Application of piezoelectric actuator to simplified haptic feedback system

The lack of haptic feedback in minimally invasive surgery results in the dependence on high-resolution images. This study used a simplified working abstraction of a haptic feedback system, including a master manipulator, a console table, a slave indenter, and a control algorithm to construct a scalable platform for a palpation device. A piezoelectric actuator was designed using finite element simulation, and was added to the master manipulator to produce thrust force against the user's finger pressing. Button motion on the master manipulator was synchronized with the slave indenter's linear movement. If the indenter contacted an object, the loading was used to adjust the thrust force of the piezoelectric actuator in the console table. This function can be developed into a model of haptic perception, like palpating an object. Instead of a human operator, this study used a reciprocating mechanism to simulate finger pressing and tested the haptic feedback system under different contact conditions: two indentation speeds (0.84 mm/s, 4.2 mm/s) and two springs of different stiffness (214.6 N/m, 474.3 N/m). The results showed that our haptic feedback system allows estimating the stiffness of objects. Lower indentation speeds disclosed a clearer contact information. The piezoelectric actuator yielded better efficiency at the resonant frequency and smaller preload. A smaller friction force could increase the response speed. The response time of whole system was 0.36 s and the variation of the thrust force of one piezoelectric actuator was in a quite small range of 0.3 N. To improve the haptic feedback system, to integrate more actuators and to develop the embedded controller module were the potential solution.