What is the best for robotics: Electric vs Hydraulic actuators

hello and welcome to my channel for a long time in the comments you were telling me that I should try Hydraulics system on my channel and today I'm not going to try them but today I'm going to compare hydraulical oxidators with electric actuators kind of compare and I'm going to do this from surgical point of view and as I know nothing I'm going to use a mainly two scientific papers for this so let's get started I think it's super interesting to compare Hydraulics with electrical systems because if we look at the present robots we see some kind of Trends and one of the trends is that most of the robots especially if we simplify our task and take only humanoid like robots most of these humanoid-like robots which are in development now they're electric ones like digit robot like cyber one from xiaomi or Tesla bot there is no many Hydraulics robots but the one which exists humanoid hydraulic robot Atlas from Boston Dynamics is probably the most advanced robot and probably most of the people knows this one and not the electric ones so from one side the electric ones they're more used and from Another Side the hydraulic one seems like it can do much more than electric ones because it seems like it's more agile it's faster it's more powerful so from this point of view it seems like Hydraulics is better but from Another Side if we look at the robot dogs most of them are electric some of them are hydraulic and the interesting thing that Boston Dynamics the people who is behind hydraulic Atlas they have made several robot docks with a hydraulic system but for the production for the spot mini they decided to use the electrical system and not Hydraulics so why let's try to figure out this so so as I told you I mainly looked at two papers this is the first one electric Rod actuators with hydraulic cylinders a comparison of the pros and cons of each technology and this is a paper from the telematic company and it's a company which supplies linear actuators both electric and hydraulic this is the first paper the second paper is this one it's a little bit more complicated but at the same time it's a little bit more interesting so characteristics of hydraulic and electric server Motors so first of all let's look at this one and here there are several interesting figures for the robotics it's very important to be able precisely control your actuators and in this case the electric actuators it's way easier to control than hydraulic and this as you can see over here so this is kind of schematic so this is not super scientific but still so this is electric and as you can see the electric one is the best for the position velocity and acceleration the acceleration control the electro hydraulic or Servo hydraulic is uh quite good in this but not perfect and the standard hydraulic system with the open loop it's a really bad in the control but for the force control the hydraulic systems are quite good but still electric systems are also good but here the orders of this purpose they decided that hydraulic systems are a little bit easier to control in force than electric one I think this is questionable discussable but yeah anyway both of them are good to control in the force and the hydraulic systems are not really perfect from the point of view of the Hidden minion than when there is a lot of loads the oil can heat up and it's not a problem for oil to be heated but it's problem for joints the hot oil can damage the joints so here's a saying that uh 82 degrees can already damage the most seal compounds and also from the point of view of gold if you are using the actuator since the cold temperature the electric actuators they are way better in these terms because of the fluids thickening with the colder temperatures the oil becomes less liquid and the system becomes less efficient also electrical systems they require almost no maintenance and the hydraulic systems that require more maintenance I think here they put it in the medium because they're considering Electro hydraulic system when there is a closed Loops like this oil is not much exposed to the air and it requires less maintenance so Electro hydraulic actuators it's a kind of small package which contains everything like motor pump the hydraulic piston the valves and all this in small easy to use package the efficiency I send this one is is important the electric actuator efficiency typical efficiency 75 to 80 percent quite high and for the hydraulic one is 40 to 55 percent so it's almost two times lower this means that for the mobile robots probably electric systems are better than the hydraulic ones and also from the point of view of environmental risk the electric one has a low risk and the hydraulic one has quite high risk because the possibility of the leakage of oil so this was the key points of this paper as you can see this is kind of educational video so that's why I think you are going to appreciate the sponsor of this video brilliant.org this is an interactive tool which allows you to learn a new Concepts in mathematics physics science computer science machine learning and stuff like this and also it's a great tool to remind you what you already knew but did not use that for some time and probably forget like it happens with me quite often and the sort point which I think the brilliant is perfect is to train your brain we all know that in the age of AI when the technology becomes more and more