We describe a small, inexpensive, teleoperated robot for use in microgravity (µG) environments such as those found onboard the Space Shuttle and the International Space Station (ISS). The primary function of this device is to allow scientists and other 'virtual crew' on the surface to interact with science packages and crew on orbit. Providing this capability allows experts to be present on orbit without the need to lift them there. By employing self-mobile telepresence devices, a number of benefits are possible including:
Our experience building robots that, collectively, have tested most
of the components of a µG telePOD, indicates that the development
of a basic telepresence device can be accomplished in a reasonable time
and cost. Once the device is proven to be reliable, additional capabilities,
such as articulated manipulation, can be added.
The main body of the device is made of resilient, space-qualified foam. This provides cushion for the inevitable bumps into walls, as well as protection against rough handling by the crew.
The initial device is designed within a volume defined by a 7 inch (18
cm) diameter sphere. While small enough to be deployed from a standard
Middeck Locker, it is reasonably large enough to allow proper spacing of
cameras and microphones for realistic telepresence. It may also be
built using many off-the-shelf parts.
|The fans associated with pitch and yaw are all oriented to the fore-aft axis of the device (see Figure 2), thus allowing the majority of the fans to contribute to propulsion. This supports more rapid movement when traveling long distances. Fan-pairs when run together produce translations, while fan-pairs run in opposition produce rotations. Variable speed fans are employed to allow fine control forces.||
Control electronics include drivers for the fans, switches for lights, selection and interfacing of sensors, etc. The wireless link is straightforward with specifics to be decided by available infrastructure. Battery life, speed, and other performance characteristics depend on usage, and can be decided given specific mission requirements.
Design considerations for extraction and replacement of batteries allow a variety of battery placements. By centrally locating the batteries (the greatest mass), rotations about the device's origin can have higher acceleration and be easier to stop over-shoot. Should other control philosophies later seem more natural, this mass can be distributed to the periphery to adjust these handling characteristics.
Features of the Device
The on-board environment of a facility such as the ISS lends itself well to the deployment of small, wireless mobile robots. Refer to Figure 1 along with the following descriptions:
Mobility can be elegantly achieved by taking advantage of both the microgravity and the atmosphere in the space station modules. Simple fans, simply controlled, orient and propel the device. We envision the µG telePOD as a five-degree of freedom platform with control for roll, pitch, yaw, translation fore and aft, and vertically. It will be wireless, allowing travel to all parts of the environment.
Vision is provided by the stereoscopic camera system with a true, three-dimensional view, facilitating accurate movement and positioning as well as the realistic monitoring of the setup and operation of science packages. Audio is stereophonic to enhance the reality of presence and assist in navigation. Audio output provides a means for the user to communicate verbally with crew members. Other sensory modalities, e.g. "smell" (gas analysis) can be provided as needed. See "Additional Optional Features".
Even without explicitly providing jointed manipulator arms, the µG telePOD need not merely be a passive observer of the environment. The multi-purpose snout can be used to point at or lightly press on items. With it's simple clamping gripper, it can transport any free object, such as a tool, clipboard, or a stowage bag from one part of the station to another without the need for a crew member to carry it.
The snout also serves as a grapple for the support hardware to position the device for service: changing batteries, cleaning lenses, etc.
Additional and Optional Features
Bright headlights allow the user good visibility even in poorly lit areas. A visible laser pointer further allows the ground-based scientist to point at objects when discussing with crew members. A sonar range sensor allows further confirmation of relative position which may be useful when attempting accurate positioning; it also provides some capability for non-contact assessment of surface properties.
A stereoscopic micro/endoscope may be added inside the snout for extreme closeup inspection. The normal stereoscopic camera system provides a proprioceptive view to align the snout (it can see it's own nose), and then the user can switch to the microscopic view. A fibre-optic illumination system can serve double duty both for the endoscope and as a near spot illuminator.
