This paper describes the validation of time-delay compensation by communication disturbance observers (CDOBs) of different orders in bilateral teleoperation systems. A time-delay compensation method based on the concept of network disturbance (ND) and CDOB is novel and is as effective as the Smith predictor. Furthermore, the method can be used even when the value of delay time is not available, since the method does not employ delay-time model. Therefore, it is expected that the method can be used in the case of time-varying delays such as delays over the Internet. However, time-delay compensation in the case of time-varying delays has not been sufficiently verified yet. In this study, we compare the time-delay compensation by CDOBs of different orders. The experimental results pertaining to both constant and time-varying delays are shown to compare the time-delay compensation by CDOBs of different orders.
The dynamics modeling of a plant was developed by using Q-learning, which is one method of reinforcement learning. We thought the modeling of the dynamical system to be the function approximation problem for the system output response signal, and enhanced reinforcement learning to the modeling method of the dynamical system. We describe that this modeling method guarantee to offer highly accurate dynamics models by numerical samples, which deals with incinerator's combustion. Results of numerical simulation show that the predictive control method using these models has robust tracking property.
We have developed a new fast-seeking method for the control of optical disk drives. Fast-seeking is performed by means of velocity control in two modes. The lens velocity in the first mode, which is estimated using a multi-rate observer, is equal to the pickup unit velocity, and it is controlled in order to prevent the lens from vibrating. The lens velocity in the second mode is equal to the specified target velocity, and it is controlled in order to improve the laser-spot positioning accuracy. A DVD-ROM drive is tested to confirm that the control system we propose significantly improves the seeking capabilities.
Recently, there has been increasing demand for quiet motors, and the same trend has been observed in the case of induction motors. In induction motors, electromagnetic noise is sometimes the predominant acoustic noise. In small motors, the major cause of vibration and noise is electromagnetic forces resulting from the combination of harmonic fluxes in the air gap. In this study, the spatial distribution of fundamental and harmonic time electromagnetic forces was studied by using search coils, by performing FEM analysis, and by using conventional equations. In a four-pole 2.2kW motor, harmonic electromagnetic forces were measured using 36 search coils on the inner surface of the stator teeth, and the spatial distribution of electromagnetic forces was obtained at each time harmonic frequency. Spatial distribution was also analyzed by FEM, and the results were analytically validated by using conventional equations. On the basis of these analyses, the spatial distribution of electromagnetic forces for various time harmonics was confirmed. These results can be used in the design and development of quiet motors.
In this study, we examine the relationship between harmonic voltage injection, acoustic noise, and position estimation performance in a PMSM when a position-sensorless control method involving harmonic voltage injection is used at low speeds. Further, we propose a novel control method for voltage injection; this method can be used to reduce acoustic noise in the motor. The proposed control method is verified by performing numerical simulations and carrying out experiments using a 4-pole, 2-kW, 2100-rpm IPMSM (interior permanent-magnet synchronous motor).
This paper proposes a method for compensating voltage errors using a parallel disturbance observer and a current controller for V / f control in the d-q rotational frame. The parallel disturbance observer uses a fast-responce observer and a slow-responce observer to separate the back electromotive force (EMF) from the estimated disturbance voltage. The voltage error is thus efficiently corrected using the proposed method. The proposed method is validated on the basis of the experimental results. This method can be used to decrease current distortion to less than 1/9 that observed in the conventional method.
A novel double-series resonant filter is implemented in order to reduce the high-frequency return current noise generated by AC-powered electric cars with AC/DC PWM converters and inverters. The double-series resonant filter is placed between a main transformer and a converter. The resonant filter is tuned so that the noise signal due to the return current is attenuated at the exact noise frequency; for example, the 105-kHz component of an ATS (Automatic Train Stop) signal is attenuated by this filter. The filter has two LCR resonant circuits, one of which is in parallel with a resistance. This filter design helps achieve good attenuation at the noise frequency and helps limit unnecessary amplification at other frequencies. First, a test filter is realized, and the inductance and capacitance of this filter are in good agreement with the corresponding values in the filter design. Then, the filter is included in a full-scale test system with a main transformer and a converter. Then it is confirmed that a 5-dB reduction in the return current noise is achieved by using the proposed filter. Finally, the return current noise in the test system is confirmed to be well below the desired regulation level. This is expected to help realize simple methods for dealing with the effects of impedance at high frequencies in the main transformer.
