Showing papers on "Kinematics published in 2012"

Mechanical determinants of 100-m sprint running performance.

Abstract: Sprint mechanics and field 100-m performances were tested in 13 subjects including 9 non-specialists, 3 French national-level sprinters and a world-class sprinter, to further study the mechanical factors associated with sprint performance. 6-s sprints performed on an instrumented treadmill allowed continuous recording of step kinematics, ground reaction forces (GRF), and belt velocity and computation of mechanical power output and linear force–velocity relationships. An index of the force application technique was computed as the slope of the linear relationship between the decrease in the ratio of horizontal-to-resultant GRF and the increase in velocity. Mechanical power output was positively correlated to mean 100-m speed (P 0.683; P 0.21). Last, anthropometric data of body mass index and lowerlimb- to-height ratio showed no significant correlation with 100-m performance. We concluded that the main mechanical determinants of 100-m performance were (1) a ‘‘velocity-oriented’’ force–velocity profile, likely explained by (2) a higher ability to apply the resultant GRF vector with a forward orientation over the acceleration, and (3) a higher step frequency resulting from a shorter contact time.

Patterned control of human locomotion

Abstract: There is much experimental evidence for the existence of biomechanical constraints which simplify the problem of control of multi-segment movements. In addition, it has been hypothesized that movements are controlled using a small set of basic temporal components or activation patterns, shared by several different muscles and reflecting global kinematic and kinetic goals. Here we review recent studies on human locomotion showing that muscle activity is accounted for by a combination of few basic patterns, each one timed at a different phase of the gait cycle. Similar patterns are involved in walking and running at different speeds, walking forwards or backwards, and walking under different loading conditions. The corresponding weights of distribution to different muscles may change as a function of the condition, allowing highly flexible control. Biomechanical correlates of each activation pattern have been described, leading to the hypothesis that the co-ordination of limb and body segments arises from the coupling of neural oscillators between each other and with limb mechanical oscillators. Muscle activations need only intervene during limited time epochs to force intrinsic oscillations of the system when energy is lost.

Fundamentals of Biomechanics: Equilibrium, Motion, and Deformation

Abstract: Preface -- 1. Introduction -- 2. Force Vector -- 3. Moment And Torque Vectors -- 4. Statics: Systems in Equilibrium -- 5. Applications of Statics to Biomechanics -- 6. Introduction to Dynamics -- 7. Linear Kinematics -- 8. Linear Kinetics -- 9. Angular Kinematics -- 10. Angular Kinetics -- 11. Impulse and Momentum -- 12. Introduction to Deformable Body Mechanics -- 13. Stress & Strain -- 14. Multiaxial Deformations & Stress Analyses -- 15. Mechanical Properties of Biological Tissues -- Appendix A. Plane Geometry -- Appendix B. Vector Algebra -- Appendix C. Calculus -- Index.

Shoulder and Elbow Joint Angle Tracking With Inertial Sensors

Abstract: Wearable inertial systems have recently been used to track human movement in and outside of the laboratory. Continuous monitoring of human movement can provide valuable information relevant to individuals’ level of physical activity and functional ability. Traditionally, orientation has been calculated by integrating the angular velocity from gyroscopes. However, a small drift in the measured velocity leads to increasing integration error over time. To compensate that drift, complementary data from accelerometers are normally fused into tracking systems using the Kalman or extended Kalman filter. In this study, we combine kinematic models designed for control of robotic arms with state-space methods to continuously estimate the angles of human shoulder and elbow using two wearable inertial measurement units. We use the unscented Kalman filter to implement the nonlinear state-space inertial tracker. Shoulder and elbow joint angles obtained from 8 subjects using our inertial tracker were compared to the angles obtained from an optical-tracking reference system. On average, there was an RMS angle error of less than 8 $^\circ$ for all shoulder and elbow angles. The average correlation coefficient for all movement tasks among all subjects was $r\ge \hbox{0.95}$ . This agreement between our inertial tracker and the optical reference system was obtained for both regular and fast-speed movement of the arm. The same method can be used to track movement of other joints.

