Motion Control

Compact Active Vibration Control System

A highly directional actuator can be shaped so that it couples to the response of a flexible structure in the same manner as point sensors.This innovation consists of an analog controller, diamond-shaped patch actuator, and point sensors (such as accelerometers). The actuator is designed to couple to the flexural response of the structure in the same manner as a group of point sensors. This results in a co-located transducer pair. The signals from all sensors are combined, filtered, and amplified within the analog controller. The resulting signal is then applied to the actuator, which generates a control force out-of-phase with the measured response. Because the transducers are co-located, the vibration control system is inherently robust to variations in properties of the underlying structure that is being controlled. This type of control system actively suppresses the vibration of a flexible structure using surface-mounted transducers without any external mechanical connections.

Posted in: Briefs, TSP, Motion Control, Electronic control systems, Vibration

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Deep Throttling Turbopump

Advancement in space exploration necessitates deep throttling of liquid cryogenic rocket engines. Both lunar and Martian robotic and human exploration require engines that can be deep throttled,can start and restart, have a long life, and require minimal maintenance. An engine that is capable of deep throttling at low thrust levels and is versatile enough to accommodate multiple applications would advance the state of the art and enable NASA to meet space exploration objectives. An advanced partial emission turbo pump design is an enabling technology for developing such low thrust level engines. This will complement the current state-of-the-art full emission pump technology.

Posted in: Briefs, Motion Control, Rocket engines, Throttles

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Analyzing Rollover Stability of Capsules With Airbags Using LS-Dyna

This method interpolates data to predict the stability boundaries for a capsule on airbags.As NASA moves towards developing technologies needed to implement its new Exploration program, studies conducted for Apollo in the 1960s to understand the rollover stability of capsules landing are being revisited. Although rigid body kinematics analyses of the rollover behavior of capsules on impact provided critical insight to the Apollo problem, extensive ground test programs were also used. For the new Orion spacecraft, airbag designs have improved sufficiently for NASA to consider their use to mitigate landing loads to ensure crew safety and to enable reusability of the capsule.

Posted in: Briefs, TSP, Motion Control, Stability control, Airbag systems, Spacecraft

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Test Fixture for Isolation of Vibration Shaker from G-Loading

Combined testing is possible in a controlled, calibrated, and repetitive manner.The first step in implementing the capability to test sensitive launch vehicle instruments in a combined environment has been completed. The test environment consists of specific vibration spectra induced under sustained Gs, using NASTAR’s ATFS-400 centrifuge. Fixtures allow mounting of the device under test (DUT) to a vibrational shaker in a centrifuge for generating moderate G-loading (1.4 to 9G) such that the vibrational shaker’s capabilities are only slightly affected by the G-loads applied during testing. Two configurations were designed, with the vibrational load parallel to the G-loads, and with the vibration loads transverse (at right angles) to the G-loads. The results are extremely encouraging, and demonstrate the potential of the NASTAR centrifuge to perform this kind of combined testing in a controlled, calibrated, and repetitive manner.

Posted in: Briefs, TSP, Motion Control, Aircraft instruments, Vibration, Launch vehicles

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Rotary Series Elastic Actuator

The actuator provides motion and sensing for the degrees of freedom in the upper arm of a dexterous humanoid robot. In order to perform human-like movement, an actuator is placed at each degree of freedom (DOF) in a humanoid robot. Additionally, these actuators must be packaged in an arrangement that approximates human structure and appearance. In this innovation, a rotary actuator assembly incorporates a brushless DC motor, a gear reduction, a variety of sensors, and a custom planar torsion spring to provide motive force, passive compliance, and torque sensing within an anthropomorphic package. The actuator, in various size scales, was designed for the humanoid robot described in “Dexterous Humanoid Robot,” (MSC-24739), NASA Tech Briefs, Vol. 38, No. 6 (June 2014), p. 52.

Posted in: Briefs, Motion Control, Sensors and actuators, Robotics

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Submersible Pressure Transducer for Tank Fluid Level Monitoring

Monitoring the level of liquid can be accomplished through the use of a pressure transducer. The density of the liquid and its height create pressure on the diaphragm of the pressure transducer to generate an accurate and cost-effective level measurement. Generally, pressure transducers can be used for level measurement from 10 inches of water column up to 10,000 PSI (700 bar).

Posted in: Application Briefs, Motion Control, Sensors and actuators

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Probe Positioning System for Antenna Range

Three or more cables provide the desired positioning.In situ measurements of antenna patterns on rovers in a simulated terrain are difficult to make with conventional antenna range techniques. The desired pattern data covers a hemisphere above the antenna of interest, which is close to the ground. This is incompatible with traditional measurements that place the antenna under test on a movable support that tilts and rotates.

Posted in: Briefs, TSP, Motion Control, Antennas, Sensors and actuators, Spacecraft

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