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A real-time solar cell based in vivo dosimetry system (SC-IVD) was developed using a flexible thin film solar cell and scintillating powder. The present study evaluated the clinical feasibility of the SC-IVD in electron beam therapy.A thin film solar cell was coated with 100 mg of scintillating powder using an optical adhesive to enhance the sensitivity of the SC-IVD. Calibration factors were obtained by dividing the dose, measured at a reference depth for 6-20 MeV electron beam energy, by the signal obtained using the SC-IVD. Dosimetric characteristics of SC-IVDs containing variable quantities of scintillating powder (0-500 mg) were evaluated, including energy, dose rate, and beam angle dependencies, as well as dose linearity. To determine the extent to which the SC-IVD affected the dose to the medium, doses at R90 were compared depending on whether the SC-IVD was on the surface. Finally, the accuracy of surface doses measured using the SC-IVD was evaluated by comparison with surface doses measured using a Markus chamber.Charge measured using the SC-IVD increased linearly with dose and was within 1% of the average signal according to the dose rate. The signal generated by the SC-IVD increased as the beam angle increased. The presence of the SC-IVD on the surface of a phantom resulted in a 0.5%-2.2% reduction in dose at R90 for 6-20 MeV electron beams compared with the bare phantom. Surface doses measured using the SC-IVD system and Markus chamber differed by less than 5%.The dosimetric characteristics of the SC-IVD were evaluated in this study. The results showed that it accurately measured the surface dose without a significant difference of dose in the medium when compared with the Markus chamber. The flexibility of the SC-IVD allows it to be attached to a patient's skin, enabling real-time and cost-effective measurement.

This article proposes a precise identification scheme of an interior permanent-magnet synchronous motor (IPMSM) flux linkage through experimental tests considering motor nonlinearities, such as the magnetic saturation and spatial harmonics. In the proposed scheme, the flux linkage is identified based on the voltage equation of IPMSM. The fundamental and harmonic electromotive force in the rotor reference frame is obtained in real time by applying a discrete Fourier transform with the phase compensation of the time delay due to digital control and pulsewidth modulation. The effect of the inverter nonlinearity is compensated using an experimentally obtained lookup table. Based on the identified flux-linkage map, a flux-based IPMSM model that accurately simulates motor behavior can be constructed. The effectiveness of the proposed flux-linkage identification scheme is verified through the comparison of simulation and experimental results.

This paper presents the developments of sensorless control of an interior permanent-magnet synchronous motor (IPMSM) based on signal injection for the last five years. At first, modeling of an IPMSM is discussed. In contrast to the conventional inductance based voltage model, the flux model considering saturation and spatial harmonics of IPMSM is introduced. For the identification of the flux model, either finite element analysis or experimental test is required. Secondly, based on the flux model, some sensorless control methods of IPMSM for the traction of a vehicle, where IPMSMs are heavily saturated for higher torque density, are described. In contrast to the belief that there should be a certain saliency for the sensorless control based on the signal injection, it is explained that sensorless control is possible even in a reversed saliency region. Thirdly, the methods to decrease the magnitude of the injected signal itself are discussed together with the optimization of the frequency of the signal. The simulation and test results for typical automotive-grade IPMSMs with several sensorless methods exploiting square-wave signal injection are presented, and the physical meaning of the test results are discussed. Finally, future outlook based on recent developments is addressed.

This article analyzes the instantaneous flux trajectory of a permanent-magnet synchronous machine (PMSM) in the six-step operation. Not only the flux dynamics but also the instantaneous voltage vector are included in the analysis. Based on the analysis, a time-optimal voltage vector transition scheme is proposed for the six-step operation of a PMSM. In the proposed scheme, a few steps are added in the transition of the voltage vectors to bring additional degrees of freedom, and they can enhance the dynamic performance conspicuously under the given current constraint. Simulation and experimental results are provided to verify the proposed scheme. For the stepwise torque command, the proposed scheme saves the settling time more than 50% with 60% reduction of the peak current compared to the conventional transition method.