Set-Valued Force Laws: Dynamics of Non-Smooth Systems

Abstract: 1. Introduction.- 1.1 Friction Laws.- 1.2 Literature Survey.- 1.3 Subjects and Contents.- 2. Fundamental Concepts.- 2.1 Internal and External Forces.- 2.2 The Law of Interaction.- 2.3 The Dynamic Equilibrium.- 2.4 The Virtual Work of a Dynamic System.- 2.5 Resultant Force and Inertia Terms.- 3. Rigid Body Systems.- 3.1 Preliminaries on the Vector Product.- 3.2 Rigid Body Kinematics.- 3.3 Rigid Body Kinetics.- 3.4 The Dynamic Equilibrium of a Rigid Body.- 3.5 The Virtual Work of a Rigid Body System.- 3.6 Classical Bilateral Constraints.- 3.7 Generalized Coordinates.- 4. Motion and Discontinuity Events.- 4.1 Preliminaries on Integration of Functions.- 4.2 Displacements, Velocities, and Accelerations.- 4.3 Restriction to Finite Numbers of Discontinuities.- 5. Displacement and Velocity Potentials.- 5.1 Directional Newton-Euler Equations.- 5.2 Set-Valued Force Laws.- 5.3 Scalar Potential Functions.- 5.4 On the Modeling of Force Laws.- 6. Representation of Scalar Force Laws.- 6.1 Decomposition into Unilateral Primitives.- 6.2 Variational Formulations and Upper Subderivatives.- 6.3 The Convex Case: Conjugate Potentials and Duality.- 6.4 Force Elements in Engineering Dynamics.- 7. Force Laws on Different Kinematic Levels.- 7.1 Continuity Properties of the Trajectories.- 7.2 Displacement Force Laws on Acceleration Level.- 7.3 Velocity Force Laws on Acceleration Level.- 8. Index Sets and LCP-Formulation.- 8.1 Index Sets.- 8.2 Formulation on Different Kinematic Levels.- 8.3 The Linear Complementarity Problem.- 8.4 The Dual Principle of Least Constraints.- 9. Principles in Dynamics.- 9.1 The Principle of Least Constraints.- 9.2 The Principle of Gauss.- 9.3 The Principle of Jourdain.- 9.4 The Principle of d'Alembert/Lagrange.- 9.5 Remarks on d'Alembert/Lagrange's Principle.- 10. Spatial Coulomb Friction.- 10.1 Geometry of Surfaces.- 10.2 Contact Kinematics.- 10.3 Kinetics.- 10.4 Contact Laws.- 10.5 Sliding Contacts.- 10.6 Friction Pyramid for Rolling Contacts.- 10.7 Friction Cones and NCP Formulations.- 10.8 A Differentiable NCP for Rolling Contacts.- 10.9 Example and Remarks.- 11. Velocity Jumps due to C0-Constraints.- 11.1 On Impacts in Mechanical Systems.- 11.2 Mechanical Model and Problem.- 11.3 Bilaterally Constrained Motion.- 11.4 Velocity Jump by Time-Scaling.- 11.5 Velocity Jump by Reflection.- 11.6 Reflections and Collisions - Remarks.- 12. Electropneumatic Drilling Machine.- 12.1 Mechanical Model.- 12.2 Simulations.- 13. Percussion Drilling Machine.- 13.1 Mechanical Model of the Drilling Machine.- 13.2 Mathematical Model for Non-Contact.- 13.3 The Contact Model.- 13.4 State Transitions.- 13.5 Results.- 14. Turbine Blade Damper.- 14.1 The Damper Model and the Non-Contact Case.- 14.2 Contact Kinematics of the Damping Device.- 14.3 Numerical Results.- 15. Concluding Remarks.- References.

