A major robotics opportunity for NASA will be the Mars Rover/Sample Return Mission which could be launched as early as the 1990s. The exploratory portion of this mission will include two autonomous subsystems: the rover vehicle and a sample handling system. The sample handling system is the key to the process of collecting Martian soils. This system could include a core drill, a general-purpose manipulator, tools, containers, a return canister, certification hardware and a labeling system. Integrated into a functional package, the sample handling system is analogous to a complex robotic workcell. Discussed here are the different components of the system, their interfaces, forseeable problem areas and many options based on the scientific goals of the mission. The various interfaces in the sample handling process (component to component and handling system to rover) will be a major engineering effort. Two critical evaluation criteria that will be imposed on the system are flexibility and reliability. It needs to be flexible enough to adapt to different scenarios and environments and acquire the most desirable specimens for return to Earth. Scientists may decide to change the distribution and ratio of core samples to rock samples in the canister. The long distance and duration of this planetary mission places a reliability burden on the hardware. The communication time delay between Earth and Mars minimizes operator interaction (teleoperation, supervisory modes) with the sample handler. An intelligent system will be required to plan the actions, make sample choices, interpret sensor inputs, and query unknown surroundings. A combination of autonomous functions and supervised movements will be integrated into the sample handling system

Chun, Wendell

English

NASA Technical Reports Server

N90-29070
ROBOTIC SAMPLING SYST_I FOR AN
_ED MARS MISSION
WENDELL CHUM
MARTIN MARIETTA ASTRONAUTICS GROUP
SPACE SYSTEMS COMPANY
ABSTRACT
Major robotics opportunity for NASA will be the Mars Rover/Sample Return
Mission which could be launched as early as the 1990s. The exploratory
portion of this mission will include two autonomous subsystems: the rover
vehicle and a sample handling system. The sample handling system is the key
to the process of collecting Martian soils. This system could include a core
drill, a general-purpose manipulator, tools, containers, a return canister,
certification hardware and a labeling system. Integrated into a functional
package, the sample handling system is analogous to a complex robotic
workcell. This paper discusses the different components of the system, their
interfaces, forseeable problem areas and many options based on the scientific
goals of the mission.
The various interfaces in the sample handling process (component to component
and handling system to rover) will be a major engineering effort. Two
critical evaluation criteria that will be imposed on the system are
flexibility and reliability. It needs to be flexible enough to adapt to
different scenarios and environments and acquire the most desirable specimens
for return to Earth. Scientists may decide to change the distribution and
ratio of core samples to rock samples in the canister. The long distance and
duration of this planetary mission places a reliability burden on the
hardware. The communication time delay between Earth and Mars minimizes
operator interaction (teleoperation, supervisory modes) with the sample
handler. An "intelligent" system will be required to plan the actions, make
sample choices, interpret sensor inputs, and query unknown surroundings. A
combination of autonomous functions and supervised movements will be
integrated into the sample handling system.
I. Introduction
In the 1990s, robotic systems will be in operation in space and especially
about the space station. The specific tasks include all forms of servicing,
such as assembly, inspection, module changeout, refueling. However, there is
a unique task that is not servicing, i.e. exploration. In particular, the
Mars RoverlSample Return mission promises to be a unique opportunity that
could be launched in the 1990s. Exploration conjures up a sense of adventure
and the unknown. This uncertainty separates a structured servicing task from
an unstructured exploratory task. There are many issues that make this
mission unique. This paper discusses the Mars mission, sampling hardware,
sampling operations, and technical issues.
2. Mars Mission
It is man's inquisitive nature that drives him to explore the surface of
Mars. Mars holds answers to many scientific questions about the origin of
this universe. Refer to table I for some facts on Mars.
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https://ntrs.nasa.gov/search.jsp?R=19900019754 2020-03-19T21:34:50+00:00Z
Table 1 SomeMars Facts
Planet Radius
Mass
Bulk Density
Gravitational Acceleration at the Surface
Maximum Temperature
Minimum Temperature
Atmosphere
Mean Pressure
Wind
Dust Storms
3397.2 km (equator)
6.418 x 1023kg
3.94 gm / cm3
3.73 m / sec 2 (0.38 Earth G)
288 K (At Equator)
150 K (Polar CO 2 )
CO2, N2, Ar, 02, CO
(.089 psi)
2 to 7 m / sec
1 or 2 / year
Mars is characterized by lava flows, crevices, boulder fields, mountains,
dunes and craters. The terrain varies from drift material ranging in
consistency from ordinary kitchen flour I to jagged rocks and boulders.
