Parallel Continuum Robots: Modeling, Analysis, and Actuation-Based Force Sensing

Benefiting from the deformability of soft robots, calibration and force sensing for soft robots are possible using an external vision-based system, instead of embedded mechatronic force sensors. In this paper, we first propose a calibration method to calibrate both the sensor-robot coordinate system and the actuator inputs. This task is addressed through a sequential optimization problem for both variables. We also introduce an external force sensing system based on a realtime Finite Element (FE) model with the assumption of static configurations, and which consists of two steps: force location detection and force intensity computation. The algorithm that estimates force location relies on the segmentation of the point cloud acquired by an RGB-D camera. Then, the force intensities can be computed by solving an inverse quasi-static problem based on matching the FE model with the point cloud of the soft robot. As for validation, the proposed strategies for calibration and force sensing have been tested using a parallel soft robot driven by four cables.

Section: Related Workmentioning

confidence: 99%

Section: Calibrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Calibration and External Force Sensing for Soft Robots Using an RGB-D Camera

Zhang

Petit

Dequidt

et al. 2019

“…In addition, Orekhov et al [19] proposed a surgical Parallel Continuum Manipulator with a large workspace and a precision of 0.88 mm in position and 1.96 deg in rotation. Black et al [20] studied the pros and cons of Parallel Continuum Robots (PCR) and pointed out that an analysis of their performance was still needed.…”

Section: Introductionmentioning

confidence: 99%

Nanometer Precision With a Planar Parallel Continuum Robot

Mauzé

Dahmouche

Laurent

et al. 2020

In many cases, soft and continuum robots represent an interesting alternative to articulated robots because they have the advantages of miniaturization capability, safer interactions with humans and often simpler fabricating and integration. However, these benefits are usually considered to arise at the expense of accuracy and precision because of the soft or flexible limbs. This paper demonstrates that, with a proper design, a planar parallel continuum robot is capable of great precision. Indeed, the proposed 3-Degrees-of-Freedom planar parallel continuum robot exhibits a precision of 9.13 nm in position and 1.2 µrad in orientation. In addition, the novel robotic design leverages the effect of the actuators' defects, making the robot more precise than its own actuators. Finally, the workspace of the proposed robot (62.3 mm 2 , 0.6452 rad) is significantly larger than most compliant mechanisms, which is particularly interesting when both very high precision and relatively large displacements are required.

“…Recently, Takano et al employed this idea for shape estimation of continuum rods with moving ends achieving simple forward-integration, real-time performance, small error (3-15%) and occlusion free tracking, but limited accuracy due to discrete implementation of the Kirchhoff Elastic Rod method [15]. Rucker et al have briefly investigated this idea as a part of their actuation-and deflection-based force sensing method for parallel continuum robots [16]. However, geometric constraint (actuation port overlapped with base force sensor placement) and large sensitivity of the method to noise in dynamic scenarios prevented them from effectively implementing the idea.…”

mentioning

confidence: 99%

Stiffness Imaging With a Continuum Appendage: Real-Time Shape and Tip Force Estimation From Base Load Readings

Sadati

Shiva

Herzig

et al. 2020

Self Cite

In this paper, we propose benefiting from load readings at the base of a continuum appendage for real-time forward integration of Cosserat rod model with application in configuration and tip load estimation. The application of this method is successfully tested for stiffness imaging of a soft tissue, using a 3-DOF hydraulically actuated braided continuum appendage. Multiple probing runs with different actuation pressures are used for mapping the tissue surface shape and directional linear stiffness, as well as detecting non-homogeneous regions, e.g. a hard nodule embedded in a soft silicon tissue phantom. Readings from a 6-axis force sensor at the tip is used for comparison and verification. As a result, the tip force is estimated with 0.016-0.037 N (7-20%) mean error in the probing and 0.02-0.1 N (6-12%) in the indentation direction, 0.17 mm (14%) mean error is achieved in estimating the surface profile, and 3.4-15 [N/m] (10-16%) mean error is observed in evaluating tissue directional stiffness, depending on the appendage actuation. We observed that if the appendage bends against the slider motion (toward the probing direction), it provides better horizontal stiffness estimation and better estimation in the perpendicular direction is achieved when it bends toward the slider motion (against the probing direction). In comparison with a rigid probe, ≈ 10 times smaller stiffness and ≈ 7 times larger mean standard deviation values were observed, suggesting the importance of a probe stiffness in estimation the tissue stiffness.