Research On Fault-tolerant Robust Placement Of Wireless Chargers For Directional Charging

Wireless Power Transfer(WPT)technology can eliminate the use of the wires and batteries,thus increasing the mobility,convenience,and safety of the electronic devices for all users.WPT has been widely used to replenish energy for Wireless Rechargeable Sensor Networks(WRSN).Previous studies have focused on maximizing charging power.Since wireless chargers and rechargeable sensors have a large number of precise electronic components,which are easy to be damaged,it is of practical significance to study the fault-tolerant performance of WRSN.This thesis studies the problem of fault-tolerant robust placement of wireless chargers for directional charging,focusing on the issue of charger and sensor failure in WRSN.This thesis designs the placement method of directional wireless chargers to improve the fault-tolerant performance of WRSN.For the case of charger failure in WRSN,it is expected that each sensor can receive non-zero power from multiple wireless chargers.Firstly,Charger Placement for Robust Coverage(CPRC)problem is formalized,that is to minimize the number of wireless chargers such that each sensor node can meet its coverage demand.We transform the problem to the equivalence integer program problem without performance loss through area partition and dominating strategy extraction.The CPRC algorithm is designed to solve the CPRC problem.It is proved that the CPRC algorithm has polynomial running time and approximation ratio of Hn,where Hn=1+1/2+…+1/n.Finally,largescale simulation experiments and small-scale physical experiments are conducted to verify the superiority of CPRC algorithm.The results show that the number of chargers of CPRC algorithm is at least 17.48%less than that of the comparison algorithm.For the case of sensor node failure in WRSN,it is expected to distribute the charging energy to each sensor as evenly as possible,so that the other normal sensor nodes can undertake the task of the failed sensor nodes.Firstly,the Charger Placement for Robust Utility(CPRU)problem is formalized,that is to determine the placement of wireless chargers to maximize the minimum charging utility of all sensor nodes.We transform the problem to the combinational optimization problem with finite strategy space by charging power approximation,area discretization and dominating strategy extraction.Then,through combining the greedy approach and binary search algorithm,we propose the CPRU algorithm to solve the problem.Finally,large-scale simulation experiments and small-scale physical experiments are carried out to verify the superiority of CPRU algorithm.The results show that the minimum charging utility of CPRU algorithm is at least 21.15%higher than that of the comparison algorithm.