IEEE Trans Vis Comput Graph. 2018 Dec;24(12):3123-3136. doi: 10.1109/TVCG.2017.2772236. Epub 2017 Nov 10.
Haptic-based tissue stiffness perception is essential for palpation training system, which can provide the surgeon haptic cues for improving the diagnostic abilities. However, current haptic devices, such as Geomagic Touch, fail to provide immersive and natural haptic interaction in virtual surgery due to the inherent mechanical friction, inertia, limited workspace and flawed haptic feedback. To tackle this issue, we design a novel magnetic levitation haptic device based on electromagnetic principles to augment the tissue stiffness perception in virtual environment. Users can naturally interact with the virtual tissue by tracking the motion of magnetic stylus using stereoscopic vision so that they can accurately sense the stiffness by the magnetic stylus, which moves in the magnetic field generated by our device. We propose the idea that the effective magnetic field (EMF) is closely related to the coil attitude for the first time. To fully harness the magnetic field and flexibly generate the specific magnetic field for obtaining required haptic perception, we adopt probability clouds to describe the requirement of interactive applications and put forward an algorithm to calculate the best coil attitude. Moreover, we design a control interface circuit and present a self-adaptive fuzzy proportion integration differentiation (PID) algorithm to precisely control the coil current. We evaluate our haptic device via a series of quantitative experiments which show the high consistency of the experimental and simulated magnetic flux density, the high accuracy (0.28 mm) of real-time 3D positioning and tracking of the magnetic stylus, the low power consumption of the adjustable coil configuration, and the tissue stiffness perception accuracy improvement by 2.38 percent with the self-adaptive fuzzy PID algorithm. We conduct a user study with 22 participants, and the results suggest most of the users can clearly and immersively perceive different tissue stiffness and easily detect the tissue abnormality. Experimental results demonstrate that our magnetic levitation haptic device can provide accurate tissue stiffness perception augmentation with natural and immersive haptic interaction.
基于触觉的组织硬度感知对于触诊训练系统至关重要，它可以为外科医生提供触觉提示，以提高诊断能力。然而，目前的触觉设备，如 Geomagic Touch，由于固有的机械摩擦、惯性、有限的工作空间和有缺陷的触觉反馈，无法在虚拟手术中提供沉浸式和自然的触觉交互。为了解决这个问题，我们设计了一种基于电磁原理的新型磁悬浮触觉设备，以增强虚拟环境中的组织硬度感知。用户可以通过使用立体视觉跟踪磁笔的运动来与虚拟组织自然交互，从而可以通过磁笔在我们设备产生的磁场中移动来准确地感觉到硬度。我们首次提出有效磁场 (EMF) 与线圈姿态密切相关的想法。为了充分利用磁场并灵活地生成用于获得所需触觉感知的特定磁场，我们采用概率云来描述交互应用程序的要求，并提出一种算法来计算最佳线圈姿态。此外，我们设计了一个控制接口电路，并提出了一种自适应模糊比例积分微分 (PID) 算法来精确控制线圈电流。我们通过一系列定量实验评估了我们的触觉设备，实验结果表明，实验和模拟的磁通密度高度一致，磁笔的实时 3D 定位和跟踪精度高达 0.28 毫米，可调线圈配置的功耗低，并且自适应模糊 PID 算法可将组织硬度感知精度提高 2.38%。我们进行了一项有 22 名参与者参与的用户研究，结果表明，大多数参与者都能清晰、沉浸式地感知到不同的组织硬度，并且很容易检测到组织异常。实验结果表明，我们的磁悬浮触觉设备可以通过自然和沉浸式的触觉交互提供准确的组织硬度感知增强。
