Extracting Grip Areas From Feature Information

Abstract In flexible assembly, an important problem is grip planning, in which possible grips on a component are determined. The first step in determining these grips is to find all finger domains on the component, areas where a gripper finger can be positioned. Finger domains are commonly computed from geometric information of the component only. One way to do this, is to find so-called non-free regions, areas where the finger cannot be positioned, using the Expanded Face Solid (EFS) method. This method creates for every face in the model an envelope volume depending on the finger geometry. The areas where the model intersects the envelope volumes are the non-free regions. The EFS method must be executed for every face in the model, and is therefore time consuming. We present a new method to retrieve the finger domains, minimizing the number of faces that have to be investigated with the EFS method, by making use of feature information stored in the product model of the component. Not only design features, but also assembly features storing assembly-specific information are used for this purpose. We distinguish two types of assembly features: connection and handling features, storing information on connections between components, respectively information for handling a component. In our method, information from these features is exploited in a number of steps to compute the finger domains. The results presented in this paper show that the computation times of finding finger domains using our method are considerably lower compared with using the EFS method.