Apoorva Kapadia

Task-space control of extensible continuum manipulators

In this paper, we present a new approach towards the control of continuous backbone (continuum) “trunk and tentacle” robots. Development of model-based control algorithms for this new and emerging class of robots has been relatively slow due to the inherent complexity of their mathematical models. Based on the recently developed kinematics, velocity Jacobian and full dynamic model, a simple nonlinear task-space controller, established for rigid-link robots, is adapted and extended for continuum manipulators for the regulation of its tip or any location along its backbone in the task-space. This approach is applicable to all continuum robots with extension/contraction and bending capabilities. Simulation results are shown using a three-section, six degree-of-freedom planar continuum robot.

Autonomous continuum grasping

A continuum manipulator, such as a multi-section trunk/tentacle robot, is promising for deft manipulation of a wide range of objects of different shapes and sizes. Given an object, a continuum manipulator tries to grasp it by wrapping tightly around it. Autonomous grasping requires realtime determination of whether an object can be grasped after it is identified, and if so, the feasible whole-arm wrapping around configurations of the robot to grasp it, which we call grasping configurations, as well as the path leading to a grasping configuration. In this paper, we describe the process for autonomous grasping from object detection to executing the grasping motion and achieving force-closure grasps, with a focus on a general analysis of all possible types of planar grasping configurations of a three-section continuum manipulator. We further provide conditions for existence of solutions and describe how to find a valid grasping configuration and the associated path automatically if one exists. Experimental results with the OctArm manipulator validate our approach, and shows that the entire process to determine an autonomous grasping operation, which includes automatic detection of the target object and determination of a grasping configuration and a path to the grasping configuration that avoids obstacles, can take just a small fraction of a second. Once a grasping configuration is reached, the manipulator can lift the object stably, i.e., a force-closure grasp can be achieved.

Empirical Investigation of Closed-Loop Control of Extensible Continuum Manipulators

This paper details closed-loop control experiments that were conducted on an extensible continuum manipulator, the OctArm. The performance of three controllers are shown here. The controllers can be classified into two categories: Closed-loop configuration-space control and closed-loop task-space teleoperation. Two controllers were tested in the configuration-space control experiments: a proportional-derivative (PD) controller and a nonlinear sliding-mode controller. The third controller is also shown in which the redundant extensible continuum manipulator tip tracks the motion of a kinematically-dissimilar non-redundant rigid-link master system. The results of these experiments confirm the ability of the control strategies to effectively control continuum robot hardware.

Self-motion analysis of extensible continuum manipulators

While the field of continuum manipulators has been the subject of increasing attention from the robotics community, knowledge of their inherent capabilities is still limited. Controllers have been proposed that exploit the null-space of redundant continuum manipulators, however studies of the nature of continuum robot null-spaces have not yet been done. In this paper, we first develop a convenient set of extensible, continuum manipulator forward kinematics and resolved-motion rate inverse kinematics. This allows us to analyze the null-space of 2-section, planar, extensible, redundant continuum manipulators to consider the underlying structure of general continuum robot self-motions and discuss their importance to real-world examples and applications.

“Architectural Robotics”: An interdisciplinary course rethinking the machines we live in

We discuss disciplinary barriers which have traditionally prevented robotics from significantly impacting the built (architectural) environment we inhabit. Specifically, we describe the implementation of, and lessons learned from, a multidisciplinary graduate-level course in Architectural Robotics. The results from class interactions and projects provide insight into novel ways in which robotics expertise can be effectively leveraged in architecture. Conversely, our outcomes suggest ways in which the knowledge and perspective of architects could stimulate significant innovations in robotics.

Lyapunov-based continuous-stirred tank bioreactor control to maximize biomass production using the haldane and monod specific growth models

A novel robust controller is proposed for a continuous-stirred tank bioreactor that controls the culture dilution rate into the bioreactor in order to maximize a cost function representing the biomass yield. To that end, an optimal desired biomass concentration trajectory is designed based on a numerical extremum-seeking algorithm to maximize the biomass yield. A nonlinear robust controller is designed to ensure the biomass concentration tracks the desired trajectory while providing stable operation. Lyapunov-based stability analyses are used to prove semi-global tracking.

Set-point navigation of a redundant robot in uncertain environments using finite range sensors

In this work, control of redundant robot manipulators in an uncertain environment is considered. The manipulator is equipped with finite range sensors to detect obstacles in its workspace. A navigation function-based kinematic controller is proposed to ensure the regulation of the end-effector to a desired set-point while the entire manipulator simultaneously avoids the obstacle points detected by the sensors. A joint-space controller is then utilized to ensure asymptotic tracking of the desired joint-space trajectory.

Teleoperation control of a redundant continuum manipulator using a non-redundant rigid-link master

In this paper, teleoperated control of a kinematically redundant, continuum slave manipulator with a non-redundant, rigid-link master system is considered. This problem is novel because the self-motion of the redundant robot can be utilized to achieve secondary control objectives while allowing the user to concentrate on controlling only the tip of the slave system. To that end, feedback linearizing controllers are proposed for both the master and slave systems, whose effectiveness is demonstrated using numerical simulations for the case of singularity avoidance as a subtask.

Robot tongues in space: continuum surfaces for robotic grasping and manipulation

In this paper, we introduce a novel, continuously bending “robot tongue.” The tongue replaces the existing parallel jaw gripper at the end of a KUKA industrial robot manipulator. The resulting system augments the precise positioning of the KUKA with unique capabilities for adaptive grasping afforded by the new robot tongue. We demonstrate the ability of the system to grasp and manipulate objects over a wide range of scales and geometries and evaluate the potential for use of such tongues in various applications.

Intuitive Interfaces for Teleoperation of Continuum Robots

This paper presents a novel teleoperation interface for continuous backbone continuum robots. Previous teleoperation interface methods for continuum robots were less intuitive due to a degree-of-freedom mismatch, using non-continuum interface input devices with fewer degrees-of-freedom than the robot that was being operated. The approach introduced in this paper uses a graphical 3D model on screen to directly operate the continuum robot for an easier user experience. This paper details the development of both the model and software. The teleoperation interface was developed specifically for a nine degree-of-freedom pneumatically driven extensible continuum robot, but it can easily be extended to any continuum robot with an arbitrary number of section due to its modular design. Experiments using the aforementioned system on two different continuum robots are reported and areas for future work and improvement are detailed.