A previously reported vector control method for position sensorless permanent magnet synchronous motors involves the use of controllers with simple block configurations. However, the performance of this method can be affected by the erroneous setting of the motor parameters because a feedback compensator is not used. In this study, the effects of these errors on the steady-state performance of the drive control examined under various error conditions. It was found that the amplitude of the motor current increases when the parameter error is nonzero; the effect of the back-EMF parameter error was especially found to be large. On the basis of this observation, the use of a new compensator named “back-EMF parameter adjustment” is proposed. Simulation results and experimental results showed that the proposed method can compensate for the increase in the amplitude of the motor current resulting from the occurrence of motor parameter errors. A theoretical analysis showed that the performance of our vector control method, which involves the use of the new compensator, is affected only by errors in the d-axis inductance parameter Ld. Therefore, even if there are errors in the other motor parameters, the motor current for the constant load condition can be minimized by using the proposed method.
In this paper, we present an excellent method named pole-zero cancellation (PZC) for designing motor control systems. PZC is performed in the z plane. A control system consists of three controllers, i.e., a speed controller, a position controller, and an adaptive identifier. The speed controller has two degrees of freedom: disturbance suppression and tracking speed, both of which can be regulated. The pulse transfer function used for regulating the tracking speed has two poles and one zero. When one pole and one zero coincide and cancel each other, the pulse transfer function is of the first-order lag type, and overshoots do not appear. The adaptive controller determines the coefficients of the pulse transfer function and adjusts the speed controller automatically so that the poles and zeros coincide. The transfer function of the position controller also has one pole and one zero, which cancel another pole and zero; pole 1 in the closed loop is not cancelled, and hence, position overshoots do not appear. A 2.2-kW induction motor is tested. The motor torque is controlled using a rapid torque control method. In this paper, first, the tracking-speed characteristics and the tracking-position characteristics are presented. Next, the identified transient coefficients are given, and finally, the disturbance-suppression characteristics are discussed. The experimental results prove the usefulness of the proposed method.
In this paper, a digital predictive valley current control is proposed for the 4th order boost converter. Detailed mathematical models of the converter system are formulated and then predictive average, peak and valley current control laws, in terms of valley current, are derived. Stability analysis of average, peak and valley current control, under trailing-edge modulation is carried out in the discrete domain. These investigations show that the average and peak current control schemes, with trailing edge-modulation, are unstable for certain duty ratio's, while the valley current control scheme is stable for all duty ratio's, 0 < D < 1. These theoretical studies are validated through the time-domain simulation studies. Discrete compensator is designed using digital direct design approach in order to realize the load voltage regulation together with the valley current control. Closed-loop performance of the proposed control scheme is simulated for different operating conditions. Experimental results are provided to validate the simulation results and theoritical stability predictions.
Permanentmagnet (PM) motors have become increasingly popular owing to their use in many applications. PM motor drives require rotorposition sensors. Many techniques that do not involve the use of sensors have been developed for estimation the rotor position from voltage and current measurements. We proposed a novel sensorless control system for PM motor drives that did not require position estimation(3). The system can be easily constructed without using any motor parameters. The system works well over a wide speed-control range; from low to high speeds. In this paper, we describe in detail the principle underlying the proposed sensorless control system for PM motor drives and demonstrate the implementation of the system. Further we present experimental results that confirm the feasibility of the proposed control system.
This paper describes a 6.6-kV adjustable-speed motor drive for use in fans, blowers, and pumps without a transformer. The power-conversion system consists of a diode rectifier, a five-level diode-clamped PWM inverter, and a voltage-balancing circuit. A 200-V 5.5-kW downscale model is developed, constructed, and tested. The five-level PWM inverter and the voltage-balancing circuit are studied in detail. Experimental results obtained from testing the 200-V downscale model confirm the viability and effectiveness of the 6.6-kV adjustable-speed motor drive, indicating that the dc mean voltages of the four split dc capacitors are well balanced under all the given operating conditions.
Flywheel energy storage systems can be used as uninterrupted power supply system because they are environmentally friendly and have high durability. The use of a simple voltage sag compensator with a low-speed heavy flywheel and a low-cost squirrel-cage induction motor/generator is proposed. First, the ability of the proposed system to maintain the load voltage at 100% when the grid is under voltage sag is experimentally-validated. Next, design guides of the flywheel stored energy are discussed. Experimental verification of a 50-kW class system are carried out, and the results show good agreement with the developed design guides.
The one-phase switching method (one-phase modulation) for the three-phase voltage-fed inverter was proposed. The author presents an applying method of the one-phase modulation for the three-phase current-fed inverter. This letter describes a comparison of the switching patterns for the current-fed inverter between the conventional methods and presented method. To prove the validity of the presented method, the simulated results are shown.