The capability to rapidly augment airbases with bio-concrete infrastructure to support parking, loading, unloading, rearming, and refueling operations is of interest to the Air Force, because it requires transportation of fewer raw materials to remote sites. Automation of the bio-cement delivery further reduces logistical requirements and mitigates hazards to personnel, especially in contested or austere environments. In this paper we discuss the full-stack development and integration of a robotic applique for a commercial tractor and present the test results for autonomous delivery of bio-cement bacteria, feed stock, and water for stabilization of a sandy test area. The tractor autonomously navigates, sprays, and avoids obstacles using robust and economical off-the-shelf components and software. For this first phase of the project, we employ GNSS for localization and automotive lidar for obstacle detection. We report on the design of the robotic applique, including the mechanical, electrical, and software components, which are mostly commercial-off-the-shelf or open source. We discuss the results of testing and calibration including tests of towing capacity, calibration of steering, measurement of liquid spray distribution, measurement of tracking errors, and determination of repeatability of positioning for refilling of the reservoir. We also examine higher order behaviors and chart a path forward for future development, which includes GNSS-denied navigation.
Within this work a model of a 6 DOF (degree-of-freedom) vibration isolation system with semi-active control, using magnetorheological (MR) technology, is investigated. Parallel platform mechanisms are ideal candidates for 6 DOF positioning and vibration isolation. While active and passive vibration control have been extensively used in parallel platforms, a 6 DOF parallel platform which utilizes semi-active vibration control has not received as much attention. The advantages of semi-active control include reduced cost by using a simpler actuator intended for only positioning, reduced power requirements, and improved stability. Within this work, the legs of a parallel platform model are investigated by implementing a two DOF Simulink model. Each leg of the platform is modeled as a two DOF system with a magnetorheological (MR) damper for adjustable damping.
The objective of this research is to extend the sensing capabilities of a multi-vehicle ground system by incorporating the environmental perception abilities of unmanned aerial vehicles.
The aerial vehicle used in this research is a Miniature Aircraft Gas Xcell RC helicopter. It is outfitted with a sensor payload containing stereo vision cameras, GPS, and a digital compass. Geo- referenced images are gathered using the above sensors that are used in this research to create a map of the operating region. The ground vehicle used in this research is an automated Suzuki Mini-Quad ATV. It has the following onboard sensors: single-vision camera, laser range device, digital compass, GPS, and an encoder. The ground vehicle uses the above sensors and the map provided by the helicopter to traverse the region, locate, and isolate simulated land mines. The base station consists of a laptop that provides a communication link between the aerial and ground vehicle systems. It also provides the operator with system operation information and statistics.
All communication between the vehicles and the base station is performed using JAUS (Joint Architecture for Unmanned Systems) messages. The JAUS architecture is employed as a means to organize inter-vehicle and intra-vehicle communication and system component hierarchy. The purpose of JAUS is to provide interoperability between various unmanned systems and subsystems for both military and commercial applications. JAUS seeks to achieve this through the development of functionally cohesive building blocks called components whose interface messages are clearly defined. The JAUS architecture allows for a layered control strategy which has specific message sets for each layer of control. Implementation of the JAUS architecture allows for ease of software development for a multi- vehicle system.
This experiment demonstrates how an air-ground vehicle system can be used to cooperatively locate and dispose of simulated mines.
This paper presents the development and testing of a sensor payload for use on unmanned helicopters. This payload is designed to be used to detect and geo-position unexploded ordnance termed UXOs. This technology will be beneficial to explosive ordnance disposal personnel in their test range clearance operations. This payload is capable of gathering image, attitude, and position information during flight, and a suite of software programs was developed capable of modeling, classifying, and geo-positioning UXOs.
