• The Journal of Korea Robotics Society
• /
• v.18 no.2
• /
• pp.143-154
• /
• 2023

In this study, a fast motion planning method for the swing motion of a 6x6 wheel-legged robot to traverse large obstacles and gaps is proposed. The motion planning method presented in the previous paper, which was based on trajectory optimization, took up to tens of seconds and was limited to two-dimensional, structured vertical obstacles and trenches. A deep neural network based on one-dimensional Convolutional Neural Network (CNN) is introduced to generate keyframes, which are then used to represent smooth reference commands for the six leg angles along the robot's path. The network is initially trained using the behavioral cloning method with a dataset gathered from previous simulation results of the trajectory optimization. Its performance is then improved through reinforcement learning, using a one-step REINFORCE algorithm. The trained model has increased the speed of motion planning by up to 820 times and improved the success rates of obstacle crossing under harsh conditions, such as low friction and high roughness.

• Biomedical Engineering Letters
• /
• v.8 no.4
• /
• pp.345-353
• /
• 2018

This study suggested a new EMG-signal-based evaluation method for knee rehabilitation that provides not only fragmentary information like muscle power but also in-depth information like muscle fatigue in the field of rehabilitation which it has not been applied to. In our experiment, nine healthy subjects performed straight leg raise exercises which are widely performed for knee rehabilitation. During the exercises, we recorded the joint angle of the leg and EMG signals from four prime movers of the leg: rectus femoris (RFM), vastus lateralis, vastus medialis, and biceps femoris (BFLH). We extracted two parameters to estimate muscle fatigue from the EMG signals, the zero-crossing rate (ZCR) and amplitude of muscle tension (AMT) that can quantitatively assess muscle fatigue from EMG signals. We found a decrease in the ZCR for the RFM and the BFLH in the muscle fatigue condition for most of the subjects. Also, we found increases in the AMT for the RFM and the BFLH. Based on the results, we quantitatively confirmed that in the state of muscle fatigue, the ZCR shows a decreasing trend whereas the AMT shows an increasing trend. Our results show that both the ZCR and AMT are useful parameters for characterizing the EMG signals in the muscle fatigue condition. In addition, our proposed methods are expected to be useful for developing a navigation system for knee rehabilitation exercises by evaluating the two parameters in two-dimensional parameter space.

• PNF and Movement
• /
• v.9 no.1
• /
• pp.1-9
• /
• 2011

Purpose : The purpose of this study is to analyze the effect of closed-chain exercise on weight supporting rate change within hemiplegic side and static dynamic balance ability in stroke patients. Methods : The subjects of the study were 13 hemiplegic patients who carried out closed-kinematic chain exercise program over 6 weeks. The exercises of the program are stand to sit with stall bar, stair-up & down by a hemiplegic leg and bridging exercise crossing the non-hemiplegic leg onto the hemiplegic leg. Each exercise was carried out over 3 sets of 10reps. Results : The results of this study were summarized as follows: 1. After intervention, there was a statistically significant change in the weight supporting rate within hemiplegic and non-hemiplegic side(P<0.05). 2. After intervention, there was a statistically significant change in the static balance(FICSIT-4) ability(P<0.05). 3. After intervention, there was a statistically significant change in the dynamic balance(FSST, TUG, FRT) ability(P<0.05). Conclusion : The results of the study suggests that closed-chain exercise program in stroke patients improves their weight supporting rate and enhance the static dynamic balance.

• Journal of Pharmacopuncture
• /
• v.4 no.2
• /
• pp.105-112
• /
• 2001

In Oriental Medicine, mononeuropathy belongs to or . Common peroneal neuropathy(CPN) is the most frequently encountered mononeuropathy in the lower extremity. It is usually caused by direct surgery injury, compression, leg crossing, trauma, traction etc, occasionally by nerve tumor. A 47-year-old healthy man was complained of the sudden development of left foot drop and sensory manifestation owing to suspected compression and habitual leg-crossing. Acupuncture along with bee-venom acupuncture, moxibustion was performed mainly at Stomach and Gallbladder Meridian specially ST36, ST37, ST40, GB34 and GB39. Nerve conduction study and electromyography was also performed three times. Symtoms was relieved fast, and full recovery took about 110 days. Acupuncture and bee-venom acupuncture are considered to be beneficial to CPN. More clinical trials and studies are needed.

• Archives of Plastic Surgery
• /
• v.50 no.2
• /
• pp.188-193
• /
• 2023

Vascular injury following traumatic knee injury quoted in the literature ranges from 3.3 to 65%, depending on the magnitude and pattern of the injury. Timely recognition is crucial to ensure the revascularization is done within 6 to 8 hours from the time of injury to avoid significant morbidity, amputation, and medicolegal ramifications. We present a case of an ischemic limb following delayed diagnosis of popliteal artery injury after knee dislocation. Even though we have successfully repaired the popliteal artery, the evolving ischemia over the distal limb poses a reconstruction challenge. Multiple surgical debridement procedures were performed to control the local tissue infection. Free tissue transfer with chimeric latissimus dorsi flap was done to resurface the defect. However, the forefoot became gangrenous despite a free muscle flap transfer. His limb appeared destined for amputation in the vicinity of tissue and recipient vessels, but we chose to use a cross-leg free flap as an option for limb salvage.

