• Journal of the Korean Society of Industry Convergence
• /
• v.19 no.1
• /
• pp.10-17
• /
• 2016

In general, articulated robot control technology is limited to the design of robot arm control systems considering each joint of the robot joint as a simple servomechanism. This method describes the varying dynamics of a manipulator inadequately because it neglects the motion and configuration of the whole arm mechanism. The changes of the parameters in the controlled system are significant enough to render conventional feedback control strategies ineffective. This basic control system enables a manipulator to perform simple positioning tasks such as in the pock and place operation. However, joint controllers are severely limited in precise tracking of fast trajectories and sustaining desirable dynamic performance for variations of payload and parameter uncertainties. In many servo control applications the linear control scheme proposes unsatisfactory, therefore, a need for nonlinear techniques that increasing. for Forging process automation.

• Journal of Biomedical Engineering Research
• /
• v.32 no.1
• /
• pp.1-6
• /
• 2011

An active training system has been developed to assist the upper extremity function in patients with spasticity. We also evaluated the performance of the developed assistive system in five normal subjects and one hemiplegic patient. The maximum voluntary contraction (MVC) tests for biceps brachii and triceps brachii were performed and the relationship between linear enveloped EMG signal and the elbow joint torque was found. In order to implement an active training, our system was designed to allow isokinetic movement only when the subject generates elbow joint motion larger than the pre-fixed threshold level. The proposed EMG-feedback control method could provide active exercises, resulting in better rehabilitation protocol for spastic patients.

• The Journal of Korea Robotics Society
• /
• v.8 no.3
• /
• pp.186-196
• /
• 2013

Since its introduction (e.g., [4, 6]), virtual coupling technique has been de facto way to connect a haptic device with a virtual proxy for haptic rendering and control. However, because of the single dependence on spring-damper feedback action, this virtual coupling suffers from the degraded transparency particularly during contact tasks when large device/proxy-forces are involved. In this paper, we propose a novel virtual coupling technique, which, by utilizing passive decomposition, reduces device-proxy position deviation even during the contact tasks while also scaling down (or up) the apparent inertia of the coordinated device-proxy. By doing so, we can significantly improve transparency between multiple degree of freedom (possibly nonlinear) haptic device and virtual proxy. In other to use passive decomposition, disturbance observer of [3] is adopted to estimate human force with some dead-zone modification to avoid "winding-up" force estimation in the presence of device torque saturation. Some preliminary experimental results are also given to illustrate efficacy of the proposed technique.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.53 no.9
• /
• pp.552-561
• /
• 2004

This paper is concerned with a new speed sensorless induction motor scheme which can be successfully applied to at any speed including even zero speed. The proposed method is robust against rotor resistance variations. In addition, simultaneous on-line estimations of speed and rotor resistance are realized based on a feedforward type torque control approach. The rotor flux with a low frequency sinusoidal waveform has been utilized to help the simultaneous estimation for both speed and rotor resistance. The control scheme has no current minor loop to determine voltage references. Since the proposed estimation does not depend on any derivative terms of currents and stator voltages, it offers a good performance at extremely low speed region for sensorless induction motor. Furthermore, the proposed control is simply using motor parameters and stator currents without determining any PI gains for current feedback and any signal injection for the rotor resistance estimation. Finally, both simulation and experimental results are given to show the effectiveness of this method.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.2
• /
• pp.297-304
• /
• 1997

This paper presents a systematic design method of an anti-swing control law for overhead cranes. A velocity servo system for the trolley of a crane is designed based on the dynamics of the trolley and its load. The velocity servo system compensates for the effects of load swing on the trolley dynamics so that the velocity servo is independent of load swing. The velocity servo system is used for the design of a position servo system for the trolley via the loop shaping method. The position servo system and the swing dynamics of the load are then used to design an angle control system for load swing based on the root locus method. The combined position servo and the angle control systems constitute the overall control system. In the presence of low frequency disturbances, the proposed control law guarantees accurate position control for the trolley and fast damping for load swing. Furthermore, the performance of the proposed control law is independent of the mass of the load. Experimental results on a prototype crane show the effectiveness of the proposed anti-swing control law.