Temperature, humidity, smoke, and toxic gas sensors may also be incorporated into the µG telePOD. Micro-manipulators may be added for delicate tasks. Tanks for small quantities of gases or fluids may be added and dispensed when required. Clearly, a variety of optional sensors and effectors can be considered given the µG telePOD as an effective remote-controlled mobile base.
Ground Stations for Scientists and Other Users
All functions associated with operation and service are carried out
by ground-based personnel. This eliminates need for crew to service
the µG telePODs. The ground-based teleoperation stations, based
on a desktop computer workstation, are designed to minimize training requirements
for the scientists, virtual crew, and visitors. Presentation of the
stereoscopic video is provided on a monitor using any of several commercially
available formats. Roll, pitch, and yaw movements are joystick controlled.
Optional stereoscopic headsets and other controls (i.e. footpedals) can
|By basing the ground stations on readily available hardware, cost is
minimized and multiple stations may be made available to scientists and
other users who then share time visiting the ISS as virtual crew members.
It is also possible to monitor and control the device at a much lower fidelity via a Web page. This would allow a very great number of potential visitors (especially well suited to students).
Onboard Support of the µG telePOD
Support is carried out by ground-based personnel via a teleoperated
service bay, mounted in a standard Middeck locker (where the devices
are stored during lift). In normal operation, the user flies the
device to the service bay, where it is grappled it by its snout, has the
batteries changed, and lenses cleaned. The wireless links originate
at the service bay and interconnect here with the ISS's utilities and communications
Issues to be Resolved
The stereoscopic video, stereophonic audio, and sensor and telemetry data are carried on frequencies dependent on the ISS system specifications. Bandwidth within the ISS, and down- and up-link bandwidth are to be determined through interaction with ISS system designers. Down-link bandwidth (the majority of data flow) needs to be real-time with minimal frame delay. New compression techniques for stereoscopic video streams combined with graceful resolution/bandwidth tradeoffs when necessary, will provide the best experience possible to the scientists.
A research component to the development of the µG telePODs is determining the capabilities and preferred interfaces for devices actually flying in microgravity environments. Missions on the Space Shuttle can provide the environment for such experimentation.
A number of limitations are inherent in a facility such as the ISS. Cost to support life in the hazardous environment of space, and cost to lift weight into orbit are two. With so rich an opportunity for research, and so high a price for putting scientists there, telepresence is an ideal technology to exploit. It's application allows a limitless number of experts to 'fly'. And by providing this access to virtually anyone, many forms of additional interaction become available with minimal additional impact on mission requirements.
The ability of a scientist to be present with a crew member in the setup, operation, restocking, and repair of experiment packages is fundamental to the successful outcome of the research. Crew time in training and carrying out procedures for each of the many experiment packages is lessened by having the expert present to assist. Additionally, the µG telePODs allow additional ground-based crew to be present on-board for inspection, systems monitoring, and consultation. This also allows experienced engineers to directly assess conditions and more effectively determine actions for maintenance as the ISS ages.
Safety is another area where the µG telePOD may serve the needs of the crew. Should there be an ISS module which becomes dangerous to the crew (such as by contamination), the device may be able to provide remote assessment, monitoring, and possible other uses.
The "visits" of family, educators, students, and the press, allow interactions with members of the crew unlike any before possible. In addition to the reality of on-orbit presence for the visitors, their more-tangible presence as embodied by the mobile vehicle and verbal communication may also serve to lessen some of the psychological pressures experienced by long-term assignment of the space station crew. To ensure safe 'driving' by naive users, a layer of monitoring and control software can be provided.
We describe a system for telepresence on the International Space Station and the Space Shuttle with many benefits and with relatively low costs (to budgets of money, weight, space, and mission). Adoption of µG telePOD technology by NASA opens up new avenues of research, ensures that planned research is effectively executed, and provides access to many individuals who would never otherwise have personal experience of space.
Sr. Research Engineer
Intelligent Sensor, Measurement, and Control Lab
Senior Research Scientist, Director
Intelligent Sensor, Measurement, and Control Lab
The Robotics Institute
Pittsburgh, PA 15213