Compliant actuation of parallel-type variable stiffness actuator based on antagonistic actuation

Nam, Ki Hoon; Kim, Byeong Sang; Song, Jae Bok

doi:10.1007/s12206-010-0813-6

Cited by 30 publications

(25 citation statements)

References 12 publications

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“…The higher the preload of both antagonistic springs, the higher is the stiffness of the actuator (see Figure 2.1e). The Parallel Dual Action Unit (PDAU) is a compact realization of the antagonistic-controlled stiffness approach, including a force limitation mechanism (Nam et al, 2010).…”

Section: Antagonistic-controlled Stiffnessmentioning

confidence: 99%

Safety of Autonomous Cognitive-oriented Robots

Ertle¹

2015

Künstl Intell

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Service robots shall very soon autonomously provide services in all spheres of life. They have to execute demanding and complex tasks in a dynamic environment, collaborate with human users in a natural and intuitive way and adapt themselves to varying conditions. It can be assumed that complex robots have to be able to learn, if they shall be able to provide complex tasks in unstructured environments in an autonomous fashion. The capability to 'act autonomously' is often mentioned in conjunction with robots, however, the perception and understanding of the term autonomy varies among the different research fields. Therefore, a closer look is taken at robot autonomy and intelligence, in particular, with regard to current and future robots. From this perspective, implications for safety are derived concerning safe autonomous behavior.In order to push forward the robot safety in the light of safe behavior in complex environments, a novel classification of robot hazards is provided. Based on this, the so-called object interaction hazards are derived which arise when objects that are, for instance, located in the near environment, interact with objects that are manipulated by a robot. Taking into account the current state-of-the-art, it can be stated that this denotes a novel problem area. This problem area is so far addressed neither in current research work, nor in the relevant standards.The new type of hazards can be assigned to a group of hazards that originate from the interaction with a complex and unstructured environment. In order to sufficiently consider the environment and operation context, the robot has to be aware of it. In the field of cognitive (technical and biological) systems, this key capability can be called 'situation awareness ' (cf. Söffker, 2008). Based on Endsley (1995)'s definition of situation awareness, Wardziński (2008) proposes the 'dynamic risk assessment' approach, which shall enable the robot perceive the risk of current and upcoming situations. In order to realize such a risk-aware planning system for the first time, dynamic risk assessment is integrated within a cognitive architecture in order to utilize cognitive functions, such as anticipation, planning and learning. Here, the so-called action spaces (sets of possible upcoming situations) are dynamically anticipated within the underlying cognitive architecture, and a risk assessment component assesses them with regard to comprised risks. Thus, the generated risk information can be utilized for a risk-aware action planning. The proper operation of this integrating concept is demonstrated via simulations and with a robot experiment.In order to consider (object interaction) hazards by means of dynamic risk assessment, (initial) knowledge about hazards is required. Thus, a novel procedural model is developed for systematically generating a safety knowledge base. In this connection, the concept is to formalize risk models (risk description rules) in a generalized manner so that they remain valid for future, and so far unknown si...

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Section: Antagonistic-controlled Stiffnessmentioning

confidence: 99%

Safety of Autonomous Cognitive-oriented Robots

Ertle¹

2015

Künstl Intell

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“…By replacing l S B from (3) with (l 0 + l p l ), the joint stiffness k j is given by k j = k s (l 0 + r r (θ r − θ c )) 2 (9) within the boundary condition for θ c and θ r given by r m in < l 0 + r r (θ r − θ c ) ≤ r com p for compliant motion r com p < l 0 + r r (θ r − θ c ) < r m ax for rigid motion (10) where r m in is the minimum moment arm related to the radius of the roller follower, r m ax is the maximum moment arm associated with the diameter of the ring gear, and r com p is the length to switch from the compliant motion to the rigid motion.…”

Section: A Principle Of Operationmentioning

confidence: 99%

“…Recently, the VSA-CubeBot [6] and the German Aerospace Center (DLR) hand-arm system [20] were equipped with small and lightweight VSAs. A variety of VSAs can be classified into two groups according to their principle of operation: the antagonistic actuation inspired by the musculoskeletal system [5]- [10], which is applied in the VSA [5], VSA-CUBE [6], VSA based on Harmonic Drives [7], quasi-antagonistic joint [8], floating spring joint [9], parallel-type variable stiffness actuator [10], and the variable stiffness actuation based on a main actuator and a variable stiffness mechanism (VSM) [11]- [18]. Several types of VSMs can be realized by using different power transmission mechanisms, such as the variable effective length mechanism and the cam-follower mechanism.…”

Section: Introductionmentioning

confidence: 99%

Design and Control of a Variable Stiffness Actuator Based on Adjustable Moment Arm

2012

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For tasks that require robot-environment interaction, stiffness control is important to ensure stable contact motion and collision safety. The variable stiffness approach has been used to address this type of control. We propose a hybrid variable stiffness actuator (HVSA), which is a variable stiffness unit design. The proposed HVSA is composed of a hybrid control module based on an adjustable moment-arm mechanism, and a drive module with two motors. By controlling the relative motion of gears in the hybrid control module, position and stiffness of a joint can be simultaneously controlled. The HVSA provides a wide range of joint stiffness due to the nonlinearity provided by the adjustable moment arm. Furthermore, the rigid mode, which behaves as a conventional stiff joint, can be implemented to improve positioning accuracy when a robot handles a heavy object. In this paper, the mechanical design features and related analysis are explained. We show that the HVSA can provide a wide range of stiffness and rapid responses according to changes in the stiffness of a joint under varying loads by experiments. The effectiveness of the rigid mode is verified by some experiments on position tracking under high-load conditions. Index Terms-Adjustable moment arm, compliant joint, lever mechanism, variable stiffness actuator (VSA).

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“…Multiple mechanical design idea to achieve variable stiffness has been developed. From the arrangement of the actuators, Nam et al, 4 Petit et al, 5 and Tagliamonte et al 6 pointed out that there are two categories. The first is in serial configurations: a bigger motor to adjust the joint torque/position and another smaller motor to adjust the joint stiffness.…”

Section: Introductionmentioning

confidence: 99%

Analysis on variable stiffness of a cable-driven parallel–series hybrid joint toward wheelchair-mounted robotic manipulator

Zhang

Cao

Hou

et al. 2019

Advances in Mechanical Engineering

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The design of variable stiffness mechanism is of great importance to wheelchair-mounted robotic manipulators. In this article, the authors propose a cable-driven parallel-series hybrid joint toward wheelchair-mounted robotic manipulators with adjusting the system stiffness actively. The joint is a cable-driven, compression-spring-supported hybrid mechanism. Then, the kinematic analysis and cable tension analysis through static modeling are established to derive the joint stiffness model. Finally, cable-driven parallel-series hybrid joint stiffness adjustment ability analysis is carried out in four different load cases with MATLAB. Featured with light structure, stiffness adjustability, and large workspace, the proposed cabledriven parallel-series hybrid joint proves to be of great potential use for wheelchair-mounted robotic manipulators.

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Compliant actuation of parallel-type variable stiffness actuator based on antagonistic actuation

Cited by 30 publications

References 12 publications

Safety of Autonomous Cognitive-oriented Robots

Safety of Autonomous Cognitive-oriented Robots

Design and Control of a Variable Stiffness Actuator Based on Adjustable Moment Arm

Analysis on variable stiffness of a cable-driven parallel–series hybrid joint toward wheelchair-mounted robotic manipulator

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