• International Journal of Control, Automation, and Systems
• /
• v.4 no.1
• /
• pp.42-52
• /
• 2006

In order to utilize hydrodynamic drag force on articulated robots moving in an underwater environment, an optimum motion planning procedure is proposed. The drag force acting on cylindrical underwater arms is modeled and a directional drag measure is defined as a quantitative measure of reaction force in a specific direction in a workspace. A repetitive trajectory planning method is formulated from the general point-to-point trajectory planning method. In order to globally optimize the parameters of repetitive trajectories under inequality constraints, a 2-level optimization scheme is proposed, which adopts the genetic algorithm (GA) as the 1st level optimization and sequential quadratic programming (SQP) as the 2nd level optimization. To verify the validity of the proposed method, optimization examples of periodic motion planning with the simple two-link planner robot are also presented in this paper.

• Journal of Korean Physical Therapy Science
• /
• v.15 no.4
• /
• pp.27-34
• /
• 2008

Background: This study was designed to analyze Repetitive dorsiflexion exercises in ankles have effects on the active range of flexion and extension motion through lumbar, cervical spine and ankle, wrist joints. Methods: 30 female college students in their twenties who frequently wear high heels participated the number of the experimental group was 15 persons and the number of the control group was 15 persons. They did exercise at the physical therapy room in M college, from the 8th of March to the 11th of April 2007. The experimental group had used the model of dorsiflexion repetitive exercise three times per week, for 4 weeks, but the control group did not exercise at all. In the sagittal plane active ROM of the these spine and joints were measured before and after the experiment using a digital goniometer. The results of two groups were compared and analyzed using paired T-test. Results: The active range of flexion and extension motion of the vertebra(especially lumbar flexion) and distal joints were significantly different in exercise group(p<.05). Conclusion: The model of repetitive dorsiflexion exercise of the ankle joint had positive effects on improving the active range of flexion and extension motion of the lumbar vertebra and distal joints of limbs. The results suggest that the repetitive dorsiflexion exercise is useful and also effective therapy for improving motion in women usually wearing high-heel.

• Journal of Institute of Control, Robotics and Systems
• /
• v.4 no.4
• /
• pp.420-426
• /
• 1998

It is the purpose of this paper to make a preliminary study on the use of repetitive control to improve velocity accuracy by eliminating repetitive disturbances caused by machining inaccuracies of the axis of rotation location. If the control system can be intelligent enough to compensate for such machining errors, then one may be able to improve the accuracy of the velocity control, or alternatively, one may maintain the same accuracy and relax the machining tolerances required. This could decrease cost significantly. Experiments are performed testing repetitive control methods on a constant speed rolling operation testbed. The experimental results show very substantial decreases in the tracking error of the system. Spectral data of the output motion are given to demonstrate the attenuation of the disturbance frequencies and harmonics, related to the bandwidth being used. It is seen that the simplest form of repetitive control which is very easily implemented, can produce striking improvement in control system performance in such belt drive rolling operations, and the learning can be accomplished in a short time.

• The Journal of Korean Physical Therapy
• /
• v.33 no.1
• /
• pp.34-39
• /
• 2021

Purpose: The purpose of this study was to verify the effectiveness of repetitive sit to stand training to improve knee extensor strength and walking ability of total knee replacement patients. Methods: In this study, 12 patients with total knee replacement patients were recruited from a rehabilitation hospital. They were divided into two groups: a repetitive sit to stand group (n=6) and a control group (n=6). They all received 30 minutes of continuous passive motion (CPM). After that, the repetitive sit to stand group performed repetitive sit to stand training, and the control group performed resistance exercise for 15 minutes five times a week for 2 weeks. After 2 weeks of training, knee extensor strength and spatiotemporal gait parameters were measured. Knee extensor strength was measured by Biodex system 3, walking ability was measured by Biodex gait trainer 2. Paired t test was performed to verify the difference between before and after intervention within the group, and analysis of covariance was used to verify the differences between the two groups. Results: After the training periods, the repetitive sit to stand group showed a significant improvement in knee extensor muscle strength, walking speed, step length of the operated side, and step length of the non-operated side (p<0.05). Conclusion: The results of this study showed that repetitive sit to stand training was more effective in improving knee extensor muscle strength and walking ability. Therefore, to strengthen knee extensor muscles and improve the walking ability of total knee replacement patients, it is necessary to consider repetitive sit to stand training.

• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.538-538
• /
• 2000

This paper presents a learning controller for repetitive gate control of biped robot. The learning control scheme consists of a feedforward learning rule and linear feedback control input for stabilization of learning system. The feasibility of teaming control to biped robotic motion is shown via dynamic simulation with 12 dof biped robot.

