Parallel robots

Parallel robots are a category of robots with closed kinematic chains. The range of possible kinematic architectures is vast, as are the number of possible applications, from micromanipulation to high load handling, as well as more traditional industrial applications such as high-speed pick-and-place (up to 3 or 4 products moved per second). The performance of parallel robots is complementary to, and generally the opposite of, that of serial robots. They therefore open up new avenues for the robotization of certain tasks. Although they currently account for only a small share of the market for industrial robots on the market, they are a natural choice for certain applications. For others, they compete with their serial counterparts. Once their kinematic architecture has been chosen, their study requires methodology and detailed modeling in order to evaluate their performance. This aspect must not be neglected, as performance is extremely sensitive to geometry, particularly in view of the presence of new types of singularities compared to series robots.

This article begins by reviewing the most common types of parallel kinematics known to date. This presentation will be ordered according to the number of degrees of freedom (ddl) of the end-member (from 2 to 6).

We then propose a generic modeling method capable of taking into account all kinematic cases of existing and future parallel robots. This method covers all parallel robots, regardless of the number of ddl of their terminal organ, whether they are redundant from a kinematic or actuation point of view, whether they have complex kinematic chains or not, or whether they have a rigid or articulated moving platform.

In the following section, we'll review the fields in which applications are currently available, and the kinematics used.

The article concludes with a technological section reviewing the constructive arrangements used for these robots, and sharing the authors' experience of their design.