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SUMMARY This paper proposes a current controller for signal injection-based control schemes such as those for parameter identification and position sensorless control. In a conventional current control system with voltage signal injection, the separation of the injected frequency components from the current is carried out by using band stop filters. However, the separation is not accurate, especially when the system is in the transient state and/or when the current controller bandwidth is close to the injected signal frequency. This leads to distortion of the transient response and affects the stability of the current control system. The proposed controller estimates the injected frequency components in the current on the basis of a motor model by using the injected signal as the input. Therefore, accurate signal separation is accomplished even in the transient state. The current controller's stability and dynamic performance are improved significantly. Experimental results are presented to validate the proposed method. Factors that play an important role in the implementation of the controller, such as time delay and parameter variation, are discussed. © 2014 Wiley Periodicals, Inc. Electr Eng Jpn, 187(1): 58–66, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22416

A new voltage limiter for fast torque response of IPMSM in the voltage saturation region is proposed, which we name the “maximum torque response voltage limiter.” In transient condition, the fastest response is vital while voltage saturation occurs. Thus, the problem is to divide the limited voltage into d- and q-axis voltages so as to generate the fastest torque response. The nonlinear relation between the torque and the d-q axis currents of the IPMSM makes the problem complicated. In our proposed method, both voltage equations and a torque equation of the IPMSM are considered and, based on the Lagrange optimization technique, explicit expressions for the d- and q-axis voltages are derived. Compared with conventional voltage limiters such as the constant phase angle method, the constant back emf method, and the constant d-axis voltage method, the proposed limiter yields faster torque response in the voltage saturation region, which is confirmed by computer simulation and experimental results. Furthermore, the proposed method uses simple software calculations, and it can be readily implemented without any modification of the hardware system. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(4): 57–69, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21078

When a reusable launch vehicle (RLV) returns to earth, it flies just by gliding without thrust. In this phase, one of the most likely and important faults to occur in the airframe is a jamming of the elevon. To tolerate this failure, the flight control system must keep stability and performance during such a failure. One of the effective ways to overcome this problem is to switch the controllers based on the information of the detected failure in the plant. Generally speaking, the controller must have integrators so as to yield the zero steady-state error for the controlled output even if there exist some perturbations in the plant dynamics. In this paper, the design of controller switching scenario is addressed especially focusing on the decision of the controller state at the instant of switching the controllers with integrator. Then, the proposed switching scenario is applied to the control of ALFLEX (Automatic Landing FLight EXperiment), which is the automatic landing experimental vehicle being developed for RLV, considering the occurrence of the jamming fault. Some simulations are shown to verify the usefulness of the proposed idea. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 80–90, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20356

The slip-frequency type vector control and the flux-feedback type vector control arc typical control methods of induction motors. It is shown that the two methods are similar except for a frame of reference. The flux-feedback-type vector control using the rectangular coordinate uses vertical and horizontal components of the rotor flux. The slip-frequency type vector control using the polar coordinate employs absolute value and angle of the rotor flux. Usually, the flux-feedback vector control does not use the rotor flux model but instead, the rotor flux observer for flux estimation. On the other hand, the slip-frequency type control uses the rotor flux model. Therefore the slip-frequency type vector control using the rotor flux observer is proposed. The proposed method is equivalent to the flux-feedback type vector control using the rotor flux observer. Then it is more robust than the conventional slip-frequency type vector control.

In this paper, sensorless control for synchronous reluctance motors (SynRMs) without signal injection and an inductance measurement for position estimation are proposed. In the case of SynRMs, accuracy of inductances is the most important factor in realizing precise position estimation because inductances are largely varied by a magnetic saturation phenomenon. Therefore, the inductance measurement method, which can measure appropriate inductances for position estimation, is important as well as a sensorless control method. The inductance measurement based on the observer is discussed, and the measurement method and the parameter adjustment method for improved stability of the closed loop are proposed. The proposed method can measure inductances easily and be applied for permanent magnet synchronous motors, too. Finally, the proposed sensorless control method is verified experimentally. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(4): 70– 80, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ eej.20274

This paper presents a novel on-line parameter identification method for sensorless control of Synchronous Reluctance Motors (SynRMs). Although conventional sensorless control methods based on mathematical models usually need some complex measurements of motor parameters in advance, the proposed identification method does not require them and can be realized on-line. The proposed method identifies motor parameters under sensorless control, so rotor position and velocity cannot be used to identify these parameters. However, the proposed method does not need rotor position and velocity, and identified parameters are not affected by these estimation errors. The sensorless control using identified motor parameters is realized, and the effectiveness of the proposed method is verified by experimental results. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(3): 62–69, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20258

This paper proposes new identification laws of an adaptive flux observer for speed sensorless vector controls. In speed sensorless vector controls of an induction motor with the adaptive observer, the speed identification system is known to be unstable in a part of the regenerating region. In addition, it is pointed out that the stator resistance variation interferes with the speed identification. Thus, it is necessary to find an adaptive scheme which can stabilize the identification system. In this paper, first, the stability on the parameter identification is discussed from the viewpoint of Popov's hyperstability. Second, identification laws for the speed and the stator resistance are proposed based on the new identification system which is derived by using the augmented error. Finally, the effectiveness of the proposed method is shown by experiments. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(1): 52–63, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20187

