Analysis and design optimization of in-parallel haptic devices
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The overall kinesthetic immersive experience in a haptic interactive virtual environment is the synthesis of the human user , the haptic user interface (HUI) , and virtual environment (VE)—all of which playing critical roles. Our focus will be on the development of advanced HUIs for providing the users with sophisticated tactile or force feedback during interaction with virtual environments with innovative features including active and passive manipulation assists. Desirable features for high-performance HUIs include: human matched force capabilities, sizeable workspace, low inertia, high stiffness, low friction, back-drivability, near-zero backlash, and gravitational counterbalancing. Parallel-architecture haptic devices offer significant advantages over serial-architecture counterparts in applications requiring high stiffness and high accuracy. To this end, many haptic devices have been created and deployed by modularly piecing together multiple serial-chain arms to form an in-parallel system. Furthermore, recent haptic device designs such as the Sensable’s Phantom Premium line of haptic devices and Quanser’s High Definition Haptic Device (HD) 2 transfer the distal actuation to the base via a parallelogram/fourbar linkage in order to reduce the moving inertia in the system. However, such design choices can affect the overall system performance which now depends both on the nature of the individual arms as well as the interactions. The multiple closed-kinematic chains constrains effective degree-of-freedom and require careful selection of type, number, location and actuation of the individual articulations (within the chain) completes the determination of the workspace, mobility, controllability, and overall performance of the system. In this work, we build on the rich theoretical background of constrained articulated mechanical systems to provide a systematic framework for formulation of system-level performance from individual module characteristics. Specifically, we discuss: (i) development of pertinent symbolic equations; (ii) generalization to arbitrary architectures; and (iii) perform combined symbolic/numeric analyses, focusing on salient zeroth order (workspace), first order (manipulability), and second order (stiffness) kinematics performance measures. We demonstrated our studies using Sensable Phantom Premium line of haptic devices and Quanser’s High Definition Haptic Device (HD) 2 . In particular, we highlight the effect of the added parallelogram sub-system to the overall system-level manipulability and stiffness measure. Finally, we note that traditional performance analysis on haptic devices focuses solely on the device. However, haptic devices are typically employed in close coupling with a human user creating a need to include their characteristics in the design and analysis. We therefore examined the use of a musculoskeletal analysis framework to study the performance of haptic devices, extracted biomechanically relevant performance measures from the human user, and use this to tailor the ergonomics and regimen within a rehabilitation program.