• Journal of the Ergonomics Society of Korea
• /
• v.18 no.2
• /
• pp.103-120
• /
• 1999

The purpose of this study was to evaluate the manual workload in repetitive wrist and finger motion. To evaluate manual workload, angular displacement of the joint, EMG of the muscle and subjective rating were studied. Both wrist motion and finger motion were studied. A screw-driving task was used for the wrist motion experiment. A keyboard typing task was used for the finger motion experiment. All finger joint angles and wrist angles were measured by an angle-measuring glove($CyberGlove^{TM}$, Virtual Technologies, Inc.). Surface EMG was recorded from FCU muscle and FDS muscle simultaneously with the angle measurement. Subjective ratings of exertion were also recorded using the modified Borg's CR-10 scale. Repetition rates of 0.5, 1, 2 motions per second were used with each task. As a result, manual workload increased with increasing repetitiveness. Peak spectral magnitude and frequency components corresponded closely with joint angular displacement amplitudes and repetition rates. Results of the correlation analysis showed that there were significant correlation among EMG, frequency-weighted motion and subjective measurement. Both EMG and frequency-weighted filtering showed consistent workload estimation with increasing task frequency. Subjective ratings showed slight over-estimation of the workload as the task frequency is increased.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.21 no.6
• /
• pp.850-856
• /
• 2018

In this paper, a controller based on repetitive learning control is designed to control an unmanned surface vessel with nonlinear characteristics and unknown parameters. First, we define the equations of motion and error system of the unmanned vessel, and then design an repetitive learning controller composed of system error and estimated unknown parameters based on repetitive learning control and adaptive control. The stability of the unmanned vessel model controlled by the designed controller is verified through the analysis of the Lyapunov stability. Simulation shows that the error converges asymptotically to zero with semi-global result, confirming that the unmanned vessel is moving toward a given ideal path, and verifies that the controller is also feasible.

• Journal of the Korean Institute of Telematics and Electronics B
• /
• v.28B no.11
• /
• pp.913-924
• /
• 1991

In this paper, we propose a motion estimation algorithm using hierarchical structure. The algorithm uses the image pyramids from the repetitive application of Gaussian filtering and decimation, and performs an inter-level displacement propagation in its motion estimation process. The motion estimation algorithm based on the hierarchical structure is shown to be very effective since this scheme utilizes the local imformation as well as the global imformation. The experimental results on the various data imdicate that compared to the Horn and Schunck's method, the proposed algorithm yields an accurate motion estimation with a fast convergence behaviour.

• Journal of the Ergonomics Society of Korea
• /
• v.26 no.1
• /
• pp.39-46
• /
• 2007

The purpose of this study was to develop a comprehensive posture classification scheme considering the effects of external load and motion repetition as well as those of working posture. The scheme was developed based on a series of existing empirical studies dealing with postural classification scheme, effects of external load and motion repetition. Ranges of joint motions, external load and motion repetition were divided into the groups with the same degree of discomforts. Each group was assigned a numerical relative discomfort score of code on the basis of discomfort values for the neutral position of elbow flexion. The criteria for evaluating stress of working postures were proposed based on the four distinct action categories, in order to enable practitioners to apply appropriate corrective actions. The proposed scheme was compared with OWAS, RULA and REBA. The comparison revealed that while the proposed scheme and RULA showed similar results for the working postures with light external load and non-repetitive postures, the former overestimated postural load for postures with moderate or heavy external load and repetitive postures than the latter.

• Journal of the Ergonomics Society of Korea
• /
• v.33 no.6
• /
• pp.565-575
• /
• 2014

Objective: The aim of this study is to evaluate the effect of weight of load and time on the physical workload of repetitive upper-limb tasks with handling light weight loads using EMG and perceived discomfort, and to investigate the relationship between EMG and perceived discomfort for those repetitive tasks of moving light weight loads. Background: Repetitive upper-limb motion is known as one of the main risk factors of musculoskeletal disorders, and a lot of repetitive tasks are carried out while handling light weight loads in the industry. In evaluating the workload of repetitive tasks handling light weight loads, EMG and perceived discomfort can be used, though their relationship in those work conditions are not much investigated. Method: A laboratory experiment with 18 healthy males were conducted to record EMG signals from 5 muscle sites of the right arm and shoulder and rate perceived discomforts for the body parts and the whole body while carrying out repetitive materials-handling tasks for 52min. The subjects were divided into 3 groups which handled the loads of 1kg, 2kg and 3kg, respectively. ANOVAs were conducted to analyze the effects of the weight and time on RMS of EMG amplitude (normalized RMS: NRMS), median frequency of power spectrum of EMG (normalized MDF: NMDF) and perceived discomfort. The correlations between NRMS and NMDF and perceived discomfort were also analyzed. Results: Statistically significant muscular fatigue effects were not found from NRMS and NMDF in most muscles, while there were significant increases of discomfort as the task time elapsed. It was shown that there were an increasing trend of the muscular activity as the weight of load increased and a decreasing trend of median frequency of EMG of upper and lower arms as time elapsed. It was found that there were significant negative correlations between NMDFs from the lower arm and discomfort ratings, though the relationships were weak. Conclusion: It can be concluded that the working conditions adopted in this study were not enough to induce muscular fatigue, while there was significant increase in perceived discomfort. A further study is necessary to integrate the objective and subjective measures for more reliable and sensitive evaluation of workload of repetitive tasks of handling light weight loads. Application: This study can be used as a basic study for the evaluation of workload of repetitive tasks handling light weight loads.