Jack Aldrich

Wireless piezoelectric acoustic-electric power feedthru

There are numerous engineering applications where there is a need to transfer power and communication data thru the walls of a structure. A piezoelectric acoustic-electric power feedthru system was developed in this reported study allowing for wireless transfer of electric power through a metallic wall using elastic waves. The technology is applicable to the transfer of power for actuation, sensing and other tasks inside sealed containers and vacuum/pressure vessels. A network equivalent circuit including material damping loss was developed to analyze the performance of the devices. Experimental test devices were constructed and tested. The power transfer capability and the transfer efficiency were measured. A 100W feed though capability with 38 mm diameter device and 88% transmission efficiency were demonstrated. Both analytical and experimental results are presented and discussed in this paper.

Studies of acoustic-electric feed-throughs for power transmission through structures

There are numerous engineering design problems where the use of wires to transfer power and communicate data thru the walls of a structure is prohibitive or significantly difficult that it may require a complex design. Using physical feedthroughs in such systems may make them susceptible to leakage of chemicals or gasses, loss of pressure or vacuum, as well as difficulties in providing adequate thermal or electrical insulation. Moreover, feeding wires thru a wall of a structure reduces the strength of the structure and makes the structure prone to cracking due to fatigue that can result from cyclic loading and stress concentrations. One area that has already been identified to require a wireless alternative to electrical feedthroughs would be the container of any Mars Sample Return Mission, which would need wireless sensors to sense a pressure leak and to avoid potential contamination. The idea of using elastic or acoustic waves to transfer power was suggested recently by [Y. Hu, et al., July 2003]. This system allows for the avoidance of cabling or wiring. The technology is applicable to the transfer of power for actuation, sensing and other tasks inside any sealed container or vacuum/pressure vessel. An alternative approach to the modeling presented previously [Sherrit et al., 2005] used network analysis to solve the same problem in a clear and expandable manner. Experimental tests on three different designs of these devices were performed. The three designs used different methods of coupling the piezoelectric element to the wall. In the first test the piezoelectric material was bolted using a backing structure. In the second test the piezoelectric was clamped after the application of grease. Finally the piezoelectric element was attached using a conductive epoxy. The mechanical clamp with grease produced the highest measured efficiency of 53% however this design was the least practical from a fabrication viewpoint. The power transfer efficiency of conductive epoxy joint was 40% and the stress bolts (12%). The experimental results on a variety of designs will be presented and the thermal and non-linear issues will be discussed.

High-power piezoelectric acoustic-electric power feedthru for metal walls

Piezoelectric acoustic-electric power feed-through devices transfer electric power wirelessly through a solid wall using elastic waves. This approach allows for the elimination of the need for holes through structures for cabling or electrical feed-thrus . The technology supplies power to electric equipment inside sealed containers, vacuum or pressure vessels, etc where holes in the wall are prohibitive or may result in significant performance degradation or requires complex designs. In the our previous work, 100-W of electric power was transferred through a metal wall by a small, piezoelectric device with a simple-structure. To meet requirements of higher power applications, the feasibility to transfer kilowatts level power was investigated. Pre-stressed longitudinal piezoelectric feed-thru devices were analyzed by finite element modeling. An equivalent circuit model was developed to predict the characteristics of power transfer to different electric loads. Based on the analytical results, a prototype device was designed, fabricated and successfully demonstrated to transfer electric power at a level of 1-kW. Methods of minimizing plate wave excitation on the wall were also analyzed. Both model analysis and experimental results are presented in detail in this paper.

Rotary hammer ultrasonic/sonic drill system

Subsurface sampling systems for future planetary robotic missions which include reliable methods of generating, acquiring, and delivering samples to a scientific instrument for analysis are of extreme importance to the success of future in situ and sample return missions. Operating at remote locations the sampler needs to deal with a variety of disparate rock sources while being essential to deliver samples in different forms and to accommodate the requirements of a wide range of scientific instruments. Existing highly efficient terrestrial drilling techniques have limited space applications due to their need for large axial forces and holding torques, high power consumption and inability to efficiently duty cycle, and the use of rigid handling platforms. This paper describes the work performed at Jet Propulsion Laboratory (JPL) and Honeybee Robotics for the development of a rotary percussive drill that uses an ultrasonic/sonic drill/corer as the hammering device integrated in a sampling system capable of automatic operation in a Mars environment.

Subsurface sampler and sensors platform using the ultrasonic/sonic driller/corer (USDC)

The search for existing or past life in the Universe is one of the most important objectives of NASAs mission. For this purpose, effective instruments that can sample and conduct in-situ astrobiology analysis are being developed. In support of this objective, a series of novel mechanisms that are driven by an Ultrasonic/Sonic actuator have been developed to probe and sample rocks, ice and soil. This mechanism is driven by an ultrasonic piezoelectric actuator that impacts a bit at sonic frequencies through the use of an intermediate free-mass. Ultrasonic/Sonic Driller/Corer (USDC) devices were made that can produce both core and powdered cuttings, operate as a sounder to emit elastic waves and serve as a platform for sensors. For planetary exploration, this mechanism has the important advantage of requiring low axial force, virtually no torque, and can be duty cycled for operation at low average power. The advantage of requiring low axial load allows overcoming a major limitation of planetary sampling in low gravity environments or when operating from lightweight robots and rovers. The ability to operate at duty cycling with low average power produces a minimum sample temperature rise allowing for control of the sample integrity and preventing damage to potential biological markers in the acquired sample. The development of the USDC is being pursued on various fronts ranging from analytical modeling to mechanisms improvements while considering a wide range of potential applications. While developing the analytical capability to predict and optimize its performance, efforts are made to enhance its capability to drill at higher power and high speed. Taking advantage of the fact that the bit does not require rotation, sensors (e.g., thermocouple and fiberoptics) were integrated into the bit to examine the borehole during drilling. The sounding effect of the drill was used to emit elastic waves in order to evaluate the surface characteristics of rocks. Since the USDC is driven by piezoelectric actuation mechanism it can designed to operate at extreme temperature environments from very cold as on Titan and Europa to very hot as on Venus. In this paper, a review of the latest development and applications of the USDC will be given.

