IEEE Transactions on Robotics and Automation, Apr 1, 1997
... Although these methods are more efficient than the traditional search over the entire visibil... more ... Although these methods are more efficient than the traditional search over the entire visibility graph ... This paper presents a novel approach to the on-line shortest path problem. ... Bellman (HJB) theory, which establishes a sufficient condition of optimality for optimal control problems ...
This paper presents a design method of multi-degree-of-freedom mechanisms for near-time optimal m... more This paper presents a design method of multi-degree-of-freedom mechanisms for near-time optimal motions. The design objective is to select system parameters, such as link lengths and actuator sizes, so as to minimize the optimal motion time of the mechanism along a given path. The exact time optimization problem is approximated by a simpler procedure that maximizes the acceleration near the end points. Representing the directions of maximum acceleration with the acceleration lines, and the reachability constraints as explicit functions of the design parameters, we transform the constrained optimization to a simpler curve fitting problem that can be formulated analytically. This allows the use of efficient gradient type optimizations, instead of the pattern search optimization that is otherwise required. Examples for optimizing the dimensions of a five-bar planar mechanism demonstrate close correlation of the approximate with the exact solutions, and an order of magnitude better computational efficiency than the previously developed unconstrained optimization methods.
A method is presented which finds the minirnum time motions for a manipulator between given end s... more A method is presented which finds the minirnum time motions for a manipulator between given end states. Tne method considers the full nonlinear manipulator dynamics, actuator saturation characteristics , and accounts for both the presence of oostacles in the work spaca and restrictions on the motions of the manipulator's joints. The method is computationally practical and has been irnplemanted
This paper describes an interactive software system , developed at the Robotics and Automation La... more This paper describes an interactive software system , developed at the Robotics and Automation Laboratory at UCLA to demonstrate innovative approaches to of f-line robot programming and work-cell layout design . The software computes the time-optimal motions along specified paths , local optimal paths around an initial guess , and the global optimal path between given end-points . It considers the full robot dynamics , actuator constraints , on the payload acceleration or the gripping force , and any number of polygonal obstacles of any shape . The graphic displays provide a useful tool for interactive motion planning and workcell design .
ABSTRACT Motion planning in dynamic environments is made possible using the concept of velocity o... more ABSTRACT Motion planning in dynamic environments is made possible using the concept of velocity obstacles. It maps the colliding velocities of the robot with any moving or static obstacle to the robot’s velocity space. Collision avoidance is achieved by selecting the robot velocity outside the velocity obstacles. This concept was first proposed in [3] for the linear case of obstacles moving on straight line trajectories, and is extended here to obstacles moving along arbitrary trajectories. The non-linear velocity obstacle (NLVO) takes into account the shape, velocity and path curvature of the moving obstacle. It allows to select a single avoidance maneuver (if one exists) that avoids any number of obstacles that move on any known trajectories. The nonlinear v-obstacle can be generated as a time integral of the colliding velocities, or by computing its boundaries using analytic expressions.
Proceedings., IEEE International Conference on Robotics and Automation
A method is presented for optimally planning the motions of autonomous vehicles, considering vehi... more A method is presented for optimally planning the motions of autonomous vehicles, considering vehicle dynamics, terrain topography, obstacles, and surface mobility. The terrain is represented by a smooth cubic B patch, and the geometric path consists of a two dimensional B spline curve mapped to the three-dimensional surface. The path is optimized with a parameter optimization procedure, using motion time
American Journal of Engineering Education (AJEE), 2016
This article presents a case study that illustrates the paradigmatic shift in higher education fr... more This article presents a case study that illustrates the paradigmatic shift in higher education from content-centered teaching to learning-centered academic programs. This pragmatic change, triggered by the STEM movement, calls for the introduction of success measures in the course development process. The course described in this paper illustrates such a goal-driven approach to the development of an entire multidisciplinary curriculum in mechanical engineering and mechatronics. The effectiveness of this new curriculum was confirmed by findings of a survey of graduates of the first six graduating classes who studied on the basis of this curriculum.
"The Traction Trebuchet: A Triumph of Four Civilizations." This study of the traction t... more "The Traction Trebuchet: A Triumph of Four Civilizations." This study of the traction trebuchet offers new perspectives on the development and employment of the piece of ordnance that dominated warfare far longer than any other form of artillery. The inquiry is both interdisciplinary and intercultural, combining an historical investigation with an engineering analysis of manually-powered artillery used for a millennium across Eurasia and North Africa. It reviews the accomplishments of China, Islam, Byzantium, and the Latin West to the development of the traction trebuchet and describes how Islamic, Byzantine, and European trebuchets were able to surpass their Chinese counterparts, despite the fact that China was the first to devise this class of artillery. Contrary to prevailing opinion, the traction trebuchet reached an advanced stage of development, comparable to the performance of the stone-projectors of the gravity-powered age of artillery; and it remained in use long after the invention of counterwei...
This paper presents a method for computing themotions of a robot in dynamic environments, subject... more This paper presents a method for computing themotions of a robot in dynamic environments, subjectto the robot dynamics and its actuator constraints.This method is based on the concept ofVelocity Obstacle, which defines the set of feasiblerobot velocities that would result in a collisionbetween the robot and an obstacle moving at agiven velocity. The avoidance maneuver at a specifictime is thus computed by selecting robot'svelocities out of that set. A trajectory consistingof a...