This paper describes the development and performance of a sensor system that was utilized for autonomous navigation of an unmanned ground vehicle. Four different sensor types were integrated to identify obstacles in the vicinity of the vehicle and to identify smooth terrain that could be traversed at speeds up to thirty miles per hour. The paper also describes a sensor fusion approach that was developed whereby the output of all sensors was in a common grid based format. The environment around the vehicle was modeled by a 120×120 grid where each grid cell was 0.5m× 0.5m in size and where the orientation of the grid lines was always maintained parallel to the north-south and east-west lines. Every sensor output an estimate of the traversability of each grid cell. For the three dimensional obstacle avoidance sensors (rotating ladar and stereo vision) the three dimensional point data was projected onto the grid plane. The terrain traversability sensors, i.e. fixed ladar and monocular vision, estimated traversability based on smoothness of the spatial plane fitted to the range data or the commonality in appearance of pixels in the grid cell to those directly in front of the vehicle, respectively.
KEYWORDS: Sensors, Data modeling, Data storage, Systems modeling, Unmanned systems, Control systems, Roads, Raster graphics, Unmanned ground vehicles, Nonlinear control
This paper describes how the functionality of the DoD Joint Architecture for Unmanned Systems (JAUS) was expanded by developing experimental components related to off-line and reactive path planning and world modeling. JAUS defines a set of reusable components and their interfaces. In order to ensure that the JAUS architecture will be applicable to the entire domain of unmanned mobile systems, the following four characteristics were considered throughout its development: vehicle platform independence, mission isolation, hardware independence, and technology independence. The new experimental components described in this paper have these same characteristics. Existing JAUS components readily allow for autonomous path tracking. In this work the JAUS Version 3.0 Global Path Segment Driver, Global Pose Sensor, Velocity State Sensor, and Primitive Driver components were utilized for that task. What is described in this paper is the development of the following new experimental components: World Model, Sensor Arbiter, and Path Manager. The functionality and interface messages of each of these components are presented, followed by a discussion of the performance of the overall system.
A new way to perform vibration control on a single-degree-of-freedom system using a piezoelectric friction damper is developed. The damper consists of an actuator, which is based on a piezoelectric stack with a mechanical amplifying mechanism that provides symmetric forces within the isolator. The advantages of such an actuator are its high bandwidth, actuating response and its ability to operate in vacuum environments such as in space. The damper is constrained to move using an air bearing that produces a virtually ideal single-degree-of-freedom spring-mass system. Within this work, the actuating ability of the friction-based actuator is characterized. The relationship between the force generated by the actuator and the applied voltage was found to be linear. The maximum force generated by the friction damper in this study is 85 N for the specific friction pads used.
A novel concept for large aperture lightweight deformable mirrors is presented. This new concept is based on using a flexure-hinged truss substrate as opposed to monolithic substrates used in all past and current deformable mirror technologies. With its ability to deform in tangential as well as normal directions, this new concept solves the problem of coefficient of thermal expansion (CTE) mismatch between face sheet and substrate. It takes advantage of the newly emerging face sheet technologies such as nanolaminates that produce extremely lightweight optical quality face sheets and require very small forces to deform them. It also provides rigidity to the thin face sheet mirror, necessary for the uniqueness of response to actuator commands and for tolerance to disturbances. Any stresses in substrate structure are mainly limited to those induced by the forces in the face sheet itself, which are small in the new lightweight face sheets. The dynamic range of deformation is limited only by the actuator stroke, and not by the stresses induced in the substrate. Therefore it drives the actuator design to small force large stroke actuators, as opposed to the current designs that use large force small stroke moment actuators.
