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We report that high absorption PbSe colloidal quantum dots (QDs) having a peak absorbance beyond 2100 nm were synthesized and incorporated into InSnZnO (ITZO) channel layer-based thin film transistors (TFTs). It was intended that PbSe QDs with proportionally less photocurrent modulation can be remedied by semiconducting and low off-current ITZO-based TFT configuration. Multiple deposition scheme of PbSe QDs on ITZO metal oxide thin film gave rise to nearly linear increase of film thickness with acceptably uniform and smooth surface (less than 10 nm). Hybrid PbSe/ITZO thin film-based phototransistor exhibited the best performance of near infrared (NIR) detection in terms of response time, sensitivity and detectivity as high as 0.38 s, 3.91 and 4.55 × 107 Jones at room temperature, respectively. This is indebted mainly from the effective diffusion of photogenerated carrier from the PbSe surface to ITZO channel layer as well as from the conduction band alignment between them. Therefore, we believe that our hybrid PbSe/ITZO material platform can be widely used to be in favour of incorporation of solution-processed colloidal light absorbing material into the high-performance metal oxide thin film transistor configuration.

Ultrasonic physiotherapy systems should comply with IEC 60601-2-5(particular requirements for safety of ultrasonic physiotherapy equipment) standard for safety of patients and clinical performances. One of the most important parameters in the standard is the effective radiating area (). It has to be measured in accordance with IEC 61689 (field specifications and methods of measurement in the frequency range 0.5MHz to 5MHz). Typical ultrasonic physiotherapy system works in the frequency range 1MHz ~ 3MHz to comply with the IEC 61689. However, ultrasonic physiotherapy system using frequencies over 5MHz is out of the IEC 61689`s scope. That is, even if such ultrasonic physiotherapy systems are developed by demands of the market, there is no standard to apply. It is the motivation for this study. Whereas there are other parameters to be considered, this study focuses on the effective radiating area and shows effectiveness of applying IEC 61689 in measuring effective radiating area of ultrasonic physiotherapy systems using frequency range over 5MHz by comparing the results of computer simulation and experiment. Results of this study shows that applying the IEC 61689 standard to ultrasonic physiotherapy system using frequency range over 5MHz is possible.

Deptartment of Mechanical Systems Engineering, Hansung University(Received March 7, 2013 / Accepted July 24, 2013)Abstract : For safe remote control, information on remote environment has to be delivered to operator realistically, and there have been numerous research efforts on this respect. Among them, haptic technology can significantly enhance safety and overall effectiveness of remote operation by delivering various kinds of information on virtual or real environment to operator. In this study, remote control based on haptic feedback is applied to control of mobile robot moving according to the command from operator avoiding collision with environmental obstacles and maintaining safe distance from them using ultrasonic sensors. Specifically, a remote feedback control structure for mobile robot is proposed. The controller is based on the inner feedback loop that directly utilizes information on distance to obstacles, and the outer feedback loop that the operator directly commands using the haptic device on which the computed reaction force based on the distance information is acting. Effectiveness of the proposed remote control scheme using double feedback loops is verified through a series of experiments on mobile robot. Key Words : haptics, tele-operation, mobile robot.

Haptic feedback force is often suggested to complement visual information through the sense of touch to improve efficiency and safety in the teleoperation of mobile robot. The efficiency and safety of teleoperation are strongly dependent upon how haptic feedback is presented to the operator. In this study a haptic feedback scheme for teleoperation of mobile robot is developed and its effectiveness is experimentally verified. Experimental results show that the developed scheme improves the quality of mobile robot teleoperation in terms of improvement in efficiency and safety.

Virtual device network (VDN) is an intelligent integrated form of a device (control) network and IP network. If a fieldbus based distributed control system (DCS) is implemented on a global VDN, efficiency and flexibility can be significantly improved. In this study DCS implemented on the LonWorks/IP VDN is investigated with an example of model reference adaptive control (MRAC) of a geared DC motor. In order to compensate for the network induced uncertain time delay inherently present on VDN, the modified Smith predictor based internal model controller was integrated to MRAC (MRAC–IMC). The effectiveness of the proposed control scheme was tested through experiment. The proposed control scheme exhibited the robustness to noise and external disturbances and the good tracking performance around zero velocity point occurring due to overshoot and stick friction. Result of this study suggests that sophisticated servo control of dynamic systems is possible from a remote client PC on VDN by properly compensating the network delay.

LonWorks over IP (LonWorks/IP) network is an integrated form of LonWorks device network and IP data network. LonWorks/IP network can offer ubiquitous access to the information on the factory floor and the real-time distributed control can be made possible. Timely response is inevitable for the real-time distributed control on the factory floor. Network induced uncertain time delay deteriorates the performance and stability of the real-time distributed control system on LonWorks/IP network. Therefore, time-varying uncertain time delay needs to be compensated for, in order to guarantee the stability and to improve the performance of the networked distributed control system. In this paper a control scheme based on disturbance observer and repetitive controller for the real-time distributed control on LonWorks/IP network with time-varying delay is proposed and tested through experiment. The result of the proposed control is compared with that of internal model controller (IMC) based on Smith predictor and disturbance observer. It is shown that the proposed control scheme can improve the tracking performance of the periodic reference.

Requirements for Distributed Monitoring and Control Networks (DMCN) differ greatly from those of typical data networks. Specifically, any DMCN technology which employs a fieldbus protocol is different from IP network protocol TCP/IP. In general, one needs to integrate fieldbus protocol and TCP/IP to realize DMCN over IP network or internet, which can be viewed as Virtual Device Network (VDN). Interoperability between devices and equipments is essential to enhance the quality and the performance of predictive maintenance (PM). This paper suggests a basic framework for VDN using DMCN over IP network and a method to guarantee interoperability between devices and equipments.

