Estimated Reaction Force Research Articles

Characterizing Lumbar Spine Kinematics and Kinetics During Simulated Low-Speed Rear Impact Collisions.

Recent work has demonstrated that low back pain is a common complaint following low-speed collisions. Despite frequent pain reporting, no studies involving human volunteers have been completed to examine the exposures in the lumbar spine during low-speed rear impact collisions. Twenty-four participants were recruited and a custom-built crash sled simulated rear impact collisions, with a change in velocity of 8km/h. Randomized collisions were completed with and without lumbar support. Inverse dynamics analyses were conducted, and outputs were used to generate estimates of peak L4/L5 joint compression and shear. Average (SD) peak L4/L5 compression and shear reaction forces were not significantly different without lumbar support (compression = 498.22N [178.0N]; shear = 302.2N [98.5N]) compared to with lumbar support (compression = 484.5N [151.1N]; shear = 291.3N [176.8N]). Lumbar flexion angle at the time of peak shear was 36° (12°) without and 33° (11°) with lumbar support. Overall, the estimated reaction forces were 14% and 30% of existing National Institute of Occupational Safety and Health occupational exposure limits for compression and shear during repeated lifting, respectively. Findings also demonstrate that, during a laboratory collision simulation, lumbar support does not significantly influence the total estimated L4/L5 joint reaction force.

Finite-element kalman filter with state constraint for dynamic soft tissue modelling

This research work proposes a novel method for realistic and real-time modelling of deformable biological tissues by the combination of the traditional finite element method (FEM) with constrained Kalman filtering. This methodology transforms the problem of deformation modelling into a problem of constrained filtering to estimate physical tissue deformation online. It discretises the deformation of biological tissues in 3D space according to linear elasticity using FEM. On the basis of this, a constrained Kalman filter is derived to dynamically compute mechanical deformation of biological tissues by minimizing the error between estimated reaction forces and applied mechanical load. The proposed method solves the disadvantage of costly computation in FEM while inheriting the superiority of physical fidelity.

Imitation model of unbalanced rotor on fluid-film bearings

Diagnostics of rotating machines is taking a new step forward with the development of intellectual technologies based on predictive and machine learning tools. Despite having a range of advantages compared to humans in terms of big data processing powers, correlation and various feature extraction possibilities, and swiftness of operation, such systems are limited by measurement system elements in terms of their parameters: sensors and ADCs with their sensitivity properties and accuracy restrictions, microprocessors with limitation of processing powers, etc. Experimental data is used to recreate experimental environment in simulation of induced unbalance. The imitation model is based on rotor dynamics equations of rotor motion, Reynolds equation to estimate reaction forces of a fluid-film bearing and takes into account sensor parameters and position, gear coupling effect and other measurement system elements parameters. The results show that under certain conditions it becomes impossible to successfully track unbalance which in real conditions could lead to malfunction or failure of a rotor machine.

Tele-Operated Bilateral Control of Hydraulic Manipulator Using a Robust Controller Based on the Sensorless Estimated Reaction Force

In nuclear power plants (NPP), dismantling is the most technically involved process during their life time. During the dismantling process, public safety must be ensured. In crisis situations, a remotely controlled robot system is needed for the dismantling of NPP. Therefore, in this research, a bilateral tele-operation system is proposed to tackle these emergency conditions. Transparency can be improved by using force and position signal in the control strategy. In some applications, force cannot be determine directly using physical sensors. In this work, a novel tele-operated bilateral control strategy is proposed to estimate the reaction force of 3-degree-of-freedom (DOF) master and hydraulic slave manipulators without the use of a sensor. The control strategy is developed by using sliding mode control with sliding perturbation observer (SMCSPO). The sliding perturbation observer (SPO) estimates the reaction force at the end effector and second link without using sensors. The sliding mode control (SMC) is used as a tele-operated bilateral controller for the robust position tracking and control of the slave device. The impedance model is used to differentiate between the applied force (force exerted by operator) and the reaction force due to the remote environment. Different experiments were performed to verify the proposed strategy. The results indicate that the slave manipulator exactly follows the trajectory of the master device. A camera is used to take visual feedback of the workspace for safety purpose. This technique can also be applied for higher-order DOF manipulators in NPP.

Implementation of a TSMCSPO Controller on a 3-DOF Hydraulic Manipulator for Position Tracking and Sensor-Less Force Estimation

In this study, a three-degree-of-freedom hydraulic system device configured as a master-and-slave manipulator system is considered. A methodology to estimate reaction force in aforementioned system is proposed without utilizing any force sensor/signal. A terminal sliding control with a sliding perturbation observer (TSMCSPO) is designed for coupled master-slave system. The fundamental benefit of the proposed scheme is that the sliding perturbation observer estimates the reaction force related to the end effector and second link without utilizing a force sensor. Robust and accurate position tracking is achieved with terminal sliding-mode control in addition to control of the slave manipulator. The position and force tracking for master-slave is estimated based upon bilateral control strategy. The difference in the reaction and operating force is included in the impedance model. The impedance model is implemented in the master device to provide the operator with a sense of the reaction force when it connects with the environment. The experimental results confirm the robust position and force tracking of the slave manipulator.

