• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.6
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• pp.389-395
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• 2019

This paper presents the sensorless position control of an auxiliary scaffolding step system for vehicles using DC motors. The designed auxiliary scaffolding step has a mechanical protector at the stop position. At this position, the scaffolding is forcibly stopped by the mechanical protector, and the motor current is dramatically increased to the stall current of the DC motor, thereby increasing the electrical damage. In this study, the estimated back EMF- and current model-based observers are proposed to estimate the motor speed and stop position. A simple V/F acceleration voltage pattern is used to operate the auxiliary scaffolding system. The estimated moving position is adopted to determine the stop position of the DC motor with the load current state. The operating current of the DC motor can be reduced by the estimated moving position and V/F acceleration pattern. At the stop position, the proposed sensorless position controller can smoothly stop the DC motor with the estimated moving position and reduced load current without any mechanical and electrical stress from the stall current from the mechanical protector. The proposed control scheme is verified by the comparison of simulations and experiments.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.6
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• pp.693-698
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• 2004

In this paper, an iterative learning control method is applied to suppress a vibration of a 2-mass system which has a flexible coupling between a load and a motor. More specifically, conditions for the load speed without vibration are derived based on the steady-state condition. And the desired motor position trajectory is synthesized based on the relation between the load and motor speed. Finally, a PD-type iterative learning control law is applied for the desired motor position trajectory. Since the learning law applied for the desired trajectory guarantees the perfect tracking performance, the resulting load speed shows no vibration even when there exist model uncertainties. A modification to the learning law is also Presented to suppress undesired effects of an initial position error, The simulation results show the effectiveness of the proposed learning method.

• Journal of The Korean Society of Integrative Medicine
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• v.8 no.1
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• pp.169-175
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• 2020

Purpose : This study was performed to comparison of distance change of subacromial space according to shoulder abduction angle in loaded and unloaded conditions. Methods : The subjects were 20 male college students, and the subacromial space was measured using an ultrasound diagnostic apparatus. The participants shoulder abduction was measured during each shoulder resting position and 45 ° abduction with loads of 1 kg, 2 kg, 3 kg. The collected data were analyzed by a paired t-test and repeated measure ANOVA with the SPSS (Ver. 22) program. Results : The subacromial space showed statistically significant decreased in 45 ° abduction than resting position (p<.001). All the subacromial space increased during the according to loads (1 kg, 2 kg, 3 kg) at the resting position but at 45 ° abduction showed statistically significant decreased as the load increases (p<.05). Also, subacromial space showed significant changes in the 2kg, 3kg compared with the 0kg loads. Conclusion : These results identified that shoulder abduction angle and load were related to subacromial space. When resting position, subacromial space is larger at loads than unload. As the load and shoulder abduction angle increase, subacromial space is reduced compared to resting.

• Journal of Power Electronics
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• v.13 no.6
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• pp.975-984
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• 2013

This paper proposes a robust optimal nonlinear control with an observer to reject the offset errors of position tracking for surface mounted permanent magnet synchronous motors. We provide the control method to reject offset errors and load torque for designing field oriented control (FOC) based the alternating current (AC) frame. The proposed method consists of a torque generator, a commutation scheme, an electrical controller, and a load torque observer. The mechanical controller is designed to compensate for load torque and the offset error and generate the desired torque. The commutation scheme is proposed to create the desired currents for the desired torque. The electrical controller is developed to guarantee the desired currents. The observer is designed to estimate both the velocity and the load torque. In order to obtain the robustness to parameter uncertainties and a gain tuning guide, the linear quadratic regulator method is applied to the proposed method. The closed-loop stability is proven. A detailed process for the FOC design and an analysis of the control methods based on the AC frame are presented. The performance of the proposed method was validated via experiments. The proposed method obtains the FOC based on the AC frame. Furthermore, the position tracking performance of the proposed method is superior to that of the conventional method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.3
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• pp.430-438
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• 2019

For a pump or a compressor motor, a high periodic load torque variation is induced by the mechanical works, and it causes system vibration and noise. To minimize these problems, load torque compensation method, injecting periodic torque current, could be utilized. However, with the sensorless control method, which is usually utilized in the pump and compressor for low cost, the periodic torque current degrades the accuracy of the rotor position estimation owing to the inductance variation. This paper analyzes the rotor position and speed estimation error of sensorless control method with constant motor parameters under period loading. Assuming the constant speed by the accurate load torque compensation, the speed error equation is derived in frequency domain with inductance depending on the stator current. Further, it is also shown that the rotor position error could be minimized by compensating the inductance variation. The simulation and experimental results verify that the derived speed error model and the validity of the inductance compensation method.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.5
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• pp.435-442
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• 1997

