This paper proposes the stability improvement of two wheeled mobile manipulator using nonlinear Proportional Derivative (PD) controller. Nonlinear PD controller is a controller which automatically adjusts its gains according to the stability conditions on running. Lyapunov function based on kinetic energy of the system and position error are used to re-schedule the gains of the nonlinear PD controller. This method will expand the stability margin of the two wheeled mobile manipulator. Further advantages of this method are reducing the parameter uncertainty and difficulty of adjusting gains due to nonlinear nature of system. In the proposed approach, virtual double inverted pendulum is introduced for the control of the two wheeled mobile manipulator. The model based on the double inverted pendulum, makes it easy to design the controller. Here, wheel control and manipulator control are designed separately and unified by using two nonlinear PD controllers. Two nonlinear PD controllers are implemented for better stability. The method proposed in this paper has used nonlinear PD controller in work space of the manipulator controller together with null space control. Here the null space control increases the control stability of manipulator configuration. The effectiveness of the proposed method was confirmed by the experiment of two wheel mobile manipulator.
Because the application range of motors for position control is extending in industry, hybrid stepping motors that can realize position control easily have become popular. However, stepping motors have some disadvantages: there is pull-out phenomenon according to load conditions, and low efficiency originates in the iron loss generating. Consequently, a system designer has to choose motor-driver very carefully. In this paper, the high efficiency drive of hybrid stepping motor on wide speed range by vector control, which has no pull-out phenomenon, is proposed. Furthermore, it was shown that lead angle control is equivalent to flux-weakening control, and it was shown that the maximum torque is decided by the maximum voltage, which an inverter generates at high speed. The effect, which suppresses iron loss by flux-weakening control, was checked from the experiment.
This paper proposes a new rotor phase estimation method for sensorless drive of permanent-magnet synchronous motors (PMSMs), which uses motor-driving stator voltage and current information for estimation. The proposed estimation method utilizes two high order low-pass filters that can change their bandwidth according to speed estimate. The high order filters have a potential to attenuate sufficiently harmonics contaminating the stator voltage and current and to produce almost-pure-sinusoidal rotor flux estimate consisting of fundamental component only. Such a sinusoidal rotor flux estimate allows high accurate estimation of rotor phase even at very low speed. In order to separate the fundamental component of the rotor flux estimate from its harmonics with no phase lag/lead in variable-speed environments, the proposed low-pass filters have a function to change its bandwidth adaptively to rotor speed. The sensorless drive system using the proposed phase estimation method can show such high performance that 1) it can startup PMSMs from standstill under the rated load; 2) it can drive PMSMs stably even at very low speed such as 1/60 of the rated speed under the rated motoring/regenerating load; 3) it can drive PMSMs accompanied with a load of over 50 times large inertia. The proposed estimation method is simple and easily installed into sensorless drive systems. This paper presents the new estimation method in detail and show how it is installed into the drive systems by using a concrete example. The usefulness of the method and the performance of the drive system are examined and confirmed through extensive experiments.
SCADA systems in water reclamation centers have been constructed based on hardware and software that each manufacturer produced according to their design. Even though this approach used to be effective to realize real-time and reliable execution, it is an obstacle to cost reduction about system construction and maintenance. A promising solution to address the problem is to set specifications that can be used commonly. In terms of software, information model approach has been adopted in SCADA systems in other field, such as telecommunications and power systems. An information model is a piece of software specification that describes a physical or logical object to be monitored. In this paper, we propose information models for operations of water reclamation centers, which have not ever existed. In addition, we show the feasibility of the information model in terms of common use and processing performance.
