Magnetic Levitation Haptic Augmentation for Virtual Tissue Stiffness Perception

Perception and knowledge of learners about the use of 3D technologies in manual therapy education - a qualitative study

OBJECTIVES

Manual therapy is a specific hands-on approach used and taught by various professions such as physiotherapy and osteopathy. The current paradigm of teaching manual therapy incorporates the traditional 'See one, do one, teach one' approach. However, this 'teacher centred' approach may not enable learners to develop the complex clinical skills of manual therapy. In this context, 3D technologies such as virtual reality may facilitate the teaching and learning of manual therapy. Hence the aim of the current study was to investigate the perception, knowledge and attitude of manual therapy learners about the use of 3D technologies in manual therapy education.

METHODS

An exploratory qualitative research design using semi-structured interviews was used in this study. A total of ten manual therapy (5 physiotherapy and 5 osteopathic) students (mean age = 32; 80% female) enrolled in an appropriate physiotherapy or osteopathic degree provided by a New Zealand recognized institution (e.g., university or polytechnic) participated in this study. Data saturation was achieved after 10 interviews (average duration: 35 min) that provided thick data. A thematic analysis was used for data analysis.

RESULTS

Six factors were identified which appeared to influence participants' perception of role of technology in manual therapy education. These were (1) the sufficiency of current teaching method; (2) evolution as a learner (a novice to an expert); (3) need for objectivity; (4) tutor feedback; (5) knowledge and (6) barriers and enablers. These six factors influenced the participants' perception about the role of 3D technologies in manual therapy education with participants evidently taking two distinct/polarized positions ('no role' (techstatic) versus a 'complete role' (techsavvy)).

CONCLUSION

Although 3D technology may not replace face-to-face teaching, it may be used to complement the traditional approach of learning/teaching to facilitate the learning of complex skills according to the perceptions of manual therapy learners in our study. The advantage of such an approach is an area of future research.

Individuals with and without Visual Impairments Use a Force Feedback Device to Identify the Friction and Hardness of Haptic Surfaces

The general purpose of this study is to promote access to haptic virtual environments. Using a haptic device, people with and without visual impairments (VI) are able to feel different textures and compare these textures based on different surface properties, i.e., friction and hardness. The objectives of this study were to examine the following: (a) whether the variables of friction and hardness were identifiable through the Touch device (Phantom Omni) and could therefore function as 3D haptic variables; (b) if there were differences between people with VI and sighted individuals in terms of their performance; (c) the differences that should exist between the values of each variable so that the virtual surfaces could be identified as different to each other; and (d) if the individual characteristics of participants have an impact on their performance. The results showed that it is necessary to use surfaces which are differentiated based on the degree of friction and hardness because the haptic properties of a virtual object are then better perceived. Individuals with VI need more time and more effort to understand friction and hardness, respectively. With the motivation of increasing access to object perception for people with VI in a virtual environment, accessibility advisors and experts can extract useful information for the development of functional and efficient 3D objects for haptic perception.

Contactless Haptic Display Through Magnetic Field Control

Haptic rendering enables people to touch, perceive, and manipulate virtual objects in a virtual environment. Using six cascaded identical hollow disk electromagnets and a small permanent magnet attached to an operator's finger, this paper proposes and develops an untethered haptic interface through magnetic field control. The concentric hole inside the six cascaded electromagnets provides the workspace, where the 3D position of the permanent magnet is tracked with a Microsoft Kinect sensor. The driving currents of six cascaded electromagnets are calculated in real-time for generating the desired magnetic force. Offline data from an FEA (finite element analysis) based simulation, determines the relationship between the magnetic force, the driving currents, and the position of the permanent magnet. A set of experiments including the virtual object recognition experiment, the virtual surface identification experiment, and the user perception evaluation experiment were conducted to demonstrate the proposed system, where Microsoft HoloLens holographic glasses are used for visual rendering. The proposed magnetic haptic display leads to an untethered and non-contact interface for natural haptic rendering applications, which overcomes the constraints of mechanical linkages in tool-based traditional haptic devices.

