# 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 sliding sensor is equipped with an RGB LED that signals when the sensor is activated and when the sliding movement is performed by changing colors, and this can be observed through the slot (6) in Figure 2b. With the aid of component (11) in Figure 2b, the sliding sensor that detects the grabbed object by translational movement guarantees its movement by preventing rotation. With a comprehensive illustration in Figure 3a, the rod that executes the translational movement has a toothing that resembles a rack and imprints the rotational movement on the gear wheel (10). Figure 3a provides a detailed view of the circled area in Figure 2b, highlighting the driving zone between the rack and pinion where the motion is amplified in terms of output rotations [17]. Rotation amplification is necessary because sensitivity in sliding is crucial. The translation system makes a stroke of 13 mm, and the rotation system makes 13 complete rotations, which means that at 1 mm, it rotates 360\({}^{\circ}\). The sliding sensor's movement is divided according to the translation stroke--namely, the object is gripped over 8 mm, with the rotation system rotating 280\({}^{\circ}\); 5 mm of the stroke is left to compensate for the movement of the flat strip during sliding, where it performs both rotation and translation; to determine the sliding, a rotational movement of 25\({}^{\circ}\) is allowed. Following the translational movement, the entire system tensions an extension spring (14), which has the role of returning the mechanism to the forward position [15]. In the section of the sensory system in Figure 4b, it is highlighted that all movements made aim to generate rotations in component (12), which has the role of transmitting the final rotational movement to the encoder, which has the final role of determining the slip. In Figure 3c, an isometric representation of the designed slip sensor assembly is shown, where 1 is the encoder and 2 is the sensor body. Following the detailed design of all components, the CAD version was obtained (Figure 4a), respecting the dimensional integration conditions in the gripper module mechanism assembly. This led to the physical realization of the component parts and the slip sensor assembly shown in Figure 4b,c. Figure 3: Detail of the probe retraction mechanism (**a**), section through the slip sensor (**b**), and isometric representation of the slip sensor assembly (**c**). 1. Encoder; 2. Encoder support; 12. Encoder shaft; 14. Extension spring. Figure 2: The components of the slip sensor (**a**) and the transmission of movement to the encoder (**b**). 1. Component for returning to position 0; 2. Extension spring for return to 0 position; 3. Probe translation axis; 4. Translation shaft guide bushing; 5. Flat-type probe; 9. Rack type shaft; 10. Pinion; 9-10 rack-and-pinion system; 11. Anti-rotation guide. For the components of the slip sensor, we used the aluminum alloy AlCu4 MgSi (alloy 2017 or similar), chosen for its high mechanical strength, lightness, good machinability, corrosion resistance, and relatively low cost. For the side parts that flank the jaws, we opted for black POM C (polyoxymethylene). The choice of this material is justified because it has high wear resistance, dimensional stability, impact resistance, and chemical compatibility with numerous lubricants and chemicals, which is important in the industrial environment. The data from the encoder are processed by the controller of the respective module. If the sensor detects slippage, the controller automatically adjusts the gripping force to stabilize the object. The RGB LED provides visual feedback on the sensor's status (active, slippage detected). The dimensional and kinematic integration of the sensor in the module is crucial for the optimal functioning of the entire system.