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Construction of an Avionics Box for a Non-Prehensile RobotChris Swanson - Vermont Space Grant, Vytas SunSpiral - Intelligent Robotics Group

Ames Research Center

AbstractThis summer I designed and built an avionics box for a robot constructed by a senior design team at the University of Idaho. The senior design team, called the Lunartics, is part of Idaho’s Robotic Lunar Exploration Program (RLEP) and is being sponsored by NASA to build a robot capable of non-prehensile soil manipulation. The robot’s responsibilities, which include plowing, digging trenches, and taking soil samples, are of interest to NASA for future missions to the moon.

The Lunartics’ robot originally possessed a simple avionics box that manipulated the motors of the robot’s arm and a shovel for digging. Plans to upgrade the motors’ power required several new components, and after talking with senior design lead John Lacy, I began designing a new avionics box for the robot. I included many new features such as a battery box which housed eight Lithium-ion batteries to power the motors and circuit boards, DC to DC converters to increase and regulate the voltage, a CPU and mini-screen to allow mobile troubleshooting of the robot, and a remote kill switch to protect against accidental damage to the robot’s arm. Some of these parts I cannibalized from an obsolete avionics box that two interns constructed last summer to power a robotic arm in the lab. Other parts required that I spec the needs of the robot and order them individually. I integrated these components with the components the Lunartics already possessed in a new plexiglass avionics box designed to fit on their robot’s back.

The larger avionics box provided volume to spread components out for easy access and the upgraded DC converters allowed more powerful motors to be added to the robot’s arm. These new components add power and versatility to the robot, allowing additional applications that were previously unattainable.

BackgroundIn the previous summer, two interns constructed the avionics box pictured below to power an Amtec arm and analyze the force-torque signals from a robotic hand attached to it. Between then and the beginning of this summer, their box became obsolete and was replaced.

In an effort to increase sustainability, I constructed a separate box to house the components necessary to analyze the hand’s force-torque readings. The other components were offered to a group of RAP students testing and modifying the Lunartics’ robot. We decided to use several of the new components in building a new avionics box to replace the current one (pictured top of next column.)

Obselete Avionics Box

The Lunartics’ Original Avionics Box

Features to be added:

•Larger plexiglass box

•Battery pack with Lithium-ion batteries for power

•CPU and MiniScreen for mobile troubleshooting

•DC Converters to power stronger motors

•Remote kill-switch for safety

DesignI used an OceanServer power system consisting of eight Lithium-ion batteries, an XP-08 power consolidation board that drew 16V from the batteries, and two DC-DC converters that converted the 16V to 24V, 12V, and 5V. Two of the robot’s motors are controlled by and receive their power (24V for brakes, 12V for motors, and 5V for encoders) from identical Motor Mind circuit boards that I took from the Lunartics’ original avionics box. These Motor Minds receive commands from two BASIC stamp controllers (one taken from the original box and one newly ordered) that interface with Labview. The other motor is a brushless motor controlled by a special controller we ordered. This controller requires 24V to power the brushless motor (24V) and its encoders (5V). The Mini ITX Board is a Commell LV-675D Pentium M supplied by Logic and supplies features such as a wireless card, hard drive, fan power, battery management capability, and USB connections for mouse and keyboard. The MiniScreen attached to the ITX board is a 7 inch touchscreen with an 800x600 pixel VGA monitor. Pictured at the top of the next column is an electrical diagram for the avionics box.

8 Li-ion Batteries

XP-08 Power ManagementDC123S DC Converter

Brushless

Motor Minds

Basic Stamps

Mini ITX Board

To Brake

To Brake

16V

16V

16V

16V

24V 24V 24V 24V

24V

24V

24V

5V

5V 5V

5V

12V

12V

To Motor

To Motor

12V

12V

To Encoder

To Encoder

5V

5V

To Encoder

5V

24V

To Motor

Results and Conclusion

Electrical Diagram for New Avionics Box

The newly constructed avionics box (pictured below) is capable of powering the three DC motors that control the robot’s arm. The CPU can be accessed anywhere because of the touchscreen. The killswitch can be activated from over 50 meters away via a key fob and will instantly kill power to the motors while leaving the electronics running. The eight Lithium-ion batteries each provide 95 watts of power to run the robot. Ports mounted on the side of the box allow easy connections for a serial cable, computer monitor, keyboard, and mouse. The components are laid out in an easily accessible manner to facilitate further upgrades, fixes, or additions to the electronics system. The end result is an avionics box that is robust in design and suited for control of an autonomous robot.

AcknowledgementsI would like to thank

John Lacy, project lead for the University of Idaho Lunartics senior design group

Vytas Sunspiral, my mentor and head of the ArmLab

Terry Fong, head of the Intelligent Robotics Group

and the Vermont Space Grant Consortium

DC1HV DC Converter

The Lunartics’ New Avionics Box (Mid-construction)

12V

Kill Switch

Controller