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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

The human vestibulo-ocular reflex during linear locomotion

During locomotion, there is a translation and compensatory rotation of the head in both the vertical and horizontal planes. During moderate to fast walking (100 m/min), vertical head translation occurs at the frequency of stepping (2 Hz) and generates peak linear acceleration of 0.37 g. Lateral head translation occurs at the stride frequency (1 Hz) and generates peak linear acceleration of 0.1 g. Peak head pitch and yaw angular velocities are approximately 17 degrees/s. The frequency and magnitude of these head movements are within the operational range of both the linear and angular vestibulo-ocular reflex (IVOR and aVOR). Vertical eye movements undergo a phase reversal from near to far targets. When viewing a far (>1 m) target, vertical eye velocity is typical of an aVOR response; that is, it is compensatory for head pitch. At close viewing distances (<1 m), vertical eye velocity is in phase with head pitch and is compensatory for vertical head translation, suggesting that the IVOR predominantly generates the eye movement response. Horizontal head movements during locomotion occur at the stride frequency of 1 Hz, where the IVOR gain is low. Horizontal eye movements are compensatory for head yaw at all viewing distances and are likely generated by the aVOR.

NASA Discipline Neuroscience↗
NASA NTRS1999

Effect of viewing distance on the generation of vertical eye movements during locomotion

Vertical head and eye coordination was studied as a function of viewing distance during locomotion. Vertical head translation and pitch movements were measured using a video motion analysis system (Optotrak 3020). Vertical eye movements were recorded using a video-based pupil tracker (Iscan). Subjects (five) walked on a linear treadmill at a speed of 1.67 m/s (6 km/h) while viewing a target screen placed at distances ranging from 0.25 to 2.0 m at 0. 25-m intervals. The predominant frequency of vertical head movement was 2 Hz. In accordance with previous studies, there was a small head pitch rotation, which was compensatory for vertical head translation. The magnitude of the vertical head movements and the phase relationship between head translation and pitch were little affected by viewing distance, and tended to orient the naso-occipital axis of the head at a point approximately 1 m in front of the subject (the head fixation distance or HFD). In contrast, eye velocity was significantly affected by viewing distance. When viewing a far (2-m) target, vertical eye velocity was 180 degrees out of phase with head pitch velocity, with a gain of 0. 8. This indicated that the angular vestibulo-ocular reflex (aVOR) was generating the eye movement response. The major finding was that, at a close viewing distance (0.25 m), eye velocity was in phase with head pitch and compensatory for vertical head translation, suggesting that activation of the linear vestibulo-ocular reflex (lVOR) was contributing to the eye movement response. There was also a threefold increase in the magnitude of eye velocity when viewing near targets, which was consistent with the goal of maintaining gaze on target. The required vertical lVOR sensitivity to cancel an unmodified aVOR response and generate the observed eye velocity magnitude for near targets was almost 3 times that previously measured. Supplementary experiments were performed utilizing body-fixed active head pitch rotations at 1 and 2 Hz while viewing a head-fixed target. Results indicated that the interaction of smooth pursuit and the aVOR during visual suppression could modify both the gain and phase characteristics of the aVOR at frequencies encountered during locomotion. When walking, targets located closer than the HFD (1.0 m) would appear to move in the same direction as the head pitch, resulting in suppression of the aVOR. The results of the head-fixed target experiment suggest that phase modification of the aVOR during visual suppression could play a role in generating eye movements consistent with the goal of maintaining gaze on targets closer than the HFD, which would augment the lVOR response.

NASA Discipline Neuroscience↗
NASA NTRS1997

The role of reafference in recalibration of limb movement control and locomotion

The reafference model has frequently been used to explain spatial constancy during eye and head movements. We have found that its basic concepts also form part of the information processing necessary for the control and recalibration of reaching movements. Reaching was studied in a novel force environment--a rotating room that creates centripetal forces of the type that could someday substitute for gravity in space flight, and Coriolis forces which are side effects of rotation. We found that inertial, noncontacting Coriolis forces deviate the path and endpoint of reaching movements, a finding that shows the inadequacy of equilibrium position models of movement control. Repeated movements in the rotating room quickly lead to normal movement patterns and to a failure to perceive the perturbing forces. The first movements made after rotation stops, without Coriolis forces present, show mirror-image deviations and evoke perception of a perturbing force even though none is present. These patterns of sensorimotor control and adaptation can largely be explained on the basis of comparisons of efference copy, reafferent muscle spindle, and cutaneous mechanoreceptor signals. We also describe experiments on human locomotion using an apparatus similar to that which Mittelstaedt used to study the optomotor response of the Eristalis fly. These results show that the reafference principle relates as well to the perception of the forces acting on and exerted by the body during voluntary locomotion.

