ROBONAUT Activity Report February 2004
This month, having completed the zero-g climbing tests, the Robonaut team removed Unit B from the air-bearing sled and re-attached Unit B to the cart. Re-installation on the cart is an interim step in preparation for a trip to California to attend the DARPATech 2004 conference (3/9-3/11). Unit B will be mated to the Segway Robotic Mobility Platform (RMP) when it goes on display at the conference. Robonaut autonomy work continued this month with the newly integrated laser obstacle avoidance and stereo vision object recognition subsystems. In addition to the autonomous navigation efforts, autonomous grasping was enhanced by activating tactile sensors located in the gloves covering the mechanical hands. A Robonaut demonstration was given to Admiral Steidle of NASA Headquarters. And finally, a Zero-g Climbing Test Summary Report has been completed following the Air Bearing Floor (ABF) Climbing Test.
Re-integration of the Robonaut Unit B upper body with the Segway RMP (Robotic Mobility Platform) proceeded in preparation for the DARPATech 2004 conference (figures 1-4). The zero-g stabilizing leg was detached from Robonaut Unit B and replaced by an interface plate modified with slots to adjust the system center-of-gravity fore and aft. This allows fine-tuning of the robot's pitch during stationary balancing. The upper body was then detached from the 4-wheel cart and mounted on the RMP (figure 5). Operational performance of Unit B on the RMP base was verified through teleoperator control as shown in figure 6.
Figure 1, Unit B mounted on Air-Bearing sled.
Figure 2, Unit B being hoisted off of the Air-Bearing sled.
Figure 3, Unit B in upright orientation in preparation for cart installation.
Figure 4, Unit B installed on wheeled cart.
Figure 5, Unit B mated to RMP.
Figure 6, Unit B undergoing final checkout in preparation for the DARPATech conference.
Robonaut Autonomous Navigation
Obstacle avoidance and tracking has been added to the Robonaut B system. These functions were already developed for the EVA Robotic Assistant (ERA), so the work primarily involved transferring these functions to Robonaut. The vision system was ported to the control systems laptop for use with firewire cameras, yielding a low power mobile vision capability. As Robonaut uses Windows and NDDS, and ERA uses Linux and CORBA, a simple bridge had to be written to translate between the two architectures. Most software remained basically the same, with only configuration file changes. The only physical modification was to add a Sick laser rangefinder to the front of the Segway (figure 7). Since the Segway-mounted Robonaut does not currently have localization information, we used relative obstacle mapping and relative target positions only. This mode was already structurally in place in ERA software, but had not been tested much before, so we thoroughly debugged and tested this mode using Robonaut. Obstacle avoidance depends on knowing how the vehicle responds to driving and steering commands, so we modeled the Segway's response, mapping various turning radii to specific driving commands. Adjustments were also made based on the size and weight of Robonaut and limited driving space. All such parameters are listed in the configuration file, and required no software changes. A previously developed GUI was modified to control Robonaut obstacle avoidance and tracking. A program was also written to sequence specific demonstration elements, and to communicate with the Windows-based Robonaut software.
Figure 7, Unit B mounted on RMP w/attached Sick Laser (blue box).
Hardware and software modifications were made to Robonaut Unit B enabling the computer controller to read the tactile sensors mounted in the gloves (figure 8). The sensors provide grasp confirmation to the autonomy subsystem. The right glove sensors were tested with the new PrecisionADC software. Signal gains were adjusted so that the glove display showed a full range of force measurement for each sensor. The end result is an enhanced grasp capability for Robonaut.
Figure 8, Glove with integrated tactile sensors
A Robonaut demonstration was given to Associate Administrator, Adm. Craig E. Steidle of the
Office of Exploration Systems (Code T, NASA Headquarters).
Following the Air Bearing Floor Zero-g testing with Robonaut Unit B last month, a Zero-g Climbing Test Summary Report has been completed. The report summarizes the objectives of the Zero-g testing and the results of those testing activities. Follow-on force data analysis arising from the WIF insertions and constrained leg motions performed during the sled experiment will be published in another report. The analysis will be used to characterize the effectiveness of the Robonaut leg force controller.