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 Rotating Room entrance  Parabolic Flight |
Facilities
VR and Data Acquisition Hardware
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Rotating Room  Mpg-4 Video of the Rotating Room in action. Please note that the video has no sound. |
The rotating room facility of the Ashton Graybiel Spatial Orientation Laboratory at Brandeis University was designed for studying the influence of unusual force environments on human sensory-motor control and orientation. This facility was designed, fabricated, and assembled at Brandeis University to aid in the study of human behavioral and physiological responses to greater than 1g force environments, of adaptation to unusual forces, and of transitions between force levels. It is the newer of only two such facilities that exist in the United States, the first of which was constructed under the direction of Dr. Ashton Graybiel at the Naval Aerospace Medical Institute in Pensacola, Florida. See the Rotating Room mpg-4 video. Please note the video has no sound.  The rotating room facility is 22 feet in diameter, fully enclosed, with a ceiling height of between 7 feet, 10 inches at the center of rotation and 7 feet 3 inches at the periphery. It has a net weight in excess of 7 tons, and can carry a 6000 pound payload while producing a gravitoinertial resultant in excess of 4g at the periphery. The room has two separate drive systems. The linear induction motor system was designed specifically for our rotation application. It can accelerate the room to 35 RPM at up to 15o/sec2. The belt drive system can also operate the room over the entire 0 to 35 RPM speed range, but with a maximum acceleration rate of 4o/sec2. The belt system is used during experiments requiring minimum noise and vibration levels, or experiments requiring constant velocity over long durations. It provides the capability of running the room continuously for periods of days or even weeks. If such long runs are desired, cooking, sleeping, and sanitation facilities can be installed in the room with additional funding.The controller for both drive systems consists of a dedicated industrial computer running multitasking software that controls room speed and acceleration through feedback hardware, and also monitors many safety and operational parameters of the rotating room, while providing this information to personnel in an external control room. The software will shut down the room if certain parameters exceed pre-set limits. The feedback hardware includes three independent tachometers that close the feedback loop through a failure tolerant voting circuit with independently set able speed limits. The room speed can also be controlled by a 0 to 10 volt external speed reference. The external reference, when used, usually comes from an onboard computer, which provides the speed reference signal through slip rings. This is necessary when one computer must control both the onboard experiment and the speed of the room, or when the speed of the room must be contingent on the subject's responses. The dedicated computer usually controls room speed through previously programed speed profiles. It can accurately control room speed in either direction over the entire 0 to 35 RPM speed range in increments as small as 0.1o/sec. Feedback control ensures a constant room speed while people or objects are moving within the room. Acceleration rates of 0.1o/sec2 to 15o/sec2 in 0.1o/sec2 increments can be achieved; constant velocity can be maintained to within +/- .001% at low speeds and 0.1% at the highest speed. The room can also be sinusoidally oscillated over a wide range of frequencies. Over the entire speed range z-axis vibration has been measured at <.001g.  Room diameter = 20' 10" Door width = 45.5" Door clearance = 41.5" Door height = 77.5" Floor to ceiling height: (at walls) = 88.7" (center) = 94" Threaded holes = 3/8-16 The computer control of the rotating room is monitored by a trained operator in the control room, who also monitors the onboard experiments through onboard video cameras and microphones. The operator has redundant two way communication with the onboard experimenter, and can take over manual control of the slow rotation room, and apply emergency adjustable electric braking (independent of the two drive systems) if necessary. The rotating room can accommodate a wide variety of test devices with on board power for those requiring + or - 15 VDC, 110 VAC single phase current, or 220 VAC single or three phase current. The floor of the room is laid out with a 20 inch grid for securing apparatus. The grid pattern and screw thread are compatible with that of NASA's KC-135, reduced gravity test aircraft so that consoles can be interchanged between the test facilities. |
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| The CF-10 short-arm centrifuge is capable of both on-axis and off-axis rotation. The subject chair can be positioned anywhere along a 4-foot rail and rotational velocities can be varied up to 600o/sec (100 RPM), with acceleration rates in 1o/sec2 increments. The resultant gravitoinertial force deviates from the gravitational vertical in direct proportion to the magnitude of the centripetal force generated. A wide range of precisely defined gravitoinertial force vectors can be achieved by changing position of the chair or rotational velocity or both. The position of the subject can also be varied with respect to this force vector to align the force with any portion of the vestibular labyrinth. A replacement chair can be added which rotates in a direction opposite that of centrifuge rotation. Adjusting the velocity of counter-rotation produces a rotating linear vector. The human centrifuge is a useful device for evaluating correlations between the perceived visual and postural vertical during altered linear and angular accelerations of the body. Furthermore, the contribution of sensory information generated by the contact forces of support over the subject's body can be evaluated. The centrifuge is fully equipped with slip rings for data transfer, video camera monitoring, visual and auditory stimuli for assessing the oculogravic and audiogravic illusions. |
