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The soft robotic arm used for the experimental evaluation. The arm is actuated by three symmetrically arranged bellow-type actuators. The arm includes a suction cup as an end effector and is mounted in a horizontal configuration, which is used throughout this work.
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This paper presents the application of a learning control approach for the realization of a fast and reliable pick-and-place application with a spherical soft robotic arm. The arm is characterized by a lightweight design and exhibits compliant behavior due to the soft materials deployed. A soft, continuum joint is employed, which allows for simulta...
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... this work, we present the realization of a pick-and-place application using the antagonistically actuated spherical soft robotic arm depicted in Fig. 1. Two rotational and one translational or stiffness degree of freedom can be simultaneously controlled in a single joint based on the continuous structure of the soft ...
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... soft robotic arm consists of six main components: a static link, a movable link, a soft joint, three bellow type actuators, a vacuum gripper as an end effector and a base plate for mounting the system (see Fig. 1). The static and movable links are based on a double-shell design, consisting of an inflatable, airtight inner bladder and a sewn, inextensible outer shell. These result in a lightweight construction, where the mass of the movable link is given by 200 g. Pressurization of the links provides the structural stability of the robot arm. ...
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... consider the system as two independent (linearized) pendulums. Given the robot configuration as depicted in Fig. 1, the linearized dynamics are given ...
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... in a robust and reliable way with a vacuum gripper, it is crucial to axially approach and adhere the object. As the system is equipped with a soft joint (see Sec. II) with certain axial compliance, objects can be approached in the axial direction. To control the axial elongation of the soft joint, the lower pressure bound ¯ p is increased (see Fig. 10, bottom). However, for rapid increases in ¯ p this causes an error with respect to the constant angle reference which cannot be compensated by the feedback controller. Note that the Delta Representation solely ensures a decoupling between α, β, but not their invariance with respect to ¯ p. In order to provide accurate tracking of the constant ...
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... be compensated by the feedback controller. Note that the Delta Representation solely ensures a decoupling between α, β, but not their invariance with respect to ¯ p. In order to provide accurate tracking of the constant reference, when simultaneously approaching the object, the same ILC strategy is applied when picking an object as introduced in Fig. 10. Experimental results for an aggressive pick-and-place operation, when the warm start is applied (iteration 0) and after applying the ILC scheme for 33 additional iterations on all phases combined. The area marked as (E) corresponds to the time where the ejection impulse is switched on in order to ensure rapid purging of the vacuum ...
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... period is 2.78 sec for a reference change of approximately 60 • . The reference change occurs within 0.6 sec in phase (II) and within 0.3 sec in phase (III). An ejection impulse is applied between phases (II) and (III) when depositing an object to ensure rapid purging of the vacuum by the active pressurization of the suction cup (see phase (E) in Fig. ...
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... appropriately and concatenated resulting in the warm start correction signal. Subsequently, the ILC for the pick-and-place application is trained for the entire pick-andplace operation jointly, initialized with the warm start. The mass parameter for the underlying feedback control loop is changed continuously between the different phases. Fig. 10 shows the tracking performance during the pick-and-place application when applying the warm start and after the ILC scheme applied to the entire application has ...
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... implemented ILC approach allows for accurate and fast pick-and-place tasks. Note the high accuracy when depositing the mass, which is attributable to the non-causal nature of the ILC scheme. The interested reader is referred to Fig. 11 and to the video attachment to gain a visual impression of the system during operation and the application performed (https://youtu.be/0ovIZ-R81sg). After convergence of the ILC, the pick-and-place application works reliably, which is demonstrated in the video attachment with 50 out of 50 consecutive successful ...
