Two novel architectures of planar spring-loaded cable-loop-driven parallel mechanisms that do not require actuation redundancy are introduced in this paper. In order to avoid redundancy in the cable-driven parallel mechanisms and require only N actuators to control N-DOF motion, a new spring-loaded cable-loop-driven mechanism is proposed. By attaching springs to the cable loops, two degrees of freedom can be controlled using only two actuators and spools are eliminated in this mechanism. Therefore, the control method can be simplified compared with conventional cable-driven mechanisms making use of spools and actuation redundancy. The mechanisms can be actuated using either linear sliders or rotary actuators driving the motion of a cable or belt loop. Kinematic and static analyses are presented for the new architectures. It is verified that the cables and springs can be kept in tension within a certain workspace. Results of numerical simulations are also given in order to provide insight into the design issues.
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