NASA Discipline Neuroscience↗
NASA NTRS1996

Measuring eye movements during locomotion: filtering techniques for obtaining velocity signals from a video-based eye monitor

Video-based eye-tracking systems are especially suited to studying eye movements during naturally occurring activities such as locomotion, but eye velocity records suffer from broad band noise that is not amenable to conventional filtering methods. We evaluated the effectiveness of combined median and moving-average filters by comparing prefiltered and postfiltered records made synchronously with a video eye-tracker and the magnetic search coil technique, which is relatively noise free. Root-mean-square noise was reduced by half, without distorting the eye velocity signal. To illustrate the practical use of this technique, we studied normal subjects and patients with deficient labyrinthine function and compared their ability to hold gaze on a visual target that moved with their heads (cancellation of the vestibulo-ocular reflex). Patients and normal subjects performed similarly during active head rotation but, during locomotion, patients held their eyes more steadily on the visual target than did subjects.

NASA Discipline Neuroscience↗
NASA NTRS1992

Stabilization of gaze during circular locomotion in light. I. Compensatory head and eye nystagmus in the running monkey

1. A rhesus and cynomolgus monkey were trained to run around the perimeter of a circular platform in light. We call this "circular locomotion" because forward motion had an angular component. Head and body velocity in space were recorded with angular rate sensors and eye movements with electrooculography (EOG). From these measurements we derived signals related to the angular velocity of the eyes in the head (Eh), of the head on the body (Hb), of gaze on the body (Gb), of the body in space (Bs), of gaze in space (Gs), and of the gain of gaze (Gb/Bs). 2. The monkeys had continuous compensatory nystagmus of the head and eyes while running, which stabilized Gs during the slow phases. The eyes established and maintained compensatory gaze velocities at the beginning and end of the slow phases. The head contributed to gaze velocity during the middle of the slow phases. Slow phase Gb was as high as 250 degrees/s, and targets were fixed for gaze angles as large as 90-140 degrees. 3. Properties of the visual surround affected both the gain and strategy of gaze compensation in the one monkey tested. Gains of Eh ranged from 0.3 to 1.1 during compensatory gaze nystagmus. Gains of Hb varied around 0.3 (0.2-0.7), building to a maximum as Eh dropped while running past sectors of interest. Consistent with predictions, gaze gains varied from below to above unity, when translational and angular body movements with regard to the target were in opposite or the same directions, respectively. 4. Gaze moved in saccadic shifts in the direction of running during quick phases. Most head quick phases were small, and at times the head only paused during an eye quick phase. Eye quick phases were larger, ranging up to 60 degrees. This is larger than quick phases during passive rotation or saccades made with the head fixed. 5. These data indicate that head and eye nystagmus are natural phenomena that support gaze compensation during locomotion. Despite differential utilization of the head and eyes in various conditions, Gb compensated for Bs. There are various frames of reference in which an estimate of angular velocity that drives the head and eyes could be based. We infer that body in space velocity (Bs) is likely to be represented centrally to provide this signal.

Non-NASA Center↗
NASA NTRS1992

Potential of adult mammalian lumbosacral spinal cord to execute and acquire improved locomotion in the absence of supraspinal input

