2.1.2.2. Patient side manipulators
Arm
The da Vinci Si systems came with either 2 or 3 PSMs. PSM1, PSM2 and PSM3 are identical.
da Vinci Si PSM
Basic information:
Each PSM arm is attached to the SUJ using 4 long bolts and grooves
The arm can be tilted forward (on Si SUJ; 45 degrees for PSM1 and PSM2, 15 degrees for PSM3)
7 motorized degrees of freedom, 7 actuators with optical encoders
All motors are located in the first 2 links. The first two links use a mix of gears and belts. The last five joints use cable transmission
All actuators have digital potentiometers, used for both homing and safety checks
3 electric brakes on the first 3 joints to prevent the arm from falling when not powered (like the ECM Classic)
The second actuator controls a set of belts used to enforce a RCM point using complementary angles (remote center-of-motion, aka fulcrum point). Google search.
The kinematic chain is composed of two parts, the arm’s base (not sterilized) and a removable instrument (sterilized and disposable). This design is inherited from the Classic da Vinci so make sure you read the section for the PSM Classic
da Vinci Si PSM labeled
Cannula and sterile adapter
The design of the last 4 joints and instrument on the Si system is very similar to the PSM Classic. The main differences are the sterile adapter and cannula shapes and the cannula holder is attached to the arm.
There is also video at the end of this section describing the process.
Last 4 actuators on PSM Si base arm
da Vinci Si PSM with sterile adapter (without drape)
One difference between the PSM Classic and Si is that the cannula holder on the Si is not removable. The sterile drape comes with a piece of soft molded plastic that fits between the cannula holder and the cannula.
da Vinci Si PSM fixed cannula holder
The cannula is reusable and sterilizable. Cannulas come in different diameters, 5mm, 8mm… to match the diameter of the shaft of the instrument used. Since we don’t often use the real sterile drape, there is a small gap between the cannula holder and the cannula. To prevent mechanical, one can use masking tape as a “shim”.
da Vinci Si PSM 8mm cannula with “shim”
The cannula is held by the cannula holder (shocking) and secured using two flaps.
da Vinci Si PSM cannula in place
Note
Video on YouTube demonstrating how the PSM is prepared: https://youtu.be/F7cOVPVq_TY