**4. Acknowledgment**

148 Haptics Rendering and Applications

by the user. Only simple trials were performed with linear spring constants to vary the stiffness of the control stick but for future trials more advanced algorithms will be

A second prototype was designed with the aim of further reducing the size of the input device. Fig.14 shows the CAD design of the second prototype which has a base plate dimension reduced from 140 x 140 mm² to 84 x 84 mm² (40% reduction). The same servos will be used in a different configuration and the supporting brackets have been modified to make more efficient use of space. The material for all load bearing parts (base plate, brackets, control stick) will be aluminium to make the design more robust but will also

The sensorized surgical blade, with its large force range and high resolution, is perfectly suitable for minimal invasive surgery and has the potential to lead to a new generation of endoscopic tools for robotic aided surgery capable also of providing precise and accurate haptic force feedback. The tool can withstand a normal load of 20N and a tangential load of 3N without damage to the structure. At the same time, it is possible to perform sensitive

In applications where the crucial point of the surgical intervention is not accessible with rigid manipulators, a steerable catheter can be helpful. A novel device was developed that is equipped with a steerable tip, but also with an electrical and an optical sensor system for tissue characterisation. The catheter tip is steered by a joystick. First insertion and navigation tests in phantoms were successfully carried out. The current catheter diameter is 3.5mm, but for applications in severe cases like pulmonary atresia, a further miniaturisation to an outer diameter of 0.8mm is necessary and still feasible. Forces on the bowden wires are

Commercial available force feedback joysticks turned out not to be precise enough for haptic sensing, thus a prototype device was developed to satisfy these additional requirements. Differently from existing force feedback input devices, where the position is sensed and then a torque is applied by a motor, in this device the force is first sensed and then the position of the joystick is set according to the programmed force/angle model within a closed loop control. A design for a second prototype joystick with reduced dimensions and improved

touching and probing movements with high force sensitivity down to the mN range.

detected with strain gauges and used to generate haptic force feedback.

programmed to also feedback non-linear and damped forces to the user.

Fig. 14. CAD model of second prototype with 40% size reduction

slightly increase the manufacturing costs.

**3. Conclusion** 

The work described in this paper was supported by the ASSEMIC project, Marie Curie Research & Training Network (MRTN-CT- 2003-504826). Currently Arne Sieber is funded through the Marie Curie Project Lifeloop (EU FP7-People-IEF-2008, project nr. 237128). A special mention to Mr. C. Filippeschi for his continuous and invaluable help.
