Published papers

Insufficient thrust density is a critical issue in a solid-state electro-aerodynamic propulsion system (SSEP) during vertical takeoff and landing (VTOL) drones. Therefore, this study proposes the use of booster electrodes designed to enhance ion generation. To evaluate its performance, numerical simulations were conducted using a two-dimensional, three-species plasma fluid model. The results were experimentally validated, demonstrating that booster electrodes enhance the thrust density of SSEP by ∼4.46 times at 15 kV, 2.22 times at 20 kV, and 1.84 times at 25 kV when compared with the results of the configuration without the booster electrode. This study encourages the practical applications of VTOL drones by demonstrating the improvement in thrust density with booster electrodes through both numerical analysis and experiments.

© 2018 The Institute of Electrical Engineers of Japan. This paper aims to realize position and torque sensorless motion transmission between a generator and a motor. The proposed voltage compensation method requires only one current sensor on the generator side. Since the motor side is completely sensorless, this system is suitable for operation under harsh environments. Comparative analyses indicate that the proposed method satisfies the conditions for the transmission of an actual tactile sensation. Simulations and experiments confirmed that motion transmission is realized using the proposed method.

Interior Permanent Magnet Synchronous Motors (IPMSM) are an important component for a robotic application because of its high torque property. In order to drive IPMSM with high efficiency, feedback control with rotor position sensors is utilized. However, since those sensors make the instrument size large and the cost high, many researches on sensorless control which is feedback control without position sensors have been conducted. Especially for low-speed range, sensorless control with the use of additional high-frequency signals to detect rotor position has been proposed although these signals might cause rotor vibration or low efficiency. This paper proposes a novel position estimation method based on disturbance observer which detect position estimation error. The estimation method achieves detection of rotor position at low speed since rotor saliency and current derivative are utilized. This method differs from conventional observer-based methods in that the disturbance observer not only estimates the phase, but also estimates the term proportional to the axial error and applies a compensation voltage for it. This method also avoids to use any additional signals such as high-frequency voltage for the estimation. The effectiveness of the proposal was confirmed by simulations.

This paper analyses the robust stability and performance of the Disturbance Observer- (DOb-) based digital motion control systems in discrete-time domain. It is shown that the phase margin and the robustness of the digital motion controller can be directly adjusted by tuning the nominal plant model and the bandwidth of the observer. However, they have upper and lower bounds due to robust stability and performance constraints as well as noise-sensitivity. The constraints on the design parameters of the DOb change when the digital motion controller is synthesised by measuring different states of a servo system. For example, the bandwidth of the DOb is limited by noise-sensitivity and waterbed effect when velocity and position measurements are employed in the digital robust motion controller synthesis. The robustness constraint due to the waterbed effect is removed when the DOb is implemented by acceleration measurement. The design constraints on the nominal plant model and the bandwidth of the observer are analytically derive d by employing the generalised Bode Integral Theorem in discrete-time. The proposed design constraints allow one to systematically synthesise a high-performance DOb-based digital robust motion controller. Experimental results are given to verify the proposed analysis and synthesis methods.

The use of robots is desired as a replacement for human labor. However, it is difficult for robots to respond flexibly to changes in objects and environments and perform tasks. Recently, many systems have been proposed that can flexibly respond to changes by generating robot motions using machine learning. Many machine learning methods use a camera to acquire environmental information, and feature extraction is performed using images acquired from the camera using CNN (Convolutional Neural Network), CAE (Convolutional Auto Encoder), or other methods. Many methods estimate the input values in the next step by inputting the image features, position data and reaction force data acquired from the robot together into the RNN (Recurrent Neural Network), etc. However, in most cases, the relationship between the image and robot data is learned without explicitly stating it. Therefore, in this paper, the data acquired from the robot is converted to images and used in combination with images from the camera to make the interaction between the robot and the environment explicit and to improve the estimation accuracy of NNs. In simulations, the proposed method was used to perform the task of discriminating the target of motion, and the high estimation accuracy was confirmed. In the future, we plan to use this method as input data for motion generation to generate motion according to the object.

In micro-manipulations such as cell manipulation, it is desirable for the operator to feel the haptic sensation of the object. Bilateral control can remotely transmit position and force information between leader and follower systems. In this control, the use of a linear motor as a leader and a stacked piezoelectric actuator as a follower has been proposed to achieve micro-scale operation. There is a lot that needs to be clarified about bilateral control when the structure differs between leader and follower systems. In conventional scaled 4channel (4ch) bilateral control, a theory of oblique coordinate control has been proposed that considers differences in the inertia of leader and follower systems. However, when a piezoelectric actuator is used, the control scheme differs from using two linear motors with different inertias because the structures of the leader and follower systems are entirely different. Another method is scaled admittance bilateral control. However, the control design when structures and inertias of the two systems are different has not yet been clarified. In this paper, a scaled admittance bilateral control using a piezoelectric actuator and a linear motor is constructed. Experiments confirm that the realized scaled admittance bilateral control has the equivalent position and force tracking performances as the conventional scaled 4ch bilateral control using a piezoelectric actuator. Furthermore, the designed scaled admittance bilateral control is more robust to fluctuations in the nominal inertia of the piezoelectric actuator than the conventional scaled 4 ch bilateral control.