• Proceedings of the KIEE Conference
• /
• 1987.11a
• /
• pp.417-420
• /
• 1987

For an increased level of productivity, it is important that the end-point of a robot manipulator moves from an initial location to final position in the minimum time subject to the available maximum actuator's torque (or force) at each joints. The main issue is to develop an algorithm to compute the actuators in real-time. In this paper, a digital state feedback control algorithm has bean developed to obtain the near-minimum-time trajectory for the end-effector of a robot manipulator. In this algorithm, the poles of the linearized closed loop system are judiciously placed in the Z-plane to permit minimum-time response without violating the constraints on the actuator torques. The validity of this algorithm have been established using numerical simulations. A three-link manipulator in chosen for this purpose and results are discussed for three different combinations of initial and final station.

• Journal of Ocean Engineering and Technology
• /
• v.26 no.6
• /
• pp.59-65
• /
• 2012

In this research, a novel mater arm was studied as a teaching device for an underwater revolute robot arm used as a slave arm. The master arm was designed to be a seven-degree-of-freedom (DOF) structure, with a structure similar to that of the slave arm, and to be desktop size to allow it to be worn on a human arm. The master arm with encoders on the joints was used as an input device for teaching a slave robot arm. In addition, small electric magnets were installed at the joints of the master arm to generate the haptic force. A control system was designed to sense excessive force and torque in the joints of the master arm and protect it by controlling the position and velocity of the slave arm through the encoder signal of the master arm.

• Proceedings of the KIPE Conference
• /
• 2005.07a
• /
• pp.8-10
• /
• 2005

In a general purpose inverter, a dead-time compensation strategy is very important for reducing torque ripples and acoustic noises of motors. However, in the case of small capacity inverter, the accurate dead-time compensation is hard to be obtained because a removal of the switching noise in a feedback current signal is difficult on condition of low-cost implementation. In this paper, the operation characteristics of the general purpose inverter applied the dead time compensation algorithm using an instantaneous back calculation of the phase angle of the current are presented.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.35 no.1
• /
• pp.26-35
• /
• 1986

In this paper, non-linear state equations for a 3-phase, 220V, 0.4 KW, squirrel cage induction motor have been derived using the d-q transformation and then these equations have been linearized around an operating point by a small perturbation method. Root loci on the s-plane with repect to the changes of slip S and supply frequency f have been studied. Based on the above results, the derived linear state equations have been augmented to the 6th order, including the output velocity feedback and a discrete PI speed controller. Using the new state equations, stability regions on the Kp-Kl plane have been investigated for slip S and sampling time T. In designing a discrete PI controller, the coefficients Kp and Kl around the normal operating point (220V,1,692rpm,60Hz)have been chosen under the assumptions that each response to a perturbation input of reference speed and load torque be underdamped and dominated by a pair of complex poles. Step responses in the experimental system using an Intel SDK-86 and an optimized PWM inverter show satisfactory results that the maximum overshoots and damped frequency are well coincided with ones from the computer simulation.

• Proceedings of the KIEE Conference
• /
• 2000.07d
• /
• pp.3178-3180
• /
• 2000

In this thesis, a controller which is appropriate for uses of scanner with small error and high speed response is proposed. Recently the application field of scanner is on increase. In case of applying to laser marking, the error of scanner has bad effect to quality. Also it can make difficulties in applying laser show that makes images, unless the high speed response is not realized. For these reasons, a controller that can adjust error and response is need. Because scanner must respond to step input that is put between a few millisecond and hundreds of microsecond with small revolution angle ranges, it is advantageous to have small inertia and large torque. First, the property of scanner is treated, and then using Op-amp and passive components and applying feedback compensation PID controller to design, the effects by controller coefficients are introduced.