Optimization-Based Seated Posture Prediction Considering Contact With Environment

2011 ◽  
Author(s):  
Brad Howard ◽  
Jingzhou James Yang
Keyword(s):  
Center Of Pressure ◽  
Optimization Techniques ◽  
The Body ◽  
Human Model ◽  
Joint Torques ◽  
Pressure Mapping ◽  
Support Reaction ◽  
Posture Prediction ◽  
Reaction Forces ◽  
Recursive Dynamics

People can spend much of everyday completing seated tasks. Therefore it is important to understand postures needed to complete seated tasks, and the associated environmental contacts. This paper presents a method to predict seated postures and the general forces needed in order to support resulting postural configurations. This study uses optimization techniques to predict human posture based on a 56 degree of freedom (DOF) 50th percentile female human model. The support reaction forces (SRFs) are predicted using joint torques and the zero-moment point (ZMP) formulation derived from the Lagrangian recursive dynamics. The SRFs are applied at points on the body based on center of pressure (COP) locations gathered from pressure mapping experiments. The specific application points include the two feet, the two thighs, and back. Multiple seated orientations based on an experimental study found in published literature are simulated. When comparing these simulation results to the literature data, a good correlation can be established, which provides an initial validation of the proposed methods.

Determining the Static Joint Torques of a Digital Human Model Considering Balance

2009 ◽  
Author(s):  
Jingzhou James Yang ◽  
Yujiang Xiang ◽  
Joo Kim
Keyword(s):  
Human Model ◽  
Joint Torques ◽  
Digital Human Model ◽  
Human Models ◽  
Support Reaction ◽  
Reaction Forces ◽  
Zero Moment ◽  
The Stability ◽  
Physics Based Simulation ◽  
Digital Human

This paper presents a methodology for determining the static joint torques of a digital human model considering balance for both standing and seating tasks. An alternative and efficient formulation of the Zero-Moment Point (ZMP) for static balance and the approximated (ground/seat) support reaction forces/moments are derived from the resultant reaction loads, which includes the gravity and externally applied loads. The proposed method can be used for both standing and seating tasks for assessing the stability/balance of the posture. The proposed formulation can be beneficial to physics-based simulation of humanoids and human models. Also, the calculated joint torques can be considered as an indicator to assess the risks of injuries when human models perform various tasks.

scholarly journals Humanoid standing control: learning from human demonstration

2002 ◽  
Vol 12 (1) ◽  
pp. 16-22 ◽  
Author(s):  
Andreas Hofmann ◽  
Marko Popovic ◽  
Hugh Herr
Keyword(s):  
Ground Reaction Force ◽  
Center Of Pressure ◽  
Human Subjects ◽  
Reaction Force ◽  
Morphological Data ◽  
Human Model ◽  
Joint Torques ◽  
Double Support ◽  
High Level ◽  
Force Data

A three-dimensional numerical model of human standing is presented that reproduces the dynamics of simple swaying motions while in double-support. The human model is structurally realistic, having both trunk and two legs with segment lengths and mass distributions defined using human morphological data from the literature. In this investigation, model stability in standing is achieved through the application of a high-level reduced-order control system where stabilizing forces are applied to the model's trunk by virtual spring- damper elements. To achieve biologically realistic model dynamics, torso position and ground reaction force data measured on human subjects are used as demonstration data in a supervised learning strategy. Using Powell's method, the error between simulation data and measured human data is minimized by varying the virtual high-level force field. Once optimized, the model is shown to track torso position and ground reaction force data from human demonstrations. With only these limited demonstration data, the humanoid model sways in a biologically realistic manner. The model also reproduces the center-of-pressure trajectory beneath the foot, even though no error term for this is included in the optimization algorithm. This indicates that the error terms used (the ones for torso position and ground reaction force) are sufficient to compute the correct joint torques such that independent metrics, like center-of-pressure trajectory, are correct.

Power Assist Control Calculated by a Human Model and Joint Angles for Walking Motion Using Pneumatic Actuators

2013 ◽  
Vol 25 (6) ◽  
pp. 915-922 ◽  
Author(s):  
Motonobu Sato ◽  
◽  
Eiichi Yagi ◽  
Kazuo Sano ◽  
Keyword(s):  
Control Method ◽  
The Body ◽  
Human Model ◽  
Joint Angles ◽  
Pneumatic Actuators ◽  
Joint Torques ◽  
Rigid Link ◽  
Walking Motion ◽  
Link Model

This paper describes a method for power assist control that calculates the joint torques necessary to support an assist suit wearer’s walking. We approximate the body using a multijoint rigid link model. Joint support torques are calculated based on this model using the hip, knee and ankle angles of the wearer. Results of experiments show the effectiveness of proposed control method.