This paper proposes an analysis of the skin effect in squirrel cage induction motor under high-frequency signal injection. The high-frequency signal is usually injected for sensorless control and parameter identification. Since both of them require the accurate identification of impedance characteristics, the skin effect under the injected signal should be analyzed in detail. Meanwhile, the rotor bar is much thicker than the stator conductor, so it is severely affected by the skin effect at the frequency of the injected signal. Thus, the proposed analysis focuses on the skin effect on the rotor bar at high-frequency. The proposed analysis is entirely based on the finite element analysis, and it considers the practical operating condition of the induction machine, driven by the field oriented control. The variation of high-frequency rotor resistance and inductance according to the injected frequency and current for the torque has been represented by finite element analysis.

This paper analyzes the torque equation of an interior permanent-magnet synchronous machine (IPMSM), including magnetic saturation, spatial harmonics, and the variation of the magnetic energy. Based on the analysis, a torque-sensorless method is proposed to identify an IPMSM’s torque map. Since magnetic energy cannot be measured in the experiment, its effect on the torque is indirectly considered using the gradient to dq-currents. In this paper, the torque gradient is formularized with the flux-linkage map; it is verified by finite element analysis (FEA). With the formularized torque gradient, the proposed method reconstructs IPMSM’s torque map through the gradient theorem. Experiments veify the proposed method’s effectiveness.

The present study aims to reduce the pitch motion of an assault amphibious vehicle system in seaways by waterjet impeller revolution rate control. A series of seakeeping tests were performed in a towing tank with a 1/4.5-scale model. This vehicle is manufactured as a box-shaped hull, and since an appendage that generates lift force is attached, the amount of change in pitch motion is large according to the forward speed. For pitch motion reduction, the impeller revolution rate and resultant pitch moment were controlled through a proportional-integral-derivative controller. Improvements in seakeeping performance were examined in both regular and irregular conditions by the model tests in terms of root mean square of pitch motion. The tuned controller decreased pitch motion by more than 60%.

This paper analyzes the convergence of signal-injection sensorless control (SISC) especially for heavily saturated interior permanent-magnet synchronous motors (IPMSMs). In the analysis, it is revealed that the harmonic inductance and the operating current variation are critical factors in determining the operational limit of SISC. The clear boundary of SISC for an IPMSM can be obtained through the proposed convergence analysis. Based on this analysis, a control algorithm is proposed to extend the operational limit of SISC. With the proposed method, the torque capability under SISC can be maximized. Simulations and experiments are performed to verify the proposed method.

In this paper, the feasibility of signal injection sensorless control (SISC) in surface mounted permanent-magnet synchronous motors (SMPMSMs) is discussed. At first, dynamic inductances of a target SMPMSM according to rotor position and dq-axes currents are measured from an experimental test. Based on the measured inductances, current response induced by the injected voltage is calculated. The induced current signal in every operable dq-axes current point is analyzed with an index variable. An optimal current trajectory for the SISC is proposed after the analysis. By adopting optimal trajectory control (OTC) instead of maximum torque per ampere (MTPA) control, the performance of the conventional SISC of the SMPMSM can be conspicuously improved at the cost of slightly increased copper loss. The proposed method is verified with experimental results.

In signal injection sensorless drives, the injection voltage cannot be reduced under a certain value. The lower limit of the injection voltage is mainly enforced by the inverter nonlinearity that causes distortion of the injection voltage and degradation of the position estimation performance. After analyzing the inverter nonlinearity during the voltage injection, it is revealed that parasitic capacitances of insulated-gate bipolar transistors have positive effects on inverter output linearity and sensorless control. Based on this analysis, this paper proposes a method to reduce the injection voltage by connecting additional capacitors to the output terminals of the inverter. Simulation and experimental results are provided to verify the effectiveness of the proposed idea. In the experiments, using the capacitor-integrated inverter, it is shown that the injection voltage can be reduced by more than half without degrading the position estimation performance.

