A novel indirect vector control system for induction machines is proposed. To ensure accurate rotor flux orientation in face of severe thermal drift of the rotor resistance during practical operation, the system features a new rotor resistance adaptation method. The latter is based on the elimination of the q-axis rotor flux, which is calculated from steady-state relations of the induction machine. Compared with other rotor resistance adaptation methods found in the literature, for example, observer-based and model reference adaptive system-based methods, the proposed one poses much less computation burden and is quite convenient for online implementation. The basic principle and theoretical analysis are presented. The effects of other motor parameters on the adaptation method are also investigated. Based on the investigation results, a stator resistance compensation algorithm is incorporated to reduce the impact of incorrect stator resistance at low speeds. Some non-negligible issues in practical applications, such as dead-time effect and transport delay of digital pulse-width modulation process, are also investigated and taken care of. Simulation and experimental results show good dynamic and steady-state performance.Nomenclature u sd , u sq stator voltages in synchronously rotating frame i sd , i sq stator currents in synchronously rotating frame c rd , c rq rotor fluxes in synchronously rotating frame r s , r r stator and rotor resistanceŝ r s ,r r estimated stator and rotor resistances/stator and rotor resistances used in control system that are considered not necessarily accurate l s , l r , l m stator, rotor and main inductances σ leakage factor (= 1 − l 2 m /(l s l r )) l σ total leakage inductance ( = σl s ) t r ,t r actual and estimated rotor time constants (t r = l r /r r ) ω 1 , ω r synchronous and rotor angular frequencies θ 1 , θ r position angles of rotor flux and rotor shaft ω 2 , θ 2 slip frequency and slip angle (ω 2 = ω 1 − ω r , θ 2 = θ 1 − θ r ) T e electromagnetic torque n p number of pole pairs p differential operator ( = d/dt) T s sampling period t d delay time

To effectively perform the probabilistic fatigue/creep coupling optimization of a turbine bladed disk, this paper develops the fuzzy multi-extremum response surface method (FMERSM) for the comprehensive probabilistic optimization of multi-failure/multi-component structures, which absorbs the ideas of the extremum response surface method, hierarchical strategy, and fuzzy theory. We studied the approaches of FMERSM modeling and fatigue/creep damage evaluation of turbine bladed disks, and gave the procedure for the fuzzy probabilistic fatigue/creep optimization of a multi-component structure with FMERSM. The probabilistic fatigue/creep coupling optimization of turbine bladed disks was implemented by regarding the rotor speed, temperature, and density as optimization parameters; the creep stress, creep strain, fatigue damage, and creep damage as optimization objectives; and the reliability and GH4133B fatigue/creep damages as constraint functions. The results show that gas temperature T and rotor speed ω are the key parameters that should be controlled in bladed disk optimization, and respectively reduce by 85 K and 113 rad/s after optimization, which is promising to extend bladed disk life and decrease failure damages. The simulation results show that this method has a higher modeling accuracy and computational efficiency than the Monte Carlo method (MCM). The efforts of this study provide a new useful method for overall probabilistic multi-failure optimization and enrich mechanical reliability theory.

Since high magnetic field (MF) intensity can improve the image quality and reduce magnetic resonance imaging (MRI) acquisition time, the field intensity of MRIs has continued to increase over the past few decades. Although MRIs in most current hospitals are 0.5 T-3 T, there are preclinical studies have been carried out using 9.4 T MRI, and engineers are also putting efforts on building MRIs with even higher MFs. However, the accompanied safety issue of high-field MRIs is an emergent question to address before their clinical applications. In the meantime, the static magnetic field (SMF) has been shown to inhibit tumor growth in previous studies. Here, we investigated both the safety issue and the anti-tumor potentials of 3.7 T-24.5 T SMFs on GIST-T1 gastrointestinal stromal tumor-bearing nude mice. We followed up the mice three weeks after their exposure to high SMF and found that none of the mice died or had severe organ damage, except for slightly decreased food intake, weight gain, and liver function. Moreover, the tumor growth was inhibited by 3.7 T-24.5 T SMFs (up to ∼ 54%). It is interesting that the effects are more dependent on MF gradient than intensities, and for the same gradient and intensity, mice responded differently to hypogravity and hypergravity conditions. Therefore, our study not only demonstrated the safeness of high SMFs up to 24.5 T on mice but also revealed their anti-tumor potentials in the future.