Simulation Of Locomotion Research Articles

Dynamics Analysis and Power Allocation Strategy Research for a New Hybrid Electric Urban Rail Vehicle

In order to improve the efficiency and environment-friendliness of urban rail vehicles, a new hybrid electric locomotive is proposed. The general structure of the proposed hybrid electric locomotive is given and analyzed from a dynamics point of view. The calculation method of power output and its allocation strategy is discussed. A simulation is conducted in HELSP(Hybrid Electric Locomotive Simulation Platform) to verify the performance of the power allocation strategy. The result indicates that the function of allocating power can be properly realized, and the regeneration energy from frequent braking can be absorbed by the power storage of the vehicle.

Eye Movement Patterns during Locomotion in Real-World and Simulated Environments

Eye movements in a search-and-count walking task were compared between a simulated (SE) and real-world environment (RE). Eye movements were recorded using the mobile WearCam in either RE or the StroMoHab locomotion simulator, a treadmill-based system for gait mobility rehabilitation. For Experiment 1, a RE was prepared with objects (coloured balls) and occluding barriers placed along a 38 m long corridor. A video was captured from a walker's viewpoint at 1.3 km/hr. Fifteen subjects per environment reported the total object count after completing a walk while viewing the video in the SE (at 0, 1.3, or 2.5 km/h) and RE (at 1.3 km/h). Examining the number of eye transitions (TotET) between objects in relation to walking speed in SE, revealed significant increases between 0 and 2.5 km/h (F3, 56 =20.62, p = .02) and 1.3 and 2.5 km/h (F3, 56 =20.62, p = .039), despite no change in video speed; no significant difference was found between 0 and 1.3 km/h. In Experiment 2, 15 subjects viewed a static checkered screen and were instructed to ‘view the screen’ while walking. TotET decreased significantly, between 1.3 km/h and 5.2 km/h (F2, 27 =3.437, p = .014); no significant differences were observed between 2.6 km/h and either 1.3 km/h or 5.2 km/h. In real-world conditions, walking faster increases the difficulty of search tasks, with a likely correlated increase in eye movements. Apparently, the expectation of increased difficulty carries over to SE, even if the visual task is not more difficult. The findings point to physiological and perceptual correlations between locomotion and eye movements.

Sensitivity of maximum sprinting speed to characteristic parameters of the muscle force–velocity relationship

An accumulation of evidence suggests that the force–velocity relationship (FVR) of skeletal muscle plays a major role in limiting maximum human sprinting speed. However, most of the theories on this limiting role have been non-specific as to how the FVR limits speed. The FVR is characterized by three parameters that each have a different effect on its shape, and could thus limit sprinting speed in different ways: the maximum shortening velocity Vmax, the shape parameter AR, and the eccentric plateau Cecc. In this study, we sought to determine how specifically the FVR limits sprinting speed using forward dynamics simulations of human locomotion to examine the sensitivity of maximum speed to these three FVR parameters. Simulations were generated by optimizing the model's muscle excitations to maximize the average horizontal speed. The simulation's speed, temporal stride parameters, joint angles, GRF, and muscle activity in general compared well to data from human subjects sprinting at maximum effort. Simulations were then repeated with incremental and isolated adjustments in Vmax, AR, and Cecc across a physiological range. The range of speeds (5.22–6.91ms−1) was most sensitive when Vmax was varied, but the fastest speed of 7.17ms−1 was attained when AR was set to its maximum value, which corresponded to all muscles having entirely fast-twitch fibers. This result was explained by the muscle shortening velocities, which tended to be moderate and within the range where AR had its greatest effect on the shape of the FVR. Speed was less sensitive to adjustments in Cecc, with a range of 6.23–6.70ms−1. Increases in speed with parameter changes were due to increases in stride length more so than stride frequency. The results suggest that the shape parameter AR, which primarily determines the amount of muscle force that can be produced at moderate shortening velocities, plays a major role in limiting the maximum sprinting speed. Analysis of muscle force sensitivity indicated support for previous theories on the time to generate support forces in stance (Weyand et al., 2000, Journal of Applied Physiology, 89, 1991–1999) and energy management of the leg in swing (Chapman & Caldwell, 1983, Journal of Biomechanics 16, 79–83) as important factors in limiting maximum speed. However, the ability of the knee flexors to slow the rotational velocity of the leg in preparation for footstrike did not appear to play a major role in limiting speed.

