# Cognitive Mechatronic Devices for Reconfigurable Production of Complex Parts
## 3 Approach
### 6-DoF Electromechanical Gripper  
Aiming at avoiding the use of stationary devices, for the intermediate manipulation and the consequent cycle time increase, an electromechanical gripper with in-hand manipulation capabilities has been developed to serve both feeding and packaging operations. Figure 3: Assembly steps of the two product variants. Figure 2: States of stable equilibrium (poses) for two products. A decomposition of handling tasks, as performed by human operators has been used to define the required manipulation degrees of freedom. Results will drive the design of end-effector's configuration space and the enlistment of actuation components. Integral design constraint is the achievement of multiple-products manipulation without hardware modifications. Focusing on the decomposition of handling procedure, all variants entail a sequence of eight steps, namely: approach, grasp, align, regrasp, rotate, translate, regrasp, place and release. By using robot's degrees of freedom, \"approach\" and \"place\" can be excepted from design methodology. Referring to Figure 4, the required mechanisms and respective degrees of freedom, for feeding and packaging operations of all product variants, are summarized in Table 1.  
The end-effector includes two mechanisms, namely \"Grasping mechanism\" and \"Manipulation Mechanism\". Considering the grasping fingers as independent kinematic chains, the overall gripper consists of one closed and two open kinematic chains, leading to a total of six DoFs. The two open kinematic chains comprise of one active prismatic joint (P), actuated by a linear actuator. These chains correspond to the fingers of a parallel gripper that is used for the parts' grasping and re-grasping. This gripper configuration (Figure 5) \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Operation** & **Resource** & **Mechanism** & **DoF** \\ \hline Approach & Robot & Not Available & Not Available \\ \hline Grasp & Gripper & Grasping mechanism & TransY \\ \hline Align & Gripper & Grasping mechanism & TransY \\ \hline Regrasp & Gripper & Manipulation mechanism & TransZ, TransX \\ \hline Manipulation & Gripper & Manipulation mechanism & RotY, RotX, TransZ, TransX \\ \hline Release & Gripper & Manipulation mechanism & TransZ, TransX \\ \hline Place & Robot & N/A & N/A \\ \hline Release after placement & Gripper & Grasping mechanism & TransY \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of mechanisms and degrees of freedom per handling process. Figure 4: Degrees of freedom for indicative product’s manipulation process steps: (**a**) grasp and align, (**b**) release and regrasp, (**c**) manipulate phase 1, (**d**) manipulate phase 2, (**e**) release and regrasp, (**f**) release after placement. (d4: Prismatic joint stroke of finger 4; d5: Prismatic joint stroke of finger 5). offers the capability of grasping compensation (due to different object geometries), as well as alignment correction before and after the in-hand manipulation process. The same result is achieved by an articulated open chain including two rotary and two prismatic joints with position control. However, this configuration was avoided since open chains require heavier duty supports and bearings increasing implementation costs. The in-hand manipulation process is performed by a re-grasping component, attached onto the end-effector of the closed-loop kinematic chain. This chain consists of three active prismatic (P), one active rotational (R), two passive rotational (R) and one passive prismatic (P) joints leading to four DoF. This configuration space enables the manipulated object to be planarly moved and rotated around two axes, thus achieving the desired pose, before regrasping. Based on the configuration space illustrated in Figure 4, the position and orientation of the manipulation mechanism's end-effector can be calculated based on the closed kinematic chain forward kinematic Equation (1). \[