smarter we also should try to keep up with the technology with the computers and this is another Point why we should train our brain and keep it sharp there you can learn a lot of new Concepts from the basic to Advanced brilliant 1000 courses and the new lectures they are added on the monthly basis so I think almost everyone will find something interesting there to try everything Brilliance has to offer free for a full 30 days visit brilliance.org or click on the link in the description to this video the first 200 of you will get 20 off from brilliant's annual premium subscription now let's look at the second paper characteristics of hydraulic and electrical Servo Motors they did quite interesting analysis where they took a lot of electric and hydraulic motors not the actuators but just Motors and they take different types like AC AC direct brushless DC brush DC so on my channel we quite often use a brushless DC because uh they're probably the most advanced from the electric motors and from the hydraulic they used the swash plate type XL piston bent axis type axle piston crank type radial piston and multi-stroke type radial piston I have no idea what is this but let's find out so let's look at the Wikipedia page XL piston pump so this is going to cover Swatch Play Type XL piston and bend axis type XL piston and there is this really great animation so first all this picture Swatch Play Type XL piston is basically this kind of motor over here there is intake the high pressure is going here and here is exhaust and this part can rotate this part has a lot of pistons and over here there is no rotating Swatch plate so this wash plate which is positioned at some angle and because it's positioned at some angle when the Piston is over here it's going up when it rotates the Piston over here it's going down when the high pressure is here this high pressure here is going to push the piston and like this it's this piston is going to force this part to rotate and so this is basically how it works well you can see this over here so the the oil pressure goes here it pushes the Piston these Pistons they push this part to rotate and over here the Pistons goes up and the oil coming out and the bent axis type XL piston is the same idea it's over here from this picture it's kind of difficult to understand how it works Bend axis type XL piston I think this one is a good image this is the output shaft this has a pistons and again there is the same type of the inlet and Outlet so this is a piston and this is a chamber this is the output and so like this this Pistons they rotate with the output shaft and so when the oil is coming in it pushes the Pistons and afterwards from the other side there is exhaust so it's basically the same scene as with this swash plate but instead of inclining the these plates this wash plate what they did here they like bent the entire actuator but the idea is exactly the same I think the advantage of this one that it has probably less friction with compared with a Swatch plate another hydraulic system is a crank type radial piston this I'm not going to talk about it because I have not found exactly what it is but I found what is multi-stroke Type radial piston you can see it over here this is from this company this is a motor and this is a cross section of this motor so there is one cross session here and another cross section over here this is the output shaft and this output shaft is rigidly connected to this part so it rigidly connected to this part which rotates and this part has a lot of small Pistons at the end of each piston there is this kind of cylinder which pushes on the wall of this motor there is this shape which seems like a shape of the side in the cycloidal actuator so if you apply at some of this piston the pressure and don't apply at another pressure it will force so this Pistons they will push on the wall and this will force the entire output shaft to rotate over here there is a Inlet and outlets and this Inlet and Outlets they are not rotating so this part are not rotating and this Inlet and Outlets they put the oil they put or take the oil to this holes which are on this wheel and so when when the appropriate hole is aligned with the inlet and Outlet the oil comes in it pushes to the to this small piston and it works like this I think you can understand this from this image from this uh YouTube channel so there is uh Inlet over here over here the outlets I don't show but so basically this part does not rotate but this part it rotates so this means that at some points the inlet aligns with some Pistons at another point it aligns with another Pistons so like this there is a high pressure at exact moment when it's needed so now we know at least some of the hydraulic motors I hope that you know what are these motors at least I think most of you knows what is brushless DC and what is brushed DC I would like to start with this schematics and these schematics they compare the electrical drive system with hydraulic drive system and what components do you need for each of them and for the electrodive system I think you all know that you would need the motor you would probably need the gearbox and this gearbox is going to move your load the motor is powered by the wires in the wires there is a current because of the driver and there is a driver power supply and controller so controllers tells the driver where to go the driver takes the power from the power supply and put this power