Allowing rapid and reliable inspections and close-up in situ measurements of multiple targets distributed throughout an unstructured and unpredictable worksite-- without continuous operator supervision. This efficient goal-level commanding capability represents an order of magnitude improvement in MER class rover inspection capabilities and requires fewer operators.
This project addresses needs for high-level robotic goal commanding of exploration activities. Both the communication requirements and the number of operators and astronaut EVA on lunar and planetary surfaces can be reduced. This directly reduces both risk and cost.
We have made advances across a broad technological front:
Target tracking and instrument placement technologies enable a rover to autonomously visit and examine many samples distributed over a 10m radius area with centimeter precision.
Because of wheel slippage and cumulative inertial guidance position errors, a rover cannot keep accurate track of goal locations around it using deduced reckoning alone as it moves towards them. Our solution has been the development of stereo-vision techniques using key points and 3D target templates to continuously track targets as the rover moves. No GPS or other infrastructure is required. Traverses visiting four or more targets over a 10m distance, with centimeter precision have been done; the number of targets being limited only by execution time.
Once at the goal location, our auto-place algorithm permits the rover to distinguish rocks and other potential targets from the ground (regardless of slope or surface texture) and find instrument placements consistent with any limitations imposed by the tool and the target geometry.
Robust and flexible planning and execution for the rover to accommodate the great uncertainty associated with navigating to and deploying instruments on multiple samples, while adhering to power and resource constraint characteristics of a planetary rover.
Right: Close-up inspection of monolith at NASA’s test center.
Standard mission practice is to generate daily activity plans off board, permitting operators to modify and verify them prior to uplink. While suitable for predictable systems, such as satellites in orbit, this approach copes poorly with uncertainty.
We have developed a ground based contingency planner that generates a main line rover activity sequence with flexible time constraints and contingent activity sequences to accommodate off-nominal behavior. These include diverting to closer targets if resource use is excessive and recovering from target tracking failures:
The rover CRL Executive executes these plans while monitoring resources and faults, and doing minor plan re-evaluations as required.
This approach combines the benefits of the traditional approach with some of the flexibility, but not the risk, of an onboard planner.
Ground systems allow users to rapidly identify, prioritize and specify many potential targets, evaluate the plan of action, and understand the data returned from the multiple samples that the rover actually visited (which may differ from the highest priority set requested).
Our operator interface uses the Viz software to immerse users in a photorealistic VR, 3D display of the environment around the rover. Within this, the users rapidly specify daily mission goals and evaluate returned data.
Another tool, PlanView (built on the MERBoard), facilitates collaboration among users and graphically displays forecast activities for, and actual results from, the rover.
This research was motivated by the need of the planetary science community to acquire close up and contact measurements from a variety of targets on the surface of a planetary body. State-of-the-art planetary rovers, such as the MER rovers (Spirit and Opportunity) currently on Mars require 3 days and a standing army of operators (270 during 24/7 operations) on Earth to accomplish the task of driving up to a target and safely placing an instrument against it. With limited mission lifetimes and operations costs exceeding $1 million per day, decreasing this time and the number of operators has a significant scientific and cost-reduction pay-offs.
Right: Viz view of rover start point, inspection targets, and rover positions needed to accomplish them.
This project is building the capability for a rover to visit and examine multiple targets, scientific or otherwise, over 10’s of meters in an un-prepared environment in one command cycle and without supervision from mission control. Using K9 , a six wheeled planetary rover prototype, we have successfully demonstrated this in field locations, with operators at Ames communicating to it via satellite.