Estimated Reaction Force-Based Bilateral Control between 3DOF Master and Hydraulic Slave Manipulators for Dismantlement

This paper proposes a novel bilateral control design based on an estimated reaction force without a force sensor for a three-degree of freedom hydraulic servo system with master–slave manipulators. The proposed method is based upon sliding mode control with sliding perturbation observer (SMCSPO) using a bilateral control environment. The sliding perturbation observer (SPO) estimates the reaction force at the end effector and second link without using any sensors. The sliding mode control (SMC) is used as a bilateral controller for the robust position tracking and control of the slave device. A bilateral control strategy in a hydraulic servo system provides robust position and force tracking between master and slave. The difference between the reaction force of the slave produced by the effect of the remote environment and the operating force applied to the master by the operator is expressed in the target impedance model. The impedance model is applied to the master and allows the operator to feel the reaction force from the environment. This research experimentally verifies that the slave device can follow the trajectory of the master device using the proposed bilateral control strategy based on the estimated reaction force. This technique will be convenient for three or more degree of freedom (DOF) hydraulic servo systems used in dismantling nuclear power plants. It is worthy to mention that a camera is used for visual feedback on the safety of the environment and workspace.

Development of an algorithm to estimate reaction forces from bathtub during soaking in the bathwater

Development of an algorithm to estimate reaction forces from bathtub during soaking in the bathwater

電気静油圧アクチュエータのトルク効率と内部漏れ流量のモデリング

Recently, robots working in cooperation with humans are required. From the viewpoint of safety, it is necessary to perform flexible operation and accurate detection of external force. Electro hydrostatic actuators (EHAs) have mechanisms of high backdrivability. Therefore, by applying reaction force observers (RFOBs) to EHAs, it is possible to obtain force sensitivity and flexibility. Moreover, by considering nonlinear elements in EHAs, it is possible to estimate reaction force more accurately. In addition, experimental results showed an improvement of the reaction force estimation accuracy.

入浴姿勢の推定アルゴリズムの構築

Bathing in a bathtub filled with water is a custom common in Japan. Since comfort is important in bathing, comfortable bathtub design is desired. In the previous study, the algorithm to estimate reaction forces from bathtub was constructed. However, in order to evaluate the comfort of the bathtub in simulation completely, it was necessary to know bathing posture without experiments. The objective of this study was to construct the algorithm to estimate bathing posture. This algorithm determines the bathing posture that minimizes weighted summation of i) sum of joint torques of hip, knee, and ankle, ii) passive elastic joint torques of toes, and iii) inverse sign of the buoyancy. In the calculation, gravity, buoyancy, passive elastic joint torque and estimated reaction forces by algorithm constructed in previous study were considered. In order to examine this algorithm, a bathing experiment to obtain the data of bathing posture for 10 subjects and 4 bathtub shapes for each subject was conducted. It was found that the estimated bathing posture were consistent well with the measured bathing posture within 5.2% error.

Sliding Perturbation Observer Based Reaction Force Estimation Method of Surgical Robot Instrument for Haptic Realization

Previous research applied sliding mode control with a sliding perturbation observer (SMCSPO) algorithm as a robust controller to control a surgical robotic instrument and reported that reaction force loaded on the tip can be estimated similarly by the sliding perturbation observer (SPO). However, some factors, such as friction, in which it is difficult to find the model parameters beforehand, can have an effect on the reaction force estimation because the factors are included in the estimated perturbation. This paper addresses the SPO based reaction force estimation method to extract a pure reaction force on a surgical robot instrument in the case of including Coulomb friction due to the operation of cable-pulley structure. Coulomb friction can be estimated experimentally and compensated for from the estimated perturbation. An experimental evaluation was performed to prove the suggested estimation method. The results show that SPO can be substituted for sensors to measure the reaction force. This estimated reaction force will be used to realize the haptic function by sending the reaction force to a master device for a surgeon. The results will help to create surgical benefit such as shortening the practice time of a surgeon and providing haptic information to the surgeon by using it as haptic signal to protect an organ by forming a force boundary.

A-19 入浴姿勢における浴槽壁面反力の推定アルゴリズムの構築(映像分析,推定,構造)

In order to improve comfort in bathing, the relationship between the biomechanical load and the bathtub shape has to be clarified. For this purpose, many bathing experiments had to be conducted since it was necessary to measure the reaction forces acting on a human from the bathtub experimentally. The objective of this study was to construct an algorithm to estimate reaction forces from bathtun in order to calculate joint torque as biomechanical loads without bathing experiments. This algorithm calculates distribution of reaction forces which minimizes weighted summation of i) sum of squares of reaction forces, ii) joint torques of hip and knee joints and iii) friction force of the back, considering gravity, buoyancy and passive elastic joint torque. Weighting were expressed as a function of bathing posture including parameters determined for each person to reflect influence of differences among the individual. In order to examine this algorithm, a bathing experiment to obtain the data of bathing posture and reaction forces for 10 subjects and 24 posture conditions was conducted. It was found that the estimated reaction forces were consistent well with the measured values.