Static Joint Torque Determination of a Human Model for Standing and Seating Tasks Considering Balance

2010 ◽  
Vol 2 (3) ◽  
Author(s):  
Jingzhou (James) Yang ◽  
Joo H. Kim
Keyword(s):  
Material Handling ◽  
Weight Lifting ◽  
Joint Torque ◽  
Human Model ◽  
Computational Time ◽  
Joint Torques ◽  
Human Models ◽  
Support Reaction ◽  
The Stability ◽  
Physics Based Simulation

Estimation of the risk of injury to human different joints during occupational tasks plays an important role to reduce injuries before the operators carry out the tasks. This paper presents a methodology for determining the static joint torques of a human model considering balance for both standing and seating tasks such as weight lifting, material handling, and seated operating tasks in the assembly line. A high fidelity human model has been developed, and recursive dynamics has been used to formulate the static equation of motion. An alternative and efficient formulation of the zero-moment point for static balance and the approximated (ground/seat) support reaction forces/moments are derived from the resultant reaction loads, which includes the gravity and externally applied loads. The proposed method can be used for both standing and seating tasks for assessing the stability/balance of the posture. The proposed formulation can be beneficial to physics-based simulation of humanoids and human models. Also, the calculated joint torques can be considered as an indicator to assess the risks of injuries when human models perform various tasks. The computational time for each case is close to 0.015 s.

Predictive Simulation of Human Ladder Climbing

2013 ◽  
Author(s):  
Hyun-Joon Chung ◽  
Yujiang Xiang ◽  
Mahdiar Hariri ◽  
Rajan Bhatt ◽  
Jasbir S. Arora ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Motion Tracking ◽  
Mechanical Energy ◽  
Joint Torque ◽  
Human Model ◽  
Joint Torques ◽  
Contact Points ◽  
Design Variables ◽  
Reaction Forces ◽  
Hands And Feet

An optimization formulation for human ladder climbing simulation is presented. The human model has 55 degrees of freedom — 49 revolute joints and 6 global translation & rotation joints. It is assumed that the ladder climbing motion is symmetric and periodic. The formulation starts with four contact points with both hands and feet. Then, hand and foot moves up and it ends with four contact points again. Design variables are the joint angle profiles and contact reaction forces. The objective function is combined with dynamic efforts and motion tracking. The dynamic efforts are joint torque square which is proportional to the mechanical energy. The motion tracking is the motion capture data tracking so that the motion follows the natural ladder climb motion as well. The dynamics results with joint torques and reaction forces are recovered and analyzed from the simulation.

scholarly journals Strategies of elite Chinese gymnasts in coping with landing impact from backward somersault

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7914
Author(s):  
Chengliang Wu ◽  
Weiya Hao ◽  
Qichang Mei ◽  
Xiaofei Xiao ◽  
Xuhong Li ◽  
...  
Keyword(s):  
Lower Extremity ◽  
Muscle Activation ◽  
Human Model ◽  
International Level ◽  
Joint Torques ◽  
Landing Impact ◽  
Angular Velocities ◽  
Reaction Forces ◽  
Impact Phase ◽  
High Level

This study aimed to investigate how elite Chinese gymnasts manage the landing impact from a backward somersault. Six international-level male gymnasts performed backward somersault tests with a synchronous collection of kinematics (250 Hz), ground reaction forces (1,000 Hz), and surface electromyography (EMG) (2,000 Hz). A 19-segment human model was developed and lower extremity joints torques were calculated by means of a computer simulation. The angles of the lower extremity joints initially extended and then flexed. These angular velocities of extension continued to decrease and the joint torques changed from extensor to flexor within 100 ms before touchdown. The angles of the hips, knees, and ankles flexed rapidly by 12°, 36°, and 29°, respectively, and the angular velocities of flexion, flexor torque, and EMG peaked sharply during the initial impact phase of the landing. The angles of the hips, knees, and ankles flexed at approximately 90°, 100°, and 80°, respectively. The torques were reversed with the extensor torques, showing a relatively high level of muscle activation during the terminal impact phase of the landing. The results showed that the international-level gymnasts first extended their lower extremity joints, then flexed just before touchdown. They continued flexing actively and rapidly in the initial impact phase and then extended to resist the landing impact and maintain body posture during the terminal impact phase of the landing. The information gained from this study could improve our understanding of the landings of elite gymnasts and assist in injury prevention.

scholarly journals Estimation of Three-Dimensional Lower Limb Kinetics Data during Walking Using Machine Learning from a Single IMU Attached to the Sacrum

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6277
Author(s):  
Myunghyun Lee ◽  
Sukyung Park
Keyword(s):  
Center Of Pressure ◽  
Center Of Mass ◽  
Three Dimensional ◽  
Lower Limbs ◽  
Three Dimensions ◽  
Measurement Unit ◽  
Ann Model ◽  
Joint Torques ◽  
Reaction Forces ◽  
Mean Square Errors

