• Title/Summary/Keyword: joint stability

Search Result 886, Processing Time 0.026 seconds

Design of a Nonlinear Observer for Mechanical Systems with Unknown Inputs (미지 입력을 가진 기계 시스템을 위한 비선형 관측기 설계)

  • Song, Bongsob;Lee, Jimin
    • Journal of Institute of Control, Robotics and Systems
    • /
    • v.22 no.6
    • /
    • pp.411-416
    • /
    • 2016
  • This paper presents the design methodology of an unknown input observer for Lipschitz nonlinear systems with unknown inputs in the framework of convex optimization. We use an unknown input observer (UIO) to consider both nonlinearity and disturbance. By deriving a sufficient condition for exponential stability in the linear matrix inequality (LMI) form, existence of a stabilizing observer gain matrix of UIO will be assured by checking whether the quadratic stability margin of the error dynamics is greater than the Lipschitz constant or not. If quadratic stability margin is less than a Lipschitz constant, the coordinate transformation may be used to reduce the Lipschitz constant in the new coordinates. Furthermore, to reduce the maximum singular value of the observer gain matrix elements, an object function to minimize it will be optimally designed by modifying its magnitude so that amplification of sensor measurement noise is minimized via multi-objective optimization algorithm. The performance of UIO is compared to a nonlinear observer (Luenberger-like) with an application to a flexible joint robot system considering a change of load and disturbance. Finally, it is validated via simulations that the estimated angular position and velocity provide true values even in the presence of unknown inputs.

Automatic Extraction of Fractures and Their Characteristics in Rock Masses by LIDAR System and the Split-FX Software (LIDAR와 Split-FX 소프트웨어를 이용한 암반 절리면의 자동추출과 절리의 특성 분석)

  • Kim, Chee-Hwan;Kemeny, John
    • Tunnel and Underground Space
    • /
    • v.19 no.1
    • /
    • pp.1-10
    • /
    • 2009
  • Site characterization for structural stability in rock masses mainly involves the collection of joint property data, and in the current practice, much of this data is collected by hand directly at exposed slopes and outcrops. There are many issues with the collection of this data in the field, including issues of safety, slope access, field time, lack of data quantity, reusability of data and human bias. It is shown that information on joint orientation, spacing and roughness in rock masses, can be automatically extracted from LIDAR (light detection and ranging) point floods using the currently available Split-FX point cloud processing software, thereby reducing processing time, safety and human bias issues.

The Study of 3D Motion Analysis on Lower Limb during Walking with Walker on Older People (노인의 워커 사용에 따른 보행 시 하지 관절 3차원 동작 분석에 관한 연구)

  • Kim, Seonchil;Lee, Sangyeol
    • Journal of The Korean Society of Integrative Medicine
    • /
    • v.5 no.1
    • /
    • pp.19-24
    • /
    • 2017
  • Purpose : The purpose of this study was to find out the difference motion of hip, knee and ankle joint during walking according to using walker on older people. Method : Korean older people of 34 subjects was participated in this study. Participants was measured joint motion on hip, knee and ankle joint during both conditions (walking with walker and without walker). The measured data were analyzed using independent t-test to investigate the difference of joint motion on the both condition. The statistical analyses were performed using Predictive Analytics Soft Ware (PASW) for windows(Ver. 19) and p-value less than .05 were considered significant for all cases. Result : The study showed that more joint motion on hip flexion and ankle pronation is increased by using walker. And hip extension, knee external rotation and ankle plantar flexion is decreased by using walker. Conclusion : This study suggest that using walker on older people was change the motion of the lower limb joint during walking. Therefore, It is necessary to develop a new walker that can reduce dependency and ensure stability on older people during walking.

