A Kinematic Model of the Human Spine and Torso

Efforts to develop a more accurate model of the human spine and torso in order to improve realism in human motion modeling are discussed. The model of spinal motion, which is represented within Jack (a software system for human figure modeling and manipulation), is described. The impact parameters, vertebral joint movement, and the spine database are considered. Application of the motion model is examined, and examples of its use are given

Kinematic Modelling and Motion Analysis of a Humanoid Torso Mechanism

This paper introduces a novel kinematic model for a tendon-driven compliant torso mechanism for humanoid robots, which describes the complex behaviour of a system characterised by the interaction of a complex compliant element with rigid bodies and actuation tendons. Inspired by a human spine, the proposed mechanism is based on a flexible backbone whose shape is controlled by two pairs of antagonistic tendons. First, the structure is analysed to identify the main modes of motion. Then, a constant curvature kinematic model is extended to describe the behaviour of the torso mechanism under examination, which includes axial elongation/compression and torsion in addition to the main bending motion. A linearised stiffness model is also formulated to estimate the static response of the backbone. The novel model is used to evaluate the workspace of an example mechanical design, and then it is mapped onto a controller to validate the results with an experimental test on a prototype. By replacing a previous approximated model calibrated on experimental data, this kinematic model improves the accuracy and efficiency of the torso mechanism and enables the performance evaluation of the robot over the reachable workspace, to ensure that the tendon-driven architecture operates within its wrench-closure workspace

Reachable Workspace and Proximal Function Measures for Quantifying Upper Limb Motion.

There are a lack of quantitative measures for clinically assessing upper limb function. Conventional biomechanical performance measures are restricted to specialist labs due to hardware cost and complexity, while the resulting measurements require specialists for analysis. Depth cameras are low cost and portable systems that can track surrogate joint positions. However, these motions may not be biologically consistent, which can result in noisy, inaccurate movements. This paper introduces a rigid body modelling method to enforce biological feasibility of the recovered motions. This method is evaluated on an existing depth camera assessment: the reachable workspace (RW) measure for assessing gross shoulder function. As a rigid body model is used, position estimates of new proximal targets can be added, resulting in a proximal function (PF) measure for assessing a subject's ability to touch specific body landmarks. The accuracy, and repeatability of these measures is assessed on ten asymptomatic subjects, with and without rigid body constraints. This analysis is performed both on a low-cost depth camera system and a gold-standard active motion capture system. The addition of rigid body constraints was found to improve accuracy and concordance of the depth camera system, particularly in lateral reaching movements. Both RW and PF measures were found to be feasible candidates for clinical assessment, with future analysis needed to determine their ability to detect changes within specific patient populations

Kinematic modelling and motion analysis of a humanoid torso mechanism

This paper introduces a novel kinematic model for a tendon-driven compliant torso mechanism for humanoid robots, which describes the complex behaviour of a system characterised by the interaction of a complex compliant element with rigid bodies and actuation tendons. Inspired by a human spine, the proposed mechanism is based on a flexible backbone whose shape is controlled by two pairs of antagonistic tendons. First, the structure is analysed to identify the main modes of motion. Then, a constant curvature kinematic model is extended to describe the behaviour of the torso mechanism under examination, which includes axial elongation/compression and torsion in addition to the main bending motion. A linearised stiffness model is also formulated to estimate the static response of the backbone. The novel model is used to evaluate the workspace of an example mechanical design, and then it is mapped onto a controller to validate the results with an experimental test on a prototype. By replacing a previous approximated model calibrated on experimental data, this kinematic model improves the accuracy and efficiency of the torso mechanism and enables the performance evaluation of the robot over the reachable workspace, to ensure that the tendon-driven architecture operates within its wrench-closure workspace

Lower body design of the ‘iCub’ a human-baby like crawling robot

The development of robotic cognition and a greater understanding of human cognition form two of the current greatest challenges of science. Within the RobotCub project the goal is the development of an embodied robotic child (iCub) with the physical and ultimately cognitive abilities of a 2frac12 year old human baby. The ultimate goal of this project is to provide the cognition research community with an open human like platform for understanding of cognitive systems through the study of cognitive development. In this paper the design of the mechanisms adopted for lower body and particularly for the leg and the waist are outlined. This is accompanied by discussion on the actuator group realisation in order to meet the torque requirements while achieving the dimensional and weight specifications. Estimated performance measures of the iCub are presented

