**1.3 Haptic force feedback input devices**

134 Haptics Rendering and Applications


State of the art robotic assisted surgery systems like the Da Vinci System (Intuitive Surgical, (California, USA) enable minimal invasive incisions thus offering a more conservative alternative to standard open surgery. Unfortunately, due to the lack of haptic force feedback, these systems can only be used in cases where the visual information is enough and haptic sensing is not needed (Wagner et al., 2002). Often surgeons and robotic researchers point out this fact as major limitation of robotic aided surgery (Mohr et al., 2001)

A key element for enabling haptic force feedback robotic or computer assisted surgery are

"Smart medical tools" often stands for sensorized devices (Dario et al., 2003). One example are catheters with integrated pressure sensors (Strandman et al., 1997, Kalvesten et al., 1998, Melvås et al., 2002) which are mainly for diagnostic purposes, but not for surgical interventions except in the combination with so called balloon dilation for cardiac vessel

Sensorized microgrippers are described in (Houston et al., 2007). In these grippers micro strain gauges are integrated into the polymer arms, thus an accurate and precise gripping force monitoring and control is possible. On the basis of this gripper, an endoscopic tool for robotic aided surgery was developed (Houston et al., 2008) where a wire driven joint

Robotic aided surgical interventions where precise cutting tasks have to be performed are quite difficult – one main reason is again the lack of haptic force feedback. One approach to deal with this problem is to equip tools with Micro Electrical Mechanical Systems (MEMS) (Rebello, 2004). A force sensorized microsurgical tip is detailed in (Berkelman et al., 2003). A first prototype of a cutting blade based on a triaxial MEMS force sensor (Beccai et al., 2005) was presented in (Valdastri et al., 2005). With the help of an advanced assembly process (Sieber et al., 2007) the MEMS sensor could be directly mounted on a flexible substrate – which allowed a further miniaturization of the sensorized cutting device as detailed in

Another topic addressed in this chapter is the development of sensorized tools for catheter based minimal invasive surgery. One example of a smart catheter is the recently developed TactiCath® [Endosense, Switzerland]. It is an ablation catheter, that is equipped with a force

Especially during catheter navigation through thin vessels, that can easily be damaged, haptic force feedback can improve largely the safety of such interventions. A recent approach of a "smart tool", developed especially for treatment of pulmonary atresia

sensor to provides real time contact force measures (Vijaykumar et al., 2011).



with greater clarity than open surgery (Camarillo et al., 2004).

improving instrument control;

(Harada et al., 2005) allows rotation of the gripper.

(Cavasoglu et al., 2003).

force sensorized tools:

(Valdastri et al., 2007).

**1.2 Sensorized catheters** 

expansion.

Next to force sensorized tools, haptic force feedback input devices are a key element for future computer aided surgery. One approach is to use visual force feeback. A study (Reiley et al., 2008) was carried out demonstrating that visual force feedback offers benefits like reduced suture breakage, lower forces, and decreased force inconsistencies; however it was concluded, that these benefits are mainly an advantage for novice robot-assisted surgeons and diminishing benefits among experienced surgeons.

Song et al. (2006) have developed a laboratory set up for haptic force feedback tele-operation consisting of a 6-DOF robot and a commercially available haptic force feedback input device (PHANTOM Omni). Forces on a tool (like a blade) were acquired with a 3DOF force sensor. A different group proposed to incorporate haptic force feedback into the ZEUS system by integrating a PHANTOM input device (Ortmaier et al., 2001). Another PHANTOM based system was discussed in (Tavakoli et al., 2003). In the PHANTOM haptic force feedback system, force feedback is generated with DC motors that apply a torque on the joints. Similar, but very simplified, technology is used in haptic force feedback joysticks for gaming, where the position of the joystick is acquired with 2 potentiometers and force feedback is generated by the torque of a DC motor.

For our work with the sensorized microgripper (Houston et al, 2011) we have developed a force feedback haptic tweezer. In contrast to the operating principle of the PHANTOM and haptic force feedback joysticks, the haptic tweezer is an active servo actuated tool, where the force on the tweezer is measured with a strain gauge and the tweezer is moved actively in a closed control loop. Advantages are precise movement control and low manufacturing costs. In the third part of this chapter a novel haptic force feedback joystick is described which derives from the haptic tweezer. The force on the joystick is measured with strain gauges and the joystick is actuated with servos in a control loop. The same principle can be used for designing low cost haptic input devices with 3 or more DOFs.