The scientific goals for planetary exploration are: (I) to understand how the
solar system originated, (2) to understand how the planets evolved and to
understand their present state, (3) to learn what conditions led to the origin
of life, and (4) to learn how physical laws work in large systems. 2 Mare is
the next focus because of its accessibility and relationship to Earth. By
returning samples, their analysis will determine the chemical composition and
mineralogy of materials from a selected region.
In particular, the absolute age of the rock and soil can be determined.
Looking at a scene of continuous rocks (Fig. I), it is hard to imagine that
system could differentiate and pick up a unique rock.
a
Figure 1 Photos of Rocks on the Martian Surface
3. Sampling Hardware
The functional steps of sample handing are outlined by JSC 2 and illustrated
in Figure 2.
OF POOR Q_A!.!TY
ORr rVA. PAG 
_t.ACK Arid WHilE P_-;Oi-O',.3RAPH
284
ACQUISITION PROCESSING CERTIFICATION
I  'vPu 
IPRESERVATK: I- I CONTAINERIZATION ANALYSIS
Figure 2 Sample Handling Functions
Sample acquisition is the physical interaction with the planet surface, e.g.
picking up a rock or scooping loose soil. The captured sample then is
transferred to processing. Processing prepares the sample for certification
or analysis. In some cases, the rock sample might be too large for the test
apparatus and needs to be split into smaller pieces. At other times, the soil
is screened by a sieve.
Certification is the preliminary check to diagnose the character of a sample.
At this point, the sample will be diagnosed from preliminary measurements to
decide whether to return the sample to Earth or put it through analysis.
Analysis entails further measurements and is the principal source of
scientific information. The samples that are to be returned are packaged in
containers and tagged with pertinent information such as location,
temperature, humidity, etc. Sample preservation is the final step and
protects the sample until it is received on Earth. A successful mission
requires the specimen to arrive in pristine condition (no contamination,
shock, or vibration damage).
The hardware for sampling is depicted in Figure 3. The subsystems shown
include the manipulator, tools, and rover. The desired scientific samples
dictate the tools required and the tools affect the container design that in
turn drives the canister design.
I._
SClENT_
DNIDER$
Hardware InterfaceFigure 3
285
The current thinking is to have two manipulators: one on the rover and one on
the lander. Both arms should be compatible with a coHuon set of tools. The
sample return lander manipulator is used for contingency samples at the
beginning of the mission, while the second manipulator is primarily used for
sample acquisition on the rover.
In addition to the above tools, a core drill is required. The drill will take
samples Im to 2m long. A rotary percussion drill requires an axial thrust of
I00 Ib and thus is assumed not to be held from the rover by the arm. Drilling
would benefit from a stable base and the mass of the rover should be used to
help the percussion motion.
There are two tool options: to be positionable by a manipulator, or to use
specialized tools that do not require an manipulator. Without an arm for
positioning the tool, that tool must locate itself. To an extent, the rover
could be used to position a specialized tool, but the chances are good that
several tools would duplicate a comon positioning mechanism if there was no
arm. A manipulator is desirable to acquire samples, move samples to the
various processes, gimbal special sensors (similar to metal detectors) and
possibly aid the rover in mobility.
The manipulator is itself a very versatile tool. By combining the arm with
various acquisition tools like a gripper, the system becomes very flexible.
As stated earlier, the samples determine the desired tools (except for the
drill) as shown in Figure 4.
Figure 4 The Samples, Tools and Containers
The envisioned tools include a drum scoop, a chipper, a rake, a mini drill, a
drive tube, and a general-purpose gripper. This list is not at all exhaustive
and other tools, like a sectioning saw, a hook or additional lights and
sensors are also options. The many tools require an end effector able to
switch tools back and forth according to the step in the sequence.
286
The tools will be stored in a quick-release tool rack similar to Figure 5.
such a system, the tools will be held in an orderly manner for automated
attach and detach. A compact and reliable fixture must be developed to
survive launch loads and yet lock and unlock quickly and simply.
In
Figure 5 ITA Tool Rack
Sensors are critical to the success of this mission. The most powerful sensor
is vision. Vision and possibly range imaging are needed for navigation. In
addition, pictures of the environment are needed from which specimens will be
picked by scientists. Another key function is the labeling of the samples.
