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NASA Johnson Space Center’s (JSC) Simulation, Emulation, Navigation, Sensors and STAR (SENSS) Laboratory has developed a large-scale six degree of freedom tendon-actuated robot (STAR) for emulation of spacecraft proximity operations and Entry, Descent, and Landing approach trajectories to aid in the rapid development and testing of a wide range of guidance, navigation, and control algorithms at low cost.
The NASA Johnson Space Center (JSC) Safe and Precise Landing – Integrated Capabilities Evolution (SPLICE) project has developed a large-scale six degree of freedom tendon-actuated robot (STAR). STAR is intended to reproduce lunar approach trajectories across subscale terrain in order to rapidly develop and test terrain relative and hazard relative navigation/detection algorithms at low cost. NASA is interested in hosting external partners at the facility to enable them to advance their own algorithm development and testing. Contact us for more information.
The NASA Johnson Space Center (JSC) Safe and Precise Landing – Integrated Capabilities Evolution (SPLICE) project is developing a large-scale six degree of freedom tendon-actuated robot (STAR). STAR is intended to reproduce lunar approach trajectories across subscale terrain in order to rapidly develop and test terrain relative and hazard relative navigation algorithms at low cost. NASA is interested in hosting external partners at the facility to enable them to advance their own algorithm development and testing and intends to activate the facility in Fall 2020. Contact us for more information.
In the Space Station era, more operations will be performed robotically in space in the areas of servicing, assembly, and experiment tending among others. These robots may have various sets of requirements for accuracy, speed, and force generation, but there will be design constraints such as size, mass, and power dissipation limits. For actuation, a leading motor candidate is a dc brushless type, and there are numerous potential drive trains each with its own advantages and disadvantages. This experiment uses a harmonic drive and addresses some inherent limitations, namely its backdriveability and low frequency structural resonances. These effects are controlled and diminished by instrumenting the actuator system with a torque transducer on the output shaft. This noncollocated loop is closed to ensure that the commanded torque is accurately delivered to the manipulator link. The actuator system is modelled and its essential parameters identified. The nonlinear model for simulations will include inertias, gearing, stiction, flexibility, and the effects of output load variations. A linear model is extracted and used for designing the noncollocated torque and position feedback loops. These loops are simulated with the structural frequency encountered in the testbed system. Simulation results are given for various commands in position. The use of torque feedback is demonstrated to yield superior performance in settling time and positioning accuracy. An experimental setup being finished consists of a bench mounted motor and harmonic drive actuator system. A torque transducer and two position encoders, each with sufficient resolution and bandwidth, will provide sensory information. Parameters of the physical system are being identified and matched to analytical predictions. Initial feedback control laws will be incorporated in the bench test equipment and various experiments run to validate the designs. The status of these experiments is given.
The invention controls an under-actuated manipulator by first obtaining predetermined active joint accelerations of the active joints and the passive joint friction forces of the passive joints, then computing articulated body qualities for each of the joints from the current positions of the links, and finally computing from the articulated body qualities and from the active joint accelerations and the passive joint forces, active joint forces of the active joints. Ultimately, the invention transmits servo commands to the active joint forces thus computed to the respective ones of the joint servos. The computation of the active joint forces is accomplished using a recursive dynamics algorithm. In this computation, an inward recursion is first carried out for each link, beginning with the outermost link in order to compute the residual link force of each link from the active joint acceleration if the corresponding joint is active, or from the known passive joint force if the corresponding joint is passive. Then, an outward recursion is carried out for each link in which the active joint force is computed from the residual link force if the corresponding joint is active or the passive joint acceleration is computed from the residual link force if the corresponding joint is passive.
A tendon tensioning system includes a tendon having a proximal end and a distal end, an actuator, and a motor controller. The actuator may include a drive screw and a motor, and may be coupled with the proximal end of the tendon and configured to apply a tension through the tendon in response to an electrical current. The motor controller may be electrically coupled with the actuator, and configured to provide an electrical current having a first amplitude to the actuator until a stall tension is achieved through the tendon; provide a pulse current to the actuator following the achievement of the stall tension, where the amplitude of the pulse current is greater than the first amplitude, and return the motor to a steady state holding current following the conclusion of the pulse current.
This invention relates to an operator interface for controlling a telerobot to perform tasks in a poorly modeled environment and/or within unplanned scenarios. The telerobot control system includes a remote robot manipulator linked to an operator interface. The operator interface includes a setup terminal, simulation terminal, and execution terminal for the control of the graphics simulator and local robot actuator as well as the remote robot actuator. These terminals may be combined in a single terminal. Complex tasks are developed from sequential combinations of parameterized task primitives and recorded teleoperations, and are tested by execution on a graphics simulator and/or local robot actuator, together with adjustable time delays. The novel features of this invention include the shared and supervisory control of the remote robot manipulator via operator interface by pretested complex tasks sequences based on sequences of parameterized task primitives combined with further teleoperation and run-time binding of parameters based on task context.