The roof crane system is used for transporting a variable load to a target position. The goal of crane control system is transporting the load to a goal position as quick as possible without rope oscillation. The crane is generally operated by an expert operator, but recently an automatic control system with high speed and rapid tansportation is required. In this paper, we developed a simple fuzzy controller which has been introduced expert's knowledge base for anti-swing and rapid tranportation to goal position. In particular, we proposed the synthesis reasoning method which synthesizes on the basis of expert knowledge of the angle control input and position control input which are inferenced parallel and simultaneously. And we confirmed that the performance of the developed controller is effective as a result of applying it to crane simulator and also verified whether the proposed synthesis rules have been applied correctly using clustering algorithm from the measured data.

• Structural Engineering and Mechanics
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• v.4 no.1
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• pp.49-59
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• 1996

This paper considers large deflection problem of a simply supported beam with variable are length subjected to a point load. The beam has one of its ends hinged and at a fixed distance from this end propped by a frictionless support over which the beam can slide freely. This highly nonlinear flexural problem is solved by elliptic-integral method and shooting-optimization technique, thereby providing independent checks on the new solutions. Because the beam can slide freely over the frictionless support, there is a maximum or critical load which the beam can carry and it is dependent on the position of the load. Interestingly, two possible equilibrium configurations can be obtained for a given load magnitude which is less than the critical value. The maximum arc-length was found to be equal to about 2.19 times the fixed distance between the supports and this value is independent of the load position.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1048-1057
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• 2015

This paper proposes a sensorless speed control algorithm for parallel-connected dual Surface-mounted Permanent Magnet Synchronous Motors (SPMSMs) fed by a single inverter. For stable parallel operation of synchronous motors with a single inverter, each motor has to be constantly kept in the synchronization state regardless of load torque. If the master motor with the larger load is controlled, the synchronous state will be maintained. Therefore, detection of the master motor is essential. Conventionally, the master motor is determined by comparing the rotor position error from the relation between the back-EMF for torque angle and the flux position; consequently, the position sensor is deemed essential for finding the rotor position. The parallel sensorless speed control method proposed in this paper uses no position sensor, instead it compares the flux-axis current from the connection between the back-EMF for torque angle and current in unbalanced load conditions. The results of simulation and experiment conducted verify the efficacy of the proposed method.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.201-210
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• 2018

This paper proposes a new start-up method for a load commutated inverter (LCI) in a large synchronous gas-turbine generator. The initial rotor position for start-up torque is detected by the proposed initial angle detector, which consists of an integrator and a phase-locked loop. The initial rotor position is accurately detected within 150ms, and the angle difference between the real position and the detected position is less than 1%. The LCI system operates in two modes (forced commutation mode and natural commutation mode) according to operating speed range. The proposed controllers include a forced commutation controller for the low-speed range, a PI speed controller and a PI current controller, where the forced commutation controller is connected to the current controller in parallel. The current controller is modeled by Matlab/Simulink, where a six-pulse delay of the thyristor and a processing delay are considered by using a zero-order hold. The performance of the proposed start-up method is evaluated in Matlab/Psim at standstill and at low speed. To verify the feasibility of the method, a 5kVA LCI system prototype is implemented, and the proposed initial angle detector and the system performance are confirmed by experimental results from standstill to 900rpm.

• The Journal of the Korea institute of electronic communication sciences
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• v.3 no.4
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• pp.266-275
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• 2008

The sensorless speed control technique for BLDC motor using digital IP control is proposed in this paper for advanced speed characteristic which is robust to motor parameters and load variations. The sensorless drive of BLDC motor using terminal voltages is affected by load or speed because it uses analog filters to estimate the rotor position. For this reason, the robust speed controller with the accurate rotor position estimator is needed for sensorless control which is robust to load and insensitive to motor parameters. The constant speed robust to load variation and the stable sensorless control of BLDC motor robust to the increase or decrease of speed with constant load is implemented using digital IP control in this paper. The validity to these is established with experimentation.