 Good day everyone, I am Ruchad Mistry, Assistant Professor Mechanical Engine Department at Valgen Institute of Technology Sholok. And this is the second session on industrial robot configurations. In the previous session, we looked at the definition of the industrial robot and the Cartesian configuration. So, we are going to continue from there and we are going to discuss spherical and cylindrical configuration. So, the learning outcomes of this particular lecture that you will be able to explain cylindrical and spherical configuration of industrial robots and identify applications of this configuration based on their features. So, let me just recall the definition of industrial robot which we even saw in the previous video. There is industrial robot is defined as an automatically controlled reprogrammable multipurpose manipulator. It can be programmable in three or one axis, it can be either fixed in place or mobile and is used for industrial automation applications. So, this is the definition. And we also looked at in the previous slide the classification of industrial robots. So, this is just a review of the same. So, classification as per remember this is classification as per most textbooks. You have Cartesian cylindrical, spherical, jointed arms, car and parallel configuration along another alternative way of classifying obviously is degrees of freedom and it let me try it once again that typically you would not get industrial robots which are less than 4 degrees of freedom from the practical point of view. So, they are always at the 4, 5, invariably 6 degrees of freedom. Another way of classifying obviously from application. So, you have welding robots, assembly robots, metal handling robots, inspection robots and so on. Another way of classifying which is a bit popular in the past was as per the control method. You had server and non-server robots and among server robots you had continuous path control and point to point control. This way of classifying I think it is redundant given the fact that almost every robot which is made today has very sophisticated closed-loop server control systems. So, this is just from the point of from an academic perspective since most textbooks tend to include this particular classification. Now, we saw this even in the previous video. Industrial robots as per international federation of robotics where they classified based on mechanical structure and as per this classification you have linear robots which we show last time that is Cartesian entry robots. Scarra robots, articulated robots, parallel robots, cylindrical robots and others. Now, obviously this classification doesn't include spherical configuration which is obsolete. However, a lot of textbooks actually do include them. So, I have included as a part of this discussion today. So, today we will be discussing cylindrical configuration and spherical configuration. So, moving on to the cylindrical configuration. The reason we call this as you can see from the figure the work envelope of this particular robot is a cylinder. So, that is why that time it was labeled as a cylindrical robot or cylindrical configuration robot. So, we can say that these are robots whose three principle axis is the first three axis. They form a cylindrical coordinate system. As you can see over here you have the z axis which is perpendicular you have theta and y. So, this is often labeled as RPP. So, revolving this first axis then you have prismatic or linear. The second axis and this third axis. So, often called as RPPP or PRP configuration that is prismatic revolution and prismatic. So, it's a slight difference among different authors. So, some authors actually take this you can say joint first first. So, they call it prismatic then this revolute and then prismatic. Alternatively, I have seen RPP configuration. The first joint is rotary about the vertical axis which is followed by two translations in horizontal and vertical relation. Very simple robot control solution. It was very popular till the 80s. This configuration is obsolete. Like if you look up any the website of any top manufacturer, top ten industrial robot manufacturer. You will not come across this configuration in their product line up. So, I don't think they offer it off the shelf. Probably it may be a customized solution somewhere. But I have not come across a single configuration offered by the top manufacturer which is a cylindrical configuration. I've seen Cartesian, I have seen parallel delta configurations. But invariably all configurations are the joint arm configuration. So, nowadays this is just not in use. It's very popular till the 80s. So, here are some images of the cylindrical configuration. These are images from actually they look like phano robots, which is obvious from the color. The most top manufacturers do have a sort of strategy when it comes to color. These are quite old and even if you do come across these, these are probably older robots which have been recurved and upgraded. Like I said, I doubt very much that these configurations are being used. At least I have not come across any of this configuration in the line up when I studied the data which is available on the internet. The other obviously is polar or spherical configuration. Like I said, the reason is you have a polar coordinate system or you can say the robot work envelope is actually a sphere. Hence, it's called as a spherical configuration. So, here we typically label it as RRP configuration that is revolute, revolute and prismatic. So, the first two joints are rotary joints and you have the third joint as prismatic joint. So, these are robots whose first principle axis, three principle axis. They form a sphere or a polar coordinate system. They are called as RRP that is revolute, revolute, prismatic or RRL that is revolute, revolute, linear configuration. You have two rotary