The bilateral system is expected to be a key technology for the next generation of robots. However, in previous studies, bilateral systems consisted of ground-based devices with limited workspaces. In order to solve this problem, a two-wheel driven mobile manipulator is used as a slave robot in this research. This robot has excellent mobility, and it can turn on the spot and overcome a step. However, the robot is unstable because it lacks casters. If the robot tends to be unstable, it naturally cannot achieve bilateral control. Therefore, in this study, a method that takes into considering the stability of the two-wheel driven mobile manipulator is proposed. The experimental results confirm the efficiency of the proposed method.
The operation of integrated water supply systems has become increasingly complicated owing to reorganization of waterworks. We developed a new method to plan pump operation schedules for large-scale water supply systems. In the proposed method, we define solution space as a network model in which the nodes are cumulative flow rates and the edges are the flow rates at each time step. We treat pump scheduling as a shortest path problem, and the A* search algorithm is used to find the optimum path. One of the characteristics of the proposed method is that the search area is restricted by constraints, such as the water level of tanks. The experimental results show that calculation times increase quadratically, nevertheless, the number of solution states shows an exponential growth with increasing number of pumps. We confirmed that the proposed method can be used effectively for large-scale water supply systems.
Temperature controllers are used for various industrial machines. Recently, network solutions have become standard services for controllers. Because each mechanical specification is required as a priori information, it is difficult to perform an identification based on the open-loop step response. In this study, an identification method based on closed-loop operating data is proposed. A closed-loop transfer function is estimated from operating data based on the orthonormal properties of Laguerre series. The process model is extracted from the Laguerre model taking dipole into consideration. The extracted process model is replaced with a low order model based on pole-zero cancellation. The characteristics of the thermal process are considered in the proposed method. Simulation and experimental results show that the proposed method is successful in estimating the process model from the closed-loop response data.
This paper discusses the development of a vehicle-type tele-mobility system, and proposes a novel control structure on the basis of bilateral control with dimensional scaling taking into account a braking effect. In the field of teleoperations of mobile systems, information on work objects at a remote site is necessary for precise and safe manipulations. Conventionally, audiovisual information is fed back to the operators. However, these approaches cannot fully deal with contact conditions owing to the lack of force information. To tackle this problem, a mobile-hapto has been proposed. In the configuration of this system, the master system is a joystick, whereas the slave system is a mobile robot. From the standpoint of the operability of mobile robots, the master system should comprise not only joysticks but also pedals and steering handle, similar to automobile systems. Furthermore, for actual manipulations, visual information is essential in addition to force information. The proposed system addresses the above requirements, and it is expected that the functionality of the mobile robot systems will be enhanced and facilitated. The applicability of the developed system and the proposed control structure are experimentally confirmed.
A method to determine minimum DC-link capacitance in PWM rectifier-inverter systems is proposed. First, a method to calculate the required DC-link capacitance at the steady state is investigated. Next, a method to calculate the DC-link voltage variation of PWM rectifier-inverter systems at a stepwise change in the output power is proposed. The results of the calculation are confirmed by experimental investigation. In addition, when the capacitance of the DC-link is reduced, the parameters that have a significant influence on the DC-link voltage variation are extracted. Then, based on the proposed calculation method for the DC link voltage variation and the constrained conditions determined by the parameters of the PWM rectifier, a calculation method for the minimum required DC-link capacitance at a stepwise change in output power is proposed.
Robustness to parameter variation is required for rotor position sensorless control of a permanent magnet synchronous motor (PMSM) using a motor model. Therefore, various methods for measuring parameter variation or eliminating the influence of this variation have been proposed. This paper describes a rotor position sensorless control system of the PMSM that is based on a model reference adaptive system with a winding resistance and a back emf coefficient estimator. Only the winding resistance estimator minimizes the rotor position estimation error by compensating for the variation of the winding resistance and the back emf coefficient concurrently. Experimental results indicate that the winding resistance estimator is effective against both variations.
This paper presents a modular multilevel cascade converter based on triple-star bridge-cells (MMCC-TSBC) with a focus on its decoupled control. The TSBC is one of the direct ac-to-ac power converters having the capability of bidirectional power flow with three-phase sinusoidal input (supply-side) and output (motor-side) currents. Therefore, it is suitable for a medium-voltage motor drive requiring regenerative braking. This paper has an intensive discussion on control strategy for the TSBC, which includes current control, capacitor-voltage-balancing control, and fluctuation-mitigating control for low-speed operation. This control strategy succeeds in achieving decoupling among supply (input) currents, motor (output) currents, and circulating currents, using the αβ0 coordinate transformation. The validity and effectiveness of the control strategy are confirmed by theoretical analysis and computer simulation.
This paper describes a new model predictive control method for buck DC-DC converters. The objective is to achieve a good trade-off between fast response and low overshoot in the transient response of the output voltage. In the well-known PWM-PI method, such a trade-off is difficult to attain. The proposed model predictive control is based on an analytic algorithm that can be easily implemented online. Further, a PI outer loop is introduced to improve the robustness against load uncertainty. Moreover, the advantage of the proposed model predictive control is verified experimentally. The experimental results show that the proposed method outperforms the PWM-PI method.
This paper deals with the speed-up effect of maximum power point tracking (MPPT) control for vehicle applications. A photovoltaic panel is set on a car running on a city road and its static characteristics are recorded by the proposed high-speed measurement system. The effectiveness of MPPT controllers with various sampling frequencies is evaluated with the recorded data by simulation. In the car application, a higher sampling frequency achieves higher MPPT efficiency.
Overhead rigid conductor lines are adopted in many subways, because a few wire breaks due to wear occur, and the space required for installation is small. However, when undulating wear occurs on sliding surfaces, arcs due to contact loss cause extreme wear of the contact lines and contact strips of pantographs. In order to investigate the formation mechanism of the undulating wear of overhead rigid conductor lines, we carried out precise measurements of the sliding surface unevenness, excitation tests of pantographs, theoretical analyses with a dynamic model and a questionnaire survey among domestic railway companies. This paper describes the mechanism of formation of undulating wear in relation to the mechanical impedance of the pantograph, and suggests methods to inhibit undulating wear, such as the installation of a side-wound contact wire, grinding of the sliding surface and pantograph design based on undulating-wear-inhibiting guidelines.
This paper proposes a controller tuning method for sinusoidal PWM inverters using fictitious reference iterative tuning. The proposed method enables the tuning of the controller parameters, without any iterative experiments and mathematical inverter models. The effectiveness of the proposed method is demonstrated by the experimental results.
Our research focuses on the design and its applications of systems control to Motor drive system, Vehicle, Robot, and so on. Utilizing future rich computer resources for modeling and control of non-linear and/or complex system, the limit of the various applications are challenged.