A tracking position control method is proposed and experimentally evaluated for a linear positioning system. The positioning system is composed of a pneumatic actuator and a 5-port proportional valve. The proposed controller has an inner pressure control loop and an outer position control loop. A PID controller with feedback linearization is used in the pressure control loop to nullify the nonlinearity arising from the compressibility of air. The position controller is also a PID controller augmented with friction compensation using either neural network or nonlinear observer. In the former case, the nonlinearity due to friction is coded on the neural network in the training mode. During the operation, the neural network calculates the proper input voltage that counterbalances the inherent friction. This input voltage is used to cancel out the friction and to linearize the plant dynamics. In the latter case, the compensation method uses an observer to estimate the friction which is assumed to be proportional to the sign of the velocity. The positioning system can then be regarded as a linear one, provided that both nonlinearities in the inner loop and in the outer loop are completely compensated for. Experimental results indicate that the proposed controller significantly improves the tracking performance.

In crowded subway stations indoor air quality (IAQ) is a key factor for ensuring the safety, health and comfort of passengers. In this study, a framework for wireless sensor network in VDN for monitoring and control of IAQ in subway stations is suggested. Since physical variables that describing IAQ such as the concentration of particulate, CO 2 , VOCs and biological agents need to be closely monitored and controlled in multiple locations in subway stations, concept of distributed monitoring and control network using wireless media needs to be implemented. Connecting remote wireless sensor network and device (LonWorks) networks to the IP network based on the concept of VDN can provide a powerful, integrated, distributed monitoring and control performance, making an innovation.

In many cases exploring robots work under harsh conditions such as presence of various kinds of obstacles, high temperature, and limited visibility, etc. So they are required to have tough mechanical structure, good sensing capability, and reliable communication capability for receiving operator's command and for sending information on the state of the robot and on environment to operator. In this study the methodology of implementing these capabilities on exploring robot is explained, and actually an exploring robot that can investigate hazardous or disaster sites is designed and implemented. Finally, the performance of the proposed exploring robot is tested under simulated disaster environment.

Line tracer robots are widely accepted in various industry for the purpose of moving objects. In this study feasibility of using line tracer robots under disaster situation is studied as the line tracing capability may be useful in case of disaster. A small scale line tracer robot is designed, implemented, and tested under disaster situation. Specifically, the MCU based robot hardware including sensor, encoder, motor, and power supply is designed and implemented. Also, the software for receiving sensor signal, for driving motor and for implementing line searching algorithm is designed. The devised robot detects the guide line using 6 infrared optical sensors and can adjust the direction of motion with the front steering servo motor according to the sensor signal. In driving test, the robot showed reliable performance both on the straight and curved paths having obstacles under limited visibility condition as in disaster situation.

Tracking position control of a linear magnetic actuator implemented on distributed control network was studied. In the distributed control system involving a discrete-time controller and a linear magnetic actuator, time delay happens as the controller reads the sensor data or sends out the control input to the actuator located at a remote site. In many cases the time delay is not ignorable, and has significant effect on the control system performance. In order to compensate for the adverse effect of the time delay, the modified Smith predictor was introduced to the control system. The results of simulation and experiment show that the performance of linear magnetic actuator can be improved by augmenting the modified Smith predictor onto the existing control system. With the modified Smith predictor, the position error is reduced and the constant disturbance is suppressed.

A tracking position control method for a linear positioning system composed of a pneumatic actuator and a 3-port proportional valve is proposed, and experimentally evaluated. The proposed controller has an inner pressure control loop and an outer position control loop. The position controller is based on a PID controller augmented with feedback linearization loop and neural network model, while a simple PID controller is used for pressure control. The influence of friction force and parameter change is regarded as a disturbance. The nonlinear relationship between the actuator velocity and acceleration, and the disturbance is coded on the neural network in training mode, and during operation proper input voltage that counterbalances the disturbance is calculated using the neural net model. Then, the outer loop PID controller is designed, assuming that the modeling error and the disturbance can be completely compensated, and, therefore, the actuator can be treated as a linear plant. Experimental verification indicates that the proposed controller significantly improves the tracking performance.

This paper discusses the repetitive tracking control method for a coarse-fine actuator which is implemented on the existing PID controller augmented with feedback linearization loop. The proposed positioning system is composed of a magnetic linear drive as a coarse actuator and a piezoelectric linear positioner as a fine actuator. In particular, the nonlinear friction in a magnetic linear drive and the hysteresis characteristic of a piezoelectric linear positioner are modeled. The feedback linearization loop uses these models in tracking position control. The control strategy is then further extended to include a repetitive control algorithm in tracking periodic inputs. The experimental results show that the performance in tracking sinusoidal waveforms is noticeably improved by augmenting a PID controller together with feedback linearization loop and a repetitive controller.

Acoustic emission (AE) has been studied extensively as a technique for monitoring machining processes. In this study, relationships between the RMS AE signals and the cutting parameters in precision diamond turning are investigated experimentally. To build such experimental relationships, each measured RMS AE signal is seperated into two components, the one associated with the chip formation and the other one resulting from the rubbing friction at the tool flank-workpiece interface. The responses of these components to variations in cutting parameters are then explained. The experimental data suggest that the AE is generated predominantly by the chip formation in diamond turning, whereas the rubbing friction is one of the primary sources of AE in the conventional turning.