State Estimation for Legged Robots - Consistent Fusion of Leg Kinematics and IMU

Abstract: This paper introduces a state estimation framework for legged robots that allows estimating the full pose of the robot without making any assumptions about the geometrical structure of its environment. This is achieved by means of an Observability Constrained Extended Kalman Filter that fuses kinematic encoder data with on-board IMU measurements. By including the absolute position of all footholds into the filter state, simple model equations can be formulated which accurately capture the uncertainties associated with the intermittent ground contacts. The resulting filter simultaneously estimates the position of all footholds and the pose of the main body. In the algorithmic formulation, special attention is paid to the consistency of the linearized filter: it maintains the same observability properties as the nonlinear system, which is a prerequisite for accurate state estimation. The presented approach is implemented in simulation and validated experimentally on an actual quadrupedal robot.

Connecting a Human Limb to an Exoskeleton

Abstract: When developing robotic exoskeletons, the design of physical connections between the device and the human limb to which it is connected is a crucial problem. Indeed, using an embedment at each connection point leads to uncontrollable forces at the interaction port, induced by hyperstaticity. In practice, these forces may be large because in general the human limb kinematics and the exoskeleton kinematics differ. To cope with hyperstaticity, the literature suggests the addition of passive mechanisms inside the mechanism loops. However, empirical solutions that are proposed so far lack proper analysis and generality. In this paper, we study the general problem of connecting two similar kinematic chains through multiple passive mechanisms. We derive a constructive method that allows the determination of all the possible distributions of freed degrees of freedom across different fixation mechanisms. It also provides formal proofs of global isostaticity. Practical usefulness is illustrated through two examples with conclusive experimental results: a preliminary study made on a manikin with an arm exoskeleton controlling the movement (passive mode) and a larger campaign on ten healthy subjects performing pointing tasks with a transparent robot (active mode).

Kinematically Versus Mechanically Aligned Total Knee Arthroplasty

Abstract: The purpose of this study was to compare 2 alignment methods for total knee arthroplasty (TKA): kinematic alignment with the use of patient-specific guides and mechanical alignment with conventional instruments A randomized, controlled trial of 41 kinematically aligned and 41 mechanically aligned patients was conducted with the patient, radiographic evaluator, and clinical evaluator blinded to the alignment technique Radiographic measurements were made from long-leg computer tomography scanograms Clinical outcome scores and motion were measured preoperatively and 6 months postoperatively The hip-knee-ankle angle (03° difference; P=693) and anatomic angle of the knee (08° difference; P=131) were similar for both groups In the kinematically aligned group, the angle of the femoral component was 24° more valgus (P<000) and the angle of the tibial component was 23° more varus (P<000) than the mechanically aligned group At 6 months postoperatively, the Western Ontario and McMaster Universities Osteoarthritis Index score was 16 points better (P<000), Oxford Score was 7 points better (P=001), combined Knee Society Score was 25 points better (P=001), and flexion was 50° greater (P=043) in the kinematically aligned group than in the mechanically aligned groupOur findings suggest that the risk of early failure related to limb or knee alignment should be similar in kinematic and mechanically aligned TKA More anatomic alignment of the implant was associated with better flexion and better clinical outcome scores in the kinematically aligned group

Indirect Measurement of Volumetric Accuracy for Three-Axis and Five-Axis Machine Tools: A Review

Abstract: The volumetric accuracy of machine tools is represented by a map of position and orientation error vectors of the tool over the volume concerned. Numerical compensation for volumetric error is possible in many latest commercial CNCs for machine tools. This paper reviews indirect measurement schemes for machine tool kinematics, in which the tool center position is measured as the superposition of error motions of linear or rotary axes. Each error motion can be separately identified by best-fitting a set of measured tool center positions to the kinematic model of machine tools. Indirect measurement schemes for the kinematics of three orthogonal linear axes, as well as the fiveaxis kinematics with two rotary axes, will be reviewed.

