Biomedical Engineering Reference
In-Depth Information
11
Teletaction Using a Linear
Actuator Feedback-Based
Tactile Display
In previous chapters, different techniques were discussed for developing tactile displays
in teletaction applications. For example, Chapter 8 presented a graphical tactile display
in which the patient could view tactile information rather than actually sensing it.
In this chapter, a tactile display is introduced which is able to reconstruct the softness
of different materials based on their inherent characteristic properties. From an analogous
point of view, most materials can be modeled as if they were springs. The compressibility
of an ideal spring is linear and, indeed, remains so when the compression is small; within
this range, the softness of a material can be characterized with accuracy. When measuring
greater compression, however, the spring becomes more compressed and enters a range
in which it becomes proportionately more nonlinear, and affects measurement accuracy.
Most tactile displays that are driven by a servomotor, or any kind of actuator, use the
spring model to simulate softness [1]. In this research work, the nonlinear behavior of
materials is considered to describe the softness of touched materials. The objective of this
work is to provide the user with a tactile display that is able to simulate different material
compliances.
11.1 System Design
In this design, an actuator which converts rotational motion of a motor to linear motion
was used as a softness display. The idea of this was to measure the force applied by the
finger to a linear actuator shaft, then calculate the displacement of the shaft in response
to the applied force, according to the mechanical properties of the simulated material,
and move the shaft to the calculated position. In this study, one actuator shaft and one
