IEEE Robotics & Automation Magazine - March 2022 - 70

complex as the tests were performed both by expert surgeons
and lay users with no previous experience in teleoperation.
For immersive vision inside the virtual surgical
environment designed in Unity, we used an HTC Vive virtual
reality (VR) headset. Control of the virtual surgical tool
was enabled with IMU sensors placed on the hands and
arms of the users, including HTC Vive trackers, Manus VR
gloves, and an Xsens suit (Figure 1). After each trial, participants
were asked to complete the system usability scale
(SUS) and NASA-Task Load Index (TLX) questionnaire. The
former is used to assess the overall usability of the system to
perform the given task, while the latter provided scores of
users' perceived workload during task completion. Finally, a
user-experience form (UEF) collected users' subjective feedback.
The robotic surgeons were recruited at Southmead
Hospital in Bristol, United Kingdom. Their participation
provided a comparison of the usability of the system with the
existing surgical robotic platforms.
Patient Side Manipulator and Tool
to Surgical Master Mapping
Posing of the tool shaft was controlled using a HTC Vive
tracker placed on the participants' forearm, while the opening
and closing of the end-effector tool was controlled with
Manus VR gloves. We mapped metacarpophalangeal joints
of the thumb and index finger to the virtual DV grasper
joints (open/close). For the 3 F tool, we additionally mapped
the proximal interphalangeal joint of the thumb, index, and
middle fingers to the second joint of each digit of the 3 F tool
(Figure 2). The details of the kinematic mapping to the DV
tool are available in the calibration, and sampling of the
Manus gloves are automatically managed by Manus' proprietary
VR Apollo software. Users can simply open and close
the DV grasper by opening and closing the hand. This is
similar to the DV's primary controller (Figure 2). The
motion of the articulated shaft was controlled with the IMU
sensors of the Xsense, which were placed on the forearm,
upper arm, and hands of the user. After calibrating the IMU
sensors for each participant, the wrist joint (W) of the instrument
was mapped to the user's wrist and the shaft of the
instrument was mapped to the user's arm. A shaft with an
elbow joint (E) was also tested, and it was mapped to the
user's elbow. The joint values on the surgical tools were limited
to their maximum physical values. The tool insertion
velocity was calculated from the velocity of the user's arms in
the forward direction and in respect to the global reference
frame, taking into account the limitations of the fulcrum
point, and scaling the tool velocity with a factor of 0.7 to
maintain better tool control.
User Studies and Surgical Tasks
Figure 1. A participant wearing a VR headset; Xsense suit with
IMUs sensors on the upper arms, forearms, and hands; and
Manus VR gloves to control surgical virtual tools.
Articulated Tooltip Comparison (Surgical Task B.1)
The first user group was composed of 12 subjects, including
two surgeons experienced in using the DV surgical robot. In
the first trial, the surgical training task of grasping and positioning
was performed with six squared colored rings, which
were picked up and placed around color-coordinated pegs
using one hand (Figure 3). In this task, we compared the
(a)
(b)
(c)
Figure 2. (a) Mapping of the finger joint angles to the 3 F and the (b) DV grasper. The DV primary only allows opening and closing of
the (c) DV grasper.
70 * IEEE ROBOTICS & AUTOMATION MAGAZINE * MARCH 2022

IEEE Robotics & Automation Magazine - March 2022

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