Abstract
In this paper, a novel variable stiffness mechanism is presented, which is capable of achieving an output stiffness with infinite range and an unlimited output motion, i.e., the mechanism output is completely decoupled from the rotor motion, in the zero stiffness configuration. The mechanism makes use of leaf springs, which are engaged at different positions by means of two movable supports, to realize the variable output stiffness. The Euler–Bernoulli leaf spring model is derived and validated through experimental data. By shaping the leaf springs, it is shown that the stiffness characteristic of the mechanism can be changed to fulfill different application requirements. Alternative designs can achieve the same behavior with only one leaf spring and one movable support pin.
Highlights
Traditional robotic systems have stiff structures and are actuated using stiff joints, i.e., they use different types of electric motors, possibly with a gear reduction
In this variable stiffness mechanism (VSM), the compliance is created between the rotor and the output by using two leaf springs that connect to the output at their ends and connect to the rotor via support pins, fixed on the gears of a hypocycloid gearing mechanism
A novel variable stiffness mechanism has been presented, which is capable of an infinite stiffness range not before encountered in this class of variable stiffness realization and completely decoupled unlimited output motion with respect to the rotor for safe passive behavior
Summary
Traditional robotic systems have stiff structures and are actuated using stiff joints, i.e., they use different types of electric motors, possibly with a gear reduction. This can be desirable for industrial applications to achieve a large position control bandwidth and, high positioning accuracy and fast operation. Many different implementations of VSA mechanisms have been presented in the literature, which can be roughly classified into three major groups [3], i.e., the spring preload group (of which an antagonistic realization closely resembles a human joint) [6,7,8], the group in which the transmission between load and spring is changed [9,10,11,12,13,14] and the group where the physical properties of the spring are changed [15,16,17].
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