the fact that hand-eye calibration is an indispensable part of
teleoperation, the accuracy of which can have a profound
impact on subsequent task implementations, we also stress
technical concerns about hand-eye calibration. Additionally,
we address potentiometer calibration after weighing up its
substantial impact on the performance of autonomous task
execution, even though, thus far, to the best of our knowl-
edge, there is no literature about this topic. In the follow-
ing sections, kinematics calibration, hand-eye calibration,
potentiometer calibration and camera calibration problems
are detailed in Sec.III, VI, IV and V, respectively. For each
of these, we first identify the nature of the problem, then
distill prevailing schools of thought concerned on how to
tackle them, and finally we point out potential paths for better
addressing these problems, placed in the dVRK framework.
A discussion is presented in Sec.VII, where we summarize
the main findings, and other miscellaneous dVRK technical
issues uncovered during the survey.
II. SEARCH METHODOLOGY
A. Literature review
To identify the most significant technical constraints that
have hampered research progress with the dVRK, we first
looked into all papers on the dVRK across different re-
search application areas and gathered common issues that
researchers claimed to have affected task performance, taking
advantage of the latest review paper on the subject, which
encompasses papers on the dVRK from year 2014 to 2021
[2]. We also employed the keywords “dVRK” paired with
“error”, “calibration” and “task performance” individually on
Google Scholar, ScienceDirect and RefWorks and included
all relevant findings in this survey.
B. Consultation with researchers
1) Leading researchers: Having gathered a list of tech-
nical issues reported by dVRK users in the literature, we
consulted with leading researchers of the dVRK community
(Mr. Anton Deguet and Dr. Simon DiMaio) about whether
these issues have been discovered under the first-generation
dVRK and thus can be regarded as universal.
2) Peer researchers: We designed a questionnaire fea-
turing selected technical issues, which we deemed to be
“universal”, and had it distributed within the dVRK com-
munity1. The design of the questionnaire and a summary of
user responses are detailed in Appendix I.
III. KINEMATICS CALIBRATION
A well-acknowledged technical issue within the dVRK
is its time-variant inaccurate forward kinematics, which
induces a poor surgical tool tip pose estimation, reflected
by a discrepancy in readings of up to 1.02mm [4], [5]
between the alleged tip pose streamed from the dVRK
and the ground truth observed by an external means. This
discrepancy, termed positioning error in this paper, has
exceeded the sub-millimetre positioning accuracy required by
1More info at: https://jhudvrk.slack.com
RMIS [6], having repercussions on diverse research projects
implemented on the dVRK. Note that kinematics errors
exist in all individual joints of the dVRK; however, it is
in the end effector position that the discrepancy caused
by the kinematics errors is most evident, because of the
accumulation of errors across all the joints.
A. Need for kinematics calibration
For research on surgical subtask automation, accurate
positioning is required, such as in debridement [7], suturing
[8], [9], needle extraction [10], and peg transfer [11]–[13],
where a surgical instrument is required to move to the target
grasping point. For research on the development of Active
Constraints (AC, also known as virtual fixtures) via the
dVRK, positioning accuracy will affect the proximity query
result, and therefore the entire enforcement stage of the AC
implementation [14]–[17]. Even for research on image-based
hand-eye calibration [18], inaccurate surgical tool kinematic
data leads to an inaccurate 3D pose estimation and thereby
affects the accuracy of its back-projected 2D pixel position,
which serves as a criterion for evaluating different hand-eye
calibration strategies.
B. Challenges in accurate positioning
1) Cable-driven effects: The dVRK surgical platform,
which is a cable-driven robotic system [19], has an inherent
issue in obtaining accurate joint readings from the built-
in encoders. This is because all encoders are mounted
adjacent to actuators but distant from joints, where the actual
joint angles are estimated through transmission kinematics
[20]. However, unknown parameters such as pulley-cable
friction and nonlinearities [21] contribute to inaccuracies in
joint angle estimation, which result in dVRK joint encoder
readings not reflecting actual joint positions. These errors
in joint space subsequently affect the estimated end effector
tip pose through Denavit-Hartenberg (DH) parameters and
forward kinematics. The DH parameters here only concern
active joints.
2) Inaccurate kinematic parameters: The wear and tear of
the dVRK not only induces cable slack [22], which affects
the parameters in the transmission kinematics, resulting
inaccurate joint encoder readings, but also entails instrument
damage which leads to additional inaccuracies in the DH
parameters of the forward kinematics, causing the estimated
tool-tip pose to stray from the actual one. Another significant
source of error is due to the potentiometers, as explained in
detail in IV.
3) Other non-kinematic error sources: Other than kine-
matic factors, non-kinematic factors such as external forces
exerted onto the tool shaft and backlash between the tool
shaft and cannula, illustrated in Fig. 2, would also con-
tribute to an overall erroneous end-tip pose estimation [23],
[24]. These external forces will affect the tension of cables
associated to tool tips, leading to an error in transmission
kinematics. In addition, they will also cause a displacement
of the tool shaft because of compliance, as illustrated in Fig.
3; this displacement is not detectable by the encoders [23],
and thus positioning error accumulates.