PneuAct-II: Hybrid Manufactured Electromagnetically Stealth Pneumatic Stepper Actuator

Farimani, Foad Sojoodi; Mojarradi, Morteza; Hekman, Edsko E.G.; Misra, Sarthak

doi:10.1109/lra.2020.2974652

Cited by 7 publications

(4 citation statements)

References 12 publications

(8 reference statements)

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“…The limitations of long response time and small output force can be overcome by the utilization of tendon-based actuation but might pose safety issues during human-robot interaction when not operated properly [11,12]. Pneumatic and hydraulic actuators (fluidic actuators) have better safety, flexibility towards harsh environments, and high mechanical output to size ratio [13] compared to conventional actuators such as electromagnetic motors.…”

Section: Introductionmentioning

confidence: 99%

“…Building robots is a slow process due to the fabrication of multiple components, followed by sequential assembly. We overcome this by 3D printing [13] the complex structure of the SMP actuator with high precision in a single step, with hydraulic channels already employed due to its design. Although several 3D printing methods [17][18][19] were developed for fabricating SMPs, most of them utilize a multi-step fabrication process unlike our single-step fabrication process.…”

Section: Introductionmentioning

confidence: 99%

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Fully-Printable Soft Actuator with Variable Stiffness by Phase Transition and Hydraulic Regulations

et al. 2021

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Actuators with variable stiffness have vast potential in the field of compliant robotics. Morphological shape changes in the actuators are possible, while they retain their structural strength. They can shift between a rigid load-carrying state and a soft flexible state in a short transition period. This work presents a hydraulically actuated soft actuator fabricated by a fully 3D printing of shape memory polymer (SMP). The actuator shows a stiffness of 519 mN/mm at 20 ∘C and 45 mN/mm at 50 ∘C at the same pressure (0.2 MPa). This actuator demonstrates a high stiffness variation of 474 mN/mm (10 times the baseline stiffness) for a temperature change of 30 ∘C and a large variation (≈1150%) in average stiffness. A combined variation of both temperature (20–50 ∘C) and pressure (0–0.2 MPa) displays a stiffness variation of 501 mN/mm. The pressure variation (0–0.2 MPa) in the actuator also shows a large variation in the output force (1.46 N) at 50 ∘C compared to the output force variation (0.16 N) at 20 ∘C. The pressure variation is further utilized for bending the actuator. Varying the pressure (0–0.2 MPa) at 20 ∘C displayed no bending in the actuator. In contrast, the same variation of pressure at 50 ∘C displayed a bending angle of 80∘. A combined variation of both temperature (20–50 ∘C) and pressure (0–0.2 MPa) shows the ability to bend 80∘. At the same time, an additional weight (300 g) suspended to the actuator could increase its bending capability to 160∘. We demonstrated a soft robotic gripper varying its stiffness to carry objects (≈100 g) using two individual actuators.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fully-Printable Soft Actuator with Variable Stiffness by Phase Transition and Hydraulic Regulations

et al. 2021

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“…Non-assembly production is also one of the unique features of AM where a complete integrated functional mechanism, with embedded moving joints, can be printed without the need for further assembly (also known as assembly printing). Currently, AM is experiencing a major transformation from demonstrative/rapid prototyping to functional manufacturing, where the parts are being directly used as/ in the actual products (Farimani and Misra, 2018;Farimani et al, 2020). Therefore, the final properties of the printed parts, including geometric, mechanical, tribological, electromagnetic and thermal characteristics, should be better understood.…”

Section: Introductionmentioning

confidence: 99%

“…Besides, they present other properties, such as being chemically inert and self-lubricating. These make FDM-ABS ideal for tribological applications and manufacturing of disposable parts, for example in surgical applications (Farimani and Misra, 2018;Farimani et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Frictional characteristics of Fusion Deposition Modeling (FDM) manufactured surfaces