in the motor with a hydraulical drive system it's a little bit different first of all the motor is smoothly here than this one I think that they just want to show that with the smaller motor you can have the higher torque than with the electrical one the motor is quite often connected directly to the load without any gearboxes over here because the torque of this motor usually is quite high and here you have a lot of different stuff like a power supply driver which Drive the motor this motor it rotates the pump the pump usually has the reservoir there is some walls and these walls are controlled by controller so basically if you compare these two systems here you have Controller driver power supply and here you have power supply driver controller so these parts are quite similar they're not the same but but they're quite similar and in addition for the hydraulic system you need motor pump reservoir and valves in this paper they compare only Motors but still it's quite interesting let me show you so this is kind of a historical chat so there is a year of the technology here and the power density so the power normalized by the weight of the motor and the green one is hydraulic motors and the radish one is electric motors and you can see that hydraulic motors they are always more power than electric motors and the difference between hydraulic motors and electric motors becomes smaller and smaller and I think the most interesting progress was over here because of the brushless DC motors and why this brushless DC motors they appeared over here because of the magnets so this is again the yeah the power density here there is only electric motors so basically this is the same part is over here but also they put here the different magnets magnets they appeared over here and thanks to this neodymium magnets it was possible to make lightweight and Powerful brushless DC motors and this is a hydraulic motors power density and as you can see with the time what is changed the rated pressure of these motors is increased from 10 megapascal to up to 40 megapascal and by the way the interesting scenes here that if you look which one is the most power dance is the most old technology over here the band axis type XL piston and what is interesting for me is also this graph this is a torque of the motor without any gearbox as a function of mass for the electrical motors and for the hydraulic motors as you can see the hydraulic motors they're more powerful than electrical one and they are more powerful around 10 times this is a log scale but this is again without gearboxes so with the gearboxes you can increase this so if you have like super light gearboxes 10 to 1 in this case this Curve will go over here and will be almost like some of the hydraulic systems not the best one but some of them and the most torky technology is multi-stroke radial piston this is also interesting graph here they compare the torque with the speed so the hydraulic motors they have the high torque but they're not really fast but at the same time that's why they can use these motors without any gearbox and connect it directly to the payload this is a power as a function of mass and as you can see the Hydraulics is higher here's a summary of this comparison Hydraulics motor versus electric motors usually the electric motors are faster than hydraulic ones but the hydraulic ones have higher torque than the electric ones hydraulic ones have higher power density and here the Q is the motor responsiveness and the hydraulic ones they also win here with respect to the motor responsiveness and here there are advantages of the electric motor and the hydraulic motor the electric motors high efficiency high RPM high control capabilities low maintenance the hydraulic motors high power to weight ratio high torque to weight ratio and high responsiveness but this is just the motors if we look at the electric drive system and hydraulic drive system so everything together not just the motors but everything together like gearboxes control system etc etc in this case the electric drive system with respect to the hydraulic drive system it has additionally the gearbox module the hydraulic drive system does not have this gearbox but instead it has the additional motor pump and Reservoir and also the control valves usually you need one motor one pump and one reservoir for several hydraulic motors and for each hydraulic motors you need the oven set of the valves as it happens quite often there is no magic solution and it's difficult to say which of these systems are but the electric one electric drive or hydraulic drive just to remind you from this graph we saw that hydraulic drive systems are not developing as fast as electric one so probably in the future the electric one will have the same kind of power to weight ratio and the same kind of torque to weight ratio and at the same time they will keep the be simple and easy to use and for the moment I would like to ask you your opinion what do you think what is better electric drive system or hydraulic one thank you for watching this video till the end huge thank you to people who support me via Patron and Via YouTube channel membership hear their names thank you as usual stay safe good luck with your projects and see you next time and I hope one day we are going to try the hydraulic drive system

Channel: Skyentific

Views: 24,631

Keywords:

Id: yc8BS9f8Zm0

Length: 18min 21sec (1101 seconds)

Published: Sun Apr 30 2023