Exceeding the speed limit in highway work zones is a safety problem for highway workers and the t... more Exceeding the speed limit in highway work zones is a safety problem for highway workers and the traveling public. Adherence to the posted speed limits can provide safety benefits by reducing the number of accidents and the potential casualties and injuries resulting from those accidents. Some states have enacted laws and have adopted the use of automated Photo Speed Enforcement for highway work zones. This research was intended to evaluate existing practices and available technologies and perform testing to establish guidelines and recommendations for the equipment and the configuration for its deployment in California highway work zones. The main research question addressed in this research is the following: Can PSE technology be configured for implementation in highway work zones in California such that it be an effective deterrent to speeding, resulting in improving work zone safety for highway workers and the traveling public? In this research, testing was performed both in a co...
This report documents work performed by the University of California at Davis in collaboration wi... more This report documents work performed by the University of California at Davis in collaboration with the California Department of Transportation (Caltrans) in relationship to a Precursor System Analysis dealing with a study of automated construction, maintenance, and operational requirements for Automated Highway Systems (AHS). This study was conducted in the activity area "K" dealing with AHS roadway operational analysis. The report documents a design analysis for a robotic system for automated installation of discrete magnetic markers for AHS. The design includes a manpower assessment and a cost-benefit analysis. Summaries for supporting research are included in appendices, including: a literature review, a reference architecture and classification system for AHS, and a computer simulation and animation of the prototype discrete magnetic marker placement system described in this report.
Page 1. Design and Mechatronic Implementation of an Accelerometer-Based, Kinematically Redundant ... more Page 1. Design and Mechatronic Implementation of an Accelerometer-Based, Kinematically Redundant Inertial Measurement Unit Kourosh Parsa, Ty A. Lasky, and Bahram Ravani Abstract ... indeterminate. Parsa et al [8] determined the ...
In this paper, we present a differential-geometric approach to analyze the singularities of task ... more In this paper, we present a differential-geometric approach to analyze the singularities of task space point trajectories of two and three-degree-of-freedom serial and parallel manipulators. At non-singular configurations, the first-order, local properties are characterized by metric coefficients, and, geometrically, by the shape and size of a velocity ellipse or an ellipsoid. At singular configurations, the determinant of the matrix of metric coefficients is zero and the velocity ellipsoid degenerates to an ellipse, a line or a point, and the area or the volume of the velocity ellipse or ellipsoid becomes zero. The degeneracies of the velocity ellipsoid or ellipse gives a simple geometric picture of the possible task space velocities at a singular configuration. To study the second-order properties at a singularity, we use the derivatives of the metric coefficients and the rate of change of area or volume. The derivatives are shown to be related to the possible task space accelerations at a singular configuration. In the case of parallel manipulators, singularities may lead to either loss or gain of one or more degrees-of-freedom. For loss of one or more degrees-of-freedom, the possible velocities and accelerations are again obtained from a modified metric and derivatives of the metric coefficients. In the case of a gain of one or more degrees-of-freedom, the possible task space velocities can be pictured as growth to lines, ellipses, and ellipsoids. The theoretical results are illustrated with the help of a general spatial 2R manipulator and a three-degree-of-freedom RPSSPR-SPR parallel manipulator.
This paper develops a method for design of Beziér and B-spline ruled surfaces taking advantage of... more This paper develops a method for design of Beziér and B-spline ruled surfaces taking advantage of the Lie group structure associated with the displacement of lines. The result is a computational method which is independent of the choice of coordinate system. The method is unique in that it can be used on a set of intersecting lines and in this way is applied to automatic mesh generation for finite element analysis.
This paper uses group theory for type synthesis or enumeration of contacts between geometric elem... more This paper uses group theory for type synthesis or enumeration of contacts between geometric elements necessary in the design of tactile sensing mechanical fixtures for robotic applications. Although the scope of the paper is limited to geometric contacts involving points, planes, and spherical surfaces, the techniques developed are general and can be applied to other geometric features and non tactile sensing elements used in robotic referencing and calibration.
