## 3 Changes Made to e-David
### Robot Replacement  
As the old RV60 robot was to be replaced with a more up to date machine, we considered different types of robots. For the general task of moving a paintbrush over a canvas automatically, multiple machine types are applicable. The choice of a certain machine is a trade-off between cost, ease of use, and suitability for the painting task. For painting high precision and a certain level of dexterity (depending on the type of painting desired) are needed. Common industry requirements like high speed, the ability to handle heavy workloads, or easy integration into an industrial network are usually not a necessity. The first group of machines to consider for painting are cartesian robots, often also referred to as \"XY-Plotters\" or just \"Plotters\" in the context of robotic painting. These allow the movement of a tool along the X-, Y-, and Z-axes and have been used for creating drawings for a long time. Plotters can be constructed cheaply and easily in many different sizes, with many parts available off the shelf. These machines are quite safe to use, but without specialized engineering they are unable to angle the tool, perform tool changes, or accomplish other advanced painting tasks. One of the most common robot types in use in industry is the 6-DoF robotic arm. These are commonly used for machine tending, welding, and spray painting. Such machines have high precision and can position a tool at almost any angle in many positions, allowing for a very human-like painting ability. Handling additional utilities, like a palette or brush cleaning setup is also easy. The major downsides of fully articulated robot arms are their cost and operational safety issues. Furthermore, painting along dynamically generated paths requires a careful setup of the painting surface, as for most industrial robots unexpected singularities cause a non-recoverable machine halt. Delta robots are 3-DoF or 4-DoF machines, which are commonly used in pick-and-place tasks. Commercially available machines are usually optimized for high-precision and high-speed handling of light objects. Delta robots provide a flat, circular workspace below the main body of the machine with translations of the end effector in the X, Y, and Z direction. Additional axes can be added, like a central rotating axle. This makes their uses comparable to plotters, which are usually more cost-effective in this domain [18]. SCARA robots also fall into this category and also allow rotation around the \(Z\)-axis [19]. Delta robots usually cost nearly as much as 6-DoF robot arms and are not a good choice for the use cases encountered in the e-David project. A final option to consider is cooperative robots or cobots, which have been introduced recently. For example, the KUKA iwa is a one-arm 7-DoF cobot, designed to work together with humans in varying tasks, for example, assembly. ABB offers the YuMi two-arm 7-DoF system for similar tasks, while also including built-in optical systems for picking up parts [20]. In traditional robotic painting, there is usually no use case for such systems: As humans do not commonly paint collaboratively there seems to be no purpose in implementing such a feature with cobots. Two arm systems are also not a necessity, as it is common in robotics to lay out accessories like the palette or tool cleaning system within reach of the robot and these can be built in such a way that one-arm manipulation is possible. A major drawback of using cobots in painting is that drawing tools are usually pointy and can be dangerous, if the machine happens to accidentally stab a human in the eye or throat area. Such interactions can lead to injury even at slow speeds and with enabled force control. Therefore, using compliant robots for programming strokes by letting a human guide the robot through the motions would require a specially secured setup [21]. The decision ultimately fell on continuing to use 6-DoF arms as primary machines, as these provide the most flexibility for tool handling. An IRB 1660 ID and an IRB 1200 by ABB were chosen.