VR Spatial
Designing Spatial 4C Mechanisms Using Virtual Reality (Larochelle, Vance, Dorozhkin, Tse, Agius)
This is a multi-institutional collaborative research project funded by the National Science Foundation's DMII Engineering Design Program. Here RASSL has partnered with Prof. Judy Vance of Iowa State University(ISU). Prof. Vance and her student Denis Dorozhkin are affiliated with ISU's Virtual Reality Applications Center (VRAC). VRAC is a world leader in developing human interfaces to computer generated virtual environments to amplify the creativity and efficiency of people. This research project explores using virtual reality (VR) as a tool for designing spatial 4C mechanisms for rigid-body guidance. Spatial 4C mechanisms are two degree of freedom closed kinematic chains consisting of four links connected by cylindrical (C) joints. A cylindrical joint provides both translational and rotational movement along its axis. Spatial mechanisms offer a better alternative to electronically controlled multiple-input devices, such as robotic manipulators. Being purely mechanical devices, spatial mechanisms are less expensive, more reliable and more energy efficient. A single spatial mechanism is often capable of completing a motion task that would otherwise require several planar mechanisms to accomplish. Despite the potential benefits associated with operation of spatial mechanisms, development of such mechanical systems has been hindered by the lack of the appropriate mechanism design software applications.
Spatial mechanisms operate within three-dimensional design space. The traditional human-computer interfaces (HCI) are limited to two dimensions and impose artificial constraints on the ability of the mechanism designers to correctly and efficiently specify the design problem and investigate the spatial mechanism synthesis results. Virtual reality provides a truly three-dimensional alternative to the traditional HCI's. The overall spatial layout of a mechanism design problem as well as the correct dimensions of the synthesized mechanisms are easily evaluated in the VR environments.
The benefits of using virtual reality applications for synthesis and analysis of spatial mechanisms have been explored at Iowa State University previously. VRNETS program was created in order to aid in the synthesis of spatial 4C mechanisms. The program allowed users to investigate the design parameters associated with spatial 4C mechanisms, such as the input design positions and the congruence planes, in a 3-D environment. Additionally, it provided the option of networking several instances of the application in order to facilitate a collaborative design process. While the program proved to be an effective tool in the synthesis and analysis of spatial 4C mechanisms, improvements and modifications to the program’s structure and functionality were needed in order to take full advantage of the virtual reality design environment. This research relies on the experience gained from operation of the VRNETS program and incorporates the needed changes into a new piece of software.
The VRSpatial application was developed as a result of this collaborative research. It is a software package for designing spatial 4C mechanisms using virtual reality that offers the mechanism designers a wide variety of methods for defining the initial design problem, solving the problem, and evaluating the solution’s feasibility. VRSpatial is written in the C++ programming language. Creation of the computer graphics objects and management of the VR environment was done by Prof. Vance and her students at Iowa State University. They used the SGI OpenGL API and the VRJuggler virtual reality software library that has been developed by the Virtual Reality Applications Center (VRAC) at Iowa State. Computation routines from RASSL are used for all of the synthesis and analysis routines need to design the spatial mechanisms. The user interaction method consists of a position-tracked wand and a set of virtual menus, along with a speech recognition interface.
When compared to the functionality of the original VRNETS application, the new spatial mechanism design program offers its users an assortment of new and improved features. Some of the novel program characteristics are: (1) implemented on a wide variety of VR systems including Iowa State University’s C6 facility, (2) improved methods of specifying the initial design problem such as the ability to numerically adjust positions of the design objects, provide for more effective design (3) multiple options are available for investigating the generated solution space, including dynamic congruence planes recalculation, the ability to select arbitrary lines from congruence planes, extension of the mechanism type identification and solution filtering options to the congruence planes, and the ability to investigate the guide map and the congruence planes simultaneously. (4) three-position mechanism synthesis functionality is provided, (5) speech command interface offers an alternative way of interacting with the application. The result of this research is an advanced, multi-functional, and highly flexible application for design of spatial 4C mechanisms for motion generation tasks. It is hoped that the use of this program will facilitate expansion of the spatial mechanism investigation activities and will lead to their expanded use in industrial applications.