Performance Indices for the Evaluation of Microgrippers Precision in Grasping and Releasing Phases

In manipulating and assembly tasks, the gripper plays a fundamental role. Tasks at the microscale are particularly challenging due to the possible effect of unwanted stiction. Many different grasping tools (generally called microgrippers) have been developed and are described in literature. The differences rely on size, shape, exchanged forces with the manipulated parts and working principle depending on the application field. Despite the large number of research and industrial cases, each author has developed different and not comparable procedures and indices to assess the device grasping and releasing performance. Therefore, the paper proposes a formalization of methods and indices for the evaluation of the performance of a generic contact microgripper in terms of precision in grasping and releasing and successful rate. This review could be helpful to support the design or the choice of the most suitable gripper according to the properties of the components to be manipulated, the task requirements and the system constraints (i.e., according to the application requirements). The validity of the proposed methodologies and indices is confirmed by theory and experimental data analysis.