Vision-based Control of Continuum Robots

We present a novel clothoid-based visual servoing method for controlling the shape of a variable length continuum manipulator. Clothoids are curves with linearly changing curvature. They allow us to obtain a smooth representation of a continuum manipulator’s shape in a compact form with few parameters. Using this curve model, we generate image features that are used in an adaptive visual servoing method to drive the robot to a desired shape. The adaptive algorithm estimates and updates a local interaction matrix that maps the rate of change in clothoid features to actuator velocities of the continuum manipulator. As such, the method does not require any robot model or even actuator encoder measurements and only uses the visual clothoid features to control the robot shape. A unique advantage of using our clothoid representation is being able to generate reference shape curves without the need for taking images of the robot at the desired shapes.  Experiments demonstrate consistently successful results for shape and end effector pose convergence for a diverse set of references. Notably, we also present the first results in the literature for the vision-based shape control of a variable length continuum robot, extending and contracting to achieve the desired shape.

The image above shows results for shape convergence. The blue curves depict the initial shape and the pink curves depict the desired shape while the dashed purple curve shows the final shape of the robot for each experiment. The markers along each curve denote the points at which we sample the curve to obtain our features. Hollow yellow markers are used for the initial and desiredshapes, while solid orange markers are used for the final shape. The last point on the curves is at the robot’s end effector.
The image above shows results for shape convergence. The blue curves depict the initial shape and the pink curves depict the desired shape while the dashed purple curve shows the final shape of the robot for each experiment. The markers along each curve denote the points at which we sample the curve to obtain our features. Hollow yellow markers are used for the initial and desired shapes, while solid orange markers are used for the final shape. The last point on the curves is at the robot’s end effector.

 

Papers related to this project:

Shape Control of Variable Length Continuum Robots using Clothoid-based Visual Servoing

[Paper] [Video]

2023 IEEE/RSJ IROS Conference on Intelligent Robots and Systems (IROS)