This paper describes a direct-power-controlled CVCF inverter and presents its experimentally examined operation characteristics. The most important feature of this strategy is the direct selection of the switching states of the CVCF inverter to restrict errors between the feedback and command values of active and reactive power. In addition, this paper presents a theoretical analysis of the relationship between the instantaneous power and the switching state, which is essential for deriving a switching-state table for the controller. The feasibility of the proposed method was verified through several computer simulations and experimental tests using a 2.0-kVA prototype setup. The output voltages were confirmed to be stable sinusoidal waveforms with a total harmonic distortion of 1.13% conditions. Furthermore, excellent voltage balance was achieved by the proposed strategy even under unbalanced load conditions.
This paper deals with dynamic control and performance of a resonant switched-capacitor converter (RSCC) based on phase-shift control method, which has capability of accurate voltage regulation by means of applying a voltage feedback control. The analysis in this paper reveals that the RSCC may superpose an unwanted current on the resonant current and cause overcurrent in a transient state. This paper proposes a new phase-shift control method including the sequence and timing control of the gate signals, resulting in elimination of the unwanted current from the resonant current. Experimental results verify the validity of the proposed control method.
The paper describes the design and experimentally characterised of a high temperature, parallel-polarised permanent magnet electromagnetic actuator developed for fail-safe applications. The actuator is designed to operate in an ambient temperature of 230°C, has a stroke of 2mm and minimum force requirement, which can be maintained with zero current, of 1kN for the entire stroke. To minimise the mass of the final design, thermal modelling has been used to determine the acceptable current rating for the device, features were added to the pole faces to linearise the force characteristic, and high temperature grades of materials were used. A prototype actuator has been constructed and experimentally validated at the rated operating temperature of 230°C.
This paper proposes a new modeling approach for circuit-filed-coupled time-stepping electromagnetic analysis of a saturated interior permanent magnet synchronous motor (IPMSM). To predict the drive performance quickly, the proposed approach consists of a dynamic simulator based on a new analytical model of the d, q-axes magnetization characteristics (λ-id-iq-θ). The model can take into account not only the cross-saturation but also the harmonics of inductance distributions and EMF waveforms. The validity of the model is verified from suitable simulation results of the instantaneous current and torque waveforms of the IPMSM. The proposed analysis has realized a dramatic reduction in the computation time compared to circuit-field-coupled time-stepping FEA, keeping analytical accuracy. The effectiveness of the proposed method is experimentally verified using 10kW-15000r/min concentrated-winding IPM motor.
In hard disk drives, it is important to enlarge the control bandwidth in order to shorten the track pitch for larger data capacity. However, it is difficult for H∞ control method to increase the control bandwidth if the mechanical resonance modes have uncertainty. This is because that the robustness of the H∞ control method is assured by the small-gain theorem for additive or multiplicative perturbation and the control bandwidth is limitted by the uncertainty. In this study, we propose a H∞ control method for high bandwidth design by introducing a new uncertainty model with a feedforward and a feedback path in order to reduce the conservatism of robust design. The effectiveness is shown by numerical simulations.
This paper presents a novel initial value compensation (IVC) with additional input by considering the optimization of control input. IVC has been used to improve the control performance of various control systems with different initial values. Essential subjects, however, have been still remained: In the conventional IVC approaches, the increase in the amplitude and number of high-frequency components of the control input that accompany an increase in the control bandwidth could not be avoided. In this research, therefore, an optimization approach for the control input is applied under the constrains of the conventional IVC approach. The effectiveness of the proposed approach has been verified by numerical simulations and experiments using a prototype.
This paper proposes a new method for estimating properly rotor initial phase (in other words, position) of newly emerging self-excited hybrid-field synchronous motors (SelE-HFSMs), which have rotor field by both permanent magnet and diode-shorted field winding. The proposed method injects spatially rotating high-frequency voltage and detects the rotor phase directly through evaluating norm of the associated current. The method is very simple, but has a high degree of usability.
Novel multi-resonant ZVS (Zero Voltage Switching) high frequency inverter applied for high frequency induction heating is developed. The current amplitude ratio of switch current and output current in the inverter is theoretically clarified. The effectiveness of the inverter is verified by experiments.