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| The Multi-Axis Tilt Device was fabricated by Neuro Kinetics, Inc. to specifications provided by the Graybiel Laboratory for a series of spatial orientation experiments. This device is unique in that it can statically and dynamically orient a subject with great precision. The subject chair is mounted to a 2-axis gimbal in a pitch-roll or pitch-yaw configuration, allowing us to tilt the subject about any virtual axis. The two axes are driven by high torque direct drive motors with modern servo controllers capable of holding a subject in a static position in force backgrounds up to 3g, rotating the subject to varying angles, and accelerating the subject at up to 800deg/s^2. The subject's seat is equipped with a 5-point restraint harness, adjustable padded straps for the head, torso and legs, and comfortable foam spacers to be positioned around the subject's body. Electrical and optical slip rings provide for conveying signals between experimental components stationary and on the chair, such as a joystick vertical indicator, a data acquisition computer, and a video camera for subject monitoring. The MAT is a useful device for evaluating the perception of the gravitational vertical at extreme body orientations and of subject orientation in altered force environments such as weightlessness and macro-gravity in parabolic flight or in our rotating room. |
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| The Turn and Reach Platform our central apparatus for studying sensorimotor control and adaptation of active torso rotation, arm movement, and combinations thereof. The experimental platform includes a motorized rotating platform, a work surface with an array of targets, an OptotrakTM 3-D (Northern Digital, Inc.) motion analysis system (for recording arm and body motion), data acquisition computers, and a safety harness and railing. The base of the device is a 1-m diameter platform on which the subject stands, which rotates around a vertical axis on a .5-m diameter roller bearing. The platform on which the subject stands can be locked in place or driven directly from below by a direct drive motor and servo controller. A height-adjustable, horizontal work surface is attached to the platform. The work surface is a 1-m radius hemi- disc, with a 30-cm radius central cut-out. The subject can stand in the cut-out with the surface wrapping around them. Visual and auditory targets can be arranged on the surface for turning and reaching tasks. Subjects wear a safety harness attached to an overhead pivot and are made aware of the safety railing, neither of which interferes with mobility. Reaching and platform movements are monitored by an OptotrakTM motion analysis system. OptotrakTM tracks active infrared light-emitting diodes with three CCD cameras rigidly mounted on a single sensor. This sensor is pre-calibrated at the factory so no length calibration procedure is required when it is moved to a new experiment. Our system has two sensor units, providing coverage of the full extent of turning and reaching movements without loss of line of sight to the tracked markers and with minimal set up time. A custom Labview application acquires data from the OptotrakTM in real time (4-ms delay) and stores the data as well as performs movement-contigent dynamic control of peripheral devices, such as driving the platform motor or a visual display. The application includes a flexible interface for designing experimental sequences. |
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| The Vicon MX Motion Capture System provides the ability to track the movement of subjects in a variety of experiments. This system allows for a passive motion capture of reflective markers on the subject. The elimination of wires and battery packs from an individual leads to a more natural motion to be captured and analyzed. The 8-camera array in an 8-ft x 12-ft space gives the ability for 3D video rendering and analysis; in addition the system has a real-time feedback option for the experimenter and subject. The Vicon Motion Capture System is utilized in experiments ranging from balance studies to limb movement and gait studies. |
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| Parabolic flight experiments are conducted through NASA's Lyndon B. Johnson Space Center (JSC) Reduced Gravity Program in Houston, TX. This program provides the unique "weightless" or "zero-g" environment of space flight for test and training purposes. This is the perfect setting for a variety experiments, including: spatial orientation, movement and balance control, motion sickness, and adaptation. The reduced gravity environment is obtained by flying a specially modified C-9 plane through a series of parabolic maneuvers going up and down in such a way that the net force experienced by anyone onboard changes between reduced (weightlessness, 0 g), the 1g of straight and level flight (normal Earth gravity), and high (almost double, 1.8 g) gravity. The maneuvers may be flown consecutively in a roller-coaster fashion or separated by breaks of straight and level flying. A typical mission is 2 to 3 hours long and consists of 30 to 40 parabolas. Lunar (0.6g) and Martian (0.38g) profiles are also available. |