Kinetics data such as ground reaction forces (GRFs) are commonly used as indicators for rehabilitation and sports performance; however, they are difficult to measure with convenient wearable devices. Therefore, researchers have attempted to estimate accurately unmeasured kinetics data with artificial neural networks (ANNs). Because the inputs to an ANN affect its performance, they must be carefully selected. The GRF and center of pressure (CoP) have a mechanical relationship with the center of mass (CoM) in the three dimensions (3D). This biomechanical characteristic can be used to establish an appropriate input and structure of an ANN. In this study, an ANN for estimating gait kinetics with a single inertial measurement unit (IMU) was designed; the kinematics of the IMU placed on the sacrum as a proxy for the CoM kinematics were applied based on the 3D spring mechanics. The walking data from 17 participants walking at various speeds were used to train and validate the ANN. The estimated 3D GRF, CoP trajectory, and joint torques of the lower limbs were reasonably accurate, with normalized root-mean-square errors (NRMSEs) of 6.7% to 15.6%, 8.2% to 20.0%, and 11.4% to 24.1%, respectively. This result implies that the biomechanical characteristics can be used to estimate the complete three-dimensional gait data with an ANN model and a single IMU.

Physics-Based Seated Posture Prediction for Pregnant Women and Validation Considering Ground and Seat Pan Contacts

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Bradley Howard ◽  
Aimee Cloutier ◽  
Jingzhou (James) Yang
Keyword(s):  
Pregnant Women ◽  
Objective Function ◽  
Linear Regression Analysis ◽  
Joint Torque ◽  
Joint Torques ◽  
Design Variables ◽  
Optimization Formulation ◽  
Posture Prediction ◽  
Seated Posture ◽  
End Effectors

An understanding of human seated posture is important across many fields of scientific research. Certain demographics, such as pregnant women, have special postural limitations that need to be considered. Physics-based posture prediction is a tool in which seated postures can be quickly and thoroughly analyzed, as long the predicted postures are realistic. This paper proposes and validates an optimization formulation to predict seated posture for pregnant women considering ground and seat pan contacts. For the optimization formulation, the design variables are joint angles (posture); the cost function is dependent on joint torques. Constraints include joint limits, joint torque limits, the distances from the end-effectors to target points, and self-collision avoidance constraints. Three different joint torque cost functions have been investigated to account for the special postural characteristics of pregnant women and consider the support reaction forces (SRFs) associated with seated posture. Postures are predicted for three different reaching tasks in common reaching directions using each of the objective function formulations. The predicted postures are validated against experimental postures obtained using motion capture. A linear regression analysis was used to evaluate the validity of the predicted postures and was the criteria for comparison between the different objective functions. A 56 degree of freedom model was used for the posture prediction. Use of the objective function minimizing the maximum normalized joint torque provided an R2 value of 0.828, proving superior to either of two alternative functions.

Characteristics of Eight Irish Dance LandingsConsiderations for Training and Overuse Injury Prevention

2021 ◽  
Vol 25 (1) ◽  
pp. 30-37
Author(s):  
Sarah Klopp Christensen ◽  
Aaron Wayne Johnson ◽  
Natalie Van Wagoner ◽  
Taryn E. Corey ◽  
Matthew S. McClung ◽  
...  
Keyword(s):  
Large Range ◽  
Force Plate ◽  
Three Dimensional ◽  
The Body ◽  
Peak Force ◽  
Warm Up ◽  
Dance Training ◽  
Rise Rate ◽  
Dance Movements ◽  
Reaction Forces

Irish dance has evolved in aesthetics that lead to greater physical demands on dancers' bodies. Irish dancers must land from difficult moves without letting their knees bend or heels touch the ground, causing large forces to be absorbed by the body. The majority of injuries incurred by Irish dancers are due to overuse (79.6%). The purpose of this study was to determine loads on the body of female Irish dancers, including peak force, rise rate of force, and impulse, in eight common Irish hard shoe and soft shoe dance movements. It was hypothesized that these movements would produce different ground reac- tion force (GRF) characteristics. Sixteen female Irish dancers were recruited from the three highest competitive levels. Each performed a warm-up, reviewed the eight movements, and then performed each movement three times on a force plate, four in soft shoes and four in hard shoes. Ground reaction forces were measured using a three-dimensional force plate recording at 1,000 Hz. Peak force, rise rate, and vertical impulse were calculated. Peak forces normalized by each dancer's body weight for each of these variables were significantly different between move- ments and shoe types [F(15, 15)= 65.4, p < 0.01; F(15, 15) = 65.0, p < 0.01; and F(15, 15) = 67.4, p < 0.01, respectively]. The variable years of experience was not correlated with peak force, rise rate, or impulse (p > 0.40). It is concluded that there was a large range in GRF characteristics among the eight movements studied. Understanding the force of each dance step will allow instructors to develop training routines that help dancers adapt gradually to the high forces experienced in Irish dance training and competitions, thereby limiting the potential for overuse injuries.

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