14 research outputs found
A bistable soft gripper with mechanically embedded sensing and actuation for fast closed-loop grasping
Soft robotic grippers are shown to be high effective for grasping
unstructured objects with simple sensing and control strategies. However, they
are still limited by their speed, sensing capabilities and actuation mechanism.
Hence, their usage have been restricted in highly dynamic grasping tasks. This
paper presents a soft robotic gripper with tunable bistable properties for
sensor-less dynamic grasping. The bistable mechanism allows us to store
arbitrarily large strain energy in the soft system which is then released upon
contact. The mechanism also provides flexibility on the type of actuation
mechanism as the grasping and sensing phase is completely passive. Theoretical
background behind the mechanism is presented with finite element analysis to
provide insights into design parameters. Finally, we experimentally demonstrate
sensor-less dynamic grasping of an unknown object within 0.02 seconds,
including the time to sense and actuate
Mantises exchange angular momentum between three rotating body parts to jump precisely to targets.
Flightless animals have evolved diverse mechanisms to control their movements in air, whether falling with gravity or propelling against it. Many insects jump as a primary mode of locomotion and must therefore precisely control the large torques generated during takeoff. For example, to minimize spin (angular momentum of the body) at takeoff, plant-sucking bugs apply large equal and opposite torques from two propulsive legs [1]. Interacting gear wheels have evolved in some to give precise synchronization of these legs [2, 3]. Once airborne, as a result of either jumping or falling, further adjustments may be needed to control trajectory and orient the body for landing. Tails are used by geckos toย control pitch [4, 5] and by Anolis lizards to alter direction [6, 7]. When falling, cats rotate their body [8], while aphids [9] and ants [10, 11] manipulate wind resistance against their legs and thorax. Falling is always downward, but targeted jumping must achieve many possible desired trajectories. We show that when making targeted jumps, juvenile wingless mantises first rotated their abdomen about the thorax to adjust the center of mass and thus regulate spin at takeoff. Once airborne, they then smoothly and sequentially transferred angular momentum in four stages between the jointed abdomen, the two raptorial front legs, and the two propulsive hind legs to produce a controlled jump with a precise landing. Experimentally impairing abdominal movements reduced the overall rotation so that the mantis either failed to grasp the target or crashed into it head first.GPS was supported by HFSP grant LT00422/2006-C. DAC was funded by a Leverhulme
Trust grant F/09 364/K to S.R. Ott, University of Leicester, whom we thank for his support.This is the accepted manuscript. The final version is available at http://www.cell.com/current-biology/abstract/S0960-9822%2815%2900086-X
Impact Testing of Different Materials on Wheels Used in Throwable Unmanned Ground Vehicles
Throwable Unmanned Ground Vehicles are light weight, small size, easily deployable and impact resistive vehicles mainly used in domestic as well as in military purposes where human life is compromised such as inspection of sewage pipes, and search and rescue operations etc. Main challenge while considering a Throwable UGV is its impact absorption capability which is seen through its material properties. Wheels of Throwable UGV absorb most of the impact without harming the internal structure. To solve this problem a honeycomb structured wheel is designed and simulated in ANSYS Workbench. Vulcanized rubber and Plastic composite PCTPE material wheels were impact tested using explicit dynamic analysis tool in ANSYS workbench. Total deformation, equivalent stress and strain results are tested in ANSYS under impact testing of wheel which is dropped from 10 meter height with velocity of 14m/s in a concrete surface. A plastic composite material PCTPE was 3D-printed and was used in Throwable Unmanned Ground Vehicle