Power loss consideration in wireless piezoelectric acoustic-electric power feedthru

Piezoelectric acoustic-electric power feedthru devices that are able to transfer electric power through metallic/ferromagnetic wall are investigated. Electric energy is converted to acoustic energy by piezoelectric transducer at one side of the wall. The acoustic wave propagates through the wall and, then, it is converted back to electric energy by another transducer on the other side. For high efficient transmission, it is critical that all the energy loss should be minimized. In addition to the electrical, mechanical and electromechanical loss in the transducers and the thickness of the wall, Lamb (plate) waves are excited by the transducers in the wall and they also result in energy losses. In this study, the energy loss caused by the Lamb waves are analyzed analytically and by finite element simulations. The results and the methods to reduce the loss are presented and discussed in this presentation.

Space-quality data from balloon-borne telescopes: the High Altitude Lensing Observatory (HALO)

We present a method for attaining sub-arcsecond pointing stability during sub-orbital balloon flights, as designed for in the High Altitude Lensing Observatory (HALO) concept. The pointing method presented here has the potential to perform near-space quality optical astronomical imaging at similar to 1-2% of the cost of space-based missions. We also discuss an architecture that can achieve sufficient thermo-mechanical stability to match the pointing stability. This concept is motivated by advances in the development and testing of Ultra Long Duration Balloon (ULDB) flights which promise to allow observation campaigns lasting more than three months. The design incorporates a multi-stage pointing architecture comprising: a gondola coarse azimuth control system, a multi-axis nested gimbal frame structure with arcsecond stability, a telescope de-rotator to eliminate field rotation, and a fine guidance stage consisting of both a telescope mounted angular rate sensor and guide CCDs in the focal plane to drive a Fast-Steering Mirror. We discuss the results of pointing tests together with a preliminary thermo-mechanical analysis required for sub-arcsecond pointing at high altitude. Possible future applications in the areas of wide-field surveys and exoplanet searches are also discussed

Ultrasonic/sonic driller/corer as a hammer-rotary drill

Rock, soil, and ice penetration by coring, drilling or abrading is of great importance for a large number of space and earth applications. Proven techniques to sample Mars subsurface will be critical for future NASA astrobiology missions that will search for past and present life on the planet. The Ultrasonic/Sonic Drill/Corer (USDC) has been developed as an adaptable tool for many of these applications [Bar-Cohen et al., 2001]. The USDC uses a novel drive mechanism to transform the ultrasonic or sonic vibrations of the tip of a horn into a sonic hammering of a drill bit through an intermediate free-flying mass. For shallow drilling the cuttings travel outside the hole due to acoustic vibrations of the bit. Various methods to enhance the drilling/coring depth of this device have been considered including pneumatic [Badescu et al., 2006] and bit rotation [Chang et al., 2006]. The combination of bit rotation at low speed for cuttings removal and bit hammering at sonic frequencies are described in this paper. The theoretical background and testing results are presented.

Demonstration of autonomous coring and caching for a Mars sample return campaign concept

An end-to-end sample acquisition and caching system has been built and tested with capabilities applicable to sample acquisition and caching for a potential 2018 mission to Mars to collect samples for eventual return to Earth. The system provides full capability to robotically perform the end-to-end sample acquisition and caching process including placing a sample tube in a coring bit, attaching the bit to the sampling tool, coring a rock and acquiring the core sample in the tube, transferring the bit to the caching mechanism, removing the sample tube from the bit, sealing the filled sample tube with a plug, and storing the tube in the sample cache canister. This paper describes the hardware and robotic steps for the sample acquisition and caching process.

Percussive Augmenter of Rotary Drills (PARoD)

Increasingly, NASA exploration mission objectives include sample acquisition tasks for in-situ analysis or for potential sample return to Earth. To address the requirements for samplers that could be operated at the conditions of the various bodies in the solar system, a piezoelectric actuated percussive sampling device was developed that requires low preload (as low as 10N) which is important for operation at low gravity. This device can be made as light as 400g, can be operated using low average power, and can drill rocks as hard as basalt. Significant improvement of the penetration rate was achieved by augmenting the hammering action by rotation and use of a fluted bit to provide effective cuttings removal. Generally, hammering is effective in fracturing drilled media while rotation of fluted bits is effective in cuttings removal. To benefit from these two actions, a novel configuration of a percussive mechanism was developed to produce an augmenter of rotary drills. The device was called Percussive Augmenter of Rotary Drills (PARoD). A breadboard PARoD was developed with a 6.4 mm (0.25 in) diameter bit and was demonstrated to increase the drilling rate of rotation alone by 1.5 to over 10 times. The test results of this configuration were published in a previous publication. Further, a larger PARoD breadboard with a 50.8 mm (2.0 in) diameter bit was developed and tested. This paper presents the design, analysis and test results of the large diameter bit percussive augmenter.