Diamond-like carbon (DLC) films are metastable amorphous carbon materials with superior tribological characteristics. In order to improve wear resistance of micro-extrusion dies with numerous imperceptible holes, DLC films were deposited on the inner wall surface of model dies with holes of 2 mm, 0.9 mm in diameter and 20 mm in depth by using pulse plasma CVD method. This paper will discuss that Argon gas, deposition pressure and time how to affect the, characteristics of films deposited on the inner wall surface of dies.
This paper considers synchronization of multiple plants over networks. The effect of time-varying transmission delay is compensated by a switching observer which uses the time-stamp information. To calculate the instantaneous value of transmission delay length via the time-stamp, the clocks of sending and receiving computers must be synchronized. It is shown that the correction of the difference of the quartz frequencies of the computers and the clock adjustment via NTP (Network Time Protocol) can provide the time synchronization within a required accuracy for moderate sampling periods. Proposed method is demonstrated by an experiment of synchronization of DC-motors over a real network.
This paper considers a leader-follower type formation control problem under drop out of vehicle. In our approach, when in-degree of vehicles corresponding to follower vehicles is changed due to the drop out, a desired formation pattern is maintained so that relative distance between other vehicles can be kept constant. Simulation results show the effectiveness of the proposed approach.
This paper considers the auto-tuning of a feedforward controller in order to improve the performance of stage positioning. Particle swarm optimization (PSO) technique is employed for the auto-tuning of the controller. In the proposed method, firstly, the dimensionality of the particle in PSO is reduced. Then, the initial placement of each particle is determined by considering the nominal value of the stage. By using these two approaches, the tuning time can be shortened. After the auto-tuning, the settling time of the positioning is improved. Effectiveness of proposed methods is shown by simulation.
This paper considers the trade-off between flow disturbance attenuation and transmissibility reduction for pneumatic isolation tables. In the active control of the pneumatic isolation table, compressed air is supplied to air springs. However, the pressure of the compressed air fluctuates. This pressure fluctuation, which is called flow disturbance, causes the vibration of the isolation tables. Since the pressure fluctuation is periodic, repetitive control is utilized so as to compensate for the flow disturbance. The feedthrough term in a repetitive controller is usually designed as a static compensator. Although the flow disturbance is further attenuated by increasing the gain of the static compensator, the transmissibility becomes large in the frequency region of mechanical resonance of the isolation tables. Therefore, this paper focuses on the setting of the feedthrough term. In the proposed approach, a dynamic compensator is adopted as the feedthrough term instead of the static compensator. Two break-point frequencies of the dynamic compensator are tuned on the basis of the bandwidth of the pressure fluctuation and the mechanical resonance. It is shown that, by using the proposed setting method, the flow disturbance can be attenuated and the peak of the transmissibility can be reduced.
This paper presents the suppression method of anti-resonance and resonance caused by use of air springs, which are the actuator of a pneumatic vibration isolator. Although the relative displacement derivative (RDD) positive feedback control is effective for the suppression of the anti-resonance and resonance, a control system is not causal under the condition that the time delay of response of air springs is present. To overcome this issue, the RDD positive feedback control combined with Smith prediction is used. The effectiveness of the proposed approach is shown by simulation and experiment.
In semiconductor manufacturing, air type-vibration apparatuses (AVAs) are widely employed. When an earthquake occurs, the AVAs have to be stopped in order to avoid serious damage to semiconductor exposure machines. Spectrum intensity (SI) value is the metric effective for the detection of earthquake though it takes time to calculate this value. To avoid long computation time, this paper uses destructive intensity (DI) value instead of SI value. Simulation demonstrates that DI value, whose computation time is short, can be applied to switching control for AVAs.
This paper deals with the temperature change in the air spring attached to an anti-vibration apparatus. Because in industrial scenes, effects of the temperature of the air spring have not been considered sufficiently, its inner/outer temperature is measured. To suppress the temperature change, the metal absorbing/exhausting the inner heat is used, and the input voltage to servo valve is adjusted. By using both methods simultaneously, the reduction of the temperature change can be further improved. The performance of the methods is evaluated by experiments. Moreover, the thermal equivalent circuit corresponding to the air spring is provided in order to analyze the heat change.
This paper considers the implementation of a proportional-integral-sinusoidal (PIS) control scheme for pneumatic vibration isolators. In this scheme, a sinusoidal compensator (S compensator), which generates a sinusoidal signal, is used to suppress flow disturbance. However, when the S compensator starts up, the vibration of an isolation table occurs. To overcome the issue, a soft switching approach is employed. Moreover, residual high-frequency vibration is attenuated by means of a phase-lead type PIS compensator. The effectiveness of the proposed methods is verified by experiments.
