Proposed packages called "remote engineering units" (REUs) would contain all the electronic circuitry needed to implement a subset of the design of the motor-control system of a robot. The REUs were conceived, specifically, for incorporation into small robotic vehicles (the Mars '03/05 Athena Rovers) to be used in exploring the surface of Mars. Some of the characteristics that make REUs attractive in the Mars Rover applications may also make them attractive for terrestrial robotic applications. These characteristics include modularity, amenability to a distributed motor-control architecture, and adaptability of both design and function.
The REUs would provide interfaces among (1) a control computer; (2) regulated and unregulated external power supplies; and (3) motors and analog and digital input/output (I/O) circuits. More specifically, each REU (see figure) would contain circuits for controlling two dc motors equipped with optical shaft-angle encoders; for receiving and processing the analog and digital outputs of motor-current sensors, temperature sensors, force sensors, potentiometers, and other sensors; and for controlling two dc power switches. Each REU would also contain an internal power regulator, plus two heaters to enable operation at low ambient temperature.
Within each REU, circuits connected to regulated sources of power would be electrically isolated from sources connected to unregulated sources of power by means of optocouplers, capacitors, inductors, and/or differential interfaces with sufficient common-mode rejection to prevent adverse effects of ground loops. There would be separate digital and power grounds, which would be brought together at a system-level single ground point. Except for the connection at the system level, electronic circuits connected to digital ground would be electrically isolated from those connected to power ground.
Each REU would contain a field-programmable gate array (FPGA) for processing digital command, data, and clock input and output signals. The REU would communicate with the control computer via a bidirectional interrupt-request serial data bus. The REU would function as a slave interface; that is, the control logic of the REU would support only the slave receiving and slave transmitting modes of bus operation.
An REU would be capable of operating according to any of three motor-control modes. In one, pulse-width modulation would be used to control the speeds of the two motors. The other two modes would involve closed-loop proportional/integral/derivative control implemented in hardware; the closed-loop controller would be capable of functioning in both rate- and position-control modes, using shaft-angle feedback from either optical or potentiometric shaft-angle encoders.
This work was done by Sung Park, Ken Mehaffey, Dave Hykes, John Waters, Gary Bolotin, Michelle Bell, and Edward Kopf of Caltech for NASA's Jet Propulsion Laboratory.
NPO-20763
This Brief includes a Technical Support Package (TSP).
Packages of Circuitry for Controlling a Robotic Vehicle
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Overview
The document titled "Prototype Remote Engineering Unit (REU) Requirements Document" by Sung M. Park, dated March 29, 1999, from the Jet Propulsion Laboratory, outlines the specifications and requirements for a Remote Engineering Unit designed for robotic applications, particularly in space exploration.
The REU is intended to enhance the capabilities of robotic vehicles, such as the Mars Athena Rovers, by providing a modular and adaptable system that can be easily integrated into various robotic platforms. The document emphasizes the importance of advanced circuitry and design principles that allow for flexibility in deployment and operation in challenging environments like Mars.
Key features of the REU include its ability to support remote operation, enabling engineers to control and monitor robotic systems from a distance. This is crucial for missions where direct human intervention is not possible due to the vast distances involved. The REU is designed to handle various tasks, including data collection, navigation, and environmental analysis, making it a versatile tool for exploration.
The document also discusses the technical requirements for the REU, including power consumption, communication protocols, and environmental resilience. These specifications ensure that the unit can withstand the harsh conditions of space, such as extreme temperatures and radiation levels, while maintaining reliable performance.
Additionally, the REU's modular design allows for easy upgrades and modifications, which is essential for adapting to new mission requirements or technological advancements. This adaptability is a significant advantage in the rapidly evolving field of robotics and space exploration.
Overall, the document serves as a comprehensive guide for the development and implementation of the REU, highlighting its potential impact on future robotic missions. By providing a robust and flexible engineering solution, the REU aims to enhance the efficiency and effectiveness of robotic operations in extraterrestrial environments, paving the way for more ambitious exploration endeavors.
In summary, the Remote Engineering Unit represents a significant advancement in robotic technology, with its design focused on modularity, adaptability, and resilience, making it a critical component for future missions to Mars and beyond.