The neural circuitry of the lumbar spinal cord can generate alternating extension and flexion of the hindlimbs. The hindlimbs of adult cats with complete transection of the spinal cord at a low thoracic level (T12-T13) can perform full weight-supporting locomotion on a treadmill belt moving at a range of speeds. Some limitations in the locomotor capacity can be associated with a deficit in the recruitment level of the fast extensors during the stance phase and the flexors during the swing phase of a step cycle. The level of locomotor performance, however, can be enhanced by daily training on a treadmill while emphasizing full weight-support stepping and by providing appropriately timed sensory stimulation, loading, and/or pharmacologic stimulation of the hindlimb neuromuscular apparatus. Furthermore, there appears to be an interactive effect of these interventions. For example, the maximum treadmill speed that a spinal adult cat can attain and maintain is significantly improved with daily full weight-supporting treadmill training, but progressive recruitment of fast extensors becomes apparent only when the hindlimbs are loaded by gently pulling down on the tail during the stepping. Stimulation of the sural nerve at the initiation of the flexion phase of the step cycle can likewise markedly improve the locomotor capability. Administration of clonidine, in particular in combination with an elevated load, resulted in the most distinct and consistent alternating bursts of electromyographic activity during spinal stepping. These data indicate that the spinal cord has the ability to execute alternating activation of the extensor and flexor musculature of the hindlimbs (stepping) and that this ability can be improved by several interventions such as training, sensory stimulation, and use of some pharmacologic agents. Thus, it appears that the spinal cord, without supraspinal input, is highly plastic and has the potential to "learn," that is, to acquire and improve its ability to execute full weight-supporting locomotion on a treadmill belt.

NASA Discipline Musculoskeletal↗
NASA NTRS2005

Biomechanical Evaluation of Russian BD-1 Treadmill during Non-Motorized Treadmill Locomotion in a Weightless Environment (KC-135)

Subjects are able to successfully perform locomotion exercise on the BD-1 treadmill in weightlessness. The BD-1 bungee system has limited adjustability and provides higher loading for small subjects and lower loading for larger subjects. Some subjects have difficulty reaching and maintaining higher speeds starting at around 14 km/h. The ground reaction force profile for BD-1 locomotion shows peak propulsive forces comparable to 1g, but the heel strike peak appears to be absent during running on the BD-1 in weightlessness. These observations have implications for exercise prescriptions for BD-1 treadmill use on-board ISS.

Schaffner, Grant↗
NASA NTRS2007

The Effect of Manipulating Subject Mass on Lower Extremity Torque Patterns During Locomotion

During locomotion, humans adapt their motor patterns to maintain coordination despite changing conditions (Reisman et al., 2005). Bernstein (1967) proposed that in addition to the present state of a given joint, other factors, including limb inertia and velocity, must be taken into account to allow proper motion to occur. During locomotion with added mass counterbalanced using vertical suspension to maintain body weight, vertical ground reaction forces (GRF's) increase during walking but decrease during running, suggesting that adaptation may be velocity-specific (De Witt et al., 2006). It is not known, however, how lower extremity joint torques adapt to changes in inertial forces. The purpose of this investigation was to examine the effects of increasing body mass while maintaining body weight upon lower-limb joint torque during walking and running. We hypothesized that adaptations in joint torque patterns would occur with the addition of body mass.

DeWitt, John K.↗
NASA NTRS2007

The Effect of Increasing Mass upon Locomotion

The purpose of this investigation was to determine if increasing body mass while maintaining bodyweight would affect ground reaction forces and joint kinetics during walking and running. It was hypothesized that performing gait with increased mass while maintaining body weight would result in greater ground reaction forces, and would affect the net joint torques and work at the ankle, knee and hip when compared to gait with normal mass and bodyweight. Vertical ground reaction force was measured for ten subjects (5M/5F) during walking (1.34 m/s) and running (3.13 m/s) on a treadmill. Subjects completed one minute of locomotion at normal mass and bodyweight and at four added mass (AM) conditions (10%, 20%, 30% and 40% of body mass) in random order. Three-dimensional joint position data were collected via videography. Walking and running were analyzed separately. The addition of mass resulted in several effects. Peak impact forces and loading rates increased during walking, but decreased during running. Peak propulsive forces decreased during walking and did not change during running. Stride time increased and hip extensor angular impulse and positive work increased as mass was added for both styles of locomotion. Work increased at a greater rate during running than walking. The adaptations to additional mass that occur during walking are different than during running. Increasing mass during exercise in microgravity may be beneficial to increasing ground reaction forces during walking and strengthening hip musculature during both walking and running. Future study in true microgravity is required to determine if the adaptations found would be similar in a weightless environment.