Bristled In-pipe Machine Inside Pipe With Geometric Deviations

Paper deals with in-pipe machine which locomotes inside pipe for inspection or drawing purposes. Several studies with bristles are known. This paper includes analysis of geometric deviations influence to bristles behaviors. Simulations of the machine locomotion have been done based on math model. Controlled bristles are proposed as improved solution of the interaction problems inside pipe.

Structure preserving simulation of muscle actuated movements

AbstractBiomechanical simulation of human locomotion is commonly done via dynamical simulations of multibody systems. The actuation of the system is thereby often represented via muscle models that create a force depending on muscle length and activation level. We show a comparison of such a simulation using a structure preserving integration framework to MATLAB/Simulink results. The conclusion is that structure preservation is important to represent such systems correctly, in particular concerning energy and angular momentum evolutions. We introduce a method for structure preserving simulation of muscle actuated movements. Additionally we show examples of a simple arm movement including only one muscle as well as a finger movement including up to six muscles as an example for more complex biomechanical systems. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Optimal locomotion trajectory for biped robot ‘D2’ with knees stretched, heel-contact landings, and toe-off liftoffs

Most of the current biped robots with active revolute joints walk with their knees bent while a human walks without bending his or her knees in “natural” gaits. This paper proposes a method to generate natural locomotion trajectory for biped robots without bending knees based on a 2-DOF model of an inverted pendulum. In addition to the natural leg motion, this paper proposes a foot trajectory that has heel-contact landing and toe-off liftoff phases similar to the human foot. The trajectory is parameterized and optimized with a genetic algorithm based on energy consumption. In simulation of locomotion of biped robot, D2, which has a double deck structure of parallel mechanisms, the resulting trajectory looks natural and requires approximately 28% less energy than the one generated by the LIPM method. In addition to proposing the method to generate trajectory for a biped robot, this paper introduces the mechanism of serially linked parallel-mechanism for a biped robot with knees.

Numerical simulation of batoid locomotion

The hydrodynamics of batoid swimming motions is investigated using the three-dimensional simulation of a self-propelled body in still water. The kinematics of batoid swimming is characterized by large amplitude undulations of the pectoral fins while the middle part of the body remains straight. The majority of the thrust is generated by pectoral fins. Linear and quadratic amplitude variations are used for the pectoral fins in analyzing the locomotion of the batoid. Navier-Stokes equations are used to solve the unsteady fluid flow. A user defined function and a dynamic mesh method are applied to track the batoid locomotion. The mean swimming velocities of 1.6 BL/s and 1.3 BL/s are achieved, respectively, with thrust coefficients of 0.13 in and 0.095 in the dynamical simulation, where BL/s is the body length per second. The maximum propulsive efficiency 19% is achieved when the frequency of the undulation is 2.2 Hz in both amplitude variations.

Miniaturized Sensors to Monitor Simulated Lunar Locomotion

Human activity monitoring is a useful tool in medical monitoring, military applications, athletic coaching, and home healthcare. We propose the use of an accelerometer-based system to track crewmember activity during space missions in reduced gravity environments. It is unclear how the partial gravity environment of the Moorn or Mars will affect human locomotion. Here we test a novel analogue of lunar gravity in combination with a custom wireless activity tracking system. A noninvasive wireless accelerometer-based sensor system, the activity tracking device (ATD), was developed. The system has two sensor units; one footwear-mounted and the other waist-mounted near the midlower back. Subjects (N=16) were recruited to test the system in the enhanced Zero Gravity Locomotion Simulator (eZLS) at NASA Glenn Research Center. Data were used to develop an artificial neural network for activity recognition. The eZLS demonstrated the ability to replicate reduced gravity environments. There was a 98% agreement between the ATD and force plate-derived stride times during running (9.7 km x h(-1)) at both 1 g and 1/6 g. A neural network was designed and successfully trained to identify lunar walking, running, hopping, and loping from ATD measurements with 100% accuracy. The eZLS is a suitable tool for examining locomotor activity at simulated lunar gravity. The accelerometer-based ATD system is capable of monitoring human activity and may be suitable for use during remote, long-duration space missions. A neural network has been developed to use data from the ATD to aid in remote activity monitoring.

