Degree Of Actuation Redundancy Research Articles

Tension distribution algorithm based on graphics with high computational efficiency and robust optimization for two-redundant cable-driven parallel robots

In this article, we present a novel tension distribution algorithm for cable-driven parallel robots (CDPRs) with two degrees of actuation redundancy. The algorithm consists of calculating the tension feasible region (TFR) and optimizing the tension distribution. The TFR has been innovatively calculated without relying on the convex hull method. The topological relationship of the vertices is maintained, so the calculation steps are greatly reduced. For optimizing TFR, various functions are proposed, especially the tension robustness index is defined. We prove the complexity and continuity of the algorithm and we study several examples. The results are compared with those obtained with the existing state-of-the-art method, and the proposed technique is shown to be more computationally efficient. The robustness of the optimal solution is also calculated. The proposed algorithm can be applied in some real-time systems with unmeasurable interference, such as interactive devices.

Planar Translational Cable‐Direct‐Driven Robots

AbstractWe present the simulated dynamics and control of a planar, translational cable‐directdriven robot (CDDR). The motivation behind this work is to improve the serious cable interference problem with existing CDDRs and to avoid configurations where negative cable tensions are required to exert general forces and moments on the environment and during dynamic motions. Generally for CDDRs the commanded rotations are more demanding than commanded translations in terms of slack cable conditions. Therefore we propose a translational CDDR whose end‐effector may be fitted with a traditional serial wrist mechanism to provide rotational freedom (assuming proper design to resist the moments). Only the translational CDDR is considered in this article, including kinematics and statics modeling, statics workspace (wherein all possible Cartesian forces and moments may be exerted with only positive cable tensions), plus a dynamics model and simulated control for planar CDDRs. Here we focus only on planar CDDRs, to clearly demonstrate our dynamics and control work; we will extend this work to spatial CDDRs in the future. Examples are presented to demonstrate simulated control including feedback linearization of the four‐cable CDDR (with one degree of actuation redundancy) performing a Cartesian task. An on‐line dynamic minimum torque estimation algorithm is introduced to ensure all cable tensions remain positive for all motion; otherwise slack cables can result from CDDR dynamics and control is lost. © 2003 Wiley Periodicals, Inc.

Translational Planar Cable-Direct-Driven Robots

A planar cable-direct-driven robot (CDDR) architecture is introduced with only translational freedoms. The motivation behind this work is to improve the serious cable interference problem with existing CDDRs and to avoid configurations where negative cable tensions are required to exert general forces on the environment and during dynamic motions. These problems generally arise for rotational CDDR motions. Thus, we propose a class of purely translational CDDRs; of course, these are not general but may only perform tasks where no rotational motion or resistance of moments is required at the end-effector. This article includes kinematics and statics modeling, determination of the statics workspace (the space wherein all possible Cartesian forces may be exerted with only positive cable tensions), plus a dynamics model and simulated control for planar translational CDDRs. Examples are presented to demonstrate simulated control including feedback linearization of the 4-cable CDDR (with two degrees of actuation redundancy) performing a Cartesian task. We introduce an on-line dynamic minimum torque estimation algorithm to ensure all cable tensions remain positive for all motion; otherwise slack cables result from the CDDR dynamics and control is lost.

Planar Cable-Direct-Driven Robots: Design for Wrench Exertion

Cable-direct-driven robots and haptic interfaces are appealing because of their structural simplicity, high stiffness, and high exerted wrench-to-weight ratio. A major drawback is that cables can only exert tension. Therefore, actuation redundancy is required to apply general wrenches (forcesmoment vectors). Even with actuation redundancy, not all desired wrenches can be applied in some configurations due to one or more negative cable forces required. In addition, cable interference can be a serious problem for these devices. The objective of this article is to present the best design for planar cable-direct-driven robots andsor haptic interfaces with one degree of actuation redundancy, with regard to general wrench exertion and cable interference. Results indicate that the cable interference constraint dominates which suggests the need for future design work to alleviate this interference.

Minimum-time control of coupled tendon-driven manipulators

Hyper-redundant manipulators have very large degrees of redundancy, thus possessing unconventional features such as the ability to enter a narrow space while avoiding obstacles. In this study, a time-optimal control scheme is proposed for a hyper-redundant manipulator that was realized by coupled tendon-driven mechanisms. In the mechanisms, a pair of tendons for driving a joint is pulled from base actuators via pulleys mounted on the base-side joints and the degrees of actuation redundancy exist. The time-optimal trajectory planning problem is solved by using the phase-plane analysis and the linear programming technique. Computer simulations were also performed to show that the proposed scheme makes full use of the actuation redundancy of tendons and their coupled function to shorten motion time.