In this paper, we investigate the robust beamforming for the magnetic-based wireless power transfer (WPT) with multiple transmitters and multiple receivers to improve the power efficiency and reliability. By taking into account the imperfection of the magnetic mutual inductances information (MII), we firstly formulate a beamforming optimization problem to minimize the total transmit power while guaranteeing the reliable power delivery for each receiver simultaneously. Then, observing that the optimization problem is highly nonconvex with infinite number of constraints, we utilize the norm-bounded MII error models to reformulate the original problem into two worst-case optimization problems for the cases of the single receiver and multiple receivers, respectively. Finally, the optimal beamforming is obtained for the case of single receiver by applying the semidefinite programming relaxation (SDR) and the approximately optimal solution is obtained for the case of multiple receivers by adopting the SDR with randomization. Extensive simulation results verify the power transfer reliability and efficiency of the proposed beamforming schemes for the magnetic-based WPT systems.

Robust Beamforming Design for Magnetic MIMO Wireless Power Transfer Systems

Recently, multiple-input multiple-output (MIMO) technology has been introduced into magnetic resonant coupling (MRC) enabled wireless power transfer (WPT) systems for concurrent charging of multiple devices. However, impedance mismatching phenomena caused by strong TX-RX or RX-RX coupling greatly affect the power delivered to load (PDL) in practical charging systems. To solve this issue, we propose an effective scheduling algorithm for Impedance Matching enhanced PDL optimization in MIMO MRC-WPT systems (called IMP), which integrates the transmitter scheduling together with the impedance matching techniques, i.e., adjusting TX coils for tuning TX-RX coupling and grouping RXs to separate strongly coupled RX pairs. We formulate this as a joint optimization problem and decouple it into three sub-problems, i.e., current scheduling, coil adjustment, and RX grouping, and solve them through alternating direction method of multipliers (ADMM) based, tabu search (TS) based, and graph clique cover based algorithms, respectively. Extensive experiments are performed on a prototype testbed, and the results demonstrate the effectiveness of our solution. Compared with the state-of-the-art power transfer efficiency (PTE) maximization solution, the proposed algorithm IMP achieves a 74.7X performance improvement of PDL on average.

IMP: Impedance Matching Enhanced Power-Delivered-to-Load Optimization for Magnetic MIMO Wireless Power Transfer System

Wireless power transfer via magnetic resonance coupling offers the prospect of autonomously charging connected devices. Previous work demonstrated that the system deployment can be facilitated by “routing” power on 2-D relay resonator arrays, using the multi-hop phenomenon. Power propagates through untethered relay resonators in such systems, and the routing strategy significantly affects the power transfer efficiency. However, most previous studies limit the routing to line-shaped routes, which compromises power transfer efficiency to preserve the simplicity of analysis. Here we show a surface routing approach, which can be orderly generated and is more efficient than linear routing. The confronting challenge is the complex representation of cross-coupled relays, which this work overcomes by conditioning the resonators’ current by appending additional loading conditions to the relays. Simulation-based evaluations show that the proposed approach improves the efficiency by up to 10% in 1.5 m range power delivery.

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Surface Routing for Wireless Power Transfer Using 2-D Relay Resonator Arrays

Magnetic resonant coupling (MRC) wireless power transfer (WPT) is a convenient and potential power supply solution for smart devices. The scheduling problem in the multiple-input multiple-output (MIMO) scenarios is essential to concentrate energy at the receiver (RX) side. Meanwhile, strong TX-RX coupling could ensure better power transfer efficiency (PTE), but may cause lower power delivered to load (PDL) when transmitter voltages are bounded. In this paper, we propose the frequency adjustment based PDL maximization scheme for MIMO MRC-WPT systems. We formulate such joint optimization problem and decouple it into two sub-problems, i.e., high-level frequency adjustment and low-level voltage adaptation. We solve these two sub-problems with gradient descent based and alternating direction method of multipliers (ADMM) based algorithms, respectively. We further design an energy-voltage transform matrix algebra based estimation mechanism to reduce context measurement overhead. We prototype the proposed system, and conduct extensive experiments to evaluate its performance. As compared with the PTE maximization solutions, our system trades smaller efficiency for larger energy, i.e., 361% PDL improvement with respect to 26% PTE losses when TX-RX distance is 10cm.

Mag-E4E: Trade Efficiency for Energy in Magnetic MIMO Wireless Power Transfer System

Magnetic resonant coupling (MRC) wireless power transfer (WPT) is a convenient and potential power supply solution for smart devices. The scheduling problem in the multiple-input multiple-output (MIMO) scenarios is essential to concentrate energy at the receiver (RX) side. Meanwhile, strong TX-RX coupling could ensure better power transfer efficiency (PTE), but may cause lower power delivered to load (PDL) when transmitter voltages are bounded. In this paper, we propose the frequency adjustment based PDL maximization scheme for MIMO MRC-WPT systems. We formulate such joint optimization problem and decouple it into two sub-problems, i.e., high-level frequency adjustment and low-level voltage adaptation. We solve these two sub-problems with gradient descent based and alternating direction method of multipliers (ADMM) based algorithms, respectively. We further design an energy-voltage transform matrix algebra based estimation mechanism to reduce context measurement overhead. We prototype the proposed system, and conduct extensive experiments to evaluate its performance. As compared with the PTE maximization solutions, our system trades smaller efficiency for larger energy, i.e., 361% PDL improvement with respect to 26% PTE losses when TX-RX distance is 10cm. 

Magnetic resonant coupling wireless power transfer (MRC-WPT) enables convenient device-charging. When MIMO MRC-WPT system incorporated with multiple relay components, both relay On-Off state (i.e., power routing) and TX current (i.e., current scheduling) could be adjusted for improving charging efficiency and distance. Previous approaches need the collaboration and feedback from the energy receiver (RX), achieved using side-channels, e.g., Bluetooth, which is time/energy-consuming. In this work we propose, design, and implement a multi-relay MIMO MRC-WPT system, and design an almost optimum joint optimization of power routing and current scheduling method, without relying on any feedback from RX. We carefully decompose the joint optimization problem into two subproblems without affecting the overall optimality of the combined solution. For current scheduling subproblem, we propose an almost-optimum RX-feedback independent solution. For power routing subproblem, we first design a greedy algorithm with $\frac{1}{2}$ approximation ratio, and then design a DQN based method to further improve its effectiveness. We prototype our system and evaluate it with extensive experiments. Our results demonstrate the effectiveness of the proposed algorithms. The achieved power transfer efficiency (PTE) on average is 3.2X, 1.43X, 1.34X, and 7.3X over the other four strategies: without relay, with non-adjustable relays, greed based, and shortest-path based ones.

Jialin Deng

Papers

Joint Power Routing and Current Scheduling in Multi-Relay Magnetic MIMO WPT System

Feruloylated oligosaccharides ameliorate MPTP-induced neurotoxicity in mice by activating ERK/CREB/BDNF/TrkB signalling pathway.

Network pharmacology-based analysis to explore the therapeutic mechanism of Cortex Dictamni on atopic dermatitis.

Mag-E4E: Trade Efficiency for Energy in Magnetic MIMO Wireless Power Transfer System

Dictamnine ameliorates chronic itch in DNFB-induced atopic dermatitis mice via inhibiting MrgprA3.