Abstract
Abstract. This paper presents the design and optimization of four versions of self-adaptive, a.k.a. underactuated, fingers based on four-bar linkages. These fingers are designed to be attached to and used with the same standard translational grippers as one finds in the manufacturing and packaging industries. This paper aims at showing self-adaptive fingers as simply as possible and analysing the resulting trade-off between complexity and performance. To achieve this objective, the simplest closed-loop 1 degree-of-freedom (DOF) linkage, namely the four-bar linkage, is used to build these fingers. However, it should be pointed out that if this work does consider a single four-bar linkage as the basic building block of the fingers, four variations of this four-bar linkage are actually discussed, including some with a prismatic joint. The ultimate purpose of this work is to evaluate whether the simplest linkages for adaptive fingers can produce the same level of performance in terms of grasp forces as more complex designs. To this end, a kinetostatic analysis of the four fingers is first presented. Then, the fingers are all numerically optimized considering various force-based metrics, and results are presented. Finally, these results are analysed and prototypes shown.
Highlights
Self-adaptive, known as underactuated (Birglen et al, 2007), hands and fingers have been used in the last decade by both the research community and the industry as a compromise between complex anthropomorphic robotic hands and classical industrial grippers
Complex dexterous hands could require more than three fingers and 9 actuated degrees of freedom (DOF) to become dexterous and provide sufficient motion capability for object manipulation, while classical industrial grippers are made for simpler tasks that only require a motion produced by a 1 DOF mechanism
Underactuated hands and fingers offer a simplicity in control not accessible to fully actuated designs since the number of actuators is smaller than the number of DOF
Summary
Self-adaptive, known as underactuated (Birglen et al, 2007), hands and fingers have been used in the last decade by both the research community and the industry as a compromise between complex anthropomorphic robotic hands and classical industrial grippers. Complex dexterous hands could require more than three fingers and 9 actuated degrees of freedom (DOF) to become dexterous and provide sufficient motion capability for object manipulation, while classical industrial grippers are made for simpler tasks that only require a motion produced by a 1 DOF mechanism. Other robotic devices close to self-adaptive fingers have been reported which use structural compliance to achieve conformal grasps. They are referred to as soft hands and grippers. Underactuation and soft grasping are two common techniques to provide robotic systems with tools for securing and manipulating arbitrarily shaped objects
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