Xiaoqi Bao

Lemur IIb: a Robotic System for Steep Terrain Access

Purpose – Introduces the Lemur IIb robot which allows the investigation of the technical hurdles associated with free climbing in steep terrain. These include controlling the distribution of contact forces during motion to ensure holds remain intact and to enable mobility through over‐hangs. Efforts also can be applied to further in‐situ characterization of the terrain, such as testing the strength of the holds and developing models of the individual holds and a terrain map.Design/methodology/approach – A free climbing robot system was designed and integrated. Climbing end‐effector were investigated and operational algorithms were developed.Findings – A 4‐limbed robotic system used to investigate several aspects of climbing system design including the mechanical system (novel end‐effectors, kinematics, joint design), sensing (force, attitude, vision), low‐level control (force‐control for tactile sensing and stability management), and planning (joint trajectories for stability). A new class of Ultrasonic/S...

Ultrasonic/sonic driller/corer (USDC) as a sampler for planetary exploration

Future NASA exploration missions to Mars, Europa, Titan, comets, and asteroids will perform sampling, in-situ analysis and possibly the return of material to Earth for further tests. One of the major limitations of sampling in low gravity environments is that conventional drills need high axial force. An ultrasonic/sonic driller/corer (USDC) mechanism was developed to address these and other limitations of existing drilling techniques. The USDC is based on an ultrasonic horn that is driven by a piezoelectric stack. The horn drives a free-mass, which resonates, between the horn and drill stem. Tests have shown that this device addresses some of the key challenges to the NASA objective of planetary in-situ sampling and analysis. The USDC is lightweight (450 g), requires low pre-load (<5N) and can be driven at low power (5 W). The device was operated from such robotic platforms as the Sojourner rover and the FIDO robotic arm and it has been shown to drill various rocks including granite, diorite, basalt and limestone. The drill can potentially operate at high and low temperatures and does not require sharpening. Although the drill is driven electrically at 20 kHz, a substantial subharmonic acoustic component is found that is crucial to drilling performance. Models that explain this low frequency coupling in the horn, free-mass, drill stem and rock are presented. Efforts are currently underway to integrate the models and experimentally corroborate the predictions.

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.

In-service monitoring of steam pipe systems at high temperatures

An effective in-service health monitoring system is needed for steam pipes to track through their wall the condensation of water in real-time at high temperatures. The system is required to measure the height of the condensed water inside the pipe while operating at temperatures that are as high as 250°C. The system needs to be able to make time measurements while accounting for the effects of water flow and cavitation. For this purpose, ultrasonic waves were used to perform data acquisition of reflected signals in pulse-echo and via autocorrelation the data was processed to determine the water height. Transmitting and receiving the waves is done by piezoelectric transducers. There are transducers with Curie temperatures that are significantly higher than the required for this task offering the potential to sustain the conditions of the pipe over extended operation periods. This paper reports the progress of the current feasibility study that is intended to establish the foundations for such health monitoring systems.

Piezoelectric stack actuator life test

Future NASA interferometer missions require actuators for precision positioning to accuracies of the order of nanometers. For this purpose, commercially available multilayer piezoelectric stack actuators are being considered for driving these precision positioning mechanisms. These mechanisms have potential mission operational requirements that exceed 5 years and the nominal actuator requirements for the most critical actuators on the these missions were estimated from the Modulation Optics Mechanism (MOM) and Pathlength control Optics Mechanism (POM) mechanisms which were developed for the Space Interferometry Mission (SIM). At a nominal drive frequency of two hundred and fifty hertz one mission life is calculated to be 40 Billion cycles. In order to test the feasibility of using these commercial actuators for these applications and to determine the reliability and the redundancy requirements of these actuators a life test study was undertaken. In this study a set of commercial PZT stacks configured in a potential actuator flight configuration (pre-stressed and bonded in flexures) were tested for up to 100 billion cycles. The test flexures allowed for two stacks to be mechanically connected in series. The tests were controlled using an automated Lab-View control and data acquisition system that set up the test parameters and monitored the waveform of the stack electrical current and voltage. The samples were driven between 0 and 20 Volts at 2000Hz to accelerate the life test and mimic the voltage expected to be applied to the stacks during operation. During the life test the primary stack was driven while the redundant stack was open circuited. The stroke determined from a strain gauge and the temperature and humidity in the chamber and the temperature of each individual stack were recorded. In addition other properties of the stacks were measured at specific intervals. These measurements included the displacement from a Capacitance gap sensor and impedance spectra. The degradation in the stroke over the life test was found to be small (&#60;3%) for the primary stacks and estimated to be &#60; 4% for the redundant stacks. It was noted that about half the stroke reduction occurred within the first 10 billion cycles. At the end of the life test it was found that by applying DC voltage levels (100 V) above the life test voltage we could initially recover about half of the lost stroke with again some degradation in the long term. The data up to 100 billion cycles for these tests and the analysis of the experimental results will be presented in this paper. 1,2

Monolithic rapid prototype flexured ultrasonic horns

Piezoelectric ultrasonic horn actuators are used in high power medical/surgical, automotive, food preparation, textile cutting, and material joining applications. Typically, these horn actuators are assembled by pre-stressing piezoelectric rings between the horn and backing layer using a pre-stress bolt. In the ultrasonic horn actuators presented in this paper the bolt was removed and the number of overall parts was reduced significantly allowing for easy fabrication and integration of the actuators into other structures. The elimination of the need for the conventional stress bolt internal to the piezoelectric stack and the reduction of the related complexity were achieved by using external flexures. The actuator structure was produced by an electron beam melting rapid prototype manufacturing process. This manufacturing process allows for horn structures with internal cavities if required. This design allows for using solid piezoelectric stacks (with no central hole) to produce a highly effective actuator. This paper presents the results of a novel design of a monolithic ultrasonic horn.

