A bilateral control system aims at realizing a fine haptic transmission between a human operator and a remote environment object. Such a system is expected to realize multiple requirements in practical applications, and the architecture design based on a layer structure has to be considered. This paper treats a surgery robot system as an example, and its system has two requirements: “large workspace” and “fine haptic sensation”. Using the conventional bilateral control system to realize these requirements simultaneously is difficult because mechanical and control designs are separately discussed. At the same time, a system that has multiple requirements such as a fine/coarse system is often designed only using position information. This study proposed to consider not only mechanical/control design but also the position/force information simultaneously from the perspective of an architecture design. The proposed architecture decomposes the functions into each motor/robot by defining roles and combining each role in the layer structure. The advantage of the proposal is that a complex system can be designed as a entire by combining multiple sub-functions that can be simply designed. As a result, the surgery robot system is designed by considering its requirements, and the experiments are carried out to verify if the requirements are satisfied.
This paper proposes a hybrid control of trajectory planning for a desired trajectory and collision avoidance based on an optimization problem for a wheeled mobile robot. In the proposed method, the priority of trajectory planning for the desired trajectory and collision avoidance is modified using the priority variable α. The priority variable α is designed by solving the optimization problem with constraints. As a constraint condition, the range of the priority variable α where the robot does not collide with multiple obstacles is derived. Under this constraint condition, the priority variable α with the highest priority of trajectory planning for the desired trajectory is selected as the optimal value. As a result, the velocity commands considering trajectory planning for the desired trajectory and collision avoidance are calculated in real time. The effectiveness of the proposed method is confirmed via experimental results.
This paper proposes a new temperature estimation method in steady state that employs a compensation method for estimating the temperature using a new voltage disturbance observer autotuning resistance (VDOB_AR). In the conventional method, the influence of rotor flux variation is eliminated by the estimation system; however, the variation in inductance is not considered. By using the proposed method, inductance variation can be compensated online with the VDOB_AR. In addition, the gains of the VDOB_AR are turned by the estimated value to compensate for the resistance variation depending on motor conditions. The effectiveness of the proposed method is verified by experiments and the analysis of the factors related to the voltage disturbance.
In the conventional design of model predictive control (MPC) for PMSM servo systems, friction is usually treated as a part of the lumped disturbances and is eliminated by disturbance observer or integral control methods. In order to obtain better control performance, a composite MPC method is proposed by introducing friction and disturbance information. Firstly, an approximate friction model is obtained by fitting the Stribeck model linearly and piecewise. Secondly, an extended state observer (ESO) is designed to estimate the lumped disturbances, which are composed of the friction compensation bias and the external load disturbance. Thereafter, a more specific prediction model is established by embedding the results of friction identification and disturbance estimation in the mechanism model. In this way, the influence of friction and disturbance are taken into account in the receding optimization process. Various experimental results demonstrate the feasibility and effectiveness of the proposed method for higher-precision motion trajectory tracking.
Previous studies have proposed various optimization algorithms, such as dynamic programming (DP) and model predictive control (MPC), to reduce the energy consumption of autonomous-driving vehicles. The difficulties in the industrial applications of these methods are their computational costs and tuning parameters. In this paper, we propose a linear quadratic regulator (LQR), a low-computational-cost algorithm. The proposed controller calculates the input within a sampling period of 10kHz. By the approximated linear-parameter-varying (LPV) modeling of a vehicle and a motor, we considered the energy loss in the cost function of the LQR. Thus, the proposed method had only one tuning parameter. The effect of changing this parameter, the solver of the LQR for the LPV model, and the influence of the approximation of the models were analyzed. We compared the proposed LQR and DP using computer simulations, a simulation bench, and field experiments. Based on these comparisons, the validity of the proposed method for enhancing the energy efficiency for industrial applications without additional computational hardware was demonstrated.
In this paper a modified zero-voltage zero-current transition network (MZVZCTN) is proposed for a charge-pump based dual boost converter. The proposed soft-switching network consists of two diodes, an auxiliary switch and a resonating inductor. To prevent the failure of zero-current transition of the main switches, auxiliary-capacitors are connected across the diodes of the soft-switching network. The high boost ratio is realized with charge-pump capacitor introduced on the load side. The MZVZCTN network is activated two times in a switching cycle in order to ensure zero-voltage turn-ON and zero-current turn-OFF of the main switching devices. Furthermore, the proposed network also ensures zero-current turn-OFF of the main diodes and does not impose any extra voltage stresses on the devices. The converter can operate at a constant frequency of operation with pulse width modulated control. A 460W prototype operating at a frequency of 50kHz is constructed, soft-transitions of the devices and improvement in efficency is validated through experiments.