In this paper, the stability of position control loop under signal-injection sensorless control (SISC) considering the non-ideal characteristics of IPMSMs has been analyzed. To take into account the effects of the torque ripple and the inductance variation due to the non-ideal characteristics in frequency-domain analysis, they are linearized using Taylor series at each rotor position and operating current. Using the small signal model, it is revealed that the non-ideal characteristics make the system unstable and cause oscillation under position control with SISC. It is also revealed that the stability varies according to the rotor position and load torque even if the same controller gains are used. The validity of the proposed analysis is verified through simulations and experiments.

In signal-injection sensorless control, the estimated rotor position includes considerable error induced by the inverter nonlinearity effects. It would degrade overall performances of the sensorless drive, and it could even result in the failure of the position tracking. In this paper, an improved signal-injection sensorless control thanks to the compensation of the voltage error is proposed. The compensation depends on a precise calculation method of the voltage error induced by the inverter nonlinearity. The proposed method effectively reduces the voltage disturbance especially under the switching frequency injection for sensorless control. The performance of the proposed method is verified by computer simulations and experimental results.

In this paper, a method to mitigate narrow pulse effect for extending operational range of low-cost motor drive system, where the bootstrap circuit is embedded, is described. Because of the narrow pulse effect, dead zone appears in output of the inverter where voltage cannot be synthesized. To overcome the narrow pulse effect, the proposed method combines the inverter nonlinearity compensation and dead time elimination (DTE) method. By mixing those two properly, the narrow pulse effect can be reduced effectively and the output capability of the inverter increases conspicuously. Simulations and experiments are carried out to verify the effectiveness of the proposed method. The experimental results reveal 6 % enhancement of torque capability at two times of base speed.

In practical IPMSMs, there are always undesirable torque ripples due to the spatial harmonics. Most existing methods attempted to reduce torque ripples based on torque modeling, but their performances were not satisfactory due to inaccurate model of an IPMSM itself. This paper analyzes the torque ripple based on an actual torque map, which is more practical and accurate compared to torque-model-based analyses. Based on the analysis, a torque ripple minimizing method implemented with a few resonant current regulators is proposed. Simulation and experimental results are provided for the verification of the proposed method. For the experiments, the proposed method is performed and evaluated through an experimental torque map. Through the experimental result, it is verified that target harmonic order of torque ripple can be reduced to a tenth of the original value by the proposed method.

In this paper, a design methodology and control algorithms of an interior permanent-magnet synchronous machines (IPMSM) for absolute position sensorless drive are proposed. In conventional research on absolute position sensorless control, initial motion of the rotor was inevitable, which was not preferred in many applications. In order to eliminate the initial motion, an IPMSM with an asymmetric rotor and search coils is devised. In the proposed IPMSM, the information of the absolute position is included in the voltage signals at the search coils. By measuring and analyzing the search coil voltages, the absolute position can be estimated without any initial motion of the rotor. Overall performances of the proposed motor are evaluated through rigorous finite element analyses and experimental tests.

In the square-wave voltage signal injection sensorless drive of the interior permanent-magnet synchronous machine, the injection voltage can be distorted by the inverter nonlinearity effects especially when the injection voltage is low. If that happens, a high-frequency (HF) current signal which contains the rotor position information could be also distorted, which directly leads to an error in the position estimation. This paper analyzes the effects of the inverter nonlinearity on injection voltage, on induced current ripple, and on the position estimation performance in sequence and proposes a voltage injection method to minimize the impact of the inverter nonlinearity by the regulation of the HF current ripple. By simulations and experiments, the performance of the proposed method has been verified. The experimental results show 19.7% reduction of position estimation error under 15% of rated voltage signal injection without increasing the current ripple at a certain operating condition. Moreover, the performance of position estimation is kept uniform regardless of the loading condition.

