Interfacing for Continuum Robots CuRL
Rigid-link robot interface for Continuum robots
Driven by the inherent difficulty in understanding the operation of continuum robots, we
sought to use a non-traditional approach to continuum robot control, using a non-redundant, rigid-
link robotic arm as a teleoperative input device. The design of this experiment merges the two
distinct topologies of rigid-link and continuum robotics with the intent of creating an intuitive
relation that allows users to control continuum robots using rigid-link systems. This scheme gives
the user physical control of a widely available system type with anthropomorphic kinematics in order
to manipulate a more specialized device with more complex and less intuitive kinematics.
As our chosen teleoperative input device, we used a Kinova Mico Research Arm: a kinematically non-redundant, rigid link arm with 6 DoF (seen below). The Mico Arm was chosen because it is representative of the large range of anthropomorphic robotic arms and its size allows for easy manipulation by a human user. During experiments, the Mico Arm was placed in ”float” mode, which allowed the user to manipulate the arm freely while the robot automatically compensated for gravity at each joint.
As our chosen teleoperative input device, we used a Kinova Mico Research Arm: a kinematically non-redundant, rigid link arm with 6 DoF (seen below). The Mico Arm was chosen because it is representative of the large range of anthropomorphic robotic arms and its size allows for easy manipulation by a human user. During experiments, the Mico Arm was placed in ”float” mode, which allowed the user to manipulate the arm freely while the robot automatically compensated for gravity at each joint.
System flow for teleoperation of a continuum robot (OctArm) using a rigid-link robot (Kinova Mico) as an input device.
From left to right: Kinova Mico joint values sent to mapping programmed in MATLAB/Simulink. Mapping converts to lengths corresponding pressures
for OctArm, which is actuated through series of pressure regulators.
Examples of how different mappings could be used to relate the 6 DoF of the Kinova Mico to the 6 DoF of a planar, three section,
continuum robot. Mapping 1 is on the left, mapping 2 on the right, and the equivalent state of the OctArm via both mappings in the middle.
Publication
C. G. Frazelle, A. D. Kapadia, K. E. Fry, and I. D. Walker. Teleoperation Mappings from Rigid Link Robots to their Extensible Continuum Counterparts. In the Proceedings of the IEEE International Conference on Robotics and Automation (ICRA), Stockholm, Sweden, May 2016.
MiniOct - A Kinematically Similar Continuum Interface
The MiniOct is a three-section continuum device that is capable of kinematically emulating
a three-section, 9 DoF continuum manipulator. The mechanical design of the device was inspired
by the spring and cable system present in the Elephant Trunk manipulator, which was an early
continuum robot that utilized tendon actuation to bend. Springs allowed the manipulator to return
to a straight, resting state. The MiniOct similarly uses tendons to hold curved shapes and springs
to return to a resting state. The total system measures 71.59cm in height and weighs approximately
1.57 kg. The device is comprised of two main hardware components: the continuum input controller
and the configuration measurement system. The length of the continuum controller section ranges
from 31.75.cm to 57.16cm.
The configuration of the MiniOct is measured using nine cables, three cables for each section, placed 120 degrees apart. The lengths of the cables are approximated using string potentiometers placed symmetrically in a circle at the base of the device. Constant curvature kinematics converts these measured cable lengths to relevant configuration parameters.
The configuration of the MiniOct is measured using nine cables, three cables for each section, placed 120 degrees apart. The lengths of the cables are approximated using string potentiometers placed symmetrically in a circle at the base of the device. Constant curvature kinematics converts these measured cable lengths to relevant configuration parameters.
The MiniOct: a kinematically similar continuum robot interface (a). Operation and subcomponents of a MiniOct subsection (b).
Cross-section of MiniOct Section divider and braking mechanism (c). String pot arrangment for configuration measurement (d). MiniOct acrylic spacer
maintains radial spread of springs and measurement tendons (e).
The MiniOct: a kinematically similar continuum robot interface (a). Operation and subcomponents of a MiniOct subsection (b).
Cross-section of MiniOct Section divider and braking mechanism (c). String pot arrangment for configuration measurement (d). MiniOct acrylic spacer
maintains radial spread of springs and measurement tendons (e).
Publication
C. G. Frazelle, A. D. Kapadia, and I. D. Walker. Developing a Kinematically Similar Master Device for Extensible Continuum Robot Manipulators. ASME Journal of Mechanisms and Robotics, 10(2), doi: 10.1115/1.4039075, April 2018, pp. 025005-1-8.
HaptOct - A Haptic Continuum Interface
The HaptOct, seen below, is a haptic continuum interface capable of providing
a one-to-one kinematic mapping between the user interface and a nine DoF extensible continuum
manipulator, the first known haptic display targeted directly at continuum manipulators. The core
of this design is based on the MiniOct above, but with the added ability to oppose user input based
on the state of a deployed secondary system located in a remote environment.
The MiniOct (left) allowed for unidirectional teleoperation. In order to enable bidirectional teleoperation, I designed
an actuator package (middle) to provide haptic feedback, realized in the construction of the HaptOct (right).
Electronics and actuator package assembly.
Publication
C. G. Frazelle, A. D. Kapadia, and I. D. Walker. A Haptic Continuum Interface for the Teleoperation of Extensible Continuum Manipulators, in IEEE Robotics and Automation Letters, vol. 5, no. 2, April 2020, pp. 1875-1882.