Detent force is caused by the interaction of a permanent magnet's flux with an armature's teeth even in the absence of armature excitation. It produces unwanted vibrations and hinders precise motion control of Permanent Magnet Linear Synchronous Motor (PMLSM). Reduction of detent force is still a challenge as it is always accompanied by reduction in the desired thrust. In this paper, a method to reduce the detent force without compromising thrust is proposed. By adjusting the position of the mover magnet with simultaneous re-arrangement of coil phases, significant reduction in the detent is achieved with negligible effect on thrust. Finally, simulation and prototype measurements were used to depict the usefulness of the proposed method.
Electric vehicles (EVs) are gaining attention, and novel use of cars such as vehicle-to-home is becoming widespread. In particular, in-wheel-motor (IWM) type EVs, which have four motors inside each wheel, are expected to be an ideal power train system because it can achieve precise driving force control and estimation. To exploit these features of IWM-EVs, researchers have proposed numerous control methods, most of which are velocity or position-based control for running or trajectory tracking. Force control technologies are quite popular in robotics divisions, and these methods are quite suitable for the new applications of EVs. By taking advantage of the precise estimation performance of IWM-EVs, the authors have proposed to apply force control to EVs and built the concept of human-friendly EVs as done in the robotics division. We show the external force estimation method using wheel resolvers and propose hand-assisted position adjustment method based on impedance control. The appropriate control structure is discussed for IWM-EVs, and its effectiveness is demonstrated with numerical simulations and experiments. We anticipate this research to generate many control applications suitable for the new application of cars.
To avoid heat leakage from a lunar rover during lunar night, this paper proposes a wireless power transfer (WPT) system to replace the wire connection between the PV panel and rover body. The WPT system is powered by a PV panel, and the generated power can be transferred to the rover body via magnetic coupling. The rover side load is connected with a DC bus, and its voltage is stabilized by a DC-DC converter. Based on this topology, a power management strategy for the proposed WPT system is also proposed. According to the variation in the solar irradiance and rover side power requirement, the PV panel can be controlled in different working modes automatically to output the appropriate power. A 45-W experimental platform is established, and the experimental results show that the proposed system can automatically switch the working mode based on the solar irradiance and power requirement. When the power is 45W, the total efficiency of the system is approximately 75%. The experimental results show that the proposed WPT system and power management strategy are effective and can be employed in the future.
This paper presents a control for maximizing the transfer efficiency of three-phase wireless power transfer systems at misalignments. The control conducts an imbalanced three-phase operation with positive- and negative-sequence components. The positive-sequence component is used to regulate the transferred power, and the negative-sequence component is used to improve the efficiency. The optimal value of the negative-sequence component is determined by a sequential search. A modulation technique for this control allows a three-phase inverter to generate imbalanced voltages required by the control in as few switching numbers as possible. The system employing the control is examined for wireless power transfer of 100W at misalignments of 100mm, the radius of the wireless transfer pad. The tests confirmed the wireless power transfer operation employing the control gains 3% improvement in the efficiency in comparison with a balanced three-phase operation.
The objective of our research is to develop a high-performance position control system for flexible industrial robots. Compared to traditional industrial manipulators with rigid links and joints, flexible robots are often more difficult to control because of the mechanical vibrations caused by the low-stiffness mechanisms and coupling torques between links. This paper proposes a decoupling control design based on a 2-Degree-of-Freedom (2-DoF) control framework for flexible two-link robots with lightweight links and strain wave gears. The effectiveness of the proposed method is verified through experiments with a prototype.
As a complementary renewable power source, the photovoltaics (PV) has played an increasingly important role in various applications. However, although the PV has been considerably developed in the past decades, the global maximum power point tracking (MPPT) under partial shading conditions still needs to be focused on. In this paper, a novel simulated annealing and particle replacement assisted Gaussian particle swarm optimization algorithm (GPSO) has been proposed. The proposed algorithm has been divided into two stages. In the first stage, the particles are replaced with Gaussian distribution at each iteration to reduce the particle distribution range, and when the distribution range is sufficiently narrow, this stage is completed. In the second stage, the GPSO update was used to track the global maximum power point for the generated particles from the reduced distribution range. The proposed algorithm has been verified with simulation and experiments. Compared with the conventional particle swarm optimization algorithm, the proposed method exhibited considerate improvement for both MPPT time and PV output power stability.
