End-effector design optimisation and multi-robot motion planning for handling compliant parts

Abstract

The deformation of compliant parts during material handling is a critical issue that can significantly affect the productivity and the parts' dimensional quality. There are multiple relevant aspects to consider when designing end-effectors to handle compliant parts, e.g. motion planning, holding force, part deformations, collisions, etc. This paper focuses on multi-robot material handling systems where the end-effector designs influence the coordination of the robots to prevent that these collide in the shared workspace. A multi-disciplinary methodology for end-effector design optimisation and multi-robot motion planning for material handling of compliant parts is proposed. The novelty is the co-adaptive optimisation of the end-effectors' structure with the robot motion planning to obtain the highest productivity and to avoid excessive part deformations. Based on FEA, the dynamic deformations of the parts are modelled in order to consider these during the collision avoidance between the handled parts and obstacles. The proposed methodology is evaluated for a case study that considers the multi-robot material handling of sheet metal parts in a multi-stage tandem press line. The results show that a substantial improvement in productivity can be achieved (up to 1.9%). These also demonstrate the need and contribution of the proposed methodology.

Quality and productivity driven trajectory optimisation for robotic handling of compliant sheet metal parts in multi-press stamping lines

“…Reversible deformations should not contribute to the value of the objective function in Eq. (16). For scenarios where any deterioration of part dimensional quality needs to be strictly avoided, it becomes necessary to determine the cycle-time threshold for which all deformations during handling are reversible.…”

“…These characteristics, together with the fact that only a single isolated material handling operation is considered, severely limits the methodology rendering it inapplicable to multi-robot systems for material handling of compliant parts. Recent research by Glorieux et al [16] proposes optimising the end-effector design co-adaptively with the robot motion planning to primarily improve productivity, and next minimise part deformations. Results showed a significant improvement in productivity of the robotic material handling system.…”

“…As it was suggested by one of the paper reviewers, currently, the flexible grippers (dexterous hand) fitting the shape of objects have not been designed and used for the stamping press applications. However, we feel that there are potential synergy between research in trajectory planning used for multi-robot handling of compliant sheet metal parts [4,16], and research in the area of dexterous robot hands [9,6,10], For example, the application of multi-robot handling of textiles and food products which are highly variable both in shape, size and structure can benefit from integrating trajectory planning work presented in this paper with work conducted in the area of dexterous robot hands design. Table 1 presents these potential synergies in the form of review and research direction in the area of trajectory planning for robotic handling of rigid and compliant objects.…”

“…The mapping of the collision between the robots that operate in the shared workspace are used to implement constraint (23) for the multi-robot coordination. The objective function (16) is then also implemented in the NLP model.…”

A Generalised Multi-Attribute Task Sequencing Approach for Robotics Optical Inspection Systems

“…); robot technological parameters; obstacles in the robot workspace; color and surface finish of the part being measured. All those attributes affect the overall robot path and trajectory [4], which impact the cycle time but also the quality of the collected data. "Data quality" is related to both: (1) amount of surface data points collected from a given pose of the robot; (2) accuracy and repeatability of the measurement process.…”