For electric mobile machinery, the battery operation time is always a major topic. While the battery capacity itself and the efficiency of the electric drives is often in the focus, there are further levers to reduce energy consumption and increase machine runtimes. In this presentation, Dr. Steffen Mutschler (Director Sales & Product Management at Bosch Rexroth) will discuss the impact of the hydraulic system: Based on application examples, simulation and test results help to concentrate engineering activities on the most beneficial efficiency optimizations.
About Dr. Steffen Mutschler
Dr. Steffen Mutschler holds a PhD Mechanical Engineering from TU Braunschweig in Germany. He is currently Director, Sales & Product Management Electrification of Mobile Machines at Bosch Rexroth AG.
His experience includes work in systems engineering at Dana Rexroth Transmission Systems SRL, and in systems integration mobile hydraulics, and systems engineering mobile hydraulics at Bosch Rexroth AG.
Hi everyone I’m M kajo I am the Director of Business Development for zapi group and I like to welcome to you to this session please remember that this session is also being recorded and will be available to watch On Demand following this session if you have any questions
During the session please add them to the Q&A part you can find that tab on the right of your screen note that your question will be sent privately with that I would like to introduce our speaker I’d like to welcome Dr Stefan Mell from boser exort who will speak today
About empowering Optimal Performance with electric Hydraulic Solutions welcome Stefan please take it away thank you very much for the introduction M we are today broadcasting from the customer benefit center of BOS rexwood in here we have the development of our electrification products for high voltage for high voltage portfolio um
With this information I would like to start into the presentation now as M was pointing out today we want to talk about optimizing the performance of mobile machines with electrohydraulic Solutions the background for this is that we are discussing a lot with our customers about the needs coming from
The change from conventional machines to electrified uh zero emission Machinery what we experience is that the customers are asking many many questions because there’s so much to learn for all of us in the field of electrification and one topic that comes up again and again in this discussion is how we can
Increase the machine runtime with respect to the battery capacity that is available on the machine and that’s why I picked exactly this topic for the presentation today because what we do is that we look together with customers not only at the characteristics of the components that they’re using we are
Rather taking uh let’s say full scope approach to optimize the complete machine and of course what can we do to increase the battery operation time looking at the complete machine we can have a look at the overall machine efficiency if we don’t use the energy
Then we still have it in the battery to use it for prolonged operation time and when we talk to the customer as I said we look at different levels how to improve the efficiency so basically there are the different levels of the machine looking at the components themselves looking at the complete
System that we are implementing together with the customer and also having a look look at dedicated software functions to improve the efficiency to the maximum level that we can achieve let’s go through these topics now together we will start with a look at one very special component currently we are introducing
To the market our new A10 V series 60 pump that is optimized for electric drives and also for electronic control it is very very Compact and has a significantly increased performance in comparison to earlier products this product will be available in different sizes starting from 45 CC up to 115
Cubic cm per Revolution and with this product we have introduced many specific let say features or improvements uh to design overall a completely new product here so as you can see here we’ve been working on the rotary group to increase the performance and make it as compact
As possible but also did we have a look at the housing to make it as small and lightweight as possible and of course on this pump that is made for electrification as well as for electron control we have introduced sensor interfaces so you can have uh pressure
Sensors placed on the unit as well as angle sensors to be always informed about the current displacement in order to control this product you have the two options to uh work with classic mechanical control or to go to electronic control and by doing this use all the flexibility that this product
Allows additionally with the pre-compression volume that is optionally available we can reduce the nbh on the machine reducing the pulsation of the Hydraulics having a much lower noise behavior in comparison to Conventional pumps and this comes without any length increase so still the product stays very compact but I was
Talking a lot now about let’s say General benefits yeah if we have a look at the real improvements you can see here in this overview that we have really done our homework so the nominal pressure is increased rotary speed is higher which helps us with the electric drives and especially the power density
Helps with a compact integration in the machine but what is now today most important for us is the relative efficiency Improvement that we have achieved on this new design as you can see here the relative efficiency goes up by a level of 7% with this new series in comparison to the previous product
Now let’s have a look what this means for the electrification so basically with this new pump due to the sensors we have the possibility to implement a power management on the machine just uh sharing the power to the implements and for example the drivve train in the
Right way the increased speed helps us to reduce the electric motor size and with a reduced pulsation we can reduce the noise level but the most important Point again for me today is the increased efficiency and here in the small calculation example at the bottom you can see the impact so basically when