Musculoskeletal Modeling of the Pelvis and Lumbar Spine During Running

Musculoskeletal modeling provides an alternative to in-vivo characteristics that are difficult to directly measure for movements such as running, especially for trunk muscles and joints. The full-body-lumbar-spine (FBLS) model by Raabe and Chaudhari, 2016 is an OpenSim model created for simulations of jogging. The lifting full-body (LFB) model by Beaucage-Gauvreau et al., 2018 is an adaptation of the FBLS created for estimating spinal loads during lifting. PURPOSE: Determine validity of the FBLS and LFB models in simulating pelvis and lumbar spine kinematics during running. METHODS: Inverse Kinematics were executed using experimental data for the FBLS and LFB models. To obtain the 3D motion data, 5 runners ran on a treadmill at self-selected jogging pace (2.6±0.2 m/s). Axial rotations at the pelvis segment and for the sum of lumbar motion (L1-L5 intervertebral disc joints) were calculated from marker data, and the range of motion (ROM) averaged for the experimental data and each computational model. RESULTS: FBLS and LFB models had the same relative movement patterns as the experimental data. However, the ROM for both models differed from the human data. For the experimental data, the average ROM was 33.6 ± 15.6° for total lumbar rotation and 24.7 ± 12.3° at the pelvis. The ROM for the pelvis was 17.97±6.87° and 19.22±7.63° for the LFB and FBLS models, respectively. The lumbar ROM was 29.53±5.46° and 18.39±10.56° for the LFB and FBLS models, respectively. The differences in ROM could be because the experimental data used a multi-segmented torso and a rigid lumbar spine marker model, whereas the OpenSim models utilized a rigid torso (lumped thoracic and cervical vertebrae, ribcage, scapulae, and head) with a coupled lumbar spine. The average maximum RMS across all participants was 0.05 ± 0.004 cm for both LFB and FBLS models. CONCLUSION: The LFB model was created for lifting simulations but provides a better simulation of running motion at the lumbar and pelvis than the FBLS model, potentially due to the LFB model having a 3-DOF joint at T12/L1 and linear kinematic coupling constraints to distribute the net trunk motion across the six intervertebral joints (T12-L5). The ROM differences at the L5/S1 could potentially be corrected with a multi-segmented torso model. Both models have potential for simulating axial rotation of the pelvis and lumbar spine during running.https://digitalcommons.odu.edu/gradposters2021_engineering/1001/thumbnail.jp

A decision forest based feature selection framework for action recognition from RGB-Depth cameras

In this paper, we present an action recognition framework leveraging data mining capabilities of random decision forests trained on kinematic features. We describe human motion via a rich collection of kinematic feature time-series computed from the skeletal representation of the body in motion. We discriminatively optimize a random decision forest model over this collection to identify the most effective subset of features, localized both in time and space. Later, we train a support vector machine classifier on the selected features. This approach improves upon the baseline performance obtained using the whole feature set with a significantly less number of features (one tenth of the original). On MSRC-12 dataset (12 classes), our method achieves 94% accuracy. On the WorkoutSU-10 dataset, collected by our group (10 physical exercise classes), the accuracy is 98%. The approach can also be used to provide insights on the spatiotemporal dynamics of human actions

Characteristics and Performance of CAUTO (CAssino hUmanoid TOrso) Prototype

An artificial torso is a fundamental part of a humanoid robot for imitating human actions. In this paper, a prototype of CAUTO (CAssino hUmanoid TOrso) is presented. Its design is characterized by artificial vertebras actuated by cable-driven parallel manipulators. The design was conceived by looking at the complex system and functioning of the human torso, in order to develop a solution for basic human-like behavior. The requirements and kinematic structure are introduced to explain the peculiarities of the proposed mechanical design. A prototype is presented, and built with low-cost and high-performance features. Tests results are reported to show the feasibility and the characteristics in replicating human torso motions. In addition, the power consumption has been measured during the tests to prove the efficiency of the Li-Po battery supply, employed for a fully portable solution of the designed torso

Low back biomechanics during manual materials handling of beer kegs

2017 Fall.Includes bibliographical references.Biomechanical risk factors such as heavy loads and awkward trunk postures have been associated with occupational low back pain. Those same risk factors are commonly experienced among workers handling beer kegs. The present study used a 3-dimensional motion capture system as a tool to investigate the low back biomechanics during keg handling at a working brewery. Specifically, five workers transferred spent kegs from a pallet to a conveyor to be cleaned and filled with beer in the present study. Data was collected during the portion of the shift workers handled kegs. Low back angular displacements were assessed during keg handling at two heights. Kegs originated from a high or low position and were defined as a high or low lift. Kinematic data from the study was used to estimate compressive and shear forces at the lumbosacral joint from a 2-dimensional static biomechanical model. Repeated measures analyses were performed with each low back angular displacement variable as a function of lift condition. Differences in low back biomechanics between high and low lifts were identified. During low lifts, torso flexion was significantly greater than high lifts. The magnitudes of flexion achieved during low lifts significantly exceeded those of high lifts. Differences between left axial rotation where significant with larger magnitudes of rotation occurring during high lifts. A broader range of angular displacements was observed in high lifts. In both lifting conditions, estimated kinetics exceeded recommended action limits, potentially putting workers at an increased risk for developing low back pain. Work design (lift condition) influenced low back motion during keg handling. Data collection during operational hours was feasible due to the portability and small design of inertial measurement units. Results from the study can help improve workplace design in a craft brewery, reduce risk, and create safer work