Robotic metamorphosis by origami exoskeletons
Changing the inherent physical capabilities of robots by metamorphosis has been a long-standing goal of engineers. However, this task is challenging because of physical constraints in the robot body, each component of which has a defined functionality. To date, self-reconfiguring robots have limitations in their on-site extensibility because of the large scale of todayโs unit modules and the complex administration of their coordination, which relies heavily on on-board electronic components. We present an approach to extending and changing the capabilities of a robot by enabling metamorphosis using self-folding origami โexoskeletons.โ We show how a cubical magnet โrobotโ can be remotely moved using a controllable magnetic field and hierarchically develop different morphologies by interfacing with different origami exoskeletons. Activated by heat, each exoskeleton is self-folded from a rectangular sheet, extending the capabilities of the initial robot, such as enabling the manipulation of objects or locomotion on the ground, water, or air. Activated by water, the exoskeletons can be removed and are interchangeable. Thus, the system represents an end-to-end (re)cycle. We also present several robot and exoskeleton designs, devices, and experiments with robot metamorphosis using exoskeletons
๋ฐฉํฅ ์ ํ, ๋์ฝ ๊ฐ๋ ์กฐ์ , ์์ธ ๊ต์ ์ด ๊ฐ๋ฅํ ์ ํ ๋ก๋ด
ํ์๋
ผ๋ฌธ (์์ฌ)-- ์์ธ๋ํ๊ต ๋ํ์ : ๊ณต๊ณผ๋ํ ๊ธฐ๊ณํญ๊ณต๊ณตํ๋ถ, 2019. 2. ์กฐ๊ท์ง.๋์ฝ ๋ก๋ด์ ๋ก๋ด ์์ ์ ํฌ๊ธฐ๋ณด๋ค ํฐ ์ฅ์ ๋ฌผ์ ๋์ด ์ด๋ํ ์ ์๋ค. ๋์ฝ ์ด๋๋ง์ผ๋ก ์ํ๋ ์์น์ ๋๋ฌํ๊ธฐ ์ํด ๋๋ฌ ๊ฐ๋ฅํ ๋ฒ์๋ฅผ ๋ํ ์ ์๋ ๋ฐฉํฅ ์ ํ, ๋์ฝ ๊ฐ๋ ์กฐ์ , ์์ธ ๊ต์ ๊ธฐ๋ฅ์ด ํตํฉ๋ ์ ํ ๋ก๋ด๋ค์ด ๊ฐ๋ฐ๋๋ค. ์ด ๋ ์ถ๊ฐ ๊ธฐ๋ฅ์ ํตํฉํ๋ฉด ๋ก๋ด์ ์ง๋์ด ์ฆ๊ฐํ๊ณ ๋์ฝ ์ฑ๋ฅ์ด ๊ฐ์ํ๋ฏ๋ก ์ง๋์ ์ค์ด๊ธฐ ์ํ ์ค๊ณ๊ฐ ํ์ํ๋ค. ๋ณธ ๋
ผ๋ฌธ์์๋ ๋ฐฉํฅ ์ ํ, ๋์ฝ ๊ฐ๋ ์กฐ์ , ์์ธ ๊ต์ ์ด ๊ฐ๋ฅํ ๋์ฝ ๋ก๋ด์ ์ ์ํ๋ฉฐ, ๋์ฝ ์ฑ๋ฅ ๊ฐ์๋ฅผ ์ต์ํํ๊ธฐ ์ํด ๋ฉ์ปค๋์ฆ๊ณผ ๊ตฌ๋๊ธฐ๋ฅผ ๊ณต์ ํ ์ ์๋๋ก ๋ก๋ด์ด ์ค๊ณ๋์๋ค. ๋ก๋ด์ ์ง๋์ 70.1 g์ผ๋ก ์ต๋ ๋์ด 1.02 m, ์ต๋ ๊ฑฐ๋ฆฌ 1.28 m๋ฅผ ๋์ฝํ ์ ์๋ค. ๋ํ, ์ ๋ฐฉํฅ์ผ๋ก ๋์ฝํ ์ ์์ผ๋ฉฐ, ๋ฐ๋ณต ๋์ฝ์ผ๋ก ๋ ๋จผ ๊ณณ์ ๋๋ฌํ ์ ์๋ค. ๋ก๋ด์ ๊ฑฐ๋์ ์์ธกํ ์ ์๋ ๋์ญํ ๋ชจ๋ธ์ ์ธ์ ์ผ๋ฉฐ, ๋ฏธ๋๋ฌ์ง์ด ์์ด ๋์ฝํ๋ ๊ฒฝ์ฐ๋ฟ๋ง ์๋๋ผ ๋ฏธ๋๋ฌ์ง์ด ํฌํจ๋ ๋์ฝ์ ๋ํด์๋ ๋ก๋ด์ ๊ฑฐ๋์ ํ์ธํ๊ณ ๋์ฝ ๊ถค์ ์ ๊ณํํ ์ ์๋ค. ๊ตฌ๋๊ธฐ์ ์๋ณด๋ค ๋ง์ ๊ธฐ๋ฅ์ ์๋ฅผ ๊ตฌํํ๋ ์ค๊ณ ๋ฐฉ๋ฒ์ ๋ค๋ฅธ ์ํ ๋ก๋ด์ ์ค๊ณ์ ์ ์ฉํ ์ ์์ ๊ฒ์ด๋ค. ์ด ๋ก๋ด์ ๋น์ ํ ํ๊ฒฝ์์ ์์, ์ ์ฐฐ ํน์ ํ์ฌ์ ๊ฐ์ ์๋ฌด๋ฅผ ์ํํ๋ ๋ฐ ํ์ฉ ๊ฐ๋ฅํ ๊ฒ์ด๋ค.Jumping enables the robot to overcome obstacles that are larger than its own size. In order to reach the desired location with only jumping, the jumping robots integrated with additional functions โsteering, adjusting the take-off angle, and self-righting โ have been developed to expand the reachable range of the robot. Design to reduce mass is required as the integration of additional functions increases the mass of the robot and reduces the jumping performance. In this thesis, a jumping robot capable of steering, adjusting the take-off angle, and self-righting is proposed with the design of actuator and mechanism sharing to minimize the jumping performance degradation. The robot, with a mass of 70.1 g jumps up to 1.02 m in vertical height, and 1.28 m in horizontal distance. It can change the jumping height and distance by adjusting the take-off angle from 40ยฐ to 91.9ยฐ. The robot can jump in all directions, and it can reach farther through multiple jumps. A dynamic model is established to predict the behavior of the robot and plan the jumping trajectory not only for jumping without slip but also for jumping with slip. The design method to implement more functions than the number of actuators can be applied to design other small-scale robots. This robot can be deployed to unstructured environments to perform tasks such as search and rescue, reconnaissance, and exploration.Abstract โ