287
HAnD PnOO|
i _mULATOR
___ "PNOORAMMARL Ir CHIP in CAP
A. HARD LINK (PROBE) TRANSFER 0ATA FROM
DATA llASSITO CHIP IN CAP
EMPTY TUBES IN
CONTAINER THAT tS
NETWORKEO TOOETHER
El, EMPTY TUBES CONTAIN CHIPS THAT ARE
PRE-WiRED TO DATA BASE
Figure 6
PHOTO IMAGE
A. DATA I$ MANUALLY TABULATED ON EARTH,
KNOWING PRE-NUMBEREO TUBES
_CHIP
B. DATA IS TRANSPIRED AS A CHIP WITH PIlE-
NUMBERED SAMPLE _IHCLUOiNO PHOTOOIqAPHS I
OPTICAL TRANSPQNDIR
'MART CHIP _.-. (VOIDE too/N_A LU_
*PASSIVE CHIP THAT WiLL STORE DATA WHEN
CALLED UPON
Labeling Options
Some examples of labeling are shown in Figure 6. The simplest method to label
the individual tubes is to etch or prestamp each tube with a number or a bar
code that could be read by the sampling system from all directions. It is
important to identify each sample with location, temperature, preliminary
certification, analysis, and local terrain conditions.
4. Sampling Operations
The manipulator is a key part of the sampling system. The goal of this
mission is to return 5 kg of Martian samples. It takes a year to get there, a
year for exploration and a year to return for a total of a three-year
mission. The first task is to scoGp 200gm of bulk material with the
contingency arm prior to sending out the rover.
The rover will continue in a circular traverse to acquire a diverse
sampling. The anticipated 5000 gm of samples include rocks, pebbles, soils,
bulk material, regolith core, and atmosphere. The rover will be navigated to
a geologically interesting site. Having studied the scene, scientists on
Earth would dictate the location and type of samples to test. On their
command, the manipulator will go to the required tool and proceed to acquire
samples. However, the system has to be flexible enough to adapt to new and
different situations.
Requirements for an exploration arm have not been defined. As opposed to
servicing, many of the exploration tasks are general in nature. As a result,
the arm should exhibit the most capability in a certain size package. The key
is versatility and is accomplished by having a flexible system. The samples
to be containerized range in diameter from 2 cm to 5 cm. This does not mean
the rocks will be small. "Big Joe" in the Viking photos is approximately 1 in
height. A situation could arise in which the arm would have to chip away
pieces from a much larger rock.
The tasks of processing, certification, analysis, containerization and
preservation are well structured and controlled. These steps can be highly
automated as analogous to a robotic workcell in manufacturing or assembly.
The various processing, certification, analysis and containerization equipment
are carefully situated for easy access. The manipulator serves to operate in
288
a pick-and-place condition. A robot centered cell best uses the workspace.
Prior to processing, the position and orientation of the particular sample
must be known. This knowledge can be obtained by vision or tactile sensing.
The gripper design is general-purpose to be able to handle all samples. For
an efficient workcell, the distances moved should be minimized. The cell
layout is designed to reach all the stations and equipment. Considerations
must be given to the movement of the end effector. Any reach aides should be
minimized. Manipulator precision and accuracy is designed to meet the minimum
requirements of this cell. The samples are moved sequentially from one
station to another.
This manipulator is expected to perform like an assembly robot by being able
to insert the samples into special tube containers. The drill also uses
tubular containers for the cores. All the selected containers are gathered
and transferred to the Sample Canister Assembly (SCA), which is returned to
Earth.
5. Technical Issues
A technology cutoff date of 1992 is required for a 1998 launch. Rising costs
and the long duration dictate that the mission and the technology must be
reliable. Two important considerations are the time delay and the weight and
power limitations on the system.
Light takes between 8 and 40 min to make the round trip. As a result, 20
percent of the available surface operations time is lost due to discontinuous
communications 3. Standard teleoperative control techniques would be
inapplicable. Rover navigation and mobility take up additional time.
Secondly, nightfall adds more restrictions in the form of downtime unless the
vehicle is able to travel and work at night. High technology could help to
reduce the burden.
Lighting and machine vision are important. Images of interesting sites are
sent to scientists. To take full advantage of the time delay problem, they
have approximately 20 min to designate an interesting area. Besides location,
the type of samples desired must be input to the sampling system. The
remaining sequences from acquisition to preservation should be autonomous.
Periodically, scientists will have a chance to review the data of the stored
samples to check their desirability. Only half the gathered samples will be
returned.
Task planning algorithms will enhance the task. Force reflection will not
work in this situation and intrusion detection and fault isolation will
upgrade the performance of the arm. The steps from sample processing to
sample preservation are hard automated (fixed). Changes in the test sequences
and checks to see that the specimen will fit in the prescribed container are
expected. An expert system is desirable to make decisions on the order of
analysis and the overall decision to save the sample.