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| The Phantom Robotic Manipulandum (Sensable Devices, Inc.) is a lightweight 2-link robotic arm, which can be driven by torque motors to create forces in three dimensions. The arm contains encoders from which the position and velocity of the tip can be computed with an accuracy that is .03 mm in the center of the workspace. The maximum force the Phantom Desktop device can deliver is 8 N (~1.8lbs) in a workspace of 16 x 12 cm horizontally and 20 cm high. The Phantom 1.5 Premium has a work space of about 30-inx 25-inx 12-in and a peak continuous force of 8.5 N (~1.9lbs). The encoder signals are made available in real-time to a controller that commands the motors to produce the desired forces. The system implements the three-dimensional equation for Coriolis force at over 1200 Hz. This allows us to study the effects of novel force perturbations on arm reaching motions without the use of the rotating room or rotating chair. An important feature of the Phantom is that when the motors are programmed for zero force, the moving arm has negligible inertia (75 g apparent mass at tip), is statically balanced throughout the workspace, and has very low friction (0.04N static). The apparatus and experimental set-up are mobile, which allows us to transport the set-up to off-site locations, giving us the opportunity to test population groups in a comfortable and familiar environment. The apparatus and set-up include the robotic manipulandum and a control computer for stimuli generation and data collection. |
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 The arrows indicate that the drum, bar and the floor can rotate coaxially, independently of one another. The floor and bar can also be locked in place. |
When a limb is used for locomotion, patterns of afferent and efferent activity related to its own motion are present as well as visual, vestibular, and other proprioceptive information about motion of the whole body. A study is reported in which it was asked whether visual stimulation present during whole-body motion can influence the perception of the leg movements propelling the body. Subjects were tested in conditions in which the stepping movements they made were identical but the amount of body displacement relative to inertial space and to the visual surround varied. These test conditions were created by getting the subjects to walk on a rotatable platform centered inside a large, independently rotatable, optokinetic drum. In each test condition, subjects, without looking at their legs, compared, against a standard condition in which the floor and drum were both stationary, their speed of body motion, their stride length and stepping rate, the direction of their steps, and the perceived force they exerted during stepping. When visual surround motion was incompatible with the motion normally associated with the stepping movements being made, changes in apparent body motion and in the awareness of the frequency, extent and direction of the voluntary stepping movements resulted.
Visual stimulation affects the perception of voluntary leg movement during walking. |
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 The rotating chair is powered by a Neuro Kinetics, Inc. (NKI) 160 ft lb Continuous Torque/320 ft lb Peak Torque servomotor rate table. An integrated low noise mechanical bearing system provides quiet operation with high loads. The chair has a maximum velocity up to 360 degrees/second with nominal acceleration up to 2000o/sec2 at 4 ft lb sec2 load inertia and a maximum of 3500o/sec2 at 4 ft lb sec2 load inertia. System electronics are contained in a NEMA enclosure with a free standing isolation transformer. The system is controlled by a PLC that is interfaced via a touch screen interface and data collection computer. The high torque rotation servomotor rate table uses a single turn absolute encoder with sin/cos 1 Vpp, +/- 20 seconds accuracy, 2048 periods per revolution, interpolated to 13 bits per period.  View of visual stimulus arc and indicator bar (above) and side view (left) and front view of the chair (right). |
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Vertical Oscillating Platform
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The Graybiel Lab constructed a vertical oscillating platform for a specific series of motion sickness experiments. The design was conceived by Dr. Simone Bortolami who also directed the construction. The platform can move up and down ± 0.85 meters at a frequency of 0.25 Hz, one complete cycle in 5 sec. This is the key frequency produced by large ships that evoke motion sickness. With this intensity of stimulation, it has been found that 50% of subjects will vomit in one hour (O’Hanlon & McCauley, 1974). The moving shuttle rides on linear bearing rails and is driven by a 2 meter long ball screw and high torque motor. The system was designed with a minimum safety factor of 4 on the weakest link (the ball screw to gearbox coupling) under the highest load conditions. An independent braking system is triggered by three automatic failure modes (one software and two hardware) and kill switches are accessible to the subject and experimenter. Both hardware safety loops were designed to OSHA standards. The seat in which the subject rides is built for racing cars and cushions the subject in the unlikely event of shock. It has a five-point safety harness designed to withstand a 9g crash load. The highest g load under operational conditions will be just under 2g, at the point where the oscillator reverses from down to up motion. |
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