 Good day, everyone. I am Assistant Professor Ruchad Mistri from the Mechanical Engineering Department at Banjan Institute of Technology, Sholapur. And for this session, I'll be discussing about actuators for industrial robots. In the previous videos, we've talked about basic robot configurations, the market scenario of industrial robots, and sensors, sensors, sensor characteristics of the ones which are typically used in industrial robots. So in this session, we'll be discussing actuators for industrial robots and also some basic components of industrial robots. So the learning outcomes of this session will be that the student will be able to list components of industrial robots and explain basic features of the actuators used in industrial robots, which are basically hydraulic, pneumatic, and electric act. Something I'd like to share with you, in fact, even before I begin discussing the actuators for industrial robots is a lot of textbooks continue to discuss and compare hydraulic, pneumatic, and electric drives for robots, basically actuators. And there's nothing wrong about it. A lot of textbooks, any textbook which deals with actuators, will compare these three. A fourth one, obviously, could be some mechanical actuators or mechanical drives. But these three are invariably compared. If you actually do a survey of the top 15 manufacturers of industrial robots, which I believe would definitely account for more than 99% of the industrial robot market, most cases that drives are AC servo motors. OK, so I don't have an exact number, but I'm pretty sure it could be in the 80s or the 90s by far. A handful of applications, we did come across DC servers. And these were some SCARA robots, some Delta robots, and some robots typically in the low payload section, under 10 kg payload, we did come across some DC servers. A couple of examples of stepper motors were also observed. Those models typically were meant for medical tasks. Most of them were Cartesian and a couple of joint arm configurations. So we didn't come across other types of drives and definitely not pneumatic drives in any of the survey that we did. It's possible that third party, you can say retrofit companies, may have come up with their own design, which may use some sort of a pneumatic arrangement. But if it's used, it's probably for some very basic pick and place task. Now, coming back to a core discussion, which is about robot actuators. So an actuator basically converts input energy typically into mechanical. The final aspect we are looking at is the output being mechanical. So these are often called as the muscles of the manipulator. Now, these may be revolute or prismatic, depending upon the configuration of the robot. And the most popular choices are electric, pneumatic, hydraulic, shape, memory, alloys, and so on. These three, obviously, by far would be most popular. And amongst us, electric drives are by far the most popular. Sometimes you may have what is called direct or indirect configuration, if the motor is driving the joint through a linkage or through a transmission. So this is another nomenclature that we have added over here. Sometimes if the torque is sufficient, the motor may have a direct drive. Now, there are pros and cons to both. And textbooks on robots discuss about the advantages of using direct drive and also of using gears for speed reduction. So that we won't be discussing as a part of this particular series. But it does come into picture once we start studying about robot control. Now, coming back to robot actuators, a revolute driver actuator is a motor, typically. So when energy is supplied, the motor acts as a response in rotary motion. Gears may be used to meet speed and torque requirements. But in many cases, they prefer a direct drive. Load attachment to the arm is typically then rotated about its axis. Now, hydraulic actuators, very typically linear rotary actuators and ramps, they provide force or torque needed to move the joints. And they are typically controlled by servo walls, servocontrolled walls. Now, a hydraulic pump is used to provide high pressure to the system. And an electric motor or even an IC engine may drive the pump. And you need some sort of cooling system to get rid of the heat for it. So this is a basic, you can say, composition of the hydraulic system. You need reservoirs to keep the fluid supply available to the system at all times. You need servo walls, which are very sensitive. And they control the amount and rate of the fluid which enters the cylinder. And it's servo wall is typically driven by what is called as a hydraulic servo motor. Sensors are necessary to control the motion of the cylinders. These are typically position velocity and others. Then you need connecting hoses to transport the pressurized fluid. You need all the safety check walls, et cetera, et cetera. So it's quite a bit of a contraption over here. Hydraulic drives do have advantages. And let me tell you some of the very first industrial robots which were built. They featured hydraulic drives. And if you look up any literature on industrial robots which date back to the 80s and 90s, the general argument which goes in favor of hydraulic drives is these were the most preferred drives when it came to heavy duty tasks. Typically when the payload exceeded 100 to 100 kgs. And especially if these were painting