We take the assumption that about 85% of our power on a certain machine is used by the Hydraulics then you can directly map the efficiency increase to this power consumption so what this means is that the operation time as you can see in the diagram is increased Yeah by
About 7% not really it’s a little less because there is always some power consumed also by auxiliary on the machine this was considered here so in the end by applying this new component you can already achieve quite some improvement now let’s come to the next
Step what happens if I go not only in component uh optimization but I have a look at the complete system for this example we have selected an excavator and let me share some information about this machine so here you can see this is our uh conventional wheeled excavator uh with a one Loop
Hydraulic system on it uh like we used the machine for The Benchmark and you can see on the right left side looking into the pressure levels that of course on such a machine you have to provide the consumers with many different pressure levels resulting in quite some
Loses in the hydraulic system so let’s have a quick look again what this system is looking like yeah this is the conventional machine and uh basically you can see here we have a pump a main control valve and with that one we are operating the cylinders as well as the
SLO drive and now of course we want to look into how to optimize the hydraulic system so for this we have many different levers coming from smaller actions like you can see on the left top looking into hoses and piping for sure you will find some optimization possibilities you can work with flow
Matching to have some uh flow optimization and then you can do a much bigger step separating the machine Hydraulics into a two-loop system and you see here already this becomes a much bigger level looking into different pressure levels in a range of about 20% efficiency Improvement and if you further go on you
Can think think about uh optimized slues with energy recovery giving quite some benefit of up to 6% and also an interesting point is to look into energy recovery from the boom which is in our experience that we have found in measurements in the range of
8% when you go into the second line here you will see that you can do still much more about the efficiency going into more advanced systems and as you can see here there’s the multi- pump system from the Purdue University uh going in the direction of 40% savings there’s multi
Pressure Network studies which was driven for example by the University of aren where we are in a similar range yeah and so there are many different ways how you can optimize the machine so the question is what did we do with our excavator basically as I already pointed
Out we introduced in the first step uh two major measures on the system the first measure was to introduce a second hydraulic pump so we can operate on two different pressure levels this uh has the consequence that we don’t have so much reducing uh throttle losses on the
Hydraulics and uh as a second step we also introduced energy recovery from the boom as well as from the slooh and then we did another step we introduced variable speed on the diesel engine machine and with all these measures we achieved a reduction of the consumption
By about 40% and if you look at again or think again about the values that I have pre pre presented on the previous slide you can understand that somehow the different portions that go into this add up to let’s say about 40% The Next Step that we did with this
Machine was to introduce electrification so the first step was really to look only at the impact of the Hydraulics but then to do the step to introduce the electrification as well and what we did here was basically that we took our Eline component portfolios in uh included our electric
Motors our inverters we included our onboard charger dcdc converter to set up a complete electric machine uh to drive our hydraulic system and with this introduction of the electric drive it was possible to reduce the energy consumption even further why is this so as you can see on the right uh
Top side we could apply with electric drive a wider range of variable speed because we’re more Dynamic what is helping here is of course the overload capability of the e Drive helping us whenever we run into situation where High Dynamic response is needed and what we implemented as well was a fully
Independent eastl Drive to maximize the energy that we can recuperate from the SLO drive so I think this value is quite impressive right talking about uh 46% of consumption reduction let’s have a look what this means in our calculation so basically when I say 46% less consumption it means that we have still
45% consumption left so if I take the inverse of this I get the runtime increase uh of a factor 1 divided by 54% and this means when I take the efficiency Improvement that I had with my series 60 pump multiply this with a possible Improvement by the system I
Arrive at an increased battery runtime up to nearly double the value I think this is quite impressive but you should not forget at this point that this is for sure due to the high portion of energy on the machine I assumed 85% that is used by the
Hydraulic system really but then we were looking even deeper and testing the machine not only with one operator we wanted to understand how big is really the impact of the operator is it the same for every machine operator or does it change and then we um gave the machine to an operator that
Is less experienced so here you can see again the uh result with operator one was to reduce the consumption by 46% while with Operator 2 we only achieved 38% so this was for us a little let’s say discouraging because in the first moment we did not really understand how
The differences can be so big but then we looked into what the operators doing and we found out that the most important topic about this is um taking care of avoiding the end stops so from this point we thought about what we can do about it but now let’s first
Have a look at the impact of this untrained operator so if we have a look at our uh energy or operation balance again with uh the less trained operator we have only about 38% savings meaning the consumption is not down to a level of 45