Study on mechanical behaviors of column foot joint in traditional timber structure

  • Wang, Juan;He, Jun-Xiao;Yang, Qing-Shan;Yang, Na
    • Structural Engineering and Mechanics
    • /
    • v.66 no.1
    • /
    • pp.1-14
    • /
    • 2018
  • Column is usually floating on the stone base directly with or without positioning tenon in traditional Chinese timber structure. Vertical load originated by the heavy upper structure would induce large friction force and compression force between interfaces of column foot and stone base. This study focused on the mechanical behaviors of column foot joint with consideration of the influence of vertical load. Mechanism of column rocking and stress state of column foot has been explored by theoretical analysis. A nonlinear finite element model of column foot joint has been built and verified using the full-scale test. The verified model is then used to investigate the mechanical behaviors of the joint subjected to cyclic loading with different static vertical loads. Column rocking mechanism and stress distributions of column foot were studied in detail, showing good agreement with the theoretical analysis. Mechanical behaviors of column foot joint and the effects of the vertical load on the seismic behavior of column foot were studied. Result showed that compression stress, restoring moment and stiffness increased with the increase of vertical load. An appropriate vertical load originated by the heavy upper structure would produce certain restoring moment and reset the rocking columns, ensuring the stability of the whole frame.

Effects of Different Shoe Heel Heights on the Kinematic Variables of the Lower Extremities during Walking on Slopes by healthy adult women

  • Yang, Yong-pil
    • Journal of the Korean Society of Physical Medicine
    • /
    • v.14 no.3
    • /
    • pp.21-27
    • /
    • 2019
  • PURPOSE: This study examined the changes in the kinematic variables during walking on a downhill ramp according to the shoe heel height. METHODS: The subjects were 10 adult women with no history of musculoskeletal disorders who agreed to participate in the study. Data were collected using a motion analysis system (VICON) consisting of six infrared cameras. The slope was 120 cm in width, 200 cm in length, and 15 in inclination. To confirm the change in gait parameters (stride length, gait speed) and lower extremity joint angle according to the heel heights of the shoes, flat, 5 cm, and 10 cm heel shoes were prepared and walked alternately. RESULTS: As a result, both the stride length and walking speed showed significant differences according to the heel height between flat and 10 cm (p<.05). In the sagittal plane, there was no significant difference in the hip joint and knee joint, but a significant difference was observed in all events in the ankle joint on all heel heights (p<.05). In particular, the heel strike and mid stance events showed significant differences among all height conditions (p<.05). No significant difference was observed in any of the joint angle changes in the frontal plane (p>.05). CONCLUSION: As the shoe heel height increased, the instability increased and efforts to secure the stability were made, leading to a shortened stride length, walking speed, and angle of the ankle joint.

Stochastic Stability Analysis of the Power System Incorporating Wind Power using Measurement Wind Data

  • Parinya, Panom;Sangswang, Anawach;Kirtikara, Krissanapong;Chenvidhya, Dhirayut
    • Journal of Electrical Engineering and Technology
    • /
    • v.13 no.3
    • /
    • pp.1110-1122
    • /
    • 2018
  • This paper proposes an alternative method to evaluate the effect of wind power to the power system stability with small disturbance. Alternatively, available techniques for stability analysis of a power system based on deterministic methods are less accurate for high penetration of wind power. Numerical simulations of random behaviors are computationally expensive. A stochastic stability index (SSI) is proposed for the power system stability evaluation based on the theory of stochastic stability and energy function, specifically the stochastic derivative of the relative well-defined energy function and the critical energy. The SSI is implemented on the modified nine-bus system including wind turbines under different conditions. A doubly-fed induction generator (DFIG) wind turbine is characterized and modeled using measured wind data from several sites in Thailand. Each of the obtained wind power data is analyzed. The wind power effect is modeled considering the aggregated effect of wind turbines. With the proposed method, the system behavior is properly predicted and the stability is quantitatively evaluated with less computational effort compared with conventional numerical simulation methods.

