This paper presents a method of simultaneously presenting tactile and thermal sensations using multilateral teleoperation. Communication using haptic sensation is expected to be a next-generation communication tool replacing telephone or television. A control technique named multilateral control can transmit haptic sensation to multiple points. In this study, robot manipulators are used for tactile sensation presentation, and Peltier devices are used for rendering thermal sensation. A position encoder is used to measure the position of a robot and also estimate the external force, while temperature and heat flow sensors are used for rendering thermal sensation. A routing method to decouple controllers compensates the effect of a time delay between the systems. Defining a modal transformation matrix in a network system eliminates the interference effect of controllers, which is a well-known problem in bilateral and multilateral teleoperation. The matrix shows how to route the information to realize mode-decoupled control in network systems. To consider the motion range of a robot manipulator, the scaling gain is inserted into the modal transformation matrix. The method also compensates the difference between the response speeds of robot manipulators and Peltier devices. This should be considered because the response speed of a Peltier device is slow compared to that of a robot manipulator. The validity of the proposed method is confirmed through experiments.
This study proposes a movement control system based on model predictive control (MPC), and a Kalman filter (KF) that can consider the influences of noise and disturbance. The KF estimates not only the motion state but also the disturbance of the controlled objects affected by noise. Disturbance is introduced by the stationary disturbance, by the system noise, and by observation noise. An MPC system filtered by the KF is robust and suppresses disturbances using the special design method proposed in this study. The feasibility of the MPC-based control system is confirmed under conditions of strong intermittent disturbances, such as road surface and sensor noises, and a friction force with less time variation. Finally, the proposed method is tested in simulations of a cart traveling in a straight line. The superior simulation results over the existing MPC system validate the proposed control system.
In a mechanical system whose control target is known, a precise control model of the controlled object is defined using a system identification method, and an optimum control method is selected and designed using modern control theory. However, with a general-purpose servo drive, the controlled model cannot be defined completely in advance. This paper proposes a method of suppressing mechanical resonance with an equivalent rigid body observer based on a motor model, which can be installed without clarifying the controlled object model. In addition, the applicability of the proposed method to both semi-closed and full-closed controlled systems is confirmed though experiments.
The software-implemented degradation detection/prediction of the current transfer ratio (CTR) of a photo-coupler installed in a digitally-controlled switching mode power supply was studied. The photo-coupler is one of the key devices in an isolated power supply circuit, which transmits a voltage/current signal to a controller though the isolation gap. If the CTR of the photo-coupler degrades to halfway between the normal value and the threshold of the hardware protection circuit, overvoltage/current may be supplied continuously to the load circuit and possibly cause a severe failure. By comparing the theoretical pulse width modulation (PWM) duty, which is calculated from the input/output voltage and the pre-measured power supply circuit efficiency, and the applied PWM duty, which is calculated via feedback control, CTR degradation is detectable online. In this paper, we describe the concept of this method and verify it using both simulation and prototyping circuits.
An autonomous DC microgrid system that uses a triple active bridge (TAB) converter as a power routing unit is proposed. A control system that can independently manage the current and voltage of each port is needed to construct the microgrid. This paper describes how the decoupling power flow control system is implemented in the prototype TAB converter rated at 400V, 10kW, and 20kHz. The validity of the system was demonstrated by measuring the step response of the TAB converter. The experimental results showed that the system provided the designed dynamic characteristics from the viewpoints of output current control and constant voltage control. Decoupling power flow control between each port was also achieved.
We developed a railway total simulator that can simulate not only each sub system such as a train, signalling system, and power supply system but also train operation and energy usage based on the collaboration of subsystems for all railroads. The purpose of this simulator is to determine the influence of the energy consumption of trains and substations depending on the change in train characteristics, timetables, power supply systems and so on. The targets of calculation for this simulator are the energy consumption of substations and trains restricted by the condition of signalling systems and traffic control systems. We evaluate the simulation accuracy of the proposed simulator for a DC feeding system by using measurements obtained from the Okinawa Urban Monorail. It is confirmed that the simulation results can help predict power behaviour with a sufficient accuracy on railway lines and the average simulation differences were within 6%, namely a 3.6% difference in rolling stock power consumption, 3.9% difference in rolling stock regenerative power, and 3.0% difference in substation power supply. On comparing the calculation results of the proposed simulator with actual measurement data from a general DC power railway system, it is concluded that the simulator and actual results have a sufficiently low difference.
We have been developing LIM-type eddy current rail brakes (LIM-ECBs). In this paper, we introduced our approach to simplify the numerical design for the armatures of LIM-ECBs focused on the geometric properties of the ring-winding armature.
Optimized pulse patterns, such as the selective harmonic elimination pulse width modulation (PWM) pattern (SHE-PWM) are used to suppress current harmonics at steady-state. However, achieving fast dynamic performance is very difficult in systems operated by SHE-PWM. This paper proposes a method that combines the performance of SHE-PWM at a steady-state with the fast torque response of model predictive direct torque control at the transient-state. Finally, the control performance of the proposed system is evaluated based on the experimental results.
Many different types of pipeline installations exist, such as pipelines used in chemical plants, water pipes and gas pipes. All must be examined and maintained to prevent severe accidents through a program of continual pipe inspection and repair. Herein, we have developed a cylindrical crawler robot for pipe inspection. We propose a simple crawler robot steering principle along with verification tests. The prototype robot with the proposed steering mechanism was able to travel through all T-branch paths.
To suppress the rotor oscillation when positioning a stepping motor, we propose a novel scheme that automatically tunes the pulse timings in back-phasing damping using a neural network, from the input of only a step response. Here, the network is learned from the response and its timings for a few loads. To validate the scheme, the drives that satisfactorily damp the rotor oscillation are demonstrated using the timings estimated with unknown loads attached.
This paper presents novel criteria for the reluctance torque utility of permanent magnet (PM) motors. The criteria can be quantified by the PM flux linkage Ψp of stator phase windings, and current I, as well as the direct- and quadrature-axis inductance Ld and Lq, respectively. Through both theoretical formulae and experiments, it is proved that a motor with large Ψp can utilize little reluctance torque even if the salient-pole ratio Lq/Ld is over 2.0. In such a case, the large salient-pole ratio only leads to an increase in iron loss, and hence a decrease in motor efficiency. The proposed criteria help one to understand the properties inherent in each motor, and also indicate that, in the above case, selecting the rotor geometry with less saliency can improve the efficiency. Results are given for two kinds of PM motors; one is a 4-pole Nd-Fe-B magnet motor with PN =0.6kW, nN =3600min-1, Y-connection; the other is a 6-pole ferrite-magnet motor with PN =0.2kW, nN =1080min-1, Y-connection.