joints about vertical and horizontal axis followed by a translation in the horizontal axis. This was actually the configuration in which the very first industrial robots were built. If you look at the animation robotics from the late 50s and early 60s, it's actually this particular configuration. The first robot which was actually built by George DeVol, it's actually this configuration. So, these were the very first robots in the 60s. They actually became obsolete by the early 80s. Once the jointed arm configuration came into picture, these became obsolete. So, the good thing about them was that robot control solution was simple. So, the controllers in the past with the limited amount of software and hardware capabilities, this was actually quite a popular solution there. So, let us now look at some of the advantages of the cylindrical configuration. One thing obviously is the structural and construction simplicity. It's a very rigid configuration, delivers good accuracy, fast operation. One really good feature is access from front and sides. Again, like the Cartesian configuration is one of the lowest cost for a given accuracy and control algorithms are easy to program and implement. Now, when it comes to these points, remember, we have to go by what the experts and the authors said, it is very difficult to prove these things nowadays. For example, we have jointed arm configuration as now the de facto configuration wherever you go. So, it's really unwise in that sense of the word to compare. But most textbooks and experts agree that for a given cost, this configuration is very robust and delivers very good accuracy. Then what were the possible limitations? Let's say dexterity, which you will notice actually once you start studying the specifications of different configurations, especially when you look at the work envelope of the jointed arm configuration, the amount of places that it can reach. This is where actually most of these older configurations, they are not at par when it comes to jointed arm configuration. So that's why we tend to say that it's less dextrous as compared to the jointed arm configuration, which is also true for the spherical configuration and where. It's definitely slower than SCARA. Often these SCARA and cylindrical configurations are compared because even with the SCARA, the work envelope is cylindrical. But the unique thing about SCARA is it's actually all joints are revolved and except for the fourth axis, which is perpendicular, and it is capable of extremely high speeds and extremely high repeatability. So for a given, let's say, assembly task, this configuration actually would be slower than a SCARA. And that's also one of the reasons SCARA configuration typically ended up replacing the cylindrical configuration in much of all the typical domains at the lower end of the payload spectrum. Like I said, it's not suited for complex tasks such as arc welding and spot welding, which requires very difficult orientation. And this is where obviously jointed arm configuration wins hands down. So most designs now have been replaced, as I said, by the jointed arm configuration. General applications like we can summarize as machine dending, handling for die casting, sometimes even for assembly and welding operations, parallelizing. These applications have been quoted on the basis of the potential applications in the past. So this information is available in textbooks and websites. And these were typical applications of cylindrical configuration in the past. Like I said, even the cylindrical configuration is quite obsolete, but it had some advantages. One, obviously, was structural construction simplicity, good accuracy over long distances, good payload capacity, and lowest cost for a given accuracy. So control algorithms, again, being easy to program. So it had very similar, you can say, features as compared to cylindrical, all cylindrical configuration as well. Limitation, again, same, less textures compared to jointed arm, slower than SCARA for a similar task, and not suited for arc welding and spot welding. Remember, these were used for welding and spot welding in the past, but in the past, you can say the work cell had to be designed in such a way that, what you can say, the whole thing was optimized from the point of view of robot. Now the robot is so flexible that you can weld in places which these robots cannot weld. So that's one advantage of jointed arm configuration, that it can do the kind of welding which these robots actually are unable to do. Most designs have been replaced now by the jointed arm configuration. Spherical configuration, again, you have generic domains, would be machine tending, handing for die casting, sometimes assembly, palletizing, and welding as well. Very common configuration similar to cylindrical configurations. Now, like I said, I discussed this topic state of the art in the previous lecture model. Now here, I don't say there is anything to be considered state of the art because both these configurations are now obsolete. Even though you may come across a few, these are probably older models which have been refurbished and updated with updated controllers. So that's clearly obsolete. That's why I said IFR even doesn't include spherical configuration as one of the aspect. It requires a lot of reading. International Federation of Robotics, the website to go for basic information and data. A very good information source is Robot Park, where there's a lot of information regarding robots in general. Again, Yamaha, Omron is a very informative website when it comes to applications. And one more thing I found very informative was a blog on industrial robots. So you can definitely look these up because some of the older robots, you end up finding on blogs rather than websites of manufacturers. So we'll discuss the other configurations in the next video.