Motion graphs++: a compact generative model for semantic motion analysis and synthesis

Abstract: This paper introduces a new generative statistical model that allows for human motion analysis and synthesis at both semantic and kinematic levels. Our key idea is to decouple complex variations of human movements into finite structural variations and continuous style variations and encode them with a concatenation of morphable functional models. This allows us to model not only a rich repertoire of behaviors but also an infinite number of style variations within the same action. Our models are appealing for motion analysis and synthesis because they are highly structured, contact aware, and semantic embedding. We have constructed a compact generative motion model from a huge and heterogeneous motion database (about two hours mocap data and more than 15 different actions). We have demonstrated the power and effectiveness of our models by exploring a wide variety of applications, ranging from automatic motion segmentation, recognition, and annotation, and online/offline motion synthesis at both kinematics and behavior levels to semantic motion editing. We show the superiority of our model by comparing it with alternative methods.

A Novel Kinematic Coupling-Based Trajectory Planning Method for Overhead Cranes

Abstract: Motivated by the desire to achieve smooth trolley transportation and small payload swing, a kinematic coupling-based off-line trajectory planning method is proposed for 2-D overhead cranes. Specifically, to damp out unexpected payload swing, an antiswing mechanism is first introduced into an S-shape reference trajectory based on rigorous analysis for the coupling behavior between the payload and the trolley. After that, the combined trajectory is further tuned through a novel iterative learning strategy, which guarantees accurate trolley positioning. The performance of the proposed trajectory is proven by Lyapunov techniques and Barbalat's lemmas. Finally, some simulation and experiment results are provided to demonstrate the superior performance of the planned trajectory.

The effects of different speed training protocols on sprint acceleration kinematics and muscle strength and power in field sport athletes.

Abstract: A variety of resistance training interventions are used to improve field sport acceleration (e.g., free sprinting, weights, plyometrics, resisted sprinting). The effects these protocols have on acceleration performance and components of sprint technique have not been clearly defined in the literature. This study assessed 4 common protocols (free sprint training [FST], weight training [WT], plyometric training [PT], and resisted sprint training [RST]) for changes in acceleration kinematics, power, and strength in field sport athletes. Thirty-five men were divided into 4 groups (FST: n = 9; WT: n = 8; PT: n = 9; RST: n = 9) matched for 10-m velocity. Training involved two 60-minute sessions per week for 6 weeks. After the interventions, paired-sample t-tests identified significant (p ≤ 0.05) within-group changes. All the groups increased the 0- to 5-m and 0- to 10-m velocity by 9-10%. The WT and PT groups increased the 5- to 10-m velocity by approximately 10%. All the groups increased step length for all distance intervals. The FST group decreased 0- to 5-m flight time and step frequency in all intervals and increased 0- to 5-m and 0- to 10-m contact time. Power and strength adaptations were protocol specific. The FST group improved horizontal power as measured by a 5-bound test. The FST, PT, and RST groups all improved reactive strength index derived from a 40-cm drop jump, indicating enhanced muscle stretch-shortening capacity during rebound from impacts. The WT group increased absolute and relative strength measured by a 3-repetition maximum squat by approximately 15%. Step length was the major limiting sprint performance factor for the athletes in this study. Correctly administered, each training protocol can be effective in improving acceleration. To increase step length and improve acceleration, field sport athletes should develop specific horizontal and reactive power.

Estimation of Human Foot Motion During Normal Walking Using Inertial and Magnetic Sensor Measurements

Abstract: A foot motion filtering algorithm is presented for estimating foot kinematics relative to an earth-fixed reference frame during normal walking motion. Algorithm input data are obtained from a foot-mounted inertial/magnetic measurement unit. The sensor unit contains a three-axis accelerometer, a three-axis angular rate sensor, and a three-axis magnetometer. The algorithm outputs are the foot kinematic parameters, which include foot orientation, position, velocity, acceleration, and gait phase. The foot motion filtering algorithm incorporates novel methods for orientation estimation, gait detection, and position estimation. Accurate foot orientation estimates are obtained during both static and dynamic motion using an adaptive-gain complementary filter. Reliable gait detection is accomplished using a simple finite state machine that transitions between states based on angular rate measurements. Accurate position estimates are obtained by integrating acceleration data, which has been corrected for drift using zero velocity updates. Algorithm performance is examined using both simulations and real-world experiments. The simulations include a simple but effective model of the human gait cycle. The simulation and experimental results indicate that a position estimation error of less than 1% of the total distance traveled is achievable using commonly available commercial sensor modules.