DeWitt, John↗
NASA NTRS2007

The Effect of Increasing Inertia upon Vertical Ground Reaction Forces during Locomotion

The addition of inertia to exercising astronauts could increase ground reaction forces and potentially provide a greater health benefit. However, conflicting results have been reported regarding the adaptations to additional mass (inertia) without additional net weight (gravitational force) during locomotion. We examined the effect of increasing inertia while maintaining net gravitational force on vertical ground reaction forces and kinematics during walking and running. Vertical ground reaction force was measured for ten healthy adults (5 male/5 female) during walking (1.34 m/s) and running (3.13 m/s) using a force-measuring treadmill. Subjects completed locomotion at normal weight and mass, and at 10, 20, 30, and 40% of added inertial force. The added gravitational force was relieved with overhead suspension, so that the net force between the subject and treadmill at rest remained equal to 100% body weight. Peak vertical impact forces and loading rates increased with increased inertia during walking, and decreased during running. As inertia increased, peak vertical propulsive forces decreased during walking and did not change during running. Stride time increased during walking and running, and contact time increased during running. Vertical ground reaction force production and adaptations in gait kinematics were different between walking and running. The increased inertial forces were utilized independently from gravitational forces by the motor control system when determining coordination strategies.

DeWitt, John K.↗
NASA NTRS2003

Coordination of Lower Limb Joints During Locomotion: The Effects of Vestibulo-Ocular Reflex Adaptation

Controlling locomotion while maintaining a stable gaze requires precise coordination between several, interdependent full-body sensorimotor subsystems (Bloomberg and Mulavara, 2003; McDonald, et al., 1997). The overall goal of this study is to determine how this full-body gaze stabilization system responds to adaptive changes in vestibuloocular reflex (VOR) function. Locomotion involves cyclical physical interactions (impacts) with the environment. Hence, focusing on a target and maintaining visual acuity during this activity may require mechanisms to manage the energy flow, so it does not disrupt the visual and vestibular sensory information processing that stabilizes gaze. It has been shown that increasing the difficulty of a gaze task (reading numbers on a screen as opposed to simply focusing on a central dot pattern) resulted in an increase in the amount of knee flexion movement during the critical phase immediately following the heel strike event (Mulavara and Bloomberg, 2003). The increase in knee flexion during the stance phase of the gait cycle has been suggested to function as a shock absorbing mechanism associated with the rapid weight transfer from the trailing to the leading leg during walking. To understand this full-body coordination, the relative contributions of each component and the resulting effects should be assessed. In this study, we hypothesized that VOR adaptation would result in a reorganization of the lower limb joint coordination during treadmill walking in a manner to facilitate the gaze stabilization task and preserve locomotor function.

Miller, Chris↗
NASA NTRS2014

Biomechanics of the Treadmill Locomotion on the International Space Station

Exercise prescriptions completed by International Space Station (ISS) crewmembers are typically based upon evidence obtained during ground-based investigations, with the assumption that the results of long-term training in weightlessness will be similar to that attained in normal gravity. Coupled with this supposition are the assumptions that exercise motions and external loading are also similar between gravitational environments. Normal control of locomotion is dependent upon learning patterns of muscular activation and requires continual monitoring of internal and external sensory input [1]. Internal sensory input includes signals that may be dependent on or independent of gravity. Bernstein hypothesized that movement strategy planning and execution must include the consideration of segmental weights and inertia [2]. Studies of arm movements in microgravity showed that individuals tend to make errors but that compensation strategies result in adaptations, suggesting that control mechanisms must include peripheral information [3-5]. To date, however, there have been no studies examining a gross motor activity such as running in weightlessness other than using microgravity analogs [6-8]. The objective of this evaluation was to collect biomechanical data from crewmembers during treadmill exercise before and during flight. The goal was to determine locomotive biomechanics similarities and differences between normal and weightless environments. The data will be used to optimize future exercise prescriptions. This project addresses the Critical Path Roadmap risks 1 (Accelerated Bone Loss and Fracture Risk) and 11 (Reduced Muscle Mass, Strength, and Endurance). Data were collected from 7 crewmembers before flight and during their ISS missions. Before launch, crewmembers performed a single data collection session at the NASA Johnson Space Center. Three-dimensional motion capture data were collected for 30 s at speeds ranging from 1.5 to 9.5 mph in 0.5 mph increments with a 12-camera system. During flight, each crewmember completed up to 6 data collection sessions spread across their missions, performing their normal exercise prescription for the test day, resulting in varying data collection protocols between sessions. Motion data were collected by a single HD video camera positioned to view the crewmembers' left side, and tape markers were placed on their feet, legs, and neck on specific landmarks. Before data collection, the crewmembers calibrated the video camera. Video data were collected during the entire exercise session at 30 Hz. Kinematic data were used to determine left leg hip, knee, and ankle range of motion and contact time, flight time, and stride time for each stride. 129 trials in weightlessness were analyzed. Mean time-normalized strides were found for each trial, and cross-correlation procedures were used to examine the strength and direction of relationships between segment movement pattern timing in each gravitational condition. Cross-correlation analyses between gravitational conditions revealed highly consistent movement patterns at each joint. Peak correlation coefficients occurred at 0% phase, indicating there were no lags in movement timing. Joint ranges of motion were similar between gravitational conditions, with some slight differences between subjects. Motion patterns in weightlessness were highly consistent at a given speed with those occurring in 1G, indicating that despite differing sensory input, subjects maintain running kinematics. The data suggest that individuals are capable of compensating for loss of limb weight when creating movement strategies. These results have important implications for creating training programs for use in weightlessness as practitioners can have greater confidence in running motions transferring across gravitational environments. Furthermore, these results have implications for use by researchers investigating motor control mechanisms and investigating hypotheses related to movement strategies when using sensory input that is dependent upon gravity.

