The development of a generic and effective force model for semi-automatic or manual virtual assembly with haptic support is not a trivial task, especially when the assembly constraints involve complex features of arbitrary shape. The primary challenge lies in a proper formulation of the guidance forces and torques that effectively assist the user in the exploration of the virtual environment (VE), from repulsing collisions to attracting proper contact. The secondary difficulty is that of efficient implementation that maintains the standard 1 kHz haptic refresh rate. We propose a purely geometric model for an artificial energy field that favors spatial relations leading to proper assembly, differentiated to obtain forces and torques for general motions. The energy function is expressed in terms of a cross-correlation of shape-dependent affinity fields, precomputed offline separately for each object. We test the effectiveness of the method using familiar peg-in-hole examples. We show that the proposed technique unifies the two phases of free motion and precise insertion into a single interaction mode and provides a generic model to replace the ad hoc mating constraints or virtual fixtures, with no restrictive assumption on the types of the involved assembly features.
In the past two decades, there have been numerous studies focused on the development of immersive VEs for solving assembly and disassembly problems. These systems have used a variety of visualization tools (e.g., stereoscopic displays and goggles) and tracking devices (e.g., head tracking devices and data gloves) to assist the user in virtual object manipulation tasks. More recently, an increasing number of studies have leveraged haptic devices to provide a more realistic assembly experience with force feedback, a thorough account of which would require a separate full paper. We refer the reader to @cite_24 for a more comprehensive survey of previous studies, and to @cite_26 @cite_2 @cite_19 for recent insight on current knowledge and expected future directions in haptic assembly. Here we provide a brief review of the most important techniques along with their advantages and limitations.
@cite_24 @cite_19 @cite_26 @cite_2
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Assembly planning and evaluation is an important component of the product design process in which details about how parts of a new product will be put together are formalized. A well designed assembly process should take into account various factors such as optimum assembly time and sequence, tooling and fixture requirements, ergonomics, operator safety, and accessibility, among others. Existing computer-based tools to support virtual assembly either concentrate solely on representation of the geometry of parts and fixtures and evaluation of clearances and tolerances or use simulated human mannequins to approximate human interaction in the assembly process. Virtual reality technology has the potential to support integration of natural human motions into the computer aided assembly planning environment ( in Proc I MECH E Part B J Eng 213(5):461–474, 1999). This would allow evaluations of an assembler’s ability to manipulate and assemble parts and result in reduced time and cost for product design. This paper provides a review of the research in virtual assembly and categorizes the different approaches. Finally, critical requirements and directions for future research are presented. Purpose – The paper aims to present interactive simulation with haptic feedback as a valid method for solving complex assembly problems in the context of industrial product development. Its purpose is to clarify the position of interactive simulation with respect to other methods, and to emphasize its specific value for design engineers.Design methodology approach – The paper describes the challenges faced by design engineers in the context of design for assembly and assembly process planning. It introduces and compares automatic path planning and interactive simulation as two different approaches for checking the feasibility of assembly tasks. It provides a review of the scientific challenges and technical issues faced when implementing interactive simulation with haptic feedback in this context. It presents recent research results in the domains of final insertion and human model simulation.Findings – The paper provides an overview of the scientific, technological and practical aspects of interactive si... The use of virtual reality (VR) in interactive design and manufacture has been researched extensively but its practical application in industry is still very much in its infancy. Indeed one would have expected that, after some 30 years of research, commercial applications of interactive design or manufacturing planning and analysis would be widespread throughout the product design domain. Similarly, investigations into virtual environments (VE) for assembly and disassembly tasks have been carried out for many years. Given the availability of moderately-priced high performance computing technology, many of these virtual manufacturing interfaces which only stimulate the visual senses – have made actual physical contact during product development an increasingly rare occurrence. Over the years, various approaches have been investigated to support natural human interaction with CAD models in an immersive virtual environment. The motivation for this avenue of research stems from the desire to provide a method where users can manipulate and assemble digital product models as if they were manipulating actual models. The ultimate goal is to produce an immersive environment where design and manufacturing decisions which involve human interaction can be made using only digital CAD models, thus avoiding the need to create costly preproduction physical prototypes. This paper presents a framework to approach the development of virtual assembly applications. The framework is based on a Two Phase model where the assembly task is divided into a free movement phase and a fine positioning phase. Each phase can be implemented using independent techniques; however, the algorithms needed to interface between the two techniques are critical to the success of the method. The paper presents a summary of three virtual assembly techniques and places them within the framework of the Two Phase model. Finally, the conclusions call for the continued development of a testbed to compare virtual assembly methods.Copyright © 2011 by ASME