Theory of Parallel Mechanisms

Abstract: Will reading habit influence your life? Many say yes. Reading theory of parallel mechanisms is a good habit; you can develop this habit to be such interesting way. Yeah, reading habit will not only make you have any favourite activity. It will be one of guidance of your life. When reading has become a habit, you will not make it as disturbing activities or as boring activity. You can gain many benefits and importances of reading.

The effect of challenge and threat states on performance: an examination of potential mechanisms.

Abstract: Challenge and threat states predict future performance; however, no research has examined their immediate effect on motor task performance. The present study examined the effect of challenge and threat states on golf putting performance and several possible mechanisms. One hundred twenty-seven participants were assigned to a challenge or threat group and performed six putts during which emotions, gaze, putting kinematics, muscle activity, and performance were recorded. Challenge and threat states were successively manipulated via task instructions. The challenge group performed more accurately, reported more favorable emotions, and displayed more effective gaze, putting kinematics, and muscle activity than the threat group. Multiple putting kinematic variables mediated the relationship between group and performance, suggesting that challenge and threat states impact performance at a predominately kinematic level.

A Compliant Parallel XY Micromotion Stage With Complete Kinematic Decoupling

Abstract: This paper presents a novel compliant parallel XY micromotion stage driven by piezoelectric actuators (PZT). With the purpose to obtain complete kinematic decoupling and good stiffness performance, the stage is designed using a symmetric 4-PP structure in which double four-bar flexure is chosen as the prismatic joint. Matrix method is employed to establish the compliance model of the mechanism. Based on the model, dynamic analysis is investigated after static analysis is carried out. The dimensions of the mechanism are optimized using the particle swarm optimization (PSO) algorithm in order to maximize the natural frequencies. Finite-element analysis (FEA) result indicates that the mechanism has an almost linear force-deflection relationship, high first natural frequency (720.52 Hz), and ideal decoupling property. To cope with the nonlinearities such as hysteresis that exists in the PZT, the control system is constructed by a proportional-integral-derivative (PID) feedback controller with a feedforward compensator based on Preisach model. The fabricated prototype has a 19.2 μm × 8.8 μm rectangular workspace with coupling less than 5%. The result of the closed-loop test shows that the XY stage can achieve positioning, tracking and contouring tasks with small errors.

The Driver of Coronal Mass Ejections in the Low Corona: A Flux Rope

Abstract: Recent Solar Dynamic Observatory observations reveal that coronal mass ejections (CMEs) consist of a multi-temperature structure: a hot flux rope and a cool leading front (LF). The flux rope first appears as a twisted hot channel in the Atmospheric Imaging Assembly 94 A and 131 A passbands. The twisted hot channel initially lies along the polarity inversion line and then rises and develops into the semi-circular flux rope-like structure during the impulsive acceleration phase of CMEs. In the meantime, the rising hot channel compresses the surrounding magnetic field and plasma, which successively stack into the CME LF. In this paper, we study in detail two well-observed CMEs occurred on 2011 March 7 and 2011 March 8, respectively. Each of them is associated with an M-class flare. Through a kinematic analysis we find that: (1) the hot channel rises earlier than the first appearance of the CME LF and the onset of the associated flare; (2) the speed of the hot channel is always faster than that of the LF, at least in the field of view of AIA. Thus, the hot channel acts as a continuous driver of the CME formation and eruption in the early acceleration phase. Subsequently, the two CMEs in white-light images can be well reproduced by the graduated cylindrical shell flux rope model. These results suggest that the pre-existing flux rope plays a key role in CME initiation and formation.

