CONTROL MOMENT GYROSCOPE (CMG) ROVER

Tetrahedral rover making a single step of locomotion. The black disk is the CMGs rotor. The long yellow axis is the gimbal axis of the CMG and the short yellow axis is the angular momentum of the CMG.

Control moment gyroscopes (CMGs) are an efficient actuation system for applying torque to body. A CMG applies a torque primarily by changing its angular-momentum direction, imparting a gyroscopic torque between the CMG and the body to which it is mounted. In some cases, CMGs can apply torque that is an order of magnitude larger per watt, compared to other contemporary methods. Because CMGs can apply torque efficiently, they are ideal for many applications, including agile spacecraft, ships, and robotic systems.

This research project focuses on developing control methodologies for CMGs that enable high-performance operation and novel implementations of CMGs that exploit their torque efficiency. Specifically, there are two main goals to this research. The first goal is to develop high-performance control methodologies for CMGs that have performance guarantees. Compared to contemporary methods, the control methods I developed achieve greater robustness due to their performance guarantees and generality. The methods’ performance guarantees dictate a minimum performance of the momentum-control system given its mechanical limitations, guaranteeing cutting-edge performance during operation. The methods’ generality enables the control methods to achieve high performance even after multiple actuator failures. The methods also achieve greater performance by as much as 40% over contemporary methods. The increased robustness and performance of the control methods enable systems to have greater capability and reliability, which are particularly important for aerospace systems, systems for national security, among others.

The second goal of this research is to develop a rover architecture that exploits the efficiency of CMGs to enable efficient exploration of extremeterrain. The rover architecture consists of a polyhedral chassis with a single CMG mounted internally, which imparts torque onto the chassis, enabling the rover to roll across a surface. The polyhedral chassis and CMG array offer three main benefits: 1) there is no interaction between the actuators and the environment because the rover uses an internal momentum device, eliminating the risk of actuator failure from interactions with the terrain; 2) due to a phenomenon called torque amplification, small CMGs can produce much higher torque than similarly sized reaction wheels, enabling the rover to navigate bodies with appreciable gravity; 3) at the corners of the polyhedral chassis, spikes or other high-friction pads are used to maximize traction on various surfaces. Simulations ofthis novel robotic system show that the rover architecture has greater mobility and energy efficiency on extreme terrain than do other contemporary technologies.

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The power- and torque-efficient CMG and the novel chassis design make this rover reliable, power-efficient, and terrain-adaptable, enabling a long mission lifetime. The rover could explore previously unexplored areas like inaccessible valleys, crags, and rock beds on Mars. Exploring these areas could help discover valuable scientific data, such as water content, mineral content, among others.

Partners:

The research is supported by NASA and the Jet Propulsion Laboratory through the NSTRF.