<jats:title>Abstract</jats:title> <jats:p>This paper presents a novel design fo... more <jats:title>Abstract</jats:title> <jats:p>This paper presents a novel design for a practical tactile-sensing mechanical fixture. The fixture consists of two tactile-sensing surfaces, a cylindrical surface and a planar surface. A mathematical procedure is developed for constructing a reference frame using point-to-surface contact locations on the fixture and the geometry of the fixture. A numerical example is given to further illustrate the use of this approach. Finally, the design of the fixture is described and a picture of the laboratory demonstration unit is shown.</jats:p>
Trajectory generation for manipulators involves generating incremental updates of joint variables... more Trajectory generation for manipulators involves generating incremental updates of joint variables to achieve a desired end–effector motion. The Jacobian matrix maps incremental joint motion to incremental end–effector motion in a linear fashion and is typically used in manipulator trajectory generation algorithms. In the case of a redundant manipulator, the Jacobian matrix is not square or invertible and therefore algorithms based on pseudoinverses and their variations are commonly used for trajectory generation. These methods either are computationally not efficient or do not utilize all the joints in motion generation and therefore do not completely exploit the redundancy of the manipulator. The method presented in this paper is a simple method that maximizes transmission of all joint variables onto a desired end–effector motion trajectory. The method is based on aligning the null–space of an augmented Jacobian matrix with the path of the desired end–effector motion, from which a ...
Avalanches pose a challenging problem for roadways traversing mountainous areas of California. An... more Avalanches pose a challenging problem for roadways traversing mountainous areas of California. An unexpected avalanche can shut down roads and endanger motorists. Conducting controlled avalanches reduces the number of naturally occurring avalanches, resulting in improved safety and lower maintenance costs. To safely trigger an avalanche requires accurate information to determine the best time and conditions. Sensors can provide the needed data, such as snow depth, temperature, wind speed, and wind direction, as well as camera imaging. This research task is the continuation of a previous effort: Task ID 1810 Field Operations for GPS assisted Winter Maintenance Vehicles (Avalanche Sensing). Task ID 1810 built a prototype avalanche sensing and detection system which measures wind speed, temperature, and snow surface heights, and provides video to give maintenance workers data to support decisions on when to initiate a controlled avalanche. Task ID 2771 was needed to complete the field ...
The boresight misalignment of a mobile laser scanning system is a major source of error for point... more The boresight misalignment of a mobile laser scanning system is a major source of error for point cloud data and cannot be measured directly. This paper presents a new boresight calibration method for a mobile laser scanner system that uses an external fixture with a simple checkerboard pattern. The boresight angles are determined by minimizing the differences between the measured relative distances of the intersection points of the squares in a checkerboard fixture with the corresponding actual distances in the fixture. Experimental results from scanning the checkerboard pattern on the fixture show that the calibrated values of the boresight angles match the manufacturer’s values within 0.22 cm. Using this simple checkerboard fixture in the field prevents surveyors from having to rely on roadway features or setting control targets and provides for an alternative approach for the boresight calibration of a mobile laser scanner system.
Volume 2: 30th Annual Mechanisms and Robotics Conference, Parts A and B, 2006
ABSTRACT In kinematics, the problem of motion reconstruction involves generation of a motion from... more ABSTRACT In kinematics, the problem of motion reconstruction involves generation of a motion from the specification of distinct positions of a rigid body. In its most basic form, this problem involves determination of a screw displacement that would move a rigid body from one position to the next. Much if not all of the previous work in this area has been based on point geometry. In this paper, we develop a method for motion reconstruction based on line geometry. An elegant geometric method is developed based on line geometry that can be considered as a generalization of the classical Reuleaux’s method used in 2D kinematics. The case of over determined system is also considered a linear solution is presented based on least squares method.
Journal of Computing and Information Science in Engineering
Physical modeling of the transient temperature during the Selective Laser Sintering (SLS) Additiv... more Physical modeling of the transient temperature during the Selective Laser Sintering (SLS) Additive Manufacturing (AM) process is essential for the characterization of the quality and structural integrity of the final products. The conventional numerical models used to simulate the thermal field of Additively Manufactured structures (AM structures) are time-consuming and could not be directly used to develop a real-time simulation or a process control system. This paper presents a deep learning encoder–decoder Convolutional Neural Network (CNN) model to predict the thermal field of AM structures. For deep learning training purposes, a time-consuming physics-based simulation was used to create a dataset including thousands of two-dimensional (2D) position-time representations of the laser head with different process parameters and their corresponding heatmap of AM structures. The deep learning model developed based on this dataset is capable of sub-second prediction of the heatmap bei...
