New concepts for parallel kinematic mechanisms using fluid actuation

Parallel kinematic mechanisms (PKMs), for example Stewart platforms, are widely used for high performance multi-axis motion systems. Their high stiffness and low mass are particularly suited to applications requiring good dynamic response, and the use of hydraulic actuators having exceptional power-to-weight ratio are also a good choice for such applications. Many configurations of PKMs have been built, including over-constrained systems with more actuators than degrees-of-freedom, but most are designed to move one rigid body with respect to another (ground). In this paper, generalized PKMs are discussed, involving the motion of multiple rigid bodies, typically within pre-stressed (i.e. overconstrained) actuator networks. Such systems could be used for morphing aircraft wings, lightweight actuated space structures, or in robotics. It is suggested that analytical techniques from the field of tensegrity structures can be used, where structural stability typically depends on geometric stiffness which results from prestressing. Keywords—parallel kinematic mechanism, multi-axis control, tensegrity, overconstraint, morphing

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