The motion stability of a vehicle depends on yaw-rate and side-slip angle. These two variables affect each other, and therefore, we performed decoupling control of yaw-rate and side-slip angle of an electric vehicle (EV) with active steering and torque difference between left and right in-wheel motors. However the robustness of decoupling control is fragile for road condition. Hence, we propose lateral force observer (LFO) that is highly robust to variations in the cornering stiffness. LFO and yaw-moment observer (YMO) are used in an EV with an active steering and two in-wheel motors. In this paper, we compare the robustness of the proposed method and that of the decoupling-control method by means of an experiment. The results show that the proposed method delivers a better performance than that of the conventional method.
In this paper, lossy data compression of haptic data is presented and the results of its application to a motion copying system are described. Lossy data compression has been studied and practically applied in audio and image coding. Lossy data compression of the haptic data has been not studied extensively. Haptic data compression using discrete cosine transform (DCT) and modified DCT (MDCT) for haptic data storage are described in this paper. In the lossy compression, calculated DCT/MDCT coefficients are quantized by quantization vector. The quantized coefficients are further compressed by lossless coding based on Huffman coding. The compressed haptic data is applied to the motion copying system, and the results are provided.
This paper presents an augmented four channel teleoperation architecture with local damping injection, which renders the teleoperation system L2 stable independent of time delay. It is well known that four channel teleoperation architecture, which is based on the transmission of force and position measurements of both the master and the slave robots, provides perfect transparency, when there is no time delay between the robots. In the presence of delay, four channel systems are not stable and they can not provide transparency. With damping injection, stability is guaranteed independent of the size of the delay, as long as it is constant, and furthermore better transparency with high frequency force feedback can be realized. This is an improvement over conventional methods. As transparency and stability are two conflicting goals, there is a tradeoff that a constant damping is felt in free motion. In this paper stability and transparency analyses are presented and the validity of the method is also confirmed with experiments.
New rolling vehicles used in dc electric railways are of the regenerative type. At less busy time a part of regenerative power is not used for powering vehicles, and canceled by changed air brake. Recently, significant attention has been paid to the development of secondary batteries for hybrid and electric motorcars. The use of this battery enables reduction in electric power consumption. Because we can charge excess regenerative power and use for powering vehicles after. Before the fact we compared the actual and simulated effective coefficient of regenerative energy, we confirmed the suitability of the simulation model. In this simulation, we studied the energy-saving effect of the battery substations and determined the battery capacity at which maximum power saving is achieved. We found that the power consumption could be reduced remarkably by using a 15-20kWh battery substation.
This paper proposes a new generalized heterodyne method that incorporates a high-frequency integral-type phase-locked loop (PLL) as a versatile rotor-phase estimation method from stator current caused by high-frequency voltage injection for sensorless drive of salient-pole permanent-magnet synchronous motors. The proposed method has the following characteristics that are in direct contrast to those of conventional heterodyne methods. 1) In principle, it can be applied to almost all voltage injection methods. 2) In principle, it can properly estimate the rotor phase over a wide range of speed. 3) It employs a new simple estimation structure based on the high-frequency integral-type PLL method, which does not require any additional filters. 4) An analytical method for designing the components of the structure has been established and no trial and error method is required for selecting the parameters for the components. 5) The stability of the phase-estimation system of the structure is guaranteed. 6) The high-frequency noises generated in the heterodyne process do not appear on the estimated rotor phase.
This paper proposes new simple realizations of the “Mirror-Phase Estimation Method (MPEM)” used for estimating the rotor phase in the sensorless drive of salient-pole permanent-magnet synchronous motors. The proposed realizations involve the use of the stator current induced by high-frequency voltage injection. The MPEM has the following advantages: 1) It is versatile, i.e., it can be applied to almost all voltage injections. 2) It makes the most of the positive correlation between the rotor phase and the high-frequency current. 3) It does not require knowledge of motor parameters. 4) It does not require redesigning the combined PLL when the amplitude and/or frequency of the injected high-frequency voltage is changed. However, the MPEM has drawback; it has a relatively large computational load. This paper proposes three simple realizations of the MPEM in which the computational load drastically reduced. The validity of the realizations is shown by conducting numerical experiments.
