• International Journal of Control, Automation, and Systems
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• v.4 no.3
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• pp.325-332
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• 2006

The dynamic responses of human standing postural control were investigated when subjects were exposed to long-term horizontal vibration. It was hypothesized that the motion of standing posture complexity mainly occurs in the mid-sagittal plane. The motor-driven support platform was designed as a source of vibration. The AC Servo-controlled motors produced anterior/posterior (AP) motion. The platform acceleration and the trunk angular velocity were used as the input and the output of the system, respectively. A method was proposed to identify the complexity of the standing posture dynamics. That is, during AP platform motion, the subject's knee, hip and neck were tightly constrained by fixing assembly, so the lower extremity, trunk and head of the subject's body were individually immovable. Through this method, it was assumed that the ankle joint rotation mainly contributed to maintaining their body balance. Four subjects took part in this study. During the experiment, the random vibration was generated at a magnitude of $0.44m/s^2$, and the duration of each trial was 40 seconds. Measured data were estimated by the coherence function and the frequency response function for analyzing the dynamic behavior of standing control over a frequency range from 0.2 to 3 Hz. Significant coherence values were found above 0.5 Hz. The estimation of frequency response function revealed the dominant resonance frequencies between 0.60 Hz and 0.68 Hz. On the basis of our results illustrated here, the linear model of standing postural control was further concluded.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.6
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• pp.579-586
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• 2002

With increase of servo motor in industrial and home application, a number of papers related to PMSM control have been researched. Among them, sensorless control schemes are especially concerned in a view point of their cost reduction. In a conventional approach, a rotor position is generally estimated by the integration of estimated rotor speed. In this method, because of their tight relationship between the amplitude of back-emf and rotor position, it is somewhat difficult to find two parameters at the same time. To solve this problem, a novel sensorless control scheme is proposed. It utilizes a back-emf normalization, so that it does not require the variables related with the amplitude of back-emf. The validity of the proposed control scheme is verified through experimental results.

• Journal of Advanced Marine Engineering and Technology
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• v.15 no.1
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• pp.85-95
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• 1991

All physical systems are nonlinear to some degree. The examples are relay, backlash, deadzone, saturation element and so on. In the linear control system design, it is useful method to restrict the nonlinearity to the linearity of system over the operation range. It is worth noting that nonlinearities may be intentionally introduced in to a system. A simple of an intentional non-linearity is the Bang-Bang controller which uses the On-Off relay. In this paper, an angular position servosystem made of a DC servomotor controlled by a microcomputer is discribed. Authors use two methods in the design of controller. The one is linear controller designed by the optimal feedback control theory only and the other is nonlinear controller designed by On-Off relay with optimal feedback control theory. To do the real time control, the controller is designed by using 16bit personal computer and A/D.D/A converter(12bit) is used in order to convert the signal. According to this way, the results from real time control are as follows. 2) Under the On-Off controller with hysterisis the influence of disturbance is considerably smaller than the linerar controller. 3) An increase in the sampling period has a destabilizing effect. 4)In the controller performance, the response time of the On-Off controller is longer than that of the linear controller. To close, we note that the On-Off controller with hysterisis is more attractive than the linear controller in the presence of the input limit.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.4
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• pp.27-35
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• 1996

The ship's propulsion efficiency depends upon a combibation of engine and propeller. The propeller has better efficiency as the engine has lower rotational speed. This situation led the engine manufacures to design the engine that has lower speed, longer stroke and a small number of cylinders. With this new trends the conventional mechanical-hydrualic governors for engine speed control have been replaced by digital speed controllers which adopted the PID control or the optimal control algorithm. But these control algorithms have not enough robustness to suppress the variations of the delay-time and the parameter perturbation especially in low speed engine. In this study we consider the perturbations of the engine parameters as the modeling uncetainties and design a robust speed controller for marine medium speed diesel engine by means of $ extit{H}_{infty}$control theory having the central solution. By comparing the results of the robust speed controller with those of mechanical governor and PID controller, the validity of the robust speed controller under parameter variations is confirmed. The speed control of the experimental diesel engine of carried out using actuator which is composed of PWM signal generator and D.C servo motor.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.4
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• pp.349-349
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• 1996

The ship's propulsion efficiency depends upon a combibation of engine and propeller. The propeller has better efficiency as the engine has lower rotational speed. This situation led the engine manufacures to design the engine that has lower speed, longer stroke and a small number of cylinders. With this new trends the conventional mechanical-hydrualic governors for engine speed control have been replaced by digital speed controllers which adopted the PID control or the optimal control algorithm. But these control algorithms have not enough robustness to suppress the variations of the delay-time and the parameter perturbation especially in low speed engine. In this study we consider the perturbations of the engine parameters as the modeling uncetainties and design a robust speed controller for marine medium speed diesel engine by means of $ extit{H}_{infty}$control theory having the central solution. By comparing the results of the robust speed controller with those of mechanical governor and PID controller, the validity of the robust speed controller under parameter variations is confirmed. The speed control of the experimental diesel engine of carried out using actuator which is composed of PWM signal generator and D.C servo motor.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.9
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• pp.946-951
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• 2009

The small multi-jointed robots for most education are developed with the way of firmware. But the firmware may be very difficult to develop as gradually increasing throughputs and control routines. Due to limit of firmware we try to use on RTOS, but hard to adapt on the small multi-jointed robots. It would be hard to install RTOS into the small multi-jointed robots because of the size capacity of RTOS, and lack of libraries for control of the particular hardware. Moreover, even its RTOS with many functions causes its to make overheads scheduling, TCB (Task Control Block), and task states. Also to keep maintenance of RTOS, it is composed of components for the whole structure of my proposed RTOS. Additionally, We provided with libraries of servo motor and sensor control and developed RMS (Rate Montonic scheduler) to handle tasks on real time and reduce overheads. Therefore, It is possible to work the fixed priority and task preemptive way. We show one example of the multi-jointed robot installed with my proposed RTOS, which shows to obstacle avoidance and climbing up the slope.