The requirement for the high-quality control of complex and/or structure-unknown plant is growing in the real-world industrial machine. Indirect Adaptive Control (IAC), which identifies model and updates the controllers automatically, is one promising way expected to meet this requirement. The conventional IAC, however, is required to know the structure of the controlled plant, that is, the order of its transfer function, in advance. This paper presents a new IAC scheme which makes use of Genetic Algorithm (GA) in its identification part. In the proposed framework, the information on the order of the plant is not required since the genetic algorithm searches both the structure of the plant dynamics and its parameters autonomously. A two-degree-of-freedom Internal Mode Control (IMC) is adopted as a basic control architecture since the indirect adaptation can be harmoniously embedded in it. The effectiveness of the proposed scheme is verified through numerical simulations and experiments applied to a velocity control of multimass systems. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 142(4): 45–55, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10103

In real control systems, certain constraints are placed on the input, state, and output values. If such constraints are violated, the system may become unstable, in a worst-case scenario. One of the promising approaches to solving this problem is to switch the controller according to the state of the closed-loop system. No useful design strategy for each controller, however, has yet been developed. In addition, the determination of the controller state at the instant of controller switching has not been investigated. First, this paper presents a new design methodology which merges the switching control and H∞ controller design into one design algorithm. Second, this paper presents a way of determining the controller state at the instant of controller switching. Finally, the proposed method is applied to force control of a one-DOF manipulator in order to demonstrate the usefulness of the proposed method. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(2): 68–75, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10082

In this paper, we present an architecture for neuro-hardware that can be realized in circuits of far smaller scale than in the conventional approach. In order to reduce the scale of the circuits, the architecture employs a new method of computing the membrane potential and the sigmoidal function by encapsulating the probabilistic properties into the relative delay between two pulses. The proposed architecture makes it possible to integrate more than 100 neurons in the latest FPGA chip, which is a 13-fold miniaturization compared to the conventional architecture. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 139(4): 48–55, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.1168

A new vector control system of an induction motor is proposed in this paper to reduce the influence of iron loss, which has been difficult to deal with. Recently, many methods have been proposed to improve the accuracy of torque control, concentrating on the identification of parameters and the adjustment of the controllers. But, it is necessary for experts to tune parameters initially in those methods. The new method can reduce the influence of iron loss by using a robust flux observer. By adding current decoupling control for compensation of the iron loss, a vector control system with high torque linearity can be constructed. © 2001 Scripta Technica, Electr Eng Jpn, 137(3): 59–66, 2001

Artificial neural networks have the potential for parallel processing with integrated circuit technology. Over 1 million gates are now available in the latest FPGA (Field Programmable Gate Array). However, the sum-of-product circuit used for evaluating inputs of the neuron model is complex and not effective for hardware implementation by FPGAs. In this paper, an improved calculation algorithm of the perceptron-type neuron model is proposed, based on multidimensional binary search. Since the search does not need the sum-of-product circuit, the designed neuron circuit is small and fast. It is suitable for hardware implementation. © 2001 Scripta Technica, Electr Eng Jpn, 138(2): 24–32, 2002

A rotor position estimation of a cylindrical brushless dc motor at standstill has been difficult to obtain. Therefore, torque control of a motor has been difficult at starting of the motor, and realization of the position estimation at standstill has been sought. This paper proposes a simple processing of a rotor for which nonmagnetic materials are pasted on the rotor surface. This processing generates an eddy current on nonmagnetic materials and causes an opened phase voltage change according to rotor position. The experimental results using a microcomputer show that it is possible to estimate rotor position of the cylindrical motor despite a standstill by using the opened phase voltage change. ©�1998 Scripta Technica, Electr Eng Jpn, 126(1): 52–60, 1999

A new parallel running system of GTO PWM inverters is proposed to achieve a high reliability and large capacity inverter system. In the system, a separate control circuit with a local processing unit is used for each inverter to prevent total system breakdown. A dc power source is also separated for each inverter. A circulating current which is caused by frequency differences of the oscillators in the control circuits and dc voltage differences is reduced by a feedback control. From amplitude and phase of the circulating current, a supervisory processing unit decides which control variable should be changed between amplitude and phase of the output voltages, and sends a signal to the local processing unit. As a result, load balance of the inverters is achieved.

Pneumatic and magnetic levitation systems for ultraspeed (500 km/h) trains are now being studied intensively in many countries. This paper analyzes the behavior of a monopolar vehicular coil-type superconducting levitation system by the steady-state periodic solution method and shows that this system behaves in the same way as the conventional system as regards lift force, drag force and lift-to-drag ratio. It also shows that the magnetic force is always positive and sufficiently strong (larger than a damping time constant of 1 sec).