Wright Laboratory, at Tyndall AFB, Florida, has contracted the University of Florida to develop autonomous navigation systems for a variety of robotic vehicles, capable of performing tasks associated with the location and removal of bombs and mines. One of the tasks involves surveying closed target ranges for unexploded buried munitions. Accuracy in path following is critical to the task. There are hundreds of acres that currently require surveying. The sites are typically divided into regions, where each mission can take up to 4.5 hours. These sites are usually surveyed along parallel rows. By improving the accuracy of path following, the distance between the rows can be increased to nearly the detection with of the ground penetrating sensors, resulting in increased acreage surveyed per mission. This paper evaluates a high-level PID and a pure pursuit steering controller. The controllers were combined into a weighted solution so that the desirable features of each controller is preserved. This strategy was demonstrated in simulation and implemented on a Navigation Test Vehicle. For a test path of varying curvature, the average lateral control error was 2 cm at a vehicle sped of 1.34 m/s.
A method for modeling a hazardous environment automatically, for real time task planning, using laser range images of multiple partial views of a single work space scene, is presented. Viewpoint invariant properties of differential- geometric shape descriptors like the mean curvature and the Gaussian curvature are utilized to classify a pre-smoothed laser range image into one of eight basic surface types. Connected components of these classified pixels, that satisfy specific planarity constraints, are clustered into planar regions. Selected image processing techniques are applied to the planar regions in order to extract their critical features, and to synthesize those polygons, with normals approximately orthogonal to the sensor view-axis. Detailed shape of the objects in the scene develop through view integration of multiple partial views of the objects in the scene.
The location and removal of buried munitions is an important yet hazardous task. Current development is aimed at performing both the ordnance location and removal tasks autonomously. An autonomous survey vehicle (ASV) named the Gator has been developed at the Center for Intelligent Machines and Robotics, under the direction of Wright Laboratory, Tyndall Air Force Base, Florida, and the Navy Explosive Ordnance Disposal Technology Division, Indian Head, Maryland. The primary task of the survey vehicle is to autonomously traverse an off-road site, towing behind it a trailer containing a sensor package capable of characterizing the sub-surface contents. Achieving 00 percent coverage of the site is critical to fully characterizing the site. This paper presents a strategy for planning efficient paths for the survey vehicle that guarantees near-complete coverage of a site. A small library of three in-house developed path planners are reviewed. A strategy is also presented to keep the trailer on-path and to calculate the percent of coverage of a site with a resolution of 0.01 m2. All of the algorithms discussed in this paper were initially developed in simulation on a Silicon Graphics computer and subsequently implemented on the survey vehicle.
KEYWORDS: Sensors, Navigation systems, Global Positioning System, Control systems, System on a chip, Magnetometers, General packet radio service, Magnetic sensors, Computing systems, Inertial navigation systems
Wright Laboratory has been tasked by the Naval Explosive Ordnance Technical Division to develop robotic platforms to perform characterization of areas set aside for ordnance testing. These areas require the identification and removal of the unexploded ordnance before they can be utilized for safe, productive use. The characterization task is performed by autonomously sweeping a designated area with the autonomous tow vehicle (ATV). The ATV tows the multiple sensor platform containing a magnetometer array and a ground penetrating radar. The ATV provides the time and position stamp for sensor data. Analysts then review the post survey sensor data to determine ordnance position. The ATV makes use of several advanced technologies. A hybrid navigation and guidance system using an external Kalman filter delivers vehicle position based on information from a real time centimeter level differential global positioning system and a strapped down laser gyro inertial navigation system. A vision-based obstacle avoidance system helps to account for unknown obstacles during survey. Sophisticated path planning algorithms, and an intelligent software architecture for planning and behavior provide a measure of autonomy. A data collection system controls the functions of the various sensors used for the characterization process and manipulates the data stream to conform to an open ASCII data format and stores it to rugged removable hard disks for later analysis.
Force reflective controllers can be divided into two classes; active and passive with the most common being active. Active force-feedback controllers are prone to self-actuation which can generate unintended commands and may injure the user. A six-degree-of-freedom positional input device was designed and constructed that was capable of providing force-feedback passively through the use of six magnetic hysteresis brakes. Special hardware and control strategies were developed to account for some of the limitations of a passive system and the characteristics of hysteresis brakes. The force-feedback input device has been interfaced to a six-degree-of-freedom robot to perform a variety of tasks. Initial research was conducted with a peg-in-hole task. Future research is to include contour following and bead-on-wire tests. Initial results indicated that force-feedback may only be an improvement in situations where visual cues are not clear, and may actually be a hindrance when a clear line of sight exists.