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Actuators are responsible to the operative capability of manipulation systems and robots. In recent years, electroactive polymers (EAP) have emerged as potential alternative to conventional actuators.
This paper describes the efforts to redesign, fabricate, assemble and test the wrist actuators on the Automated Tile Processing System (ATPS). The ATPS is a robotic system being developed at Kennedy Space Center to inspect and rewaterproof thermal protection tiles on the space shuttle orbiter prior to launch. The objective of the redesign was to eliminate backlash and provide adequate pitch and yaw actuator force. The wrist actuators have been successfully redesigned, fabricated, tested, and installed. The redesigned wrist actuators meet or exceed all design requirements. The wrist has been reinstalled on the tile processing robot and will be further evaluated during operational testing of the system.
Miniature, lightweight, low-cost actuators that consume low-power can be used to develop unmatched robotic devices to make an impact on many technolgy areas.
Actuators are used for many planetary and space applications. To meet the NASA goal to reduce the actuators size, mass, cost and power consumption, electroactie polymers (EAP) are being developed to induce large bending and longitudinal actuation strains.
This reported study is concentrating on the development of effective EAPs and the resultant enabling mechanisms employing their unique characteristics.
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Actuation devices are used for many space applications and there is increasing need to reduce their size, mass, cost and power consumption.
The Space Suit RoboGlove is a device designed to provide additional grasp strength or endurance for an EVA crew member since gloved hand performance is a fraction of what the unencumbered human hand can achieve. There have been past efforts to approach this problem by employing novel materials and construction techniques to the glove design, as well as integrating powered assistance devices. This application of the NASA/GM RoboGlove technology uses a unique approach to integrate the robotic actuators and sensors into a Phase VI EVA glove. This design provides grasp augmentation to the glove user while active, but can also function as a normal glove when disabled. Care was taken to avoid adding excessive bulk to the glove or affecting tactility by choosing low-profile sensors and extrinsically locating the actuators. Conduits are used to guide robotic tendons from linear actuators, across the wrist, and to the fingers. The second generation of the SSRG includes updated electronics, sensors, and actuators to improve performance. The following discusses the electromechanical design, softgoods integration, and control system of the SSRG. It also presents test results from the first integration of a powered mobility element onto a space suit, the NASA Mark III. Early results show that sensor integration did not impact tactile feedback in the glove and the actuators show potential for reduction in grasp fatigue over time.
Traditional robotic structures have limitations in planetary exploration as their rigid structural joints are prone to damage in new and rough terrains. In contrast, robots based on tensegrity structures, composed of rods and tensile cables, offer a highly robust, lightweight, and energy efficient solution over traditional robots. In addition tensegrity robots can be highly configurable by rearranging their topology of rods, cables and motors. However, these highly configurable tensegrity robots pose a significant challenge for locomotion due to their complexity. This study investigates a control pattern for successful locomotion in tensegrity robots through an evolutionary algorithm. A twelve-rod hardware model is rapidly prototyped to utilize a new actuation method based on friction. A web-based physics simulation is created to model the twelve-rod tensegrity ball structure. Square-waves are used as control policies for the actuators of the tensegrity structure. Monte Carlo trials are run to find the most successful number of amplitudes for the square-wave control policy. From the results, an evolutionary algorithm is implemented to find the most optimized solution for locomotion of the twelve-rod tensegrity structure. The software pattern coupled with the new friction based actuation method can serve as the basis for highly efficient tensegrity robots in space exploration.
The Lightweight Surface Manipulation System, or LSMS, is a family of long-reach cable-actuated robotic cranes. They are designed for planetary surface operations on the Moon and Mars. Their low structural weight and compact packaging reduces the fuel costs associated with space travel. The LSMS can be operated by humans, who can be on site or remotely, or autonomously. The goal of this research is to help human operators and path planning algorithms avoid unsafe states during operation. To this end, this work leverages a geometrical model of the LSMS and formulates a new dynamic model. These are later used to define the safe operational envelope for the LSMS family. The paper classifies the constraints that define the safe operational envelope in three groups: motor constraints, geometric constraints, and cable tension constraints. Keeping the cables under tension is necessary to maintain controllability over the joint angles. Two types of loss of tension events are identified for each of the cables. First, an excessive reel out of the cables can lead to a loss of tension, where the LSMS links behave like a pendulum. Second, an excessive reel in of the cables can lead to a link tip-over. This can cause a violent clash between the links on the LSMS. The paper visualizes these constraints for the LSMS-L35, the smallest robot within the family.