# Experimental Study of the Vibrations of a Roller Shutter Gripper
## 1 Introduction  
Each year, the International Federation for Robotics (IFR) publishes the \"World Robotics\" report, which is a reliable compilation of information about the robotics industry. The most important of the IFR statistics refers to the annual sales of robots. For more than a dozen years, the indicator increased rapidly until 2018, when the number of robots sold reached more than 422,000 units. Unfortunately, in 2019 and 2020, the number of robots delivered to the industry dropped to 382 and 380 thousand units, respectively (Figure 1). On the other hand, it should be pointed out that in 2020, the number of robots operating worldwide increased by 10%, exceeding three million for the first time (Figure 2) [1]. The increasing number of robots working in factories translates into an increase in robotization density (the average number of units per 10,000 workers in industry), which increased to 126. South Korea remained the leader with a ratio of 932 (Figure 3). The outlook for robotics is very good. IFR expects about 13% growth this year, which means the delivery of 435,000 units to clients. This will be due to the market's recovery from the slowdown and customers' growing needs for local unit production [2]. The most common applications for industrial robots were handling (166,000 installations), welding (66,000) and assembly (47,000). Among handling applications, a special role is given to the palletization process, which allows goods to be fully prepared for storage and further distribution. It completes the logistics of products and ensures their efficientflow between the producer and the end customer [3]. Therefore, palletization and depalletization processes are among the most common robotic processes found in practically all branches of industry [4; 5; 6]. They include the palletization of products in a variety of packages, including boxes, cartons, trays and packs, crates, drums, cans, bags, and buckets. Designers of robotic palletizing stations try to develop flexible stations using industrial robots with dedicated equipment (grippers) [7]. It would seem that such an approach gives the possibility of easy use of such workstations for various applications. Unfortunately, most gripper solutions available on the market are developed for a specific product, so the possibility of changing their parameters is very limited. The problem of palletizing products on robotic workstations is a well-known issue. Almost every robot manufacturer has solutions dedicated to palletizing operations. However, when it comes to the design of the grippers themselves, it is focused on several solutions resulting from the type of goods to be palletized. This is related to the gripping method and characteristics of the palletized goods. A distinction is made between force, shape, and force-shape gripping. Solutions are patented in world and national databases [8; 9; 10; 11]. In the case of goods packed in bulk packaging (cartons, packs), jaw grippers are often used, which cover the entire layer of goods, squeezing them from four sides. This solution is simple, cheap, and effective. However, for products that can be easily physically damaged, such solutions are problematic. The process of palletizing a layer of packages, such as jars or cans, requires a solution that allows to pick up many objects simultaneously, securing their mutual displacement during the palletizing process, as well as preventing any of the objects from dropping during the handling process. The correct palletizing process for this kind of product is provided by constructions that use roller shutters, which is why the name of this type of gripper is commonly called roller shutter grippers. In the case of goods that are characterized by an increased risk of damage because of the clamping arms of the gripper, it is necessary to use a device that allows one to pick up the goods using a shaped grip. Another example of palletized goods is powdered goods packed in bag-type packaging.