This paper proposes DC-link voltage design rules of a motor emulator (ME) for interior permanent-magnet synchronous motors (IPMSMs). The design rules are useful for the optimization of ME's ratings, which can significantly affect the cost of the whole system. For the DC-link voltage design, this paper considers not only conventional MEs that emulate only fundamental current, but also high-bandwidth motor emulator (HBME) which can emulate the current in the whole frequency range from DC to the switching frequency of the inverter under test. Through appropriate approximations, design guidelines for ME DC-link voltage are provided. Simulation and experimental results are presented with a 3.6 kW 8-pole 12-slot IPMSM model to verify the validity and effectiveness of the proposed design rule.

This paper proposes an identification scheme of interior permanent-magnet synchronous motor (IPMSM) flux-linkage through experimental tests considering the magnetic saturation and spatial harmonics. In proposed scheme, flux-linkage is identified based on the voltage equation of IPMSM. The electro-motive force in rotor reference frame is obtained in real time by applying discrete Fourier transform on the voltage reference of proportional integral and resonant current controller, with precise compensation of the time delay from digital control and PWM on fundamental and harmonic components. The effect of the inverter nonlinearity is compensated using experimentally obtained look up table. Simulation model is constructed using the identified flux-linkage map. The effectiveness of the proposed flux-linkage identification scheme in simulating IPMSM control algorithms is verified through the comparison of simulation and experimental results.

This paper proposes a compensation method for precise position-sensorless control using high-frequency pulsating voltage injection and the criterion for applicability of the proposed compensation method is discussed. Theoretical background of the proposed 3-dimensional compensation table as well as the implementation method is described and it is disclosed that the real rotor position and the convergent position should have one-to-one relationship for precise estimation of the rotor position. Also, in the proposed method, additional compensation for inductance harmonics or voltage distortion is not needed, since they are all reflected in the pre-commissioned table. Experimental results including speed and position control validate the proposed compensation method maintaining the position error within ±2°E at all load conditions and rotor positions.

This paper analyzes the convergence of the rotor position tracking in signal-injection sensorless control especially for heavily saturated IPMSMs. In the analysis, it is revealed that the harmonic inductance and the operating current variation are critical factors determining the operation limit of signal-injection sensorless control. Considering this, the feasibility region of signal-injection sensorless control is precisely identified. Based on this analysis, a control scheme to extend the feasibility region is proposed. With the proposed method, the torque capability can be maximized under signal-injection sensorless control. Simulation and experimental results are provided to verify the proposed method.

Swash plate type piston pumps, when applied to electro-hydrostatic actuators, operate mostly in the mixed lubrication speed range, compensating for position control errors of actuator parts. Therefore, their hydrostatic piston shoe bearings should be designed to minimize frictional and leakage losses as well as the wear rate, which could be increased by insufficient hydrodynamic lubrication in the low speed range. In this study the influence of the balance and recess ratios of piston shoe bearings on their power losses were investigated under mixed friction conditions. The fundamental properties of piston shoe bearings tilted on a swash plate, such as the lift force, righting moment and leakage flow rate, were computed using a simplified Navier-Stoke’s equation, to obtain an insight into methods of minimizing the power losses of piston shoes exposed to mixed friction. Six test models were designed with these two parameters decoupled and tested on apparatus which was developed to measure the friction force and leakage flow rate of a piston shoe in the motor speed range below 100 rpm. The tilting motion of the piston shoes could be observed in the mixed friction speed range and power losses could be reduced by increasing their resistance to external tilting moments.

In this paper, a design and control method of interior permanent magnet synchronous machines (IPMSMs), which is controlled in sensorless position control mode based on high frequency signal injection, for absolute position estimation and control capability has been addressed. Although conventional motor designs with symmetric structure work well in sensorless speed and torque control modes, their actual mechanical rotor position is unidentifiable since their inductance profile is repeated for every electrical revolution. To realize the mechanical rotor position estimation capability, from a given template six-pole/nine-slot IPMSM with symmetric structure, an IPMSM design with asymmetric winding and asymmetric rotor geometry is proposed and constructed as a prototype. Based on the proposed design, the mechanical rotor position can be identified at the cost of slight degradation of basic motor characteristics such as torque ripples, harmonics in back EMF, and so on. The overall performances of the proposed IPMSM have been evaluated by rigorous finite element method simulations and experiments.

