A Floating-Piston Hydrostatic Linear Actuator and Remote-Direct-Drive 2-DOF Gripper

Schwarm, Eric; Gravesmill, Kevin M.; Whitney, John P.

doi:10.1109/icra.2019.8794378

Cited by 19 publications

(11 citation statements)

References 12 publications

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“…As a testbed for internal fluid pressure force feedback for fluid-actuated systems, we use a rolling-diaphragm-actuated 2-DOF gripper [15], shown in Fig. 2.…”

Section: B Mechanical Design and Testbed Setupmentioning

confidence: 99%

“…The low-level control code uses the Simple Open EtherCAT Master (SOEM) library with the main control loop running at 2kHz on an isolated CPU core. More details of testbed setup can be found in [15].…”

Section: B Mechanical Design and Testbed Setupmentioning

confidence: 99%

“…In this paper we investigate fluid-actuated robotic systems with purposeful fluid/hose compliance [14], internal pressure force-feedback, and low-friction fiber-elastomer soft actuators. Section II describes the exemplary system, a 2-DOF lightweight gripper [15] with details on fluid pressure force feedback setup, and system identification results. Section III describes the disturbance observer (DOB) force feedback method, adapted to the case of fluid-actuated systems, and Section IV describes a model-based approach to compensating for smooth endpoint friction without any endpoint state or external force sensing, and presents detailed Z-width measurements.…”

Section: Introductionmentioning

confidence: 99%

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Series Elastic Force Control for Soft Robotic Fluid Actuators

Wang,

Whitney

2020

Preprint

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Fluid-based soft actuators are an attractive option for lightweight and human-safe robots. These actuators, combined with fluid pressure force feedback, are in principle a form of series-elastic actuation (SEA), in which nearly all driving-point (e.g. motor/gearbox) friction can be eliminated. Fiber-elastomer soft actuators offer unique low-friction and low-hysteresis mechanical properties which are particularly suited to force-control based on internal pressure force feedback, rather than traditional external force feedback using force/tactile sensing, since discontinuous (Coulomb) endpoint friction is unobservable to internal fluid pressure. However, compensation of endpoint smooth hysteresis through a modelbased feedforward term is possible. We report on internalpressure force feedback through a disturbance observer (DOB) and model-based feedforward compensation of endpoint friction and nonlinear hysteresis for a 2-DOF lightweight robotic gripper driven by rolling-diaphragm linear actuators coupled to direct-drive brushless motors, achieving an active lowfrequency endpoint impedance range ("Z-width") of 50dB.

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“…As a testbed for internal fluid pressure force feedback for fluid-actuated systems, we use a rolling-diaphragm-actuated 2-DOF gripper [15], shown in Fig. 2.…”

Section: B Mechanical Design and Testbed Setupmentioning

confidence: 99%

Section: B Mechanical Design and Testbed Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Series Elastic Force Control for Soft Robotic Fluid Actuators

Wang,

Whitney

2020

Preprint

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“…The joint angles of the gripper are used as the tactile observations. The gripper used in this work has hydro-static linear actuators [29] which allows us to set the finger joint stiffness to a low value. This way, the gripper can interact with objects without moving them.…”

Section: Data Collectionmentioning

confidence: 99%

Learning Bayes Filter Models for Tactile Localization

Kelestemur

Keil

Whitney

et al. 2020

2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

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Localizing and tracking the pose of robotic grippers are necessary skills for manipulation tasks. However, the manipulators with imprecise kinematic models (e.g. low-cost arms) or manipulators with unknown world coordinates (e.g. poor camera-arm calibration) cannot locate the gripper with respect to the world. In these circumstances, we can leverage tactile feedback between the gripper and the environment. In this paper, we present learnable Bayes filter models that can localize robotic grippers using tactile feedback. We propose a novel observation model that conditions the tactile feedback on visual maps of the environment along with a motion model to recursively estimate the gripper's location. Our models are trained in simulation with self-supervision and transferred to the real world. Our method is evaluated on a tabletop localization task in which the gripper interacts with objects. We report results in simulation and on a real robot, generalizing over different sizes, shapes, and configurations of the objects.

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“…A range of solutions have been proposed in the past years (see, e.g., [6], [8], [9], [12]), but an effective recent technology named rolling diaphragm hydrostatic transmission (RDHT) [22] has several advantages in terms of friction and backlash. Different RDHT layouts have then been proposed for the actuation of fully-passive robotic systems [21], lower limb exoskeletons [18], robotic grippers [15] and MR compatible robots [4].…”

Section: Introductionmentioning

confidence: 99%

Smith-Predictor-Based Torque Control of a Rolling Diaphragm Hydrostatic Transmission

Bolignari

Rizzello

Zaccarian

et al. 2021

IEEE Robot. Autom. Lett.

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Rolling Diaphragm Hydrostatic Transmissions (RDHT) are high-performance low-cost solutions to delocalize heavy actuators away from the joints of robotic systems. Exploiting a low-cost pressure-based sensing technique, we propose here a Smith-predictorbased joint torque control of an RDHT-based actuation system. We also use a load-cell sensor for ground truth validation. The developed feedback controller is conveniently tuned based on an arbitrary pre-specified closed-loop natural frequency and damping ratio. This preserves the open-loop bandwidth while removing the intrinsic oscillations of the lightly damped highly transparent open-loop plant. Experimental tests validate the proposed control strategy, both in a stand-alone torque setpoint configuration and in a series of Human-Robot-Interaction tests confirming the significant advantages of the closed-loop control architecture.

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A Floating-Piston Hydrostatic Linear Actuator and Remote-Direct-Drive 2-DOF Gripper

Cited by 19 publications

References 12 publications

Series Elastic Force Control for Soft Robotic Fluid Actuators

Series Elastic Force Control for Soft Robotic Fluid Actuators

Learning Bayes Filter Models for Tactile Localization

Smith-Predictor-Based Torque Control of a Rolling Diaphragm Hydrostatic Transmission

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