The Treadmill with Vibration Isolation and Stabilization System (TVIS) is an exercise system that is designed for use as a component of the CHeCS. In microgravity, astronauts do not exert as much force on their muscles as on Earth; without exercise, these muscles begin to atrophy. This can lead to bone density loss with symptoms similar to osteoporosis.Facility Manager(s)
Johnson Space Center, Houston, TX, United States
National Aeronautics and Space Administration (NASA)Expeditions Assigned
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19/20,21/22,23/24,25/26,27/28,29/30,31/32,33/34Previous ISS Missions
On the ISS, the TVIS is suspended within an opening in the SM floor and allows limited movement in six degrees of motion. The Vibration Isolation & Stabilization (VIS) System is intended to minimize the dynamic forces of exercise being transferred to the structure of the ISS Service Module, while maintaining a relatively stable exercise surface. Movement of the TVIS is counteracted with active (gyroscope and stabilizer) and passive (bungees and wire ropes) vibration isolation systems. The active VIS components are software controlled and work in unison to counteract the pitch and roll forces imparted and provide a flexible mechanical connection to the ISS by stabilizing TVIS against excessive motion caused by exercise. The active components of the VIS System are the Gyroscope, four linear slide-mass Stabilizers, four Motor Controllers and a VIS Controller. The VIS System also serves to provide current peak smoothing of the TVIS power sources.
The running surface of the treadmill is used in much the same way as any conventional treadmill, except the user is held to its surface by the Series Bungee Systems (SBS), which uses latex rubber tubes and/or by the Subject Load Device (SLD), which attach to a shoulder and waist Treadmill Harness to counter the microgravity (µg) environment. When used without the SLDs, the SBSs are considered the contingency loading configuration.
The SLDs are the primary subject restraint system. Prior to exercise, the crewmember dons the Treadmill Harness and clips the harness y-straps to the respective end stops on the SLD’s cables. The SLDs provide loading from 40 to 220 lb. The load variation of the SLD is approximately 6 lb/in. of cable extension. Each SLD makes use of 2 adjustable torsion springs tied to a cable-feed pulley. The crewmember used the Control Panel to enter the desired load. Mechanical limit switches in each SLD are used to prohibit over adjustment in either direction. Each SLD is instrumented with a load cell, which measures tension in the cable attached to the subject. This tension reading is used to determine the subject load supplied by the SLD. While the applied loads are continuously monitored and recorded every 5 seconds on the PCMCIA card, the system does not attempt to maintain constant load during exercise.
The TVIS System Electronics Box (EB) is responsible for distributing power and processing commands/data for the TVIS System. A battery circuit is used to maintain the real-time clock and maintain the relay configuration settings in case of a power failure or when the SM circuit breakers are turned off, e.g., for TVIS System maintenance. The battery has a 6-month operational life and can be changed out by the crew via a door located on the aft end of the EB. The Device Interface Board (DIB) provides subsystem interconnectivity and is used to transfer commands and data to and from the VIS System, SLDs, Control Panel, and Motor Box. TVIS System circuit breakers are located on the aft end of the EB for over current protection of the system.
Weekly tasks of the TVIS include cleaning of the handrails, closeout panels, and display covers to remove any dust, debris, sweat (Dry Wipe). Additionally, routine maintenance tasks are done Monthly, Quarterly, and every 6 months to inspect several general TVIS components, verify torque on accessible fasteners, lubricate needed components, set time and date on Control Panel, perform Speed Characterization Tests, replace electronic box battery, check gyroscope ropes and pivot spacers and check corner wire ropes. The rack space is checked for vacuum accumulated debris. Checks are done on the drive belt, belt alignment, belt tension, and for sharp edges and burrs on the running surface. Annual maintenance tasks include grease lubrication of the front and rear drums as well as rear drive shaft.
Investigations of the influence of low frequency vibrations on the microgravity environment on the Russian segment of the ISS begun after the first partial replacement of sensors IMU_128 (small acceleration meter) on the service module in March 2003. The most powerful vibrations are those created by air conditioning system (ACS) compressors and gyrodynes of the ISS stabilization system. The magnitude of these background perturbations vary from several meter-kilogram (mkg) to tens of meter-gram (mg) depending on the modes of operation and locality of the disturbance. Crewmembers performing physical exercises (PE) on the suite of exercising equipment onboard also produce micro accelerations which are collected and analyzed by researchers.
The TVIS is located in the service module of the Russian segment. The treadmill’s damper system allows a maximum displacement of 12 cm and rotation of 2.5° relative to any axis and is designed to transfer minimal impact forces, however this does not provide for complete damping of movements. Vibrating frequencies of 11 Hz (cycle per second) and less can be attributed as frequencies characteristic for exercises on the treadmill. Periodic sharp increases of low frequency perturbations for approximately two minutes can be observed, within the greater power and higher frequency vibrations of ACS compressors and air-duct fans, and are indicative of changes in modes of exercises (walking, running, etc.). Significant differences in measurements are recorded when different compressors are operating along with the normal working activity of the crew and are responsible for greater perturbations than exercises on the treadmill. However, in all compartments and at various modes, characteristic frequencies are practically identical, but the amplitudes during physical exercises are several times higher than corresponding parameters of the background environment. In the Destiny module, perturbations below 1.0 Hz is dominated by treadmill exercises, but the total power of perturbations in the frequency band 0–6 Hz is approximately 2.5 times higher for the Russian bicycle ergometer than the treadmill. In the frequency band 0–10 Hz during PE on the service module (SM), perturbations in the American segment increase almost by an order of magnitude in comparison with the “quiet conditions.” Similarly disturbances were previously recorded on the Mir space station during exercise equipment operations.
Overall, the main power of perturbations, concentrated in the band 50–200 Hz, is caused both by crew vital activity and by functioning standard onboard systems. The microgravity and vibration conditions in different compartments of the ISS at various modes of station operation can vary by more than an order of magnitude as sensors in the American segment also indicate. The data presented above show that, practically in all cases, the perturbations in the transverse plane of the Destiny module exceed perturbations along the longitudinal ISS axis, and the distribution of perturbations substantially depends on the location of measurements (Belyaev et al. 2009).