Planetary sample sealing for caching

A sample sealing technique was developed and tested for a possible Mars Sample Return mission application. The effect on the scientific viability of biological samples from storage of samples in a sample container for a long period of time on the Martian surface was also investigated. Sealing techniques were investigated and a soldering concept was developed and tested to provide a hermetic seal between a sample tube and cap. A sample caching subsystem design concept was updated to allow for sealing of sample tubes. A gas-tight vessel was constructed that could be used to simulate environmental conditions that would be experienced by a sample of regolith on Mars and to test the affects of thermal cycling of the vessel on psychrophilic microorganisms embedded in a regolith simulant to assess the degree of deterioration of the microorganisms.

Deep Drilling and Sampling via Compact Low-Mass Rotary-Hammer Auto-Gopher

Increasingly, NASA exploration missions are including in-situ sampling tasks. The difficulties of acquiring samples have been identified by the designers of the 2007 Mars Phoenix Scout and the 2011 Mars Science Laboratory missions. In particular, it has been indicated that planetary drilling faces great challenges. The associated challenges grow significantly with the depth of drilling and it is the objective of the current study to develop an autonomous wireline rotary-percussive drill (called Auto-Gopher) that can reach a depth of several meters. In developing the Auto-Gopher efforts are made to take advantage of the hammering capabilities of the Ultrasonic/Sonic piezoelectric mechanism to fracture rocks using low preload. This mechanism was demonstrated in 2005 to reach about 2-m deep in ice at Lake Vida, Antarctica. The augmentation of the hammering by rotation of the bit having flutes provides both effective cuttings removal and faster drilling. The progress in developing the Auto-Gopher will be described and discussed in this paper.

Auto-Gopher-II: a wireline rotary-hammer ultrasonic drill that operates autonomously

An important challenge of exploring the solar system is the ability to penetrate at great depths the subsurface of planetary bodies for sample collection. The requirements of the drilling system are minimal mass, volume and energy consumption. To address this challenge, a deep drill, called the Auto-Gopher II, is currently being developed as a joint effort between JPL’s NDEAA laboratory and Honeybee Robotics Corp. The Auto-Gopher II is a wireline rotaryhammer drill that combines breaking formations by hammering using a piezoelectric actuator and removing the cuttings by rotating a fluted bit. The hammering is produced by the Ultrasonic/Sonic Drill/Corer (USDC) mechanism that has been developed by the JPL team as an adaptable tool for many drilling and coring applications. The USDC uses an intermediate free-flying mass to convert high frequency vibrations of a piezoelectric transducer horn tip into sonic hammering of the drill bit. The USDC concept was used in a previous task to develop an Ultrasonic/Sonic Ice Gopher and then integrated into a rotary hammer device to develop the Auto-Gopher-I. The lessons learned from these developments are being integrated into the development of the Auto-Gopher-II, an autonomous deep wireline drill with integrated cuttings and sample management and drive electronics. In this paper the latest development will be reviewed including the piezoelectric actuator, cuttings removal and retention flutes and drive electronics.

Synchronous separation, seaming, sealing and sterilization (S4) using brazing for sample containerization and planetary protection

The return of samples back to Earth in future missions would require protection of our planet from the risk of bringing uncontrolled biological materials back with the samples. This protection would require “breaking the chain of contact (BTC)”, where any returned material reaching Earth for further analysis would have to be sealed inside a container with extremely high confidence. Therefore, the acquired samples would need to be contained while destroying any potential biological materials that may contaminate the external surface of the container. A novel process that could be used to contain returning samples has been developed and demonstrated in a quarter scale size. The process consists of brazing using non-contact induction heating that synchronously separates, seams, seals and sterilizes (S4) the container. The use of brazing involves melting at temperatures higher than 500°C and this level of heating assures sterilization of the exposed areas since all carbon bonds (namely, organic materials) are broken at this temperature. The mechanism consists of a double wall container with inner and outer shells having Earth-clean interior surfaces. The process consists of two-steps, Step-1: the double wall container halves are fabricated and brazed (equivalent to production on Earth); and Step-2 is the S4 process and it is the equivalent to the execution on-orbit around Mars. In a potential future mission, the double wall container would be split into two halves and prepared on Earth. The potential on-orbit execution would consist of inserting the orbiting sample (OS) container into one of the halves and then mated to the other half and brazed. The latest results of this effort will be described and discussed in this manuscript.