IEEE Transactions on Robotics and Automation, Apr 1, 1997
... Although these methods are more efficient than the traditional search over the entire visibil... more ... Although these methods are more efficient than the traditional search over the entire visibility graph ... This paper presents a novel approach to the on-line shortest path problem. ... Bellman (HJB) theory, which establishes a sufficient condition of optimality for optimal control problems ...
This paper presents a design method of multi-degree-of-freedom mechanisms for near-time optimal m... more This paper presents a design method of multi-degree-of-freedom mechanisms for near-time optimal motions. The design objective is to select system parameters, such as link lengths and actuator sizes, so as to minimize the optimal motion time of the mechanism along a given path. The exact time optimization problem is approximated by a simpler procedure that maximizes the acceleration near the end points. Representing the directions of maximum acceleration with the acceleration lines, and the reachability constraints as explicit functions of the design parameters, we transform the constrained optimization to a simpler curve fitting problem that can be formulated analytically. This allows the use of efficient gradient type optimizations, instead of the pattern search optimization that is otherwise required. Examples for optimizing the dimensions of a five-bar planar mechanism demonstrate close correlation of the approximate with the exact solutions, and an order of magnitude better computational efficiency than the previously developed unconstrained optimization methods.
A method is presented which finds the minirnum time motions for a manipulator between given end s... more A method is presented which finds the minirnum time motions for a manipulator between given end states. Tne method considers the full nonlinear manipulator dynamics, actuator saturation characteristics , and accounts for both the presence of oostacles in the work spaca and restrictions on the motions of the manipulator's joints. The method is computationally practical and has been irnplemanted
This paper describes an interactive software system , developed at the Robotics and Automation La... more This paper describes an interactive software system , developed at the Robotics and Automation Laboratory at UCLA to demonstrate innovative approaches to of f-line robot programming and work-cell layout design . The software computes the time-optimal motions along specified paths , local optimal paths around an initial guess , and the global optimal path between given end-points . It considers the full robot dynamics , actuator constraints , on the payload acceleration or the gripping force , and any number of polygonal obstacles of any shape . The graphic displays provide a useful tool for interactive motion planning and workcell design .
ABSTRACT Motion planning in dynamic environments is made possible using the concept of velocity o... more ABSTRACT Motion planning in dynamic environments is made possible using the concept of velocity obstacles. It maps the colliding velocities of the robot with any moving or static obstacle to the robot’s velocity space. Collision avoidance is achieved by selecting the robot velocity outside the velocity obstacles. This concept was first proposed in [3] for the linear case of obstacles moving on straight line trajectories, and is extended here to obstacles moving along arbitrary trajectories. The non-linear velocity obstacle (NLVO) takes into account the shape, velocity and path curvature of the moving obstacle. It allows to select a single avoidance maneuver (if one exists) that avoids any number of obstacles that move on any known trajectories. The nonlinear v-obstacle can be generated as a time integral of the colliding velocities, or by computing its boundaries using analytic expressions.
Proceedings., IEEE International Conference on Robotics and Automation
A method is presented for optimally planning the motions of autonomous vehicles, considering vehi... more A method is presented for optimally planning the motions of autonomous vehicles, considering vehicle dynamics, terrain topography, obstacles, and surface mobility. The terrain is represented by a smooth cubic B patch, and the geometric path consists of a two dimensional B spline curve mapped to the three-dimensional surface. The path is optimized with a parameter optimization procedure, using motion time
American Journal of Engineering Education (AJEE), 2016
This article presents a case study that illustrates the paradigmatic shift in higher education fr... more This article presents a case study that illustrates the paradigmatic shift in higher education from content-centered teaching to learning-centered academic programs. This pragmatic change, triggered by the STEM movement, calls for the introduction of success measures in the course development process. The course described in this paper illustrates such a goal-driven approach to the development of an entire multidisciplinary curriculum in mechanical engineering and mechatronics. The effectiveness of this new curriculum was confirmed by findings of a survey of graduates of the first six graduating classes who studied on the basis of this curriculum.
"The Traction Trebuchet: A Triumph of Four Civilizations." This study of the traction t... more "The Traction Trebuchet: A Triumph of Four Civilizations." This study of the traction trebuchet offers new perspectives on the development and employment of the piece of ordnance that dominated warfare far longer than any other form of artillery. The inquiry is both interdisciplinary and intercultural, combining an historical investigation with an engineering analysis of manually-powered artillery used for a millennium across Eurasia and North Africa. It reviews the accomplishments of China, Islam, Byzantium, and the Latin West to the development of the traction trebuchet and describes how Islamic, Byzantine, and European trebuchets were able to surpass their Chinese counterparts, despite the fact that China was the first to devise this class of artillery. Contrary to prevailing opinion, the traction trebuchet reached an advanced stage of development, comparable to the performance of the stone-projectors of the gravity-powered age of artillery; and it remained in use long after the invention of counterwei...
This paper presents a method for computing themotions of a robot in dynamic environments, subject... more This paper presents a method for computing themotions of a robot in dynamic environments, subjectto the robot dynamics and its actuator constraints.This method is based on the concept ofVelocity Obstacle, which defines the set of feasiblerobot velocities that would result in a collisionbetween the robot and an obstacle moving at agiven velocity. The avoidance maneuver at a specifictime is thus computed by selecting robot'svelocities out of that set. A trajectory consistingof a...
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