Identifying the young low-mass stars within 25 pc. II. Distances, kinematics and group membership

Abstract: We have conducted a kinematic study of 165 young M dwarfs with ages of <300 Myr. Our sample is composed of stars and brown dwarfs with spectral types ranging from K7 to L0, detected by ROSAT and with photometric distances of <25 pc assuming the stars are single and on the main-sequence. In order to find stars kinematically linked to known young moving groups (YMGs), we measured radial velocities for the complete sample with Keck and CFHT optical spectroscopy and trigonometric parallaxes for 75 of the M dwarfs with the CAPSCam instrument on the du Pont 2.5-m Telescope. Due to their youthful overluminosity and unresolved binarity, the original photometric distances for our sample underestimated the distances by 70% on average, excluding two extremely young (<3 Myr) objects found to have distances beyond a few hundred parsecs. We searched for kinematic matches to 14 reported YMGs and identified 9 new members of the AB Dor YMG and 2 of the Ursa Majoris group. Additional possible candidates include 6 Castor, 4 Ursa Majoris, 2 AB Dor members, and 1 member each of the Her-Lyr and beta Pic groups. Our sample also contains 27 young low-mass stars and 4 brown dwarfs with ages <150 Myr which are not associated with any known YMG. We identified an additional 15 stars which are kinematic matches to one of the YMGs, but the ages from spectroscopic diagnostics and/or the positions on the sky do not match. These warn against grouping stars together based only on kinematics and that a confluence of evidence is required to claim that a group of stars originated from the same star-forming event.

New Measurements of High-Momentum Nucleons and Short-Range Structures in Nuclei

Abstract: We present new measurements of electron scattering from high-momentum nucleons in nuclei. These data allow an improved determination of the strength of two-nucleon correlations for several nuclei, including light nuclei where clustering effects can, for the first time, be examined. The data also include the kinematic region where three-nucleon correlations are expected to dominate.

The Relationship Between Running Economy and Biomechanical Variables in Distance Runners

Abstract: In this study, we analyzed the relationship between running economy (RE) and biomechanical parameters in a group running at the same relative intensity and same absolute velocity. Sixteen homogeneous male long-distance runners performed a test to determine RE at 4.4 m.s-1, corresponding to 11.1% below velocity at the ventilatory threshold. We found significant correlations between RE and biomechanical variables (vertical oscillation of the center of mass, stride frequency, stride length, balance time, relative stride length, range of elbow motion, internal knee, ankle angles at foot strike, and electromyographic activity of the semitendinosus and rectus femoris muscles). In conclusion, changes in running technique can influence RE and lead to improved running performance.

Multicomponent interparticle-potential lattice Boltzmann model for fluids with large viscosity ratios

Abstract: This work focuses on an improved multicomponent interparticle-potential lattice Boltzmann model. The model results in viscosity-independent equilibrium densities and is capable of simulating kinematic viscosity ratios greater than 1000. External forces are incorporated into the discrete Boltzmann equation, rather than through an equilibrium velocity shift as in the original Shan and Chen (hereafter, SC) model. The model also requires the derivation of a momentum conserving effective velocity, which is substituted into the equilibrium distribution function and applies to both the single- and multiple-relaxation-time formulations. Additionally, higher-order isotropy is used in the calculation of the fluid-fluid interaction forces to reduce the magnitude of spurious currents (i.e., numerical errors) in the vicinity of interfaces. First, we compare the model to the SC model for static bubble simulations. We demonstrate that the model results in viscosity-independent equilibrium bubble densities for a wide range of kinematic viscosities, which is not the case for the SC model. Furthermore, we show that the model is capable of simulating stable bubbles for kinematic viscosity ratios greater than 1000 (when higher-order isotropy is used), whereas the SC model is known to be limited to kinematic viscosity ratios on the order of 10. Next we verify the model for surface tension via Laplace's law and show that the model results in the same surface tension values for a range of kinematic viscosities and kinematic viscosity ratios of 10, 100, and 1000. The model is also verified for layered cocurrent flow though parallel plates. We show that the simulated velocity profiles preserve continuity at the interface for kinematic viscosity ratios ranging from 0.001 to 1000 and that the model accurately predicts nonwetting and wetting phase relative permeability for kinematic viscosity ratios of 0.01 to 100.