Phase Optimization for Multipoint Haptic Feedback Based on Ultrasound Array

Ultrasound-based haptic feedback is a potential technology for human–computer interaction (HCI) with the advantages of a low cost, low power consumption and a controlled force. In this paper, phase optimization for multipoint haptic feedback based on an ultrasound array was investigated, and the corresponding experimental verification is provided. A mathematical model of acoustic pressure was established for the ultrasound array, and then a phase-optimization model for an ultrasound transducer was constructed. We propose a pseudo-inverse (PINV) algorithm to accurately determine the phase contribution of each transducer in the ultrasound array. By controlling the phase difference of the ultrasound array, the multipoint focusing forces were formed, leading to various shapes such as geometries and letters, which can be visualized. Because the unconstrained PINV solution results in unequal amplitudes for each transducer, a weighted amplitude iterative optimization was deployed to further optimize the phase solution, by which the uniform amplitude distributions of each transducer were obtained. For the purpose of experimental verification, a platform of ultrasound haptic feedback consisting of a Field Programmable Gate Array (FPGA), an electrical circuit and an ultrasound transducer array was prototyped. The haptic performances of a single point, multiple points and dynamic trajectory were verified by controlling the ultrasound force exerted on the liquid surface. The experimental results demonstrate that the proposed phase-optimization model and theoretical results are effective and feasible, and the acoustic pressure distribution is consistent with the simulation results.

Contactless Kinesthetic Feedback to Support Handwriting Using Magnetic Force

Handwriting is a fundamental human skill that is essential for communication yet is one of the most complex skills to be mastered. Pen-based interaction with touchscreen devices are increasingly used in digital handwriting practices to simulate pen and paper experience, but are mostly based on auditory-visual feedback. Given that handwriting relies on visual and motor skills, haptic feedback is recently explored to augment audio-visual systems to further support the handwriting process. In this article, we present an assistive platform entitled KATIB (means writer in Arabic) that provides high fidelity kinesthetic feedback, in addition to audio-visual feedback, to support handwriting using magnetic forces. We propose novel contactless kinesthetic guidance methods, namely proactive and retroactive guidance, to guide the handwriting stylus along a desirable trajectory based on position control. Detaching the handwriting stylus from any mechanical device enables learners to have full control over grasping and moving at their own pace and style. The proposed platform is characterized for haptic interaction. Finally, a psychophysical experiment is conducted to validate that the kinesthetic guidance is perceivable and beneficial as a sensory feedback using a novel handwriting copy task. Contactless kinesthetic feedback seems to play a significant role in supporting digital handwriting by influencing the kinematics of the handwriting process.

The Importance of Phase to Texture Discrimination and Similarity

In this article, we investigate the importance of phase for texture discrimination and similarity estimation tasks. We first use two psychophysical experiments to investigate the relative importance of phase and magnitude spectra for human texture discrimination and similarity estimation. The results show that phase is more important to humans for both tasks. We further examine the ability of 51 computational feature sets to perform these two tasks. In contrast with the psychophysical experiments, it is observed that the magnitude data is more important to these computational feature sets than the phase data. We hypothesise that this inconsistency is due to the difference between the abilities of humans and the computational feature sets to utilise phase data. This motivates us to investigate the application of the 51 feature sets to phase-only images in addition to their use on the original data set. This investigation is extended to exploit Convolutional Neural Network (CNN) features. The results show that our feature fusion scheme improves the average performance of those feature sets for estimating humans' perceptual texture similarity. The superior performance should be attributed to the importance of phase to texture similarity.

A Real-Time Numerical Decoupling Method for Multi-DoF Magnetic Levitation Rotary Table

Magnetic levitation technology shows promise for realizing multiple degrees of free precision motion for modern manufacturing, as the bearing and guiding parts are not used. However, motion decoupling in a magnetically levitated (maglev) system is difficult because it is hard to derive accurate magnetic force and a torque model considering the translation and rotation in all axes. In this work, a magnetic levitation rotary table that has the potential to realize unlimited rotation around the vertical axis and a relatively long stroke in the horizontal plane is proposed and analyzed, and the corresponding real-time numerical decoupling method is presented. The numerical magnetic force and torque model solves the current to magnetic force and torque transformation matrix, and the matrix is used to allocate the exact current in each coil phase to produce the required motion in the magnetically levitated (maglev) system. Next, utilizing a high-level synthesis tool and hardware description language, the proposed motion-decoupling module is implemented on a field programmable gate array (FPGA). To realize real-time computation, a pipelined program architecture and finite-state machine with a strict timing sequence are employed for maximum data throughput. In the last decoupling module of the maglev system, the delay for each sampling point is less than 200 μ s. To illustrate and evaluate real-time solutions, they are presented via the DAC adapter on the oscilloscope and stored in the SD card. The error ratios of the force and torque results solved by the numerical wrench model were less than 5 % and 10 % using the solutions from the boundary element method (BEM) program package RadiaTM as a benchmark.