ฐ
Contents โ
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List of Tables โ
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List of Figures โ
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Chapter 1. Introduction 1
1.1. Motivation 1
1.2. Research Objectives and Contributions 3
1.3. Research Overview 6
Chapter 2. Design 7
2.1. Jumping 8
2.2. Steering 10
2.3. Take-off Angle Adjustment 12
2.4. Self-Righting 13
2.5. Integration 16
Chapter 3. Analysis 19
3.1. Dynamic Modeling 19
3.2. Simulated Results 24
3.3. Jumping Trajectory Planning 33
Chapter 4. Result 35
4.1. Performance 35
4.2. Demonstration 40
Chapter 5. Conclusion 46
Bibliography 49
๊ตญ๋ฌธ ์ด๋ก 53Maste
A Low Profile Electromagnetic Actuator Design and Model for an Origami Parallel Platform
Thin foldable origami mechanisms allow reconfiguration of complex structures with large volumetric change, versatility, and at low cost; however, there is rarely a systematic way to make them autonomously actuated due to the lack of low profile actuators. Actuation should satisfy the design requirements of wide actuation range, high actuation speed, and backdrivability. This paper presents a novel approach toward fast and controllable folding mechanisms by embedding an electromagnetic actuation system into a nominally flat platform. The design, fabrication, and modeling of the electromagnetic actuation system are reported, and a 1.7 mm-thick single-degree-of-freedom (DoF) foldable parallel structure reaching an elevation of 13mm is used as a proof of concept for the proposed methodology. We also report on the extensive test results that validate the mechanical model in terms of the loaded and unloaded speed, the blocked force, and the range of actuation
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The Consequences of Speed: Studies of Cavitation During the Mantis Shrimp Strike and the Control of Rapid Deceleration During Toad Landing
There are consequences of moving quickly in this world. Here we investigate how two very different species, mantis shrimp (Odontodactylus scyllarus) and cane toads (Bufo marinus), negotiate forces that result from moving rapidly in different environments. To study the mechanical principles and fluid dynamics of ultrafast power-amplified systems, we built Ninjabot, a physical model of the extremely fast mantis shrimp. While mantis shrimp produce damaging cavitation upon impact with their prey, they do not cavitate during the forward portion of their strike despite extreme speeds. In order to study cavitation onset in non-linear flows common during the mantis shrimp strike, we used Ninjabot to produce strikes of varying kinematics and measured cavitation presence or absence. We found that in rotating and accelerating biological conditions, cavitation inception is best explained only by maximum linear velocity. Thus, studies of cavitation onset in biological conditions only need to focus on maximum velocity. On land, moving quickly requires avoiding or preparing for impact with other objects, often the ground. Within anurans (frogs and toads), a group well known for jumping, cane toads are known to perform particularly controlled landings in which the forelimbs are used to decelerate and balance the body after impact as the hind limbs are lowered to the ground. Here I explore whether and how toads modulate landing preparation depending on hopping and landing conditions and what this