Reverse engineering the euglenoid movement

Abstract: Euglenids exhibit an unconventional motility strategy amongst unicellular eukaryotes, consisting of large-amplitude highly concerted deformations of the entire body (euglenoid movement or metaboly). A plastic cell envelope called pellicle mediates these deformations. Unlike ciliary or flagellar motility, the biophysics of this mode is not well understood, including its efficiency and molecular machinery. We quantitatively examine video recordings of four euglenids executing such motions with statistical learning methods. This analysis reveals strokes of high uniformity in shape and pace. We then interpret the observations in the light of a theory for the pellicle kinematics, providing a precise understanding of the link between local actuation by pellicle shear and shape control. We systematically understand common observations, such as the helical conformations of the pellicle, and identify previously unnoticed features of metaboly. While two of our euglenids execute their stroke at constant body volume, the other two exhibit deviations of about 20% from their average volume, challenging current models of low Reynolds number locomotion. We find that the active pellicle shear deformations causing shape changes can reach 340%, and estimate the velocity of the molecular motors. Moreover, we find that metaboly accomplishes locomotion at hydrodynamic efficiencies comparable to those of ciliates and flagellates. Our results suggest new quantitative experiments, provide insight into the evolutionary history of euglenids, and suggest that the pellicle may serve as a model for engineered active surfaces with applications in microfluidics.

Kinematics-Based Detection and Localization of Contacts Along Multisegment Continuum Robots

Abstract: In this paper, we present a novel kinematic-based framework for collision detection and estimation of contact location along multisegment continuum robots. Screw theory is used to define a screw motion deviation (SMD) as the distance between the expected and the actual instantaneous screw axis (ISA) of motion. The expected ISA is computed based on the unconstrained kinematics model of the robot, while the actual ISA is computed based on sensory information. Collisions with rigid environments at any point along the robot are detected by monitoring the SMD. Contact locations are estimated by the minimization of the SMD between the ISA that is obtained from a constrained kinematic model of the continuum robot and the one that is obtained from sensor data. The proposed contact detection and localization methods only require the relative motion of each continuum segment with respect to its own base. This strategy allows the straightforward generalization of these algorithms for an n -segment continuum robot. The framework is evaluated via simulations and experimentally on a three-segment multibackbone continuum robot. Results show that the collision-detection algorithm is capable of detecting a single collision at any segment, multiple collisions occurring at multiple segments, and total-arm constraint. It is also shown that the estimation of contact location is possible at any location along the continuum robot with an accuracy better than 20% of the segment nominal length. We believe this study will enhance manipulation safety in unstructured environments and confined spaces.

Glenohumeral internal rotation deficit: pathogenesis and response to acute throwing.

Abstract: Overhand throwing places high loads and stresses on the joints and tissues of the shoulder and arm. As a result, throwing athletes regularly demonstrate altered shoulder internal and external ranges of motion where internal rotation (IR) is decreased and external rotation is increased in the dominant arm when compared with the nondominant arm. This alteration can exist as a result of alterations to the bones (humeral retroversion), capsule (posterior thickening), or muscle (passive stiffness known as thixotropy). When the amount of IR or total arc of motion difference reaches a certain threshold (typically 20 or more degrees of IR or 8 degrees total arc difference), it is known as glenohumeral internal rotation deficit or total arc of motion deficit. Glenohumeral internal rotation deficit and total arc of motion deficit can cause alterations in biomechanics such as scapular "wind-up" or alteration of glenohumeral joint kinematics, which can in turn lead to clinical findings of impingement and labral pathology. This study will review the causes of motion alteration, effects of altered motion on the throwing motion, provide definitions for the various types of rotation deficits, and how to evaluate and treat rotational deficits.