In this paper a new hybrid-type control system is proposed which reduces the pump speed of an electro-hydraulic actuator consisting of a pressure-compensated variable displacement piston pump and a valve-controlled hydraulic cylinder, whenever the flow rate demand is low. In order to avoid interfering with the pressure regulator which also has an effect on swash plate angle, the pump speed is changed in proportion to the mean value of the speed component of position commands. Additionally a pressure switch is employed to prevent the system pressure from getting lower than a reference value. Based on computer simulation & experimental results, it is shown that the hybrid control can save the idling power up to 44% at a stand-by mode by reducing the pump speed from 1,800 rpm to 600 rpm without affecting the dynamic response of the electro-hydraulic actuator.

In this paper a sharp-edged type damping orifice for an aircraft door damper were designed, where the dynamic viscosity of working fluid were assumed to change up to 400cSt. The discharge coefficient of the damping orifice were investigated by CFD analyses and experiments. In particular, the influences of orifice diameter, edge angle, flow direction and the Reynolds number were taken into consideration. Based on this, it has been deduced how high Coulomb friction forces of damper seals is to be allowed to meet the performance criterion with respect to the orifice size.

This paper proposes a novel control scheme for the fast current control of permanent magnet synchronous machines. The proposed method mainly works in the transient state of current control without deteriorating steady-state characteristics. The proposed method is applicable in a wide range of speed: in the speed below the base speed and in the flux weakening region. Using the proposed method, the reference values of currents are modified so that the currents follow the so-called “shortcut” trajectory in the coordinate plane. The effectiveness of the proposed method is confirmed by computer simulations and experiments. The settling time is reduced by 55% compared with that of the conventional method.

In order to provide the capsule endoscopes with active mobility in the human digestive system, a new twistable thread module mechanism which forms a neutral, right-handed or left-handed thread based on the rotating direction of the capsule is proposed in this paper. Being installed with disk-type permanent magnets, the capsule endoscope can be put into either a spiral motion or translation motion by an external permanent magnet mounted on a rotational actuator, which can also change the moving direction of the capsule by just leading it in the desired direction. In the in-vitro tests on a straight artificial tract whose properties were made similar to those of a pig’s colon, the thread module could propel the capsule as fast as 400 mm/min when the external magnetic field was rotated at 24 rpm. In order to achieve this speed, 0.6 mm thick arc-shaped wire-type blades with a curvature of 6.25 mm were used to work like helical threads. And it was also necessary that the radial and axial distance of the external magnet from the capsule were maintained at optimum values, while at the same time the rotating axes of the external magnet and the capsule were parallel to each other. To make the latter possible, a control system has been contrived, where a multi-DOF robot was employed to automatically manipulate the position and orientation of the external magnet. Using Hall-effect sensors installed inside the capsule, its position and orientation data were detected to help the manipulator compensate the parallelism and distance errors between the external permanent magnet and the capsule, in repeated cycles. The effectiveness of the control system was verified by in-vitro tests with an arcshaped curved tract, where the capsule speed was kept over 90% of its maximum.

In order to provide the capsule endoscopes with active mobility in human digestive system, a twistable thread module mechanism is proposed in this study. The twistable thread module forms a neutral, right-handed or left-handed thread based on the rotational direction of the capsule, which is rotated by the interactions of a revolving external magnet and the disk-type permanent magnets within the capsule. The performance of the twistable thread module mechanism was evaluated by measuring the moving speed of the capsule in an artificial tract, while changing the parameters such as pitch angle, number of thread modules, rotational speed of the external magnetic field and the distance between the external magnet and capsule. It was observed that the capsule moved faster as the pitch angle or the rotation speed of the external magnet was increased. In the double thread modules case, when the pitch angle was at 35° and the external magnet rotated at 24rpm, the capsule could move as fast as 300 mm/min, which is about 60% of the ideal speed of the spiral motion, caused by the threads slip. In the triple thread modules case, although the threads slip decreased, the capsule speed did not increase as expected because of its high friction torque, that hinders the steady rotation of the capsule body. And also, the magnet distance range dropped abruptly. In a living pig’s colon, the capsule endoscope propelled by the double thread modules with the pitch angle 35° and external magnet rotating at 18rpm, moved at a speed greater than 200mm/min, which was 83% of the capsule speed as measured in the in-vitro tests.

