# Design and Calibration of a Sensory System of an Adaptive Gripper
## 2 Materials and Methods
### Sensory System Design  
#### 2.2.1. Slip Sensor Design  
The self-adaptive gripper described requires a slip detection system to ensure safe and efficient gripping, especially for objects with irregular shapes and variable sizes. To this end, each of the five modules is equipped with a specialized slip sensor, designed to accurately measure the relative movements between the gripper and the manipulated object, without influencing the contact between them. Unlike existing solutions, the described sensor is optimized for gripping objects with small and medium thicknesses, commonly found in the  
Figure 1: Logical operating architecture of a gripper module. automotive industry. In order to increase the gripping power and prevent the component from slipping and maintain the hold, the slip sensor's job is to detect the part being gripped and send the appropriate signal if a slip is detected [12]. There are different architectures for slip sensors, including those presented in [13; 14]. In this case, a variation with improved performance for the particular grip scenarios under consideration--namely, the grip of components with small and medium thicknesses and different shapes from the composition of subassemblies in vehicle construction--was achieved by designing the slip sensor. As a result, the designed sensor must be able to measure slip without influencing the contact of the grasped object with the sensor jaws. To achieve this objective, the following are required:  
* The detection system for determining the slip of the object must be capable of performing simultaneous translational and rotational movements. * For the accuracy and sensitivity of the slip determination, an incremental optical encoder with a resolution of 1024 must be used. * The mechanism must not generate negative forces on the slippage measurement system. * It must be integrated dimensionally into the entire grasping module. * It must respect the kinematic structure of the grasping module from a dimensional point of view. The sensor uses a mechanical design (Figure 2a,b), combining translational and rotational motions to detect slip. A flat strip (5), with a sticky surface, is placed in contact with the object. When the object begins to slip, the relative motion between the strip and the object triggers a rotational motion, amplified by a rack-and-pinion mechanism, which transmits the information to a high-resolution (1024) incremental optical encoder. The encoder converts the mechanical motion into digital data, signaling the slip. Thus, the sliding sensor system is based on the principle of detecting sliding by rotating around an axis an adherent system that comes into direct contact with the grasped object (Figure 2a) [15; 16]. The component that comes into direct contact with the grasped object is a flat strip (5) that has an adherent surface in the contact area to ensure the transmission of movement. The flat strip is extended outside the jaws to make contact with the object by sliding the component (3), performing a translational movement by sliding through the component (4). The translational movement of the flat strip detects the contact with the object. The sensory system detects the sliding and detection of the object by transforming the movement of the R-T-R type (rotational movement into translational movement and from translation to rotation). Through this exchange of types of generated movements, the sensitivity of the movement increases [15]. After the gripping-approaching movement to the piece to be grasped is performed, the jaws are in contact with the object, and its movement can be performed. If it slides in the jaws, the flat band, from the translational movement it initially makes, performs a rotational movement with the entire translational system, moving component (1) at the same time. Component (1) is the part that ensures the return to position 0 of the sliding sensor with the help of the extension spring (2).