Abstract
This project concerns the application of haptic feedback to a virtual reality laparoscopic surgery simulator. It investigates the hardware required to display haptic forces, and the software required to generate realistic and stable haptic properties. A number of surgery-based studies are undertaken using the developed haptic device. The human sense of touch, or haptic sensory system, is investigated in the context of laparoscopic surgery, where the long laparoscopic instruments reduce haptic sensation. Nonetheless, the sense of touch plays a vital role in navigation, palpation, cutting, tissue manipulation, and pathology detection in surgery. The overall haptic effect has been decomposed into a finite number of haptic attributes. The haptic attributes of mass, friction, stiction, elasticity, and viscosity are individually modeled, validated, and applied to virtual anatomical objects in visual simulations. There are times in surgery when the view from the camera cannot be depended upon. When visual feedback is impeded, haptic feedback must be relied upon more by the surgeon. A realistic simulator should include some sort of visual impedance. Results from a simple tissue holding task suggested the inclusion of haptic feedback in a simulator aids the user when visual feedback is impeded.
Key Terms in this Chapter
Haptic Attributes: All physical objects intrinsically display haptic attributes which feedback haptic information to humans interacting with them. The haptic attributes include texture, heat, mass, friction, stiction, elasticity, viscosity, temperature, vibrations, and more.
Haptics: From the Greek word haptesthai, meaning “to touch.” Haptics broadly refers to touch interactions (physical contact) that occur for the purpose of perception or manipulation of objects (Salisbury, Conti, & Barbagli, 2004). This encapsulates both “Tactile” and “Force” information.
Force Feedback or Kinesthetic Feedback: Refers to the information received via receptors in the limbs themselves. It is responsible for awareness of movement and position of one’s limbs in space and time. Kinesthetic receptors are also responsible for the detection of size and weight of objects (Haans & Ijsselsteijn, 2006).
Haptic Display or Force Display: Refers to the transfer of force information via the mechanical interface to the user. The case of a force display is analogous to that of a visual display, where visual information is passed to a user via a medium such as a computer monitor.
Haptic Attribute Decomposition: The overall haptic effect can be decomposed into a number of haptic attributes. The decomposition attaints to determine the method in which best to decompose the overall haptic effect. Once the decomposition has occurred, the individual attributes can be measured, compared, and recreated in a simulation.
Visual Impedance: “Impedance” can be defined as something that impedes, such as an obstacle or hindrance. Therefore, a visual impedance is something that impedes vision.
Tactile Feedback or Cutaneous Feedback: Encompasses all the information acquired through sensors in the skin, with particular reference to the spatial distribution of pressure, or more generally, tractions, across the contact area. Tactile Feedback is responsible for the detection of, but not limited to, roughness, temperature, and vibrations.
Haptic Rendering: Haptic rendering is the process of converting computer algorithms containing force information to a mechanical interface capable of displaying haptic information to a user (Salisbury et al., 2004). It is analogous to visual rendering, which converts graphics from a file into visual form, as on a video display. Haptic rendering is comprised of a hardware and a software component.