In signal injection sensorless drives, the injection voltage can't be reduced under a certain value. The lower limit of the injection voltage mainly comes from the inverter nonlinearity that distorts the injection voltage and degrades the position estimation performance. After analyzing the inverter nonlinearity during the voltage injection, it is revealed that the parasitic capacitances of IGBT switches have a positive effect on sensorless control. Based on this analysis, this paper proposes a method to reduce the injection voltage by connecting additional capacitors to the inverter output. Simulation and experimental results are provided to verify the effectiveness of the proposed idea. In the experiment, using the capacitor-integrated inverter, the injection voltage can be reduced to less than a half without degrading sensorless control performance.

This paper analyzes and compares position estimation performances of fundamental-model-based sensorless control methods considering the effects of inverter nonlinearities and parameter estimation errors. Based on the investigation of four conventional sensorless control algorithms, estimated position error from each algorithm is represented in a quantitative manner. This representation is helpful in understanding how the error influences the position estimation performance. And, it is revealed that steady state position error can be expressed as a unified formula regardless of position estimation methods. The validity of the analysis is verified by computer simulations and experimental results.

In this paper, a design methodology of IPMSM for absolute position sensorless drive is proposed. In conventional researches on the absolute position estimation, initial motion of the rotor was required, which was not allowed in many applications. To eliminate the initial motion, an IPMSM with eccentric rotor with search coils is devised. In the proposed design, the information of the absolute position is included in the voltage signals at the search coils. By measuring the search coil voltages and analyzing them, the absolute position can be estimated without the initial motion of the rotor. The overall performances of the proposed motor design are evaluated by rigorous finite element analyses and experimental tests.

This paper proposed a new life test method of pneumatic cylinders used in pneumatic system, whose loads consist of working pressure, piston velocity, and working temperature. It is expected to reduce accelerated life test time greatly in case of accelerated life test with creating combined accelerated model of these three factors. We can determine the maximum accelerated factor by calculating the combined accelerated factor of working pressure, piston velocity and working temperature for various cases.

In square wave voltage signal injection sensorless drive, the injection voltage can be distorted by the inverter nonlinearity effects especially when the injection voltage is low. If that happens, High Frequency (HF) current signal which contains the rotor position information could be also distorted, which directly leads to an error in the position estimation. This paper analyzes the effects of the inverter nonlinearity to injection voltage, to induced current ripple, and to the position estimation performance in sequence and proposes a voltage injection method to minimize the impact of the inverter nonlinearity by the regulation of HF current ripple. By simulations and experiments, performance of the proposed method has been verified. The experimental results show 34.9% reduction of noise input in the position estimation and 19.7% improvement of the position estimation performance under 15% of rated voltage signal injection.

In this paper, a design and control method of Interior Permanent Magnet Synchronous Machines (IPMSMs), which is controlled in position sensorless mode based on high frequency signal injection, for absolute position detection and control capability has been addressed. Although conventional motor designs with symmetric structure work well in sensorless speed and torque control modes, their actual mechanical rotor position is unidentifiable since their inductance profile is repeated for every electrical revolution. In order to realize the mechanical rotor position detection capability, from a given template 6-pole/9-slot IPMSM with symmetric structure, an IPMSM design with asymmetric winding and asymmetric rotor geometry is proposed and constructed as a prototype. Based on the proposed design, the mechanical rotor position can be identified at the cost of slight degradation of basic motor characteristics such as torque ripples, harmonics in back EMF, and etc. The overall performances of the proposed IPMSM have been evaluated by rigorous FEM and experimental test.