FES-Assisted Walking with Spring Brake Orthosis: Simulation Studies

This paper presents a simulation of bipedal locomotion to generate stimulation pulses for activating muscles for paraplegic walking with wheel walker using functional electrical stimulation (FES) with spring brake orthosis (SBO). A new methodology for paraplegic gait, based on exploiting natural dynamics of human gait, is introduced. The work is a first effort towards restoring natural like swing phase in paraplegic gait through a new hybrid orthosis, referred to as spring brake orthosis (SBO). This mechanism simplifies the control task and results in smooth motion and more-natural like trajectory produced by the flexion reflex for gait in spinal cord injured subjects. SBO can eliminate reliance on the withdrawal reflex and foot-ground clearance without extra upper body effort. The stored energy in the spring of SBO is used to replace stimulation pulses in knee flexion and reduce total required torque for the paraplegic walking with wheel walker. The study is carried out with a model of humanoid with wheel walker using the Visual Nastran (Vn4D) dynamic simulation software. Stimulated muscle model of quadriceps is developed for knee extension. Fuzzy logic control (FLC) is developed in Matlab/Simulink to regulate the muscle stimulation pulse-width required to drive FES-assisted walking gait and the computed motion is visualised in graphic animation from Vn4D. The simulation results show that SBO can be successfully used with FES for paraplegic walking with wheel walker with all the advantages discussed over the current hybrid orthoses available.

FES-Assisted Walking with Spring Brake Orthosis: Simulation Studies

This paper presents a simulation of bipedal locomotion to generate stimulation pulses for activating muscles for paraplegic walking with wheel walker using functional electrical stimulation FES with spring brake orthosis SBO. A new methodology for paraplegic gait, based on exploiting natural dynamics of human gait, is introduced. The work is a first effort towards restoring natural like swing phase in paraplegic gait through a new hybrid orthosis, referred to as spring brake orthosis SBO. This mechanism simplifies the control task and results in smooth motion and more-natural like trajectory produced by the flexion reflex for gait in spinal cord injured subjects. SBO can eliminate reliance on the withdrawal reflex and foot-ground clearance without extra upper body effort. The stored energy in the spring of SBO is used to replace stimulation pulses in knee flexion and reduce total required torque for the paraplegic walking with wheel walker. The study is carried out with a model of humanoid with wheel walker using the Visual Nastran Vn4D dynamic simulation software. Stimulated muscle model of quadriceps is developed for knee extension. Fuzzy logic control FLC is developed in Matlab/Simulink to regulate the muscle stimulation pulse-width required to drive FES-assisted walking gait and the computed motion is visualised in graphic animation from Vn4D. The simulation results show that SBO can be successfully used with FES for paraplegic walking with wheel walker with all the advantages discussed over the current hybrid orthoses available.

Java Simulator for Quadruped Walking Robot

With advances in science and technology, the interest to study the animals walking has developed the demand for building the legged robots. Physics-based simulation and control of quadruped locomotion is difficult because quadrupeds are unstable, under actuated, high-dimensional dynamical systems. We develop a simple control strategy that can be used to generate a large variety of gaits and styles in real-time, including walking in all directions (forwards, backwards, sideways, turning). The application named JQuadRobot is developed in Java and Java3D API. A Graphical User Interface and a simulator for a custom quadruped leg's robot and the main features of the interface are presented in this paper. This application is developed in Java and is essential in a development motion for legged robot. The friendly interface, allows any user to define and test movements for this robot. The cross-platform capability was the first reason to choose Java language for developing this application.