DeWitt, John↗
NASA NTRS2003

Identifying Head-Trunk and Lower Limb Contributions to Gaze Stabilization During Locomotion

The goal of the present study was to determine how the multiple, interdependent full-body sensorimotor subsystems respond to a change in gaze stabilization task constraints during locomotion. Nine subjects performed two gaze stabilization tasks while walking at 6.4 km/hr on a motorized treadmill: 1) focusing on a central point target; 2) reading numeral characters; both presented at 2m in front at the level of their eyes. While subjects performed the tasks we measured: temporal parameters of gait, full body sagittal plane segmental kinematics of the head, trunk, thigh, shank and foot, accelerations along the vertical axis at the head and the shank, and the vertical forces acting on the support surface. We tested the hypothesis that with the increased demands placed on visual acuity during the number recognition task, subjects would modify full-body segmental kinematics in order to reduce perturbations to the head in order to successfully perform the task. We found that while reading numeral characters as - compared to the central point target: 1) compensatory head pitch movement was on average 22% greater despite the fact that the trunk pitch and trunk vertical translation movement control were not significantly changed; 2) coordination patterns between head and trunk as reflected by the peak cross correlation between the head pitch and trunk pitch motion as well as the peak cross correlation between the head pitch and vertical trunk translation motion were not significantly changed; 3) knee joint total movement was on average 11% greater during the period from the heel strike event to the peak knee flexion event in stance phase of the gait cycle; 4) peak acceleration measured at the head was significantly reduced by an average of 13% in four of the six subjects. This was so even when the peak acceleration at the shank and the transmissibility of the shock wave at heel strike (measured by the peak acceleration ratio of the head/shank) remained unchanged. Taken together these results provide further evidence that the full body contributes to gaze stabilization during locomotion, and that its different functional elements can be modified online to contribute to gaze stabilization for different visual task constraints.

Mulavara, Ajitkumar P.↗
NASA NTRS2017

A Mobile Robot for Locomotion Through a 3D Periodic Lattice Environment

This paper describes a novel class of robots specifically adapted to climb periodic lattices, which we call 'Relative Robots'. These robots use the regularity of the structure to simplify the path planning, align with minimal feedback, and reduce the number of degrees of freedom (DOF) required to locomote. They can perform vital inspection and repair tasks within the structure that larger truss construction robots could not perform without modifying the structure. We detail a specific type of relative robot designed to traverse a cuboctahedral (CubOct) cellular solids lattice, show how the symmetries of the lattice simplify the design, and test these design methodologies with a CubOct relative robot that traverses a 76.2 mm (3 in.) pitch lattice, MOJO (Multi-Objective JOurneying robot). We perform three locomotion tasks with MOJO: vertical climbing, horizontal climbing, and turning, and find that, due to changes in the orientation of the robot relative to the gravity vector, the success rate of vertical and horizontal climbing is significantly different.

