 Good day everyone. I am assistant professor Ruchad Mistry from the mechanical engine department at Walgen's data of technology show level and In today's lecture. We'll be discussing about Sensors for robots. Okay. We have already discussed sensors In general in in a previous video So what we are going to do in this particular session is try to look at sensors very specifically from the point of view of Industrial robots and to a certain extent for mobile robots as well So the learning outcomes of this particular session are that at the end of this session The student will be able to classify sensors for industrial robots and explain basic requirements of robot sensors So before we begin let us recall the definition of industrial robots as per the International Federation of Robotics Which basically uses the definition given by ISO 8373 2012 and as per this The industrial robot is defined as an automatically controlled reprogrammable multiple-purpose manipulator Programmable in three or more axes which can either be fixed in place or mobile and used for industrial automation application So I iterate this definition from time to time So that this kind of creates a certain consistency when it comes to definitions And it will also put the context of the sensors that we are going to Look at in a minute from the from the point of view of industrial robots so This is actually sensor classification in general just a brief review for everyone and Sensor classification by different textbooks tend to have slightly different Ways in which they classify sensors online sources again do the same thing but by far we can Sort of group them into the following categories So the most common way to in fact classify sensors is based on the measure and okay, so what's basically measuring? So obviously you have plenty of sensors That you can put under this particular category temperature pressure velocity Okay Flow any other proximity and so on and so forth then depending upon whether the outer from the sensor Is he the in I know log or digital you can have a classification of whether should call the sensor analog or digital Similarly based on the source of energy you can call it at the passive or active and then on the basis of The measurement process you can call it as a null or deflection type and then again whether the sensor measures a static or a quasi-static Parameter of whether it's meant for dynamic measure measures vibration. You can classify them accordingly now a very good book if you want to refer to sensors is Measurement system by Dieblen there are plenty of other books for example instrumentation handbook, but and I definitely encourage you to read this books If you want to get more information regarding sensors how they are classified Characteristics and so forth and we have covered some of this portion definitely in some of the previous lectures now when we look at Robot sensors in particular Okay And this is not just for industrial robots I have seen a similar kind of classification for mobile robots as well and Even textbooks and to agree on this particular direction So industrial robot sensors typically we classify them as internal or external so remember all industrial robots have server control joints and There is a need to know what the correct position of the joint is what its velocity is and for this We have encoders and the best example that we can Give for these internal sensors are encoders So these measure the position and the configuration in its own set of coordinate axis Therefore, we call them internal they give an estimate regarding the internal state of the sensor External sensors on the other hand allow the robot to position itself relative to its environment that is within this work cell So these include to a certain extent process proximity sensors force sensors vision systems that will typically fall under this category So let us look at these sensors into slightly more detail Now internal sensors also sometimes called as proprioceptive sensors So these are integral part of the robot and like I said they measure the robots internal state And these are typically the ones who measure the joint position the joint velocity and joint acceleration in case of Industrial robots and these are absolutely essential for the execution of all motion control tasks So basically all the control algorithms which which are joints position servers velocity servers and acceleration control systems They will all depend upon the feedback given by these sensors in order to execute the control task The next case in fact when we look for mobile robots Included this particular poor paragraph over here because there is quite a bit of write-up available on mobile robot sensors as well online So if you take a look at mobile robots now Though in a very classic sense a lot of books will not include mobile robots Under the heading industrial robots in which we mainly actually study manipulators But it was prudent given the proliferation which is happening for mobile robots to include these as well and in case of mobile robots Typically we can classify internal sensors as wheel speed sensors We have wheel load sensors the attitude and orientation Acceleration and battery voltage. So they give an idea regarding what is the state of the mobile robot. I've mentioned a few in fact There are there may be a couple of more which you can add add to this particular list So coming back to it now external or exteroceptive sensors These acquire information from the robots environment and these are basically even for distance measurement They do light intensity calculation or sound, but they give an estimate where the robot is in its environment in its work cell Okay So they are the sensor measurements are interpreted by the robot in order to extract meaningful environmental features Now in this is this is especially in the case of let's say tactile and force sensing where it tries to Estimate presence or absence of a part and so on and so forth vision system obviously is also an external sensor in this particular case Now when it comes to mobile robots again External sensors are a compass GPS beacons rain sensors and vision sensors now when it comes to GPS global positioning systems I have come across a couple of resources who have included them under internal sensors, but I have decided to include them Under external over here because they give a position of the robot in The environment so they are it doesn't give the state of the robot in itself, but where it is located So that's why it's more prudent in fact to put them under this particular category vision sensors for example mobile robots use for navigation for ranging for Obstacle detection and so on and so forth So again, there may be a plenty of sensors you may add to the list and depending upon what the features of the robot So that's why some something for you to think about is GPS an internal external sensor and On the same lines. How would you classify? Approximity sensor the reason I have this discussion is sometimes you may come across Sources which tend to contradict a few things and I have seen this in the past in both sense sources Appear to be quite credible in the sense. They are from reputed universities And this often creates confusion among students. So sometimes I I Keep this discussion open so that we can draw some conclusion from the various sources that We come across and let's and also try to find out in what context that particular author has gone ahead with his way of classification so once again here I present you a table of different sensors that you typically find in robots and Whether you should classify them as internal or external so typically if you're measuring joint angle The types of sensors you use are encoders synchronous resolvers encoders being by for the most popular optical encoders We choose gray code very popular sensors when it comes to joint angle measurement Obviously these are internal sensors then you have a Vision-based sensors over here for object identification and typical sensor is idea CCD or CMOS camera Nowadays CMOS is gaining popularity though in machine vision applications CCD still have Majority of the market share but if you if you take a look at your mobile and handheld devices Then in that case CMOS cameras typically rule the market These are obviously external sensors Then you have four sensors which Which can which basically to measure the force that the robot is executing in order to complete a task and Strain gears are by far the most popular sensors for these these are gain obviously again being external sensors Similarly you have textile sensors which can be of different types These are also external sensors then you have joint speed and acceleration This is necessary for the robot to execute a certain trajectory and hence These are internal sensors now obviously here more in many cases the encoder signal in fact is differentiated to get velocity And which is again differentiated to get acceleration, but there may be tachometers and pickups which may be specifically meant for velocity measurement as well Then you have proximity sensors which may be inductive Hall effect ultrasonic and others and these are again external sensors Now the interesting part is limit switches So these are contact or no contact type I Again, I say I have read a couple of resources when in which they have given Alternating definitions for these but I I prefer to put them as an external sensor rather than an internal sensor Okay, so because not meant really for a feedback, but it's inside of a protection Aspects, it's better grouped in as an external sensor now when it comes to Sensors for a specific assembly task. Okay, just to put things into context. I have included this If you are doing acquisition what we need is we need to understand the presence or absence of parts And typically the sensors that will be used here will be tactile and vision sensors Similarly if you want to orient it that is you want to orient the robot or the part relative to the end effect in this case Again, we need tactile and vision sensors and then for the actual assembly process We need the position and the insertion force for which we need force and talk sensors along with some active or passive compliance Devices just to put things into context. I have included this particular There are plenty of information available for this online. I Recommend the sex book James karamas, which gives you a good overview for what sensors are in addition to these textbooks. I Definitely encourage you to visit the robot manufacturers themselves They have a very interesting product lineup from which you will find very pertinent and relevant information on this particular topic with this I Take your leave and we'll be discussing more about other aspects of industrial robotics in other video sessions Thank you