robots because that time since DC motors were quite popular, the possibility of spark due to brushes was an explosion hazard. So that's how the literature in fact portrays hydraulic drives. I am not sure how far that is consistent today given the wide use of electric motors in a lot of applications which in the past would have featured hydraulic drives. But nevertheless, the advantages of hydraulic drives these maintain high and constant torque force over a wide range of speed. They definitely have a higher starting torque, very large force capacity, large power to weight ratios, good precision, definitely not as compared to electric but better than pneumatic because greater bulk modulus of the oil and can maintain large forces over longer periods. On the downside, they require external energy sources, a lot of accessories. Oil obviously has maintenance issues because there are leaks, et cetera, et cetera. And these precision walls can be quite expensive. So these are the typical disadvantages of any hydraulic system. This includes industrial robots. Now, like I said, I would definitely want you to look up websites of the top manufacturers and see if you do come across any hydraulic drive or pneumatic drive for any one of their product lineups. So if you do come up with something like this, I would be a very happy person. So far, my surveys have indicated otherwise. Now, when it comes to pneumatic actuators, again, textbooks do tend to discuss this but in my entire experience of trying to scout and look for industrial robots in industries in and around here in India, I have come across only one industrial robot, that too from a, what you can say, it's not a reputed or world-renowned robot manufacturer but more like an automation services provider who had come up with their own design and configuration which featured pneumatic drives. And it was used for very simple, very basic pick and place task. Other than that, typically all the robots that have come across used AC servo systems. So coming back to this, like hydraulic, these are very similar to the hydraulic actuators with the exception that the part is in fact air instead of it being oil. And these include pneumatic cylinders for linear motion or pneumatic motors for a revolute motion. And these are typically used in simple manipulators so piston moves uninterrupted between the drops. Like I said, the most likely application if you do find it is for a very simple pick and place task and very typically in the lower end of the payload spectrum. So what are the advantages then? Typically the one advantage which stands out is the lower cost and ease of maintenance and also to a certain extent that a lot of industrial setups have an existing pneumatic setup for a lot of other things which you can then use for this particular purpose. So cost I would say by far is the most important advantage of pneumatic drives. It's one more thing, it's simple to control and it's quite okay when it comes to point-to-point motion. On the other hand, compressibility of air reduces precision. There are quite a bit of vibrations, especially when it's suddenly stopped. And like the hydraulic system as well, you need accessories, you need external sources, you need filters and all that stuff so that definitely adds to the cost and all to the extra components of the system. And continuous motion control is very difficult and very expensive. This is where in fact electric drives have an advantage of both pneumatic and hydraulic systems. So by far, now coming to electric drives, all robots today, I can definitely claim almost all robots today are driven by electric motors. DC servo motors were quite popular in the 80s and if you look up any literature which dates back to 80s or 90s, you would definitely find DC servos. There are books available which have included service and they would indicate DC servo motors. AC servo motors now have virtually replaced DC servo motors, especially since the advent of variable frequency drives. Stepper motors, we have seen a couple of applications, typically for laboratory setups and tabletop applications which require high precision. But most classic industrial applications, we have seen mainly AC motors, AC servos followed by some DC servos. The advantages of electric drives are, these are simple. They do not require extra energy. They are extremely efficient and precise control is possible. And cost of control is in fact quite low. And with the advent of high-talk motors, in fact they have started replacing hydraulics in many applications. The disadvantages in fact, as given in textbooks, I would like to quote because a lot of manufacturers in fact, don't give disadvantages as such. So I have to refer to textbooks for these. Is the liability for damage when it comes to heavy loading. Some motors which are the cheaper end of the spectrum have poor specific outputs. And you may require gear reduction for many applications. When it comes to reading material, I would definitely recommend, in fact, a handbook of robotics as one. These two textbooks are definitely one of the which you can refer. And above all, again, the plenty of internet resources, especially the manufacturers themselves which can shed light on this topic which is more pertinent and more relevant for the day. With this, I end this particular session. Thank you.