Simultaneous Robot-World, Sensor-Tip, and Kinematics Calibration of an Underactuated Robotic Hand with Soft Fingers


Simultaneous Robot-World, Sensor-Tip, and Kinematics Calibration of an Underactuated Robotic Hand with Soft Fingers

Ning Tan, Xiaoyi Gu, and Hongliang Ren Senior Member, IEEE

Abstract—Soft robotics is a research field growing rapidly with primary focuses on the prototype design, development of soft robots and their applications. Due to their highly deformable features, it is difficult to model and control such robots in a very precise compared with conventional rigid structured robots. Hence, the calibration and parameter identification problems of an underactuated robotic hand with soft fingers are important, but have not been investigated intensively. In this paper, we present a comparative study on the calibration of a soft robotic hand. The calibration problem is framed as an AX=YB problem with the partially known matrix A. The identifiability of the parameters is analyzed, and calibration methods based on nonlinear optimization (i.e., L-M method and interior-point method) and evolutionary computation (i.e., differential evolution) are presented. Extensive simulation tests are performed to examine the parameter identification using the three methods in a comparative way. The experiments are conducted on the real soft robotic-hand setup. The fitting, interpolating, and extrapolating errors are presented as well.

Index Terms—Soft robotics, calibration and identification, robotic hand, AX=YB, hand-eye calibration, tendon-driven robot

Shape Morphing Microscale Soft Robotic Actuators


The micro actuator has been studied for its application in micro operations such as manipulating cellular aggregate, the tissues or drug delivery. The traditional actuation methods include thermo-mechanical actuation, electromagnetic actuation, electrostatic actuation and pneumatic actuation. Among these actuation methods, pneumatic actuation has the advantage of not generating heat and current during actuation.
We investigate
1) a streamlined and standardized fabrication procedure to make sub-millimeter scale soft pneumatic actuators (SPA) with customizable bending modalities achieved by shape engineering. Preliminary models are also given to interpret width-based shape engineering for customization and to compare the bending angle and radius of curvature measured from the characterization experiments.
2) a new micro pneumatic actuator consisting of two biocompatible materials is designed, fabricated and tested. The actuator has one bending degree of freedom and the largest bending deformation is about 115°.


  • X. Liang; Y. Sun & H. Ren A Flexible Fabrication Approach towards the Shape Engineering of Microscale Soft Pneumatic Actuators IEEE Robotics and Automation Letters, 2016, 1-6
  • X. Liang; C. Lee & H. Ren Towards a Micro Pneumatic Actuator with Large Bending Deformation for Medical Interventions 7th WACBE World Congress on Bioengineering, 6th to 8th July, 2015, Singapore, Springer International Publishing, 2015, 52, 76-79
  • P. M. Khin; J. H. Low; S. Kukreja; H. Ren & R. Yeow Soft Haptics Using Soft Actuator and Soft Sensor BioRob2016, 6th IEEE RAS/EMBS International Conference on Biomedical Robotics and Biomechatronics, June 26-29, 2016, Singapore, 2016

Soft Robotic Manipulators: fabrication & applications


Flexible robotic manipulators have been widely used in minimally invasive surgery (MIS) and many other applications requiring closer inspection and operation. Although a variety of manipulators enabled by different mechanism have been developed, few of them can preserve softness, thinness and decent bending capability simultaneously. We develop miniature soft robotic manipulators made of hyper-elastic silicone rubber. Along with the manipulator design, novel fabrication methods are proposed and elaborated. Detailed characterizations are specified to show the bending capability of the manipulator given different air pressure. Specifically, our manipulator, as thin as 6 mm, is able to achieve 360° directional bending, and, when given pressure over 70kPa, it can reach 180° bending angle and around 5mm bending radius easily. Due to its innate compliance and small dimension, this type of robotic manipulator can deliver safe and comfortable interactions with the subjects. More significantly, the novel fabrications in this paper diversify the fabrication methods for soft pneumatic robots and actuators (SPRA) and further scale down their sizes.
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