• Journal of the Korean Society of Physical Medicine
• /
• v.9 no.1
• /
• pp.93-99
• /
• 2014

PURPOSE: The purpose of this study was to compare three dimensional displacement and peak velocity of the center of mass (COM) during obstacle crossing in young and older adults. METHODS: 10 young adults (6 males/4 females, $24.6{\pm}1.9$ years, age range: 22.0-26.9) and 10 older adults (1 male/9 females, $76.9{\pm}5.1$ years, age range: 65.2-81.2) participated in the study. Both groups crossed an obstacle, which is 10% of leg length, and COM was measured using motion analysis system. Independent t-test was used to find significant differences between two groups. RESULTS: The older adults showed significantly greater and faster COM displacement and peak velocity in mediolateral (M-L) direction as compared with young adults (p<.01 and p<.001 respectively). However, the young adults showed significantly greater and faster COM displacement and peak velocity in anteroposterior (A-P) direction as compared with older adults (p<.05 and p<.001 respectively). Furthermore, the young adults showed faster peak velocity of COM in vertical direction as compared with older adults (p<.001). However, no significant difference was found in the COM displacement in vertical direction between two groups. CONCLUSION: Greater and faster COM displacement and peak velocity in M-L direction in older adults were due to compensatory adjustment for appropriate contact on base of support of swing limb. Thus, the motion of the COM in M-L direction may be a crucial factor to identify risk of falls in older adults.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.43 no.3 s.309
• /
• pp.16-24
• /
• 2006

In this paper, fault-tolerant gait planning of a hexapod robot for walking over irregular terrain is presented. The failure concerned in this paper is a locked joint failure for which a joint in a leg cannot move and is locked in place. Based on the previously proposed fault-tolerant tripod gait for walking over even terrain, fault-tolerant follow-the-leader(FTL) gaits are proposed for a hexapod robot with a failed leg to be able to walk over two-dimensional rough terrain, maintaining static stability and fault tolerance. The proposed FTL gait can have maximum stride length for a given foot position of a failed leg, and yields better ditch crossing ability than the previously developed gaits. The applicability of the proposed FTL gait is verified by using computer graphics simulations.

• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.523-528
• /
• 2000

In this paper, the new type biped walking robot which is composed of the minimum number or links just for walking and its appropriate gaits are proposed. The proposed new gaits for this robot are four-crossing, crawling, standing and turning gait. In designing the biped robot we propose the Performance Index which means the needed torque per a moving distance and generate foot trajectories by $3^{rd}$ order spline Interpolation. Among those, numerically we find the optimal conditions which minimize the Performance Index. Dynamically stable walking of the biped robot is realized by satisfying the stability condition of ZMP(zero moment point), which is related to maintaining the ZMP within the region of the supporting foot during the s1n91e leg support phase. We determine the region of mass center from the stability condition of ZMP and plan references which track the mass conte. trajectory of constant velocity. Finally we implement the gaits statically tracking the planned trajectories using PD control method.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.04b
• /
• pp.490-496
• /
• 1995

A four-legged mobile robot can move on the plain terrain with mobility and stability, but if there exist any obstacles on the terrain of the motion direction, it takes extra times for a mobile robot to cross those obstacles and the stability should be considered during motion. The main objevtive is the study of a quadruped which can cross obstacles with better mobility, stability and fuel economy than any other wheeled or tracked vehicles. Vertical step, isolated wall and ditch are the basic obstacles and by understanding those three cases perfectly, a quadruped can move on any mixed rough terrain as 4-legged animal moves. Each leg of a determine the crossing capability in a static analysis. A quadruped can be simplified with links and joints. By applying the research method, a quadruped can determine the control procedures as soon as it receives the terrain informations from scanner and finally can be moved as animals move with mobility and stability.

• Journal of Electrical Engineering and Technology
• /
• v.7 no.1
• /
• pp.1-8
• /
• 2012

The current paper presents a novel control strategy of a three-phase, four-wire Unified Power Quality (UPQC) to improve power quality. The UPQC is realized by the integration of series and shunt active power filters (APF) sharing a common dc bus capacitor. The realization of shunt APF is carried out using a three-phase, four-leg Voltage Source Inverter (VSI), and the series APF is realized using a three-phase, three-leg VSI. To extract the fundamental source voltages as reference signals for series APF, a zero-crossing detector and sample-and-hold circuits are used. For the control of shunt APF, a simple scheme based on the real component of fundamental load current (I $Cos{\Phi}$) with reduced numbers of current sensors is applied. The performance of the applied control algorithm is evaluated in terms of power-factor correction, source neutral current mitigation, load balancing, and mitigation of voltage and current harmonics in a three-phase, four-wire distribution system for different combinations of linear and non-linear loads. The reference signals and sensed signals are used in a hysteresis controller to generate switching signals for shunt and series APFs. In this proposed UPQC control scheme, the current/voltage control is applied to the fundamental supply currents/voltages instead of fast-changing APF currents/voltages, thus reducing the computational delay and the required sensors. MATLAB/Simulink-based simulations that support the functionality of the UPQC are obtained.