can tell us about how they utilize sensory information to help them perform controlled landings. We found that toads modulate three components of impact preparation to specific hop conditions: 1) They position the forelimbs to hit the ground first by protracting and abducting the humeri, 2) They prepare and brace for impact by extending the elbows and activating underlying musculature to stiffen the joint and 3) they control torques during the landing by retracting the hind limbs and rotating the forelimbs to align with the impact angle. By perturbing landing conditions we found that toads tune these components to specific landing conditions with a combination of passive and active control and toads do so by primarily relying on non-visual sensory feedback
Biologically inspired perching for aerial robots
2021 Spring.Includes bibliographical references.Micro Aerial Vehicles (MAVs) are widely used for various civilian and military applications (e.g., surveillance, search, and monitoring, etc.); however, one critical problem they are facing is the limited airborne time (less than one hour) due to the low aerodynamic efficiency, low energy storage capability, and high energy consumption. To address this problem, mimicking biological flyers to perch onto objects (e.g., walls, power lines, or ceilings) will significantly extend MAVs' functioning time for surveillance or monitoring related tasks. Successful perching for aerial robots, however, is quite challenging as it requires a synergistic integration of mechanical and computational intelligence. Mechanical intelligence means mechanical mechanisms to passively damp out the impact between the robot and the perching object and robustly engage the robot to the perching objects. Computational intelligence means computation algorithms to estimate, plan, and control the robot's motion so that the robot can progressively reduce its speed and adjust its orientation to perch on the objects with a desired velocity and orientation. In this research, a framework for biologically inspired perching is investigated, focusing on both computational and mechanical intelligence. Computational intelligence includes vision-based state estimation and trajectory planning. Unlike traditional flight states such as position and velocity, we leverage a biologically inspired state called time-to-contact (TTC) that represents the remaining time to the perching object at the current flight velocity. A faster and more accurate estimation method based on consecutive images is proposed to estimate TTC. Then a trajectory is planned in TTC space to realize the faster perching while satisfying multiple flight and perching constraints, e.g., maximum velocity, maximum acceleration, and desired contact velocity. For mechanical intelligence, we design, develop, and analyze a novel compliant bistable gripper with two stable states. When the gripper is open, it can close passively by the contact force between the robot and the perching object, eliminating additional actuators or sensors. We also analyze the bistability of the gripper to guide and optimize the design of the gripper. At the end, a customized MAV platform of size 250 mm is designed to combine computational and mechanical intelligence. A Raspberry Pi is used as the onboard computer to do vision-based state estimation and control. Besides, a larger gripper is designed to make the MAV perch on a horizontal rod. Perching experiments using the designed trajectories perform well at activating the bistable gripper to perch while avoiding large impact force which may damage the gripper and the MAV. The research will enable robust perching of MAVs so that they can maintain a desired observation or resting position for long-duration inspection, surveillance, search, and rescue