Exceeding the speed limit in highway work zones is a safety problem for highway workers and the t... more Exceeding the speed limit in highway work zones is a safety problem for highway workers and the traveling public. Adherence to the posted speed limits can provide safety benefits by reducing the number of accidents and the potential casualties and injuries resulting from those accidents. Some states have enacted laws and have adopted the use of automated Photo Speed Enforcement for highway work zones. This research was intended to evaluate existing practices and available technologies and perform testing to establish guidelines and recommendations for the equipment and the configuration for its deployment in California highway work zones. The main research question addressed in this research is the following: Can PSE technology be configured for implementation in highway work zones in California such that it be an effective deterrent to speeding, resulting in improving work zone safety for highway workers and the traveling public? In this research, testing was performed both in a co...
This report documents work performed by the University of California at Davis in collaboration wi... more This report documents work performed by the University of California at Davis in collaboration with the California Department of Transportation (Caltrans) in relationship to a Precursor System Analysis dealing with a study of automated construction, maintenance, and operational requirements for Automated Highway Systems (AHS). This study was conducted in the activity area "K" dealing with AHS roadway operational analysis. The report documents a design analysis for a robotic system for automated installation of discrete magnetic markers for AHS. The design includes a manpower assessment and a cost-benefit analysis. Summaries for supporting research are included in appendices, including: a literature review, a reference architecture and classification system for AHS, and a computer simulation and animation of the prototype discrete magnetic marker placement system described in this report.
Page 1. Design and Mechatronic Implementation of an Accelerometer-Based, Kinematically Redundant ... more Page 1. Design and Mechatronic Implementation of an Accelerometer-Based, Kinematically Redundant Inertial Measurement Unit Kourosh Parsa, Ty A. Lasky, and Bahram Ravani Abstract ... indeterminate. Parsa et al [8] determined the ...
In this paper, we present a differential-geometric approach to analyze the singularities of task ... more In this paper, we present a differential-geometric approach to analyze the singularities of task space point trajectories of two and three-degree-of-freedom serial and parallel manipulators. At non-singular configurations, the first-order, local properties are characterized by metric coefficients, and, geometrically, by the shape and size of a velocity ellipse or an ellipsoid. At singular configurations, the determinant of the matrix of metric coefficients is zero and the velocity ellipsoid degenerates to an ellipse, a line or a point, and the area or the volume of the velocity ellipse or ellipsoid becomes zero. The degeneracies of the velocity ellipsoid or ellipse gives a simple geometric picture of the possible task space velocities at a singular configuration. To study the second-order properties at a singularity, we use the derivatives of the metric coefficients and the rate of change of area or volume. The derivatives are shown to be related to the possible task space accelerations at a singular configuration. In the case of parallel manipulators, singularities may lead to either loss or gain of one or more degrees-of-freedom. For loss of one or more degrees-of-freedom, the possible velocities and accelerations are again obtained from a modified metric and derivatives of the metric coefficients. In the case of a gain of one or more degrees-of-freedom, the possible task space velocities can be pictured as growth to lines, ellipses, and ellipsoids. The theoretical results are illustrated with the help of a general spatial 2R manipulator and a three-degree-of-freedom RPSSPR-SPR parallel manipulator.
This paper develops a method for design of Beziér and B-spline ruled surfaces taking advantage of... more This paper develops a method for design of Beziér and B-spline ruled surfaces taking advantage of the Lie group structure associated with the displacement of lines. The result is a computational method which is independent of the choice of coordinate system. The method is unique in that it can be used on a set of intersecting lines and in this way is applied to automatic mesh generation for finite element analysis.
This paper uses group theory for type synthesis or enumeration of contacts between geometric elem... more This paper uses group theory for type synthesis or enumeration of contacts between geometric elements necessary in the design of tactile sensing mechanical fixtures for robotic applications. Although the scope of the paper is limited to geometric contacts involving points, planes, and spherical surfaces, the techniques developed are general and can be applied to other geometric features and non tactile sensing elements used in robotic referencing and calibration.