Farimani

Rooij

Hekman

et al. 2020

RPJ

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Purpose Additive manufacturing (AM) is a promising alternative to the conventional production methods (i.e., machining), providing the developers with great geometrical and topological freedom during the design and immediate prototyping customizability. However, frictional characteristics of the AM surfaces are yet to be fully explored, making the control and manufacturing of precise assembly manufactured mechanisms (i.e., robots) challenging. The purpose of this paper is to understand the tribological behavior of fused deposition modeling (FDM) manufactured surfaces and test the accuracy of existing mathematical models such as Amontons–Coulomb, Tabor–Bowden, and variations of Hertz Contact model against empirical data. Design/methodology/approach Conventional frictional models Amontons–Coulomb and Tabor–Bowden are developed for the parabolic surface topography of FDM surfaces using variations of Hertz contact models. Experiments are implemented to measure the friction between two flat FDM surfaces at different speeds, normal forces, and surface configuration, including the relative direction of printing stripes and sliding direction and the surface area. The global maximum measured force is considered as static friction, and the average of the local maxima during the stick-slip phase is assumed as kinematic friction. Spectral analysis has been used to inspect the relationship between the chaos of vertical wobbling versus sliding speed. Findings It is observed that the friction between the two FDM planes is linearly proportional to the normal force. However, in contrast to the viscous frictional model (i.e., Stribeck), the friction reduces asymptotically at higher speeds, which can be attributed to the transition from harmonic to normal chaotic vibrations. The phase shift is investigated through spectral analysis; dominant frequencies are presented at different pulling speeds, normal forces, and surface areas. It is hypothesized that higher speeds lead to smaller dwell-time, reducing creep and adhesive friction consequently. Furthermore, no monotonic relationship between surface area and friction force is observed. Research limitations/implications Due to the high number of experimental parameters, the research is implemented for a limited range of surface areas, which should be expanded in future research. Furthermore, the pulling position of the jaws is different from the sliding distance of the surfaces due to the compliance involved in the contact and the pulling cable. This issue could be alleviated using a non-contact position measurement method such as LASER or image processing. Another major issue of the experiments is the planar orientation of the pulling object with respect to the sliding direction and occasional swinging in the tangential plane. Practical implications Given the results of this study, one can predict the frictional behavior of FDM manufactured surfaces at different normal forces, sliding speeds, and surface configurations. This will help to have better predictive and model-based control algorithms for fully AM manufactured mechanisms and optimization of the assembly manufactured systems. By adjusting the clearances and printing direction, one can reduce or moderate the frictional forces to minimize stick-slip or optimize energy efficiency in FDM manufactured joints. Knowing the harmonic to chaotic phase shift at higher sliding speeds, one can apply certain speed control algorithms to sustain optimal mechanical performance. Originality/value In this study, theoretical tribological models are developed for the specific topography of the FDM manufactured surfaces. Experiments have been implemented for an extensive range of boundary conditions, including normal force, sliding speed, and contact configuration. Frictional behavior between flat square FDM surfaces is studied and measured using a Zwick tensile machine. Spectral analysis, auto-correlation, and other methods have been developed to study the oscillations during the stick-slip phase, finding local maxima (kinematic friction) and dominant periodicity of the friction force versus sliding distance. Precise static and kinematic frictional coefficients are provided for different contact configurations and sliding directions.

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MRI-guided robot intervention—current state-of-the-art and new challenges

Huang

Lou

Zhou

et al. 2023

Med-X

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Magnetic Resonance Imaging (MRI) is now a widely used modality for providing multimodal, high-quality soft tissue contrast images with good spatiotemporal resolution but without subjecting patients to ionizing radiation. In addition to its diagnostic potential, its future theranostic value lies in its ability to provide MRI-guided robot intervention with combined structural and functional mapping, as well as integrated instrument localization, target recognition, and in situ, in vivo monitoring of the therapeutic efficacy. Areas of current applications include neurosurgery, breast biopsy, cardiovascular intervention, prostate biopsy and radiotherapy. Emerging applications in targeted drug delivery and MRI-guided chemoembolization are also being pursued. Whilst promising progress has been made in recent years, there are still significant basic science research and engineering challenges. This paper provides a comprehensive review of the current state-of-the-art in MRI-guided robot intervention and allied technologies in actuation, sensing, new materials, interventional instruments, and interactive/real-time MRI. Potential future research directions and new clinical developments are also discussed.

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PneuAct-II: Hybrid Manufactured Electromagnetically Stealth Pneumatic Stepper Actuator

Cited by 7 publications

References 12 publications

Fully-Printable Soft Actuator with Variable Stiffness by Phase Transition and Hydraulic Regulations

Fully-Printable Soft Actuator with Variable Stiffness by Phase Transition and Hydraulic Regulations

Frictional characteristics of Fusion Deposition Modeling (FDM) manufactured surfaces

MRI-guided robot intervention—current state-of-the-art and new challenges

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