The Cab Technology Integration Lab: A Locomotive Simulator for Human Factors Research

The paper describes a new human factors research capability for the US Federal Railroad Administration (FRA)—The Cab Technology Integration Laboratory (CTIL). The FRA sponsored the development of the CTIL in order to assess locomotive crew performance with the integration of new market controls, displays, and automation in the locomotive cab environment. Additionally, the CTIL will be used to assess and demonstrate new technologies and workstation configurations that may enhance human performance and human reliability by increasing the locomotive engineer's capabilities to communicate, plan, and control locomotives within the railroad system. The CTIL provides a platform for integration and prototyping of new locomotive cab technologies to assess the impact of the human-machine interface on locomotive crew performance as new capabilities are mandated to meet safety, cost, and security requirements.

A computational biomimetic study of cell crawling

Cell locomotion is a result of a series of synchronized chemo-mechanical processes. Previous extensive experimental studies have revealed many chemo-mechanical processes that may contribute to cell locomotion. In parallel, theoretical works have been developed to provide deeper insight. To date, however, direct simulations of cell locomotion on a substrate have not been seen. In this paper, a finite element-based computational model is developed to study amoeboid type of cell crawling phenomenon. Here, a cell is modeled as a 2D fluid-filled elastic vesicle, which establishes its interaction with a rigid substrate through a kinetics-based cellular adhesion model. The cell derives its motion through a differential bond breaking at the trailing edge and bond formation at the leading edge. This mechanism of crawling authenticates the hypothesis that cell locomotion can be facilitated by breaking the adhesive bonds at the rear edge, which was initially proposed by Chen (J Cell Biol 90: 187-200, 1981).

The Brain in Its Body: Motor Control and Sensing in a Biomechanical Context

Although it is widely recognized that adaptive behavior emerges from the ongoing interactions among the nervous system, the body, and the environment, it has only become possible in recent years to experimentally study and to simulate these interacting systems. We briefly review work on molluscan feeding, maintenance of postural control in cats and humans, simulations of locomotion in lamprey, insect, cat and salamander, and active vibrissal sensing in rats to illustrate the insights that can be derived from studies of neural control and sensing within a biomechanical context. These studies illustrate that control may be shared between the nervous system and the periphery, that neural activity organizes degrees of freedom into biomechanically meaningful subsets, that mechanics alone may play crucial roles in enforcing gait patterns, and that mechanics of sensors is crucial for their function.

Muscle-driven forward dynamics simulation for the study of differences in muscle function during stair ascent and descent

The main scope of this study is to analyse muscle-driven forward dynamics simulation of stair locomotion to understand the functional differences of individual muscles during the movement. A static optimization was employed to minimize a performance criterion based on the muscle energy consumption to resolve muscle redundancy during forward dynamics simulation. The proposed method was employed to simulate a musculoskeletal system with ten degrees of freedom in the sagittal plane and containing 18 Hill-type musculotendon actuators per leg. Simulation results illustrated that simulated joint kinematics closely tracked experimental quantities with root-mean-squared errors less than 1 degree. In addition, estimated muscle activations have a good agreement with the salient features of the electromyographic recordings of the major muscles of the lower extremity. Distribution of mechanical power for individual muscles was estimated to elucidate the muscle's contribution to body support and forward progression during stair locomotion. The accuracy and relatively high computational performance of the proposed method make it suitable to generate subject-specific simulations of various activities for individuals with movement disorders in clinical studies.

Feedback control of the neuromusculoskeletal system in a forward dynamics simulation of stair locomotion

The aim of this study is to employ feedback control loops to provide a stable forward dynamics simulation of human movement under repeated position constraint conditions in the environment, particularly during stair climbing. A ten-degrees-of-freedom skeletal model containing 18 Hill-type musculotendon actuators per leg was employed to simulate the model in the sagittal plane. The postural tracking and obstacle avoidance were provided by the proportional-integral-derivative controller according to the modulation of the time rate change of the joint kinematics. The stability of the model was maintained by controlling the velocity of the body's centre of mass according to the desired centre of pressure during locomotion. The parameters of the proposed controller were determined by employing the iterative feedback tuning approach to minimize tracking errors during forward dynamics simulation. Simultaneously, an inverse-dynamics-based optimization was employed to compute a set of desired musculotendon forces in the closed-loop simulation to resolve muscle redundancy. Quantitative comparisons of the simulation results with the experimental measurements and the reference muscles' activities illustrate the accuracy and efficiency of the proposed method during the stable ascending simulation.

