NASA Langley Research Center
Dubowsky, S., Moore, C., Corrigan, T., Torres, M., Meller, U., Antonella, S., Mavroidis, C. and Yoshida, K.
In the future, robotic systems will be expected to perform important tasks in space, in orbit and in planetary exploration. However, such applications introduce a number of technical problems not found in conventional earth-bound industrial robots. To design useful and practical systems to meet the needs of future space missions, substantial technical development is required, including in the areas of the design, control and planning. The objective of this three-year research program is to develop such design paradigms and control and planning algorithms to enable future space robotic systems to meet their proposed mission objectives. The underlying intellectual focus of the program is to construct a set of integrated design, planning and control techniques based on an understanding of the fundamental mechanics of space robotic systems.
This method simplifies the system's dynamics by transforming a free-floating or free-flying system into an equivalent "virtual" fixed base manipulator.
These are singular configurations of free-floating and free flying systems that depend on the system's dynamic parameters and not only on its kinematic parameters. Control and planning algorithms that do not take into account this important mechanical property can present occasional problems.
Taking into account the special kinematic and dynamic properties of these systems such as the dynamic singularities, fixed based manipulator control algorithms were modified and shown to achieve good performance in the case of free-floating and free-flying systems.
This is a method to control the position and attitude of a system's spacecraft in a coordinated way by using the inherent redundancy in space robotic systems.
This method controls a space manipulator system after failure of one of its joints by maintaining the system's inertial matrix invariant with respect to the failed joint.
A graphical tool that can be used to find manipulator paths that result in minimum dynamic disturbances to the spacecraft.
A method that finds manipulator paths that transfer minimum energy to the manipulator compliant base. Three path-planning algorithms were derived based on the Coupling Map: Base Relocation, Hot Spot Method and the Redundancy Resolver Algorithm.
This is an extended jacobian transpose control algorithm developed for exploratory vehicle mounted systems. It compensates for the vehicle motions caused by the manipulator motion by measuring the vehicle position and orientation in inertial space using inclinometers and ultrasonic sensors.
A closed-loop manipulator controller for compliant based systems that enables the manipulator to damp out the lightly damped residual vibrations of its supporting structure after the manipulator reaches the final point of its path.
A closed-loop manipulator controller for long reach space manipulator systems that permits controlling the manipulator end-effector position in spite of the presence of some base vibrations using easily obtained strain meausrements on the deployable structure.
Using a six degree of freedom Stewart Platform (see section 3) two methods were developed to achieve microgravity emulation of the motion of space manipulator systems. These methods are: the Learning Micro-Gravity Compensation Method and the Model Micro-Gravity Compensation Method.
Experiments were performed to study the dynamic behavior of spaceborne manipulator systems under impact. A method called Extended Inverse Inertia Tensor that can predict impact forces in fixed base manipulator systems was extended in the case of long reach space manipulator systems. Based on this method configurations of the system that result in minimum impact forces were found.
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