Modelling and analysis of lower limb joint loads during the Naeryo chagi technique in taekwondo

Summary Study aim: estimate reaction forces and muscle torque in lower limb joints during the Naeryo chagi technique in taekwondo. Material and methods: the parameters of the Naeryo chagi kick were measured with a Vicon motion tracking system comprising ten MX T40S cameras, two reference cameras and four AMTI BP600900-2000 force plates. Additional measurements were performed using the BTS-4AP-2K force analysis system equipped with a WB-4AP punching bag. The acquired raw data were processed and synchronized using Matlab v.R2007a software. A computer simulation created on the basis of the adopted mathematical model was used to identify reaction forces and control moments. Results: the highest joint loads occurred at the moment when the striking leg reversed its movement direction from rising to rapidly falling towards the target. The knee and ankle joints of the supporting leg were subject to greatest reaction forces and muscle torque. Conclusions: it is recommended to follow an exercise routine aimed at strengthening and stabilizing the structures of motor system subject to the greatest load.

슬라이딩 섭동 관측기를 이용한 수술용 로봇 인스트루먼트의 반력 추정 가능성 평가

In spite of the difficulties and uncertain characteristic of cable driven method, surgical robot instrument has adopted it as driving mechanism for various reasons. To overcome the problem of cable system, previous research applied SMCSPO (sliding mode control with sliding perturbation observer) algorithm as robust controller to control the instrument and found that the value of SPO (sliding perturbation observer) followed force disturbance, reaction force loaded on the tip very similarly. Thus, this paper confirms that the perturbation observer is sufficient estimator which finds out the mount of loaded force on the surgical robot instrument. To prove the proposition, simulation using the similar model with an actual instrument and experimental evaluation are performed. The results show that it is possible to substitute SPO for sensors to measure the reaction force. This estimated reaction force will be used to realize haptic function by sending the reaction force to a master device for a surgeon. The results will contribute to create surgical benefit such as shortening the practice time of a surgeon and giving haptic information to surgeon by using it as haptic signal to protect an organ by making force boundary.

Ground Reaction Forces Generated by Twenty-eight Hatha Yoga Postures

Adherents claim many benefits from the practice of yoga, including promotion of bone health and prevention of osteoporosis. However, no known studies have investigated whether yoga enhances bone mineral density. Furthermore, none have estimated reaction forces applied by yoga practitioners. The purpose of this study was to collect ground reaction force (GRF) data on a variety of hatha yoga postures that would commonly be practiced in fitness centers or private studios. Twelve female and eight male volunteers performed a sequence of 28 hatha yoga postures while GRF data were collected with an AMTI strain-gauge force platform. The sequence was repeated six times by each study subject. Four dependent variables were studied: peak vertical GRF, mean vertical GRF, peak resultant GRF, and mean resultant GRF. Univariate analysis was used to identify mean values and standard deviations for the dependent variables. Peak vertical and resultant values of each posture were similar for all subjects, and standard deviations were small. Similarly, mean vertical and resultant values were similar for all subjects. This 28 posture yoga sequence produced low impact GRF applied to upper and lower extremities. Further research is warranted to determine whether these forces are sufficient to promote osteogenesis or maintain current bone health in yoga practitioners.

Estimation of reaction forces in high bar swinging

Reaction forces experienced by gymnasts swinging on the high bar may be determined indirectly using inverse dynamics analysis or may be measured using strain gauges. The accuracy of inverse dynamics analysis may be poor due to errors in the estimated inertia parameters and in the accelerations obtained from digitised data. On the other hand the use of strain gauges is not always possible in elite competition. This paper presents a method for estimating the reaction forces based on the linear displacements of the bar. The bar was modelled as a point mass attached to horizontal and vertical linear springs (obeying Hooke's Law) with stiffness coefficients determined from static loading. The stiffness coefficients of the bar were determined with three different tensions in the stabilising cables of the high bar. A force and video analysis of backward giant circles was performed. Estimates for the reaction forces were obtained by multiplying the bar displacements from the video analysis by the stiffness coefficients determined from the static loadings. Comparisons were made between the estimated reaction forces and the reaction forces recorded using strain gauges attached to the high bar. Varying the tension in the stabilising cables of the high bar did not effect the stiffness of the bar. Root mean squared differences between estimated and recorded reaction forces were on average within 99 N for three 'regular' and three 'accelerated' giant circles. This was less than 3.5% of the range of forces recorded. The bar displacement method was able to estimate the peak reaction forces to within 7% on average, which compares favourably with 24% reported by Gervais (1993) using inverse dynamics.