The Effect of Bank Liquidity on Bank's Stability in the Presence of Managerial Optimism

  • HABIB, Ashfaq;KHAN, Muhammad Asif;MEYER, Natanya
    • The Journal of Asian Finance, Economics and Business
    • /
    • v.9 no.8
    • /
    • pp.183-196
    • /
    • 2022
  • Bank stability serves as a prerequisite for the smooth functioning of economic and financial activities in the country. Banks face numerous risks, and liquidity plays an essential role in determining a bank's long-term growth and financial stability. By using the sample of 70 banks of the Gulf Cooperation Council, this study examines the association between funding the liquidity and the creation of liquidity and their impact on bank stability. Firstly, the reciprocal relationship reveals between funding the liquidity and the creation of liquidity by employing the 2SLS regression model. Further, by employing the dynamic GMM model, the research finds that funding liquidity is significant and positively influences bank stability. However, bank stability is significantly negatively influenced by the creation of liquidity, but the combined effect of funding the liquidity and creation of liquidity positively explains the bank stability. Additionally, this study reveals that managerial optimism biases contribute to determining the bank's liquidity and long-term stability. The finding of this study supports the executives, policymakers, and management of banks in understating liquidity risks, efficiency, and bank stability. The findings support regulatory guidelines mainly by the Basel III framework, which places more importance on the joint management of funding the liquidity and creation of liquidity in the economy.

Survey Equipment Development of Stability Evaluation for Rock Slope using Drone (드론을 이용한 암반사면의 안정성평가 측정장비 개발)

  • Lee, Hyun-Chol;Kwon, Ki-mun;Moon, Chang-eun;Jo, Yeong-hun
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.22 no.4
    • /
    • pp.91-99
    • /
    • 2018
  • Mechanical Properties of Rock Slope as a safe and effective interpretation should be thoroughly investigated. Clinometer, however, this new measurement due to the restrictions of the research for the joint orientation is needed. In this study, characteristics of the joint orientation can be used to analyze the joint orientation of developing a joint survey system that can be applied to the field. The system is developed and Analysis software to hardware. Hardware is composed to measure the joint orientation of measuring module, measuring the transfer of data transfer module. From the software is measuring module from the data to analyze the orientation of the joint development, and drone joint orientation survey system named. Can not be measured by the investigation, including regional development approach is a system that has been difficult if the Field Application of the lab test results of the joint orientation and effectively.

The Effects on Kinematics and Joint Coordination of Ankle and MTP Joint as Bending Stiffness Increase of Shoes during Running (달리기 시 인솔의 굽힘 강성 증가에 따른 발목과 중족골 관절의 운동학적 변인 및 관절 협응에 미치는 영향)

  • Kim, Sungmin;Moon, Jeheon
    • Korean Journal of Applied Biomechanics
    • /
    • v.31 no.3
    • /
    • pp.205-213
    • /
    • 2021
  • Objective: The aim of this study was to analyze body stability Joint coordination pattern though as bending stiffness of shoes during stance phase of running. Method: 47 male subjects (Age: 26.33 ± 2.11 years, Height: 177.32 ± 4.31 cm, Weight: 65.8 ± 3.87 kg) participated in this study. All subjects tested wearing the same type of running shoes by classifying bending stiffness (A shoes: 3.2~4.1 N, B shoes: 9.25~10.53 N, C shoes: 20.22~21.59 N). They ran 10 m at 3.3 m/s (SD ±3%) speed, and the speed was monitored by installing a speedometer at 3 m intervals between force plate, and the measured data were analyzed five times. During running, ankle joint, MTP joint, coupling angle, inclination angle (anterior-posterior, medial-lateral) was collected and analyzed. Vector coding methods were used to calculate vector angle of 2 joint couples during running: MTP-Ankle joint frontal plane. All analyses were performed with SPSS 21.0 and for repeated measured ANOVA and Post-hoc was Bonferroni. Results: Results indicated that there was an interaction between three shoes and phases for MTP (Metatarsalphalangeal) joint angle (p = .045), the phases in the three shoes showed difference with heel strike~impact peak (p1) (p = .000), impact peak~active peak (p2) (p = .002), from active peak to half the distance to take-off until take-off (p4) (p = .032) except for active peak~from active peak to half the distance to take-off (p3) (p = .155). ML IA (medial-lateral inclination angle) for C shoes was increased than other shoes. The coupling angle of ankle angle and MTP joint showed that there was significantly difference of p2 (p = .005), p4 (p = .045), and the characteristics of C shoes were that single-joint pattern (ankle-phase, MTP-phase) was shown in each phase. Conclusion: In conclusion, by wearing high bending stiffness shoes, their body instability was increased during running.