Reciprocal collision avoidance for multiple car-like robots

Abstract: In this paper a method for distributed reciprocal collision avoidance among multiple non-holonomic robots with bike kinematics is presented. The proposed algorithm, bicycle reciprocal collision avoidance (B-ORCA), builds on the concept of optimal reciprocal collision avoidance (ORCA) for holonomic robots but furthermore guarantees collision-free motions under the kinematic constraints of car-like vehicles. The underlying principle of the B-ORCA algorithm applies more generally to other kinematic models, as it combines velocity obstacles with generic tracking control. The theoretical results on collision avoidance are validated by several simulation experiments between multiple car-like robots.

Joint axis and position estimation from inertial measurement data by exploiting kinematic constraints

Abstract: We consider 6d inertial measurement units (IMU) attached to rigid bodies, e.g. human limb segments or links of a robotic manipulator, which are connected by hinge joints and spheroidal joints. Novel methods for joint axis estimation and joint position estimation are presented that exploit the kinematic constraints induced by these two types of joints. The presented methods do not require any knowledge about the sensor units' positions or orientations and do not include integration, i.e. they are insensitive to measurement bias. By means of a three-links simulation model, the estimation algorithms are validated and convergence is analyzed. Finally, the algorithms are tested using experimental data from IMU-based human gait analysis.

Constant curvature continuum kinematics as fast approximate model for the Bionic Handling Assistant

Abstract: We evaluate the use of continuum kinematics with constant curvature as a kinematic model for Festo's “Bionic Handling Assistant” (BHA). We introduce a new, elegant, and parameterless method to deal with geometric singularities in stretched positions, which allows to capture pure elongations that are not naturally expressed by the toroidal deformations underlying the constant curvature assumption. The stability of the method is shown with numeric simulations. We evaluate how well this model describes the BHA by using real-world position measurements as quantitative ground truth and find a good match between model and real BHA, with only 1% relative error. The model provides a practical, and highly efficient tool for the simulation and experimentation with continuum robots and is available as free software library1.

Design and simulation for a hydraulic actuated quadruped robot

Abstract: This paper describes the mechanical configuration of a quadruped robot firstly. Each of the four legs consists of three rotary joints. All joints of the robot are actuated by linear hydraulic servo cylinders. Then it deduces the forward and inverse kinematic equations for four legs with D-H transformation matrices. Furthermore, it gives a composite foot trajectory composed of cubic curve and straight line, which greatly reduces the velocity and acceleration fluctuations of the torso along forward and vertical directions. Finally, dynamics cosimulation is given with MSC.ADAMS and MATLAB. The results of co-simulation provide important guidance to mechanism design and parameters preference for the linear hydraulic servo cylinders.

Experimental and analytical study of the bi‐directional behavior of the triple friction pendulum isolator

Abstract: SUMMARY This paper presents a non-linear, kinematic model for triple friction pendulum isolation bearings. The model, which incorporates coupled plasticity and circular restraining surfaces for all sliding surfaces, is capable of capturing bi-directional behavior and is able to explicitly track the movement of each internal component. The model is general so that no conditions regarding bearing properties, which effect the sequence of sliding stages, are required for the validity of the model. Controlled-displacement and seismic-input experiments were conducted using the shake table at the University of California, Berkeley to assess the fidelity of the proposed model under bi-directional motion. Comparison of the experimental data with the corresponding results of the kinematic model shows good agreement. Additionally, experiments showed that the performance of TFP bearings is reliable over many motions, and the behavior is repeatable even when initial slider offsets are present. Copyright © 2011 John Wiley & Sons, Ltd.