<jats:title>Abstract</jats:title> <jats:p>This paper presents a novel design fo... more <jats:title>Abstract</jats:title> <jats:p>This paper presents a novel design for a practical tactile-sensing mechanical fixture. The fixture consists of two tactile-sensing surfaces, a cylindrical surface and a planar surface. A mathematical procedure is developed for constructing a reference frame using point-to-surface contact locations on the fixture and the geometry of the fixture. A numerical example is given to further illustrate the use of this approach. Finally, the design of the fixture is described and a picture of the laboratory demonstration unit is shown.</jats:p>
Trajectory generation for manipulators involves generating incremental updates of joint variables... more Trajectory generation for manipulators involves generating incremental updates of joint variables to achieve a desired end–effector motion. The Jacobian matrix maps incremental joint motion to incremental end–effector motion in a linear fashion and is typically used in manipulator trajectory generation algorithms. In the case of a redundant manipulator, the Jacobian matrix is not square or invertible and therefore algorithms based on pseudoinverses and their variations are commonly used for trajectory generation. These methods either are computationally not efficient or do not utilize all the joints in motion generation and therefore do not completely exploit the redundancy of the manipulator. The method presented in this paper is a simple method that maximizes transmission of all joint variables onto a desired end–effector motion trajectory. The method is based on aligning the null–space of an augmented Jacobian matrix with the path of the desired end–effector motion, from which a ...
Avalanches pose a challenging problem for roadways traversing mountainous areas of California. An... more Avalanches pose a challenging problem for roadways traversing mountainous areas of California. An unexpected avalanche can shut down roads and endanger motorists. Conducting controlled avalanches reduces the number of naturally occurring avalanches, resulting in improved safety and lower maintenance costs. To safely trigger an avalanche requires accurate information to determine the best time and conditions. Sensors can provide the needed data, such as snow depth, temperature, wind speed, and wind direction, as well as camera imaging. This research task is the continuation of a previous effort: Task ID 1810 Field Operations for GPS assisted Winter Maintenance Vehicles (Avalanche Sensing). Task ID 1810 built a prototype avalanche sensing and detection system which measures wind speed, temperature, and snow surface heights, and provides video to give maintenance workers data to support decisions on when to initiate a controlled avalanche. Task ID 2771 was needed to complete the field ...
The boresight misalignment of a mobile laser scanning system is a major source of error for point... more The boresight misalignment of a mobile laser scanning system is a major source of error for point cloud data and cannot be measured directly. This paper presents a new boresight calibration method for a mobile laser scanner system that uses an external fixture with a simple checkerboard pattern. The boresight angles are determined by minimizing the differences between the measured relative distances of the intersection points of the squares in a checkerboard fixture with the corresponding actual distances in the fixture. Experimental results from scanning the checkerboard pattern on the fixture show that the calibrated values of the boresight angles match the manufacturer’s values within 0.22 cm. Using this simple checkerboard fixture in the field prevents surveyors from having to rely on roadway features or setting control targets and provides for an alternative approach for the boresight calibration of a mobile laser scanner system.
Volume 2: 30th Annual Mechanisms and Robotics Conference, Parts A and B, 2006
ABSTRACT In kinematics, the problem of motion reconstruction involves generation of a motion from... more ABSTRACT In kinematics, the problem of motion reconstruction involves generation of a motion from the specification of distinct positions of a rigid body. In its most basic form, this problem involves determination of a screw displacement that would move a rigid body from one position to the next. Much if not all of the previous work in this area has been based on point geometry. In this paper, we develop a method for motion reconstruction based on line geometry. An elegant geometric method is developed based on line geometry that can be considered as a generalization of the classical Reuleaux’s method used in 2D kinematics. The case of over determined system is also considered a linear solution is presented based on least squares method.
Journal of Computing and Information Science in Engineering
Physical modeling of the transient temperature during the Selective Laser Sintering (SLS) Additiv... more Physical modeling of the transient temperature during the Selective Laser Sintering (SLS) Additive Manufacturing (AM) process is essential for the characterization of the quality and structural integrity of the final products. The conventional numerical models used to simulate the thermal field of Additively Manufactured structures (AM structures) are time-consuming and could not be directly used to develop a real-time simulation or a process control system. This paper presents a deep learning encoder–decoder Convolutional Neural Network (CNN) model to predict the thermal field of AM structures. For deep learning training purposes, a time-consuming physics-based simulation was used to create a dataset including thousands of two-dimensional (2D) position-time representations of the laser head with different process parameters and their corresponding heatmap of AM structures. The deep learning model developed based on this dataset is capable of sub-second prediction of the heatmap bei...
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