Modular Universal Unit for a Snake-Like Robot and Reconfigurable Robots

A modular universal unit (MUU) is developed for snake-like robots, which has 3 d.o.f. with a series of passive rollers around its cylindrical shell. Among those d.o.f., pitching and yawing are actuated by means of differential gears to accomplish a large ratio of propulsion to mass. The series of passive rollers around the cylindrical aluminum shell of the MUU form another large wheel that can be used as a driving wheel of mobile robots. The snake-like robot composed of those MUUs has more powerful propulsion and higher mobility. By connecting MUUs in different forms, we can also realize a connected mobile platform or a manipulator in addition to a snake-like robot. Owing to it having 3 d.o.f., two or more MUUs can be connected to make up many mobile robots or form a manipulator that exhibits high mobility and agility. Some typical reconfigurable robots composed of these MUUs are analyzed for locomotion control. Finally, the locomotion experiments and simulations are given to show the characteristics of this MUU.

Characterization of a lower-body exoskeleton for simulation of space-suited locomotion

In a previous analysis of suited and unsuited locomotion energetics, we found evidence that space suits act as springs during running. Video images from the lunar surface suggest that knee torques create, in large part, this spring effect. We hypothesized that a lower-body exoskeleton, properly constructed, could be used to simulate the knee torques of a range of space suits. Here we report characterization of a lower-body exoskeleton. Equivalent spring stiffness of each exoskeleton leg varies as a function of exoskeleton knee angle and load, and the exoskeleton joint-torque relationship closely matches the current NASA space suit, or Extravehicular Mobility Unit, knee torques in form and magnitude. We have built an exoskeleton with two physical non-linear springs, which achieve space-suit like joint-torques. Therefore space-suit legs act as springs, with this effect most pronounced when locomotion requires large changes in knee flexion such as during running.

Mathematical modeling and simulation of aquatic and aerial animal locomotion

In this paper, we investigate the locomotion of fish and birds by applying a new unsteady, flexible wing theory that takes into account the strong nonlinear dynamics semi-analytically. We also make extensive comparative study between the new approach and the modified vortex blob method inspired from Chorin’s and Krasny’s work. We first implement the modified vortex blob method for two examples and then discuss the numerical implementation of the nonlinear analytical mathematical model of Wu. We will demonstrate that Wu’s method can capture the nonlinear effects very well by applying it to some specific cases and by comparing with the experiments available. In particular, we apply Wu’s method to analyze Wagner’s result for a wing abruptly undergoing an increase in incidence angle. Moreover, we study the vorticity generated by a wing in heaving, pitching and bending motion. In both cases, we show that the new method can accurately represent the vortex structure behind a flying wing and its influence on the bound vortex sheet on the wing.

Neuromusculoskeletal computer modeling and simulation of upright, straight-legged, bipedal locomotion of Australopithecus afarensis (A.L. 288-1).

The skeleton of Australopithecus afarensis (A.L. 288-1, better known as "Lucy") is by far the most complete record of locomotor morphology of early hominids currently available. Even though researchers agree that the postcranial skeleton of Lucy shows morphological features indicative of bipedality, only a few studies have investigated Lucy's bipedal locomotion itself. Lucy's energy expenditure during locomotion has been the topic of much speculation, but has not been investigated, except for several estimates derived from experimental data collected on other animals. To gain further insights into how Lucy may have walked, we generated a full three-dimensional (3D) reconstruction and forward-dynamic simulation of upright bipedal locomotion of this ancient human ancestor. Laser-scanned 3D bone geometries were combined with state-of-the-art neuromusculoskeletal modeling and simulation techniques from computational biomechanics. A detailed full 3D neuromusculoskeletal model was developed that encompassed all major bones, joints (10), and muscles (52) of the lower extremity. A model of muscle force and heat production was used to actuate the musculoskeletal system, and to estimate total energy expenditure during locomotion. Neural activation profiles for each of the 52 muscles that produced a single step of locomotion, while at the same time minimizing the energy consumed per meter traveled, were searched through numerical optimization. The numerical optimization resulted in smooth locomotor kinematics, and the predicted energy expenditure was appropriate for upright bipedal walking in an individual of Lucy's body size.