The servo system of a PM motor is required to have a fine torque response and fine speed response. The current controller of the PM motor should have a fine current response. However, when the current sensors of the U phase and V phase have offset values, the servo system of the PM motor shows a torque ripple and cannot accurately identify motor parameters such as the motor resistance Ra and motor inductance La. In order to overcome these problems, this paper proposes a new method for the fine estimation and automatic adjustment of current sensor offsets and the electrical parameters of the PM motor. The proposed method involves the use of a real-time algorithm and a current simulator, which is operated using a DSP software system. The experimental results of this study confirm that the proposed method satisfactorily estimates the offsets of the current of sensors of theU phase and V phase, Ra, and La accurately; the method also helps in the fine self-tuning of the current controller of the servo system.
The design of the conventional LC filter of PWM Inverter depends on designers' experience, and trial and error. Therefore, the parameter design does not meet our demands. In order to resolve this issue a genetic algorithm is applied. This paper describes the design of an LC filter used in a PWM inverter with discrete-time model following control. Multi-objective genetic algorithm is used in computing. The pareto-optimal solution for the design of an LC filter is obtained. The possibility of obtaining a local minimum solution is less if this algorithm is used. The pareto ranking method is used to evaluate the adaptability of the genetic algorithm. The validity of the analysis was demonstrated by the comparison of the experiment with the simulation. It is concluded that the multi-objective genetic algorithm is practicable to optimize a parameter.
This paper proposes a novel task description for redundant systems as an extension of oblique coordinate control. Orthogonality of tasks are not necessary and interference between a task space and a null space is precisely described in off-diagonal parameters of “task mass matrix” in this method. Dynamics of the null space is also considered with its basic variables. In order to decouple the spaces, a null space regulator is proposed. Conventionally, this kind of decoupling is given by selecting a mass matrix as a weighting matrix of the pseudo inverse. On the other hand, arbitrary weighting matrices can be selected in our approach. Some comments for sub tasks are given. In a short word, “there is few need of sub tasks”. Validity of the proposed method is analyzed and is confirmed by experiments.
Stages are widely used as positioning devices in industrial fields. One of the applications of these stages is the precise manufacture or accurate measurement of large-scale parts. For improving the production efficiency, it is necessary to increase the stage size as well as the positioning speed. In the vertical drive of such a stage, an air spring covered by high-polymer materials is used for supporting heavy weights. This spring is viscoelastic with low-frequency resonance modes. Moreover, the stage has many mechanical high-frequency resonance modes. Therefore, a high-bandwidth feedback controller cannot be realized, and the low resonance modes hinder fast and precise positioning. Hence, realization of an accurate feedforward controller by using an appropriate model is of utmost importance. In this study, we designed three nominal models and identified the model which is the most appropriate for the vertical drive of a large-scale stage. Then, we show the advantages of the vibration suppression perfect tracking control (VSPTC) by using the fourth-order Maxwell model. Furthermore, we confirmed that a combination of a VSPTC and a disturbance observer using the same nominal model delivers a good performance by performing simulations and experiments.
In this paper, we describe the construction of an equivalent circuit that considers harmonics and stray load loss in induction motors. First, harmonic losses in the motors are investigated by electromagnetic field analysis. Using the obtained results, several equivalent circuits that consider harmonics and stray load loss are proposed and the circuit parameters are determined. Next, the best circuit is determined from the viewpoint of practical use. Finally, the motor characteristics calculated by using the proposed circuit are compared with those of experiments. It is concluded that the accuracy of the proposed equivalent circuit is considerably higher than that of the conventional circuit, particularly at high rotational speeds.
This paper investigates a 3-phase contactless power transfer system in order to realize large power transfer. This system consists of 3-phase resonant circuits and a contactless transformer, which windings have mutual inductance each other. This configuration is represented by an equivalent circuit of a single-phase contactless power transfer. Simulation results confirm that the 3-phase contactless power transfer system works effectively.