This paper describes a control strategy of null space motion of a two wheels driven mobile manipulator. Recently, robot is utilized in various industrial fields and it is preferable for the robot manipulator to have multiple degrees of freedom motion. Several studies of kinematics for null space motion have been proposed. However stability analysis of null space motion is not enough. Furthermore, these approaches apply to stable systems, but they do not apply unstable systems. Then, in this research, base of manipulator equips with two wheels driven mobile robot. This robot is called two wheels driven mobile manipulator, which becomes unstable system. In the proposed approach, a control design of null space uses passivity based stabilizing. A proposed controller is decided so that closed-loop system of robot dynamics satisfies passivity. This is passivity based control. Then, control strategy is that stabilizing of the robot system applies to work space observer based approach and null space control while keeping end-effector position. The validity of the proposed approach is verified by simulations and experiments of two wheels driven mobile manipulator.
This paper deals with analysis and reduction of dc voltage fluctuations in a single-phase active filter caused by a sudden load change. The analysis reveals that the delay time of the harmonic detection causes dc voltage fluctuations in transient states. A new control method capable of reducing the dc voltage fluctuations is proposed based on the analysis. The dc capacitor can be reduced to the required capacitance to satisfy the ripple current in steady states. Experimental results are shown to verify the viability of the analysis and the proposed control method.
This paper presents a practical implementation for an Initial Value Compensation (IVC) approach using an additional input. The authors have already proposed the IVC approach to suppress residual vibrations at iterative positioning operations. The approach, however, has an essential subject that more state variables to be compensated require more complicated computation. In the paper, the improvement of computational complexity in the IVC approach is proposed, where the compensation calculation can be simplified by giving alternative inputs for initial values. The effectiveness of the proposed compensation has been verified by numerical simulations and experiments using a prototype.
We have developed the shift lever with a spring connected link. It can detect the reaction force to the operator by using inexpensive displacement sensors such as potentiometers. For this system, we propose a model-based power assist control method. The proposed control system is composed of a reference generator and a feedback controller. The reference generator is introduced to generate an ideal reaction force to the operator. The feedback controller is designed by H∞ control theory to achieve disturbance attenuation. The effectiveness of the proposed method is shown by experiments.
In inverter-fed motor systems, output voltage of the inverter has a rectangular waveform with rise time of a few tens of nanoseconds, and consequently a motor suffers from repetitive surge pulses which may have adverse effect on motor insulation. Therefore the behavior of surge pulses should be clarified to devise the optimum insulation design of a motor. We have investigated how cable structure and grounding wire connecting inverter and motor affect the surge behavior with particular regard to peak voltage between motor input terminal and ground and peak voltage across the first coil in serially connected multi coils. As a result, we discovered phenomena whereby, when cross sectional structure of the cable is asymmetrical, the surge voltage of a specific phase can become higher than that of the other phases resulting from asymmetry among capacitances between feeder line and ground line. And we have confirmed these phenomena can be prevented by the following three methods: using cables that have symmetrical capacitance to ground among 3 phases (e.g., a 3-phase shielded cable), providing the grounding wire as a separate cable to reduce the capacitance, inserting capacitors at motor terminals or inverter terminals to cancel out capacitive asymmetry.
This paper proposes a new two-dimensional tracking method exploiting “trajectory errors”. The proposed method detects a single spatial trajectory error between the desired trajectory and a current position, generates two-axes manipulated variables through a new “trajectory compensator” using the trajectory error, and injects the manipulated variables into the two-axes plant in a feedback manner. The aforementioned process implies a new structure of trajectory tracking systems where the trajectory compensator plays a dominant role. Detailed structure of the compensator varies dependently of the desired trajectory. This paper presents new concrete structures for trajectories of straight line with offset and circle with offset, which are basic elements for arbitrary trajectories. Usefulness of the proposed method is confirmed by extensive experiments using an XY table.
5kV, 50A, 2MHz AC power supply for driving high peak and short pulse CO2 lasers with a silent discharge has been developed. The developed power supply has a full-bridge inverter that combines four switches that connect power MOSFET with 6 in series and 4 in parallel. The inverter directly switches the high voltage of 5kV DC and converts the voltage directly into 2MHz AC. The developed power supply can output much higher electric power than a conventional one, because it doesn't have a step-up transformer with a large leakage-inductance. A peak laser power of 20kW, 7 times a conventional one, and a laser pulse width of 1μsec, 1/10 of a conventional one, was obtained by using this power supply for silent discharge type CO2 lasers.
This paper deals with a transformerless hybrid active filter integrated into a medium-voltage three-phase diode rectifier used as the front end of an adjustable-speed motor drive. The hybrid filter is formed by a single LC filter tuned to the 7th-harmonic frequency per phase and a small-rated active filter based on a three-phase three-level diode-clamped PWM converter. A three-phase downscaled system rated at 400V and 15kW is designed, constructed, and tested to verify the filtering performance of the hybrid filter. Experimental results show that the current THD (total harmonic distortion) gets less than 5%, and that the voltage-balancing control proposed in this paper works properly even in transient states.
This paper proposed a calculation method of the torque and power density especially for the fractional-slot concentrated winding machines. The torque coefficient and the inductance coefficient to transform from m-slot/n-pole machine to 3-phase/2-pole machine are used. Some machines were designed and these torque densities and power densities are compared. Experimental results showed the effectiveness of the proposed calculation method and have good accordance with both calculation results and FEA results.