• Journal of the Korean Institute of Intelligent Systems
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• v.7 no.5
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• pp.46-50
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• 1997

In fuzzy logic control, static fuzzy rules cannot cope with significant changes of parameters of plants or environment. To solve this prohlem, self-organizing fuzzy control. neural-network-hased fuzzy logic control and so on have heen introduced so far. However, dynamically changed fuzzy rules of these schemes may make a fuzzy logic controller Fall into dangerous situations because the changed fuzzy rules may he incomplete or inconsistent. This paper proposes a new adaptive filzzy logic control scheme using a predictivc neural network. Although some parameters of a controlled plant or environment are changed, proposed fuzzy logic controller changes its decision outputs adaptively and robustly using unchanged initial fuzzy rules and the predictive errors generated hy the predictive neural network by on-line learning. Experimental results with a D<' servo-motor position control problem show that propnsed cnntrol scheme is very useful in the viewpoint of adaptability.

• Journal of Power Electronics
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• v.5 no.2
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• pp.151-159
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• 2005

The errors generated from current measurement paths are inevitable, and they can be divided into two categories: offset error and scaling error. The current data including these errors cause periodic speed ripples which are one and two times the stator electrical frequency respectively. Since these undesirable ripples bring about harmful influences to motor driving systems, a compensation algorithm must be introduced to the control algorithm of the motor drive. In this paper, a new compensation algorithm is proposed. The signal of the integrator output of the d-axis current regulator is chosen and processed to compensate for the current measurement errors. Usually the d-axis current command is zero or constant to acquire the maximum torque or unity power factor in the ac drive system, and the output of the d-axis current regulator is nearly zero or constant as well. If the stator currents include the offset and scaling errors, the respective motor speed produces a ripple related to one and two times the stator electrical frequency, and the signal of the integrator output of the d-axis current regulator also produces the ripple as the motor speed does. The compensation of the current measurement errors is easily implemented to smooth the signal of the integrator output of the d-axis current regulator by subtracting the DC offset value or rescaling the gain of the hall sensor. Therefore, the proposed algorithm has several features: the robustness in the variation of the mechanical parameters, the application of the steady and transient state, the ease of implementation, and less computation time. The MATLAB simulation and experimental results are shown in order to verify the validity of the proposed current compensating algorithm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.1066-1069
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• 2002

Dynamic postural control varies with the environmental context, specific task and intentions of the subject. In this paper, dynamic postural control against forward-backward perturbations of a platform was estimated using tri-axial accelerometers and a force plate. Ten young healthy volunteers stood upright in comfortable condition on the perturbation system which was controlled by an AC servo motor. With anterior-posterior perturbations, movements of ankle, knee and hip Joints were obtained by tri-axial accelerometers. and ground reaction forces with corresponding displacements of the center of pressure(CoP) by the force plate. The result showed that the ankle moved first and the trunk forward, which implies that the mechanism of the dynamic postural control in forward-backward perturbations, occurred in the procedure of the ankle, the knee and the hip. Knee flexion and hip extension in the period of acceleration, constant velocity and deceleration phase is very important fur the balance recovery. These responses depends on the magnitude and timing of the perturbation. From the present study the accelerometry-system appears to be a promising tool for understanding kinematic accelerative In response to a transient platform perturbation. A more through understanding of balance recovery mechanism may aid in designing methods for reducing falls and the resulting injuries.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1022-1027
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• 2003

The Motion controllers provide the sophisticated performance and enhanced capabilities we can see in the movements of robotic systems. Several types of motion controllers are available, some based on the kind of overall control system in use. PLC (Programmable Logic Controller)-based motion controllers still predominate. The many peoples use MCU (Micro Controller Unit)-based board level motion controllers and will continue to in the near-term future. These motion controllers control a variety motor system like robotic systems. Generally, They consist of large and complex circuits. PLC-based motion controller consists of high performance PLC, development tool, and application specific software. It can be cause to generate several problems that are large size and space, much cabling, and additional high coasts. MCU-based motion controller consists of memories like ROM and RAM, I/O interface ports, and decoder in order to operate MCU. Additionally, it needs DPRAM to communicate with host PC, counter to get position information of motor by using encoder signal, additional circuits to control servo, and application specific software to generate a various velocity profiles. It can be causes to generate several problems that are overall system complexity, large size and space, much cabling, large power consumption and additional high costs. Also, it needs much times to calculate velocity profile because of generating by software method and don't generate various velocity profiles like arbitrary velocity profile. Therefore, It is hard to generate expected various velocity profiles. And further, to embed real-time OS (Operating System) is considered for more reliable motion control. In this paper, the structure of chip-based precision motion controller is proposed to solve above-mentioned problems of control systems. This proposed motion controller is designed with a FPGA (Field Programmable Gate Arrays) by using the VHDL (Very high speed integrated circuit Hardware Description Language) and Handel-C that is program language for deign hardware. This motion controller consists of Velocity Profile Generator (VPG) part to generate expected various velocity profiles, PCI Interface part to communicate with host PC, Feedback Counter part to get position information by using encoder signal, Clock Generator to generate expected various clock signal, Controller part to control position of motor with generated velocity profile and position information, and Data Converter part to convert and transmit compatible data to D/A converter.