Static balancing with elastic systems of DELTA parallel robots

• New constructive solutions for full static balancing of DELTA robot, and mathematical models
• A new kinematic model of DELTA robot using Denavit–Hartenberg formalism is proposed.
• All elastic systems used for static balancing are of zero-free-length type.
• Performances of the proposed balancing methods are displayed in an example.

This paper presents new design solutions and the corresponding mathematical models for static balancing of DELTA parallel robot. The static balancing of parallel robots is a more difficult task than the serial robots one, because the parallel robots consist of multi-loop spatial kinematic chains. Generally, these robots can be easily statically balanced only approximately.To statically balance the DELTA robots, two constructive solutions are proposed: (i) a new constructive solution for full balancing and (ii) a simplified full balancing version, with an acceptable balancing accuracy.The term full balancing is used here to denote that the masses of all links and springs are taken into account. To obtain full balance of the DELTA parallel robot, three elastic systems for each connecting kinematic chain are assembled. It is further noted that in this study only the balancing by using the zero-free-length elastic systems is considered.The static balancing result according to the first solution is very good, but the structure is not simple, using many additional links. The second simplified version uses one single elastic system for each connecting kinematic chain.Finally, a case study is presented in order to evaluate the performances of the simplified proposed version. It was found that the maximum driving moment decreases about 20 times relative to unbalanced version.