# In-Plane Material Handling: A Systematic Review
## 3 Results
### Answer to RQ1
The main difference in vibrating systems is primarily with respect to the dimensions and power of the active plate [28]. Conversely, for ciliary systems, variation has been introduced in terms of the size of the cilia, as demonstrated by the brush feeder described in [64]. Several other solutions employing the same technology described in the retrieved papers are not reported in the paragraph above. The intention, in fact, was to provide an initial overview of the most common solutions and generalize the characteristics they share. Furthermore, since the objective of the subsequent research question was classification, the authors considered it more appropriate to include all relevant solutions in the subsequent section. On this subject, a pattern of working principles and features emerged among the analyzed devices. In particular, flexibility and adaptability have been achieved through the use of programmability and distributed actuation. These two characteristics enable the creation of controllable force fields that act on the transported object, either directly or indirectly through a platform. Programmability allows one to decide on and implement a task virtually without it being predetermined, unlike in more classic systems such as conveyor belts or vibratory linear feeders [3; 23; 36]. Distributed manipulation has a positive effect on handling flexibility [19], improving manipulation skills [9]. This permits not only linear transport, such as via conveyor belts, but also simultaneous orientations and multi-directional displacements (2D conveyors). Moreover, the programmable nature and distributed placement of actuators on a plane allow a system to easily adapt to changes in tasks and transported materials. In addition to these two primary system characteristics (programmability and distributed actuation), other commonly encountered features can also be identified. One such feature is modularity, which involves the system being composed of elementary units (modules) that can be assembled into surfaces. This property further enhances system flexibility and adaptability [3], as the modules can be assembled and disassembled arbitrarily according to the desired layout. Among these solutions, there are a few exceptions where the design is not modular; therefore their flexibility and adaptability are limited, but they are still superior to those of classic transport systems. Figure 5: Other in-plane handling technologies used over the years. (**a**) Electromagnetic smart platform [10]; (**b**) “magic carpet” based on [57]; (**c**) cilia surface [11]. Several names have been given to this class of manipulation devices over the years, such as \"Distributed Micro Motion Systems\" (DMMSs) [17], \"Modular Distributed Manipulator Systems\" (MDMSs) [31], \"Advanced Distributed Manipulator Systems\" (ADMSs) [5], and the most common \"active surfaces\" [10; 54; 55; 70] and \"smart surfaces\" [10; 21; 27; 36; 39; 41; 71; 72; 73]. Despite the use of \"smart surface\" or another of the aforementioned terms to name a device, e.g., emSS (electromagnetic modular Smart Surface) [41], generally speaking, these are not formal definitions [10; 39]. However, drawing from interpretations by both [PERSON] et al. [39] and [PERSON] et al. [10], all the mentioned types and technologies fall into the \"smart surface\" class. This is because they all exploit a distributed conveyance system, which, whether sensorized or not, is capable of the most common handling tasks, such as positioning, orienting, sorting, and feeding. In summary, a group of systems sharing common characteristics and specifications has taken shape. Some repetitive features, such as the technology used, which provides direction for clustering, have already emerged. However, there are still more sub-classes within them to investigate. At this point, the analysis shifts to the second research question (RQ2) and formal classification.