Greater artificial intelligence helps sampling by reducing human intervention
(except for a Phobos Mission4). Understanding the capabilities of the
sampling system as well as the environment is no small task. Assessing the
situation is important. For example, the system may need to determine how
deep a particular rock is lodged in a crater wall. From there, the arm
attaches the appropriate tool and approaches the specimen from an optimized
direction.
289
Sensor fusion (data correlation) will play an important role in this mission
due to the many envisioned sensors in the system. Force sensing from
manipulating an incorrect tool is just one example of versatility. There is
always a chance to fail by immobilizing the arm or breaking the tool. There
is a major problem if the drill jams or a drill bit snaps. Combining machine
vision, force sensing, and possibly range data into a complete scene analysis
will be computationally (power) intensive.
The sampling manipulator on the rover represents a design challenge. The
challenge is to determine the amount of capability that can be built into a
32 kg (70.4 Ib) arm, as reported in an early mass allocation. The arm will be
designed for both pick and place and assembly specifications. An adjustable
compliance wrist 5 can be applied to help satisfy both types of
requirements. Packaging the arm on the rover will affect its reach and
packaging in the aeroshell.
Mounted to the rover, the arm still will need a substantial reach to access
everywhere. It might want to bend around a boulder and down a narrow sllt to
pick up a desired rock. However, the close approximations of the various
sampling equipment dictate a maneuverable and dexterous manipulator. There
should be no voids in the work volume. Contamination from dust storms is an
issue. Bearing seals at each joint could clog or the wipers could fail. One
apparent solution is to place a protective boot at each joint. The cold
temperatures should minimize overheating, even if the entire structure is
coated by a fine silt.
Martian gravity is .38 of Earth's gravity and consequently the 70 ib arm will
be constructed from aerospace materials and advanced DC motor technology to
increase performance. This could be the benchmark for a flexible
manipulator. Flexible manipulators increase the load capacity of the arm
without sacrificing accuracy and repeatability. Imagine the possibilities of
having a long arm with the precision of an arm half its size (Fig. 7).
• General Purpose _1G'r_, Protective Boots
Geometry
F,ex,b,es 
Structure _./f ,11 I\\\_. _"
,,k \
 n .oint /./Z "t I\\ Oo-.os,te
Sensing "7 '_/J_' ti i_Materiai
,o,u=..2/f ! I\\\\W:
Compliant Wrist _i__llii_l_,6 _ l' ' .,/,]
Figure 7 Anatomy of a Sampling Arm
6. Conclusion
Sampling operations would benefit from advanced robotic technologies. A
cutoff date of 1992 requires a leap in research application and maturity.
Long transmission delays dictate greater autonomy. Increased autonomy in
290
terms of planning, sensor fusion, expert systems and situation assessment
would enhance the system.
The manipulator could benefit from a flexible structure and still be
dexterous. Adjustable compliance could aid the transition from pick-and-place
tasks to assembly tasks. The most important challenge is having versatility
in the system without sacrificing reliability. To obtain this versatility,
advanced technologies must be developed and made mature by the technology
cutoff date.
The sampling mission is harder to design for than a servicing mission. Using
manufacturing specifications, exploration has some general design guidelines.
The technology will have to be balanced against the reliability factor. There
is no room for error when the mission is three years long. The stakes are
high, but the rewards promise to be greater.
7. Acknowledgement
This work was sponsored in part under, IR&D Project D-46S , Lunar and
Planetary Studies.
8. References
I. H. Moore, R. Hutton, R. Scott, C. Spitzer, and R. Shorthill, "Surface
Materials of the Viking Landing Sites," Journal of Geophysical _search, Vol.
82, No. 28, September 30, 1977.
2. James Gooding, 'Mars Rover/Sample Return (MRSR) Mission: Description of
Sample Experiments," Presentation Package at Johnson Space Center, Houston,
Texas, July 13, 1988.
3. L. Allen, 'Mars Rover Sample Return: Rover Challenges," AIAA/NASA First
International Symposium on Space Automation and Robotics, Arlington, VA,
November 29-30, 1988.
4. "Adventure 2, The Phobos Factor," U.S. News & World Report, September 26,
1988, p. 56.
5. Cutkosky, M.R., Wright, P.K.: "Active Control of a Compliant Wrist in
Manufacturing Tasks." Transactions of the ASME, Journal of Engineering for
Industry, February 1986, Vol. 108, pp. 36-43.
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