Configuration synthesis, kinematic solutions, and motion analysis of digital manipulators

Deanne Clements Kemeny, Purdue University

Abstract

Digital manipulators are an alternative to traditional robotic manipulators, where continuously variable actuators are replaced with discrete, or digital actuators. Benefits include predictable manipulation at lower cost and reduced weight and complexity. The objective of this research was to develop a synthesis strategy for digital manipulators to combine individual actuated modules into an assembly configuration where the end-effector can be positioned somewhere within each specific element of an application grid. In addition to the synthesis strategy, a method to solve the inverse kinematics problem, and path planning strategies were developed. The assembly configuration synthesis method searches the space of modular configurations in order to quickly eliminate configurations and identify those that are acceptable for a specific application. The method is made up of three stages with each stage having tests or comparisons that a potential configuration must pass, with each stage the tests increase in computation and difficulty. Critical to the tests is the ability to quickly approximate the end-effector workspace of the configuration. Since calculating all of the end-effector positions for all assembly configurations is computationally intense, a model for the end-effector workspace is developed and is key to the approximation method. The final positions of the end effector for each grid element are found using inverse kinematics. This research has relaxed the inverse kinematics problem making each application position an element of a grid in which the end effector must reach. The Jacobian function, normally used to solve joint velocities, can be modified to identify the exact shift vectors that are used for the inverse kinematics. A four-part solution is used which directs and manipulates the search for the inverse kinematics solution. Two significant solutions for planning the path of the end effector have been developed in this research. The first is determining the sequence of elements by choosing the minimum energy between positions. The second is applying a boundary along the path from element to element to help determine the order of actuating, the digital joints. The culmination of these methods is a distinct and organized synthesis strategy for digital manipulators for numerous, well-defined applications. Examples are included that illustrate these methods.

Degree

Ph.D.

Advisors

Cipra, Purdue University.

Subject Area

Mechanical engineering

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