Sonar rings are widely used for indoor mobile robots. However, it is difficult to perform on-the-fly applications such as map building and localization using a conventional sonar ring due to low speed, accuracy and in...
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Sonar rings are widely used for indoor mobile robots. However, it is difficult to perform on-the-fly applications such as map building and localization using a conventional sonar ring due to low speed, accuracy and interference. Digital signal processing (DSP) techniques and interference rejection ideas are applied in this paper to design a new more sophisticated, fast and accurate sonar ring called an advanced sonar ring. The advanced sonar ring consists of 48 ultrasonic transducers, 24 acting as transceivers and 24 acting as receivers, seven DSP echo processor boards, twelve four-channel 12-bit 500 kHz ADCs and low noise variable gain preamplifiers. The sonar ring is able to cover 360 degrees around robot with simultaneously firing of all 24 transmitters. Transmission and echo analysis are performed at repetition rates of about 15 Hz, depending on the environment, for ranges up to six meters. Accurate distance and bearing measurements of objects are performed in the DSP system using matched filtering techniques. The paper presents new transmit coding based on pulse duration to differentiate neighbouring transmitters in the ring. Experimental data show the effectiveness of the proposed system.
This paper describes current progress in a project to develop a robot for locating underground chemical sources. There are important economic, environmental and humanitarian applications for systems that can find the ...
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This paper describes current progress in a project to develop a robot for locating underground chemical sources. There are important economic, environmental and humanitarian applications for systems that can find the source of an odor or volatile chemical located beneath the ground. These applications cover the spectrum from harvesting truffles, to finding the location of leaking gas pipes and land mines. In previous work the feasibility of detecting vapor percolating through the ground was demonstrated. An algorithm was then developed to control a robot enabling it to gather information about the location of the source and to guide the robot towards it. This algorithm was limited to searching in two dimensions (depth was held constant). In this paper the original algorithm is extended to 3-dimensions allowing variations in depth to be included. The 3-dimensional search algorithm involves following a path through the ground that corresponds to the edges of closely packed dodecahedra. Simulations and physical experiments both confirm the capabilities of this search algorithm.
In this paper, a distributed mechanism used by a robotic swarm to facilitate the building of a loose wall structure is discussed and results presented. The ability of a robotic swarm to utilise a spatio-temporal varyi...
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In this paper, a distributed mechanism used by a robotic swarm to facilitate the building of a loose wall structure is discussed and results presented. The ability of a robotic swarm to utilise a spatio-temporal varying template in construction tasks is verified. The work is seen as a step towards the development of a generalised methodology for collective construction building tasks and establishes a means for the building of more complex structures.
This paper addresses the problem of visual servo control for a humanoid robot in an unstructured domestic environment. The important issues in this application are autonomous planning, robustness to camera and kinemat...
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This paper addresses the problem of visual servo control for a humanoid robot in an unstructured domestic environment. The important issues in this application are autonomous planning, robustness to camera and kinematic model errors, large pose errors, occlusions and reliable visual tracking. Conventional image-based or position-based visual servoing schemes do not address these issues, which motivated the proposed hybrid position-based scheme exploiting fusion of visual and kinematic measurements. Kinematic measurements provide robustness to visual distractions, and allow servoing to continue when the end-effector leaves the field of view. Visual measurements provide the complementary benefits of accurate pose tracking and online estimation of the hand-eye transformation for kinematic calibration. Furthermore, it is shown that calibration errors in the focal length and baseline can be approximated as an unknown scale of the end-effector, which can be estimated in the tracking filter to overcome camera calibration errors. The improved accuracy and robustness compared to conventional position-based servoing is demonstrated experimentally.
This paper describes a complete vision-based framework that enables a humanoid robot to perform simple manipulations in a domestic environment. Our system emphasizes autonomous operation with minimal a priori knowledg...
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This paper describes a complete vision-based framework that enables a humanoid robot to perform simple manipulations in a domestic environment. Our system emphasizes autonomous operation with minimal a priori knowledge in an unstructured environment, with robustness to visual distractions and calibration errors. For each new task, the robot first acquires a dense 3D image of the scene using our novel stereoscopic light stripe scanner that rejects secondary reflections and cross-talk. A data-driven analysis of the range map identifies and models simple objects using geometric primitives. Objects are reliably tracked through clutter and occlusions by exploiting multimodal cues (colour, texture and edges). Finally, manipulations are performed by controlling the end-effector using a hybrid position-based visual servoing scheme that fuses visual and kinematic measurements and compensates for calibration errors. Two domestic tasks are implemented to evaluate the performance of the framework: identifying and grasping a yellow box without any prior knowledge of the object, and pouring rice from an inter-actively selected cup into a bowl.
Increasing the information content of measurements can ease some of the problems associated with simultaneous localization and mapping (SLAM). We present an approach for combining measurements from a laser range finde...
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Increasing the information content of measurements can ease some of the problems associated with simultaneous localization and mapping (SLAM). We present an approach for combining measurements from a laser range finder with measurements from an advanced sonar array capable of accurate range and bearing measurements and edge, corner and plane classification. In our approach sonar aids laser segmentation, laser aids good sonar point feature selection and laser and sonar measurements of the same object are fused. We also present a novel approach for fitting right angle corners to laser range data, which enables simple error estimation through the minimization of sum of square range residuals. The results are then used for SLAM with a mobile robot.
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