Aeronautics↗
NASA NTRS2022

Cockpit Interface for Locomotion and Manipulation Control of the NASA Valkyrie Humanoid in Virtual Reality (VR)

A virtual reality (VR) interface is presented for controlling NASA’s Valkyrie humanoid robot with flexible locomotion control options and intuitive teleoperation. Locomotion modes include navigating to a specified waypoint, sending desired velocities with a joystick, or manually placing a sequence of footsteps. On the other hand, teleoperation modes include voice commands to toggle relative whole-body tracking or high-level commandeering, and key bindings for common stored poses such as power grasps. The primary novelties of the interface are in the implementation of the cockpit mode and a floating augmented reality (AR) screen fixed with respect to the robot. The former enables embodied teleoperation and increased awareness during navigation in a mixed-reality setting. The latter preserves depth perception without the disparity clutter from a stereo point cloud. The interface is demonstrated on two real humanoids performing common explosive ordnance disposal (EOD) tasks such as door opening, vehicle inspection, and disruptor placement. Notably, the interface enables a single operator to control multiple humanoids. While the interface is motivated by EOD missions, the presented ideas are usable for other robots employing VR-based control.

Virtual-reality↗
NASA NTRS2021

Development of the Sample Fetch Rover Locomotion Subsystem

A novel system for planetary surface mobility is being designed in response to the challenging requirements of the Sample Fetch Rover (SFR) mission, part of the NASA/ESA Mars Sample Return campaign (MSR). The rover will retrieve tubes with rock and soil samples, previously acquired and cached by NASA’s Perseverance rover in depots on the Martian surface. SFR will have to acquire, transport and deliver the tubes to a lander in a tight time window. This will require significant mobility capabilities, unprecedented for Mars rovers. The highly time-constrained traverse needs, together with the strictly limited mass and volume imposed by the accommodation on the lander, have pushed the design of the SFR locomotion to seek innovative solutions. In response to that, a four-wheel drive system is being developed, integrated with a deployable pitch-averaging suspension. This will be the first time that four-wheel locomotion is used on Mars and on robotic planetary rovers in general. The system, relying on high-efficiency drive actuators designed to operate in Mars environment, shows potential for terrain and obstacle negotiation performance comparable with that of larger vehicles. The implementation also takes advantage of the superelastic Spring-Tyre technology currently being developed by NASA Glenn Research Center, which, thanks to its traction and obstacle compliance properties, will allow SFR to navigate difficult ground and achieve its mission objectives.

Rehmatullah, Faizan↗
DOE OSTI2025

Techno-Economic Analysis and Life Cycle Assessment of Alternative Fuels for Locomotives in the U.S. Freight Rail Sector

Freight rail is more energy-efficient than truck transport over long-haul distances, offering a low-energy and emissions-intensive option for transporting freight. This study evaluates techno-economic analysis and life cycle assessment of seven alternative unblended fuels for freight locomotive engines─biodiesel, renewable diesel (RD), bio-oils, methanol, dimethyl ether (DME), ethanol, and ammonia─across 16 fuel pathways utilizing soybean, corn, woody biomass, renewable hydrogen, and waste sources, e.g., sludge, manure, and industrial CO 2 , and compares these to conventional diesel. The minimum fuel selling price (MFSP) ranged from $\$2.05$ to $\$8.27$ per diesel gallon equivalent (2020 US dollars), with biocrude and RDs produced from hydrothermal liquefaction (HTL) of sludge having the lowest MFSPs due to coproduct credits and avoided waste treatment cost. Life cycle GHG emissions ranged from −41 to 53 g of CO 2 e/MJ. RD from waste via HTL achieves negative emissions by diverting sludge/manure from GHG-intensive conventional management. Few pathways such as biocrude, methanol, and DME require additional control for SO X emissions in the refinery, while ethanol, FT-diesel, and bio-oil require additional control for particulate matter emissions. Bio-oil and RD from sludge have lower marginal abatement cost or MAC (–$\$38$/tonne CO 2 lowest) while methanol and ammonia with renewable hydrogen have higher MAC ($\$490$/tonne CO 2 maximum).

29 ENERGY PLANNING, POLICY, AND ECONOMY↗