Recently, power converters have been used in various electric machines, electric devices, etc. However, depending on the power sources, it is necessary to change the circuit topology to DC/AC, AC/DC, or AC/AC. In some applications such as the AC and DC dual locomotive, the power converter should be applicable for both AC and DC sources. For the applications, a converter that combines AC/DC and DC/AC is conventionally used. On the other hand, this paper presents a direct converter that is applicable for any source, utilizing the topological common point between the three-level inverter and the matrix converter and developing a modulation method. By using the modulation method and the matrix converter (MC) circuit, it is possible to achieve either DC/three-phase AC or three-phase AC/three-phase AC power conversion with a common duty calculation scheme. In addition, the proposed system allows two features. First, a control of the neutral point fluctuation, and second, dead time compensation is not required because current commutation can be applied for the three-level DC/AC. The numerical simulations and experiments have validated the conversion and enabled the authors to propose a new concept for a power conversion system.
With the sharp increase in the global energy demands, photovoltaics (PV) have been developed significantly in recent years. However, when the PV work under partial shading conditions, the global maximum power point tracking control should be executed. In this paper, a novel particle swarm optimization (PSO) algorithm with the particle jump improvement is proposed to track the global maximum (GM) of PV output power under partial shading conditions. In the proposed method, each particle is allocated within respective intervals at initial iteration suh that the particle only explores the corresponding interval to determine the potential GM. When the corresponding interval has been traversed without determining the GM, the interval will be discarded and the particle will jump to the interval where the current tracked GM is present. Therefore, each interval of the converter duty range will be traversed by only one particle and the total algorithm tracking time will be reduced. The proposed algorithm is verified with a simulation and an experiment. Based on the experimental results, the tracking times of the proposed method are 0.8s, 0.8s, and 1.2s when the PV output power possesses 2, 3, and 4 peaks under partial shading conditions, respectively.
One-cycle current deadbeat and half-cycle current deadbeat are implemented to a two-phase interleaved DC-DC buck converter. It is confirmed that output voltage driven and outputted by half-cycle current deadbeat is more stable. When the capacitance of LC filter was reduced 3.22µF to 1µF, rise time, step-up duration of 40V to 120V, is shortened to 10.3µs significantly.
This paper presents the development of a traction system for high-speed trains by adopting SiC power devices to pursue weight reduction and compactness of the system. We found that the combination of the SiC applied conversion system with a blower-less cooling system and 6-pole induction motors is a suitable approach to highlight the merits of SiC devices. The running tests of a prototype were conducted to confirm its sound performances. The developed traction system is installed in the latest type of Shinkansen train, or the Series N700S, which debuted in March 2018 and will enter commercial service in the summer of 2020. This SiC application to the high-speed train's traction system is the first in the world.
To prepare for terrorist and/or criminal attacks using unmanned aerial vehicles (UAVs), we developed a Galvano Camera System. This system, which detects suspicious UAVs, is based on the high-speed and precise positioning technology of galvanometer scanners. The proposed system consists of galvanometer scanners, a zoom lens, a CMOS camera, an imaging processor, and a monitor. It is used with other position measurement sensors such as RADAR. The system changes the deflection angles of the galvano-mirrors, which are attached to the tip of the swaying shaft based on the location of the target provided by other sensors. Three targets are observed using proposed imaging process and changing angular process, alternately, to acquire multiple images that include the targets. The imaging processor makes three movies of each target, the monitor divides the screen, and displays these three movies on the same screen. The proposed system can simultaneously observe multiple moving objects, using the high response feature of the galvanometer scanners, and display objects on a single monitor. In addition, we have proved the effectiveness of the system through field tests.
In the conventional bus voltage controller, the concentration of heat generation in a specified circuit has been an obstacle to miniaturization. In this paper, we describe the control algorithm and the experimental result of the direct and distributed switching control (DDSC) method devised to disperse the generation of heat. Additionally, to improve the transient response while reducing the steady state switching frequency, which can reduce the generation of heat, we investigated the application of a transient mode that temporarily speeds up the control cycle when load fluctuation is detected. We also report the calculation of the heat reduction effect that can be achieved by combining these methods.