The main task of sensing for robotics and automation is to provide 3D geometrical environment information to robot control and visualization systems, which is often referred as facility characterization or environment mapping. Particularly in radioactive waste cleanup operations, such as the Tank Waste Retrieval (TWR) task where the environment is hazardous, automated sensing techniques are necessary for accurate facility characterization that will be used by remote controlled robots for a safe and orderly cleanup process. This research proposes a facility characterization system which combines the strength of computer vision and computer graphics and which maximizes the use of a priori information. Using a novel image registration method, this system is able to detect the difference between the pre-modeled virtual world and sensed real world. Combined with 3D sensing data, the information can be used for verification and reconciliation of the virtual world database. In the proposed system, the environment is pre-modeled as the virtual world. This virtual world database provides the template for the virtual/real world registration. Once the virtual/real images are registered, the comparison can be accomplished by image subtraction. As the result of the comparison, any missing objects or unanticipated objects will be detected. Utilizing the 3D information, the surfaces of these objects can be reconstructed. This information in turn is used for geometric primitives detection and virtual world updating. The initial testing demonstrates that this system has potential to accomplish the TWR task.
Virtual reality is becoming increasingly important as a tool to provide cost-effective alternatives for training and to provide enhanced capabilities for activities, such as mission preview, planning and rehearsal. The ability to generate virtual reality utilizing a photo database or remote sensed satellite imagery is particularly of interest. The key to ensure the success of remote sensing-based virtual reality is a system that is able to quickly reconstruct a 3D scene in object space with a realistic appearance. This paper proposes a system to accomplish this task. Main issues of the system include: (1) image registration, (2) feature correspondence and extrusion, and (3) realistic 3D feature rendering. The image registration is achieved by employing a novel method based on the higher-dimension concept. To obtain a high speed, the feature correspondence is implemented using a mathematically well-defined, edge-based method in a multiresolution scheme. Realistic 3D feature rendering creates a photo realistic scene. To further accelerate the processing speed, the system is to be implemented on a parallel computer nCUBE 2 with a Silicon Graphics workstation as a host machine. An example is presented in this paper to demonstrate the capability of the system.
This research proposes an algorithm to recognize a target that may differ from a reference template in position, scale, and in-plane rotation. The proposed algorithm accomplishes the recognition in two steps: rotation and scale detection followed by translation detection. In the first step, the Fourier transformation of the cepstrum is used to achieve the translation invariance, and a polar-logarithmic coordinate system is employed to convert the scale and rotation changes into linear shifts. In the second step, the template is regenerated to the correct size and orientation using rotation and scale parameters obtained from step one. In both steps matching is accomplished using template inverse filtering, which generates a Dirac delta function that appears as a sharp peak. The distinguishing features of this system are three-fold. First, while detecting the existence of the target, it provides the translation, scale, and rotation parameters, which are often needed in many applications. Secondly, it employs the template inverse filters to increase the auto-correlation peaks and suppress the cross-correlation coefficients and noise. Thirdly, it utilizes the cepstrum instead of the spectrum to enhance the high frequency components, and therefore improves the recognition significantly for scale and rotation detection. Experimental examples demonstrate recognition results.
A technique for simulating ultrasonic and laser range transducers is described in this paper. The purpose of this work is to develop a means whereby sensor data can be artificially replaced by simulated data so that navigation and path planning algorithms can be tested off- line. It is important that the simulated range data be generated in real time. Further, the simulation must display actual sensor characteristics such as reflectance. The simulation was implemented on a silicon graphics workstation by utilizing the Z-buffer hardware incorporated in the system. The technique is explained in the paper together with a brief discussion of results.
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