieve better extensibility with a small TCB. Each TEE instance of the proposed design is named a Colony. Specifically, we introduce a secure monitor for isolation and capability management. Each Colony is assigned capabilities to access only necessary system-level semantics. We use the new TEE to build four security services, including secure device accessing, VMI tools, a system call tracer, and a much more complex service to virtualize ARM TrustZone with multiple Colonies. We have implemented the system on ARMv7 and ARMv8 platforms, in Xen hypervisor and Linux kernel, and perform a detailed evaluation to show its efficiency. 1. This paper is an extended version of the conference paper published in USENIX Security’17: vTZ: Virtualizing ARM TrustZone. A brief summary of differences is in Section. [ABSTRACT FROM AUTHOR]

This article proposes and implements a compact wireless motor drive using orthogonal bipolar coils for the coordinated operation of robotic arms. The key is to orthogonally integrate two bipolar coils to form a compact magnetic coupler (CMC), while each CMC serves as the transmitting coil and receiving coil, respectively. Instead of adopting the one-to-many coil structure and operating at multiple frequencies, in this article, two bipolar coils in the CMC are mutually decoupled and separately energized to drive two permanent magnet dc (PMDC) motors. As such, the wireless and selective motor drives can be achieved via the shared power-transfer channel at a single resonant frequency. All controls and switches are concentrated at the transmitter so that the receiver is entirely sealable. Accordingly, the coordinated operation of robotic arms can be realized with the high integration and no electrocution. Theoretical calculations and experimental results are given to validate the flexibility and feasibility of the proposed system. [ABSTRACT FROM AUTHOR]

This article proposes and implements a wireless power transfer (WPT) with series-capacitor-inductor-capacitor (S-CLC) compensation network and pulse-frequency-modulation (PFM) control for dimmable low-pressure sodium (LPS) lamps. Considering the high-voltage ignition and long-time operation, the LPS lamp has the risk of causing electrocution, especially when operating in a humid environment. Thus, the wireless lighting is highly desirable since the LPS lamp can be completely isolated with maintenance-free under all-weather conditions. The proposed S-CLC compensation for WPT can directly drive the LPS lamp without utilizing any magnetic or electronic ballasts. In addition, the PFM control can achieve effective dimming control, reduced operating frequency, and zero-voltage switching (ZVS) concurrently. Theoretical calculations and experimental results are given to validate the feasibility of the proposed wireless lighting system. [ABSTRACT FROM AUTHOR]