Uh 54 % but rather only down to a level of 62% and this means that with this less experienced operator we only achieve 170% 171% of increased battery runtime so what we thought about this is what can we do and the clear step that is a way
To support here the situation to improve the result is to introduce assistance functions so basically with the introduction of assistance functions after understanding what is the reason for the reduced operation time we were able to uh again increase uh the operation time to a similar level as uh
We had achieved with the experienced operator I simplified it here a little I just wrote a a full consumption of about 25% on the operation time yeah but I must admit we did nearly get there but not completely of course as there’s always a human factor in
It so I think this is quite impressive what you can reach on the system now let’s also have a look at the software so which levels do we still have to uh improve the machine efficiency looking into software functionality and uh basically here for us one topic that is quite in the focus
Is how to operate pump and electric motor in the best way together basically when we are talking to customers there’s a lot of experience out of the combustion engine field so basically we are saying it’s a rough value that typically everybody would agree on if you reduce the engine speed
To uh let’s say uh a maximum reduction that is possible you end up somewhere between 10 15% reduced consumption yeah and this is the assumption that many of our customers also take into the electric machine but then when we start the discussion we have a look together at
The electric drive and you can see that a similar speed reduction on the electric Drive does not improve the efficiency of the Drive Unit by about 10% it rather has a negative impact on the efficiency see so for sure there’s some space for optimization yeah especially when you look at the topic
With the even higher um complexity of taking also care of the hydraulic pump and basically now for a zero emission machine we don’t need to look anymore at the combustion engine so let’s have a look at the efficiency maps of the electric drive and the hydraulic pump
And we can see that we have here contradicting requirements so basically reducing the speed helps a lot to increase the efficiency of the hydraulic pump but at the same time you reducing the efficiency of the electric drive so what we have to do here is to think about optimization of the efficiency of
The operation point to come in the end to the best result and what can we optimize here let’s have a look at the pump and electric motor functionality together so basically what we need on the machine is a certain pump flow as you can see in
The diagram on the right side we have the rotary speed on the y- AIS we have the displacement of the hydraulic pump on the x-axis and the product of both leads to a certain flow as you can see on the right hand corner there’s a curve
Of an equal flow and basically now the question that we have to answer is how do we realize this equal flow in the best way is it beneficial to increase the pump speed or is it beneficial to increase the pump displacement and this is a question you have to answer not
Only once but you can answer this question in every millisecond of the operation so we have implemented an optimization algorithm in a software solution package what we are providing as a complete solution you can see here on this slide so basically we have our control unit on
This control unit we could have the complete machine control asking for a certain flow and giving a certain power limit and then we have the citronics uh software package this package optimizes the pump and motor operation for the best efficiency if this is what you want or it optimizes for the best sound
Behavior or the best Dynamics this is all included in our citronics package with this uh software package in implemented on the controller we are then controlling the electric motor via the inverter and we are controlling the hydraulic pump to always deliver together the best flow and now you can
Think about does it really work yeah um which improvements does it really bring and of course we had a look at this so as a basis we again looking here at an excavator and uh we did measurements in different load conditions so on the left side you can see uh the time measurement
Of uh flow and pressure we were operating in a high power mode at low load and also uh in let’s say standard mode of the machine and on the right side you can see then let’s say how this is reflected uh in the Delta P flow map
Of the uh drive and this is exactly where we have to optimize to come to the best efficiency the result of the study I can directly share with you because first we did a simulation so on the left hand side you can see the advantage we achieved in the simulation
So basically we have the combination of all three different operation modes and then we have measurements uh separated here also or let’s say values here in the simulation separated for the power mode for low load operation and for the standard mode operation and you can see already here
From the power mode operation um we had let’s say the smallest improvements in the efficiency while in low load conditions uh the efficiency impact is quite high so with this information looking at your application looking at your use cases it helps to understand what can really be the benefit for your
Machine we were uh looking here at two different strategies uh the blue one it’s a minimized speed and the dark blue one it’s the optimized speed operation so you can already say from the simulation that uh reducing the nominal speed as much as possible like we do
With the diesel engine it’s not leading in the wrong direction it’s already helping a lot and however you can see that you get more benefit out of it when you go to an optimized operation strategy and here it’s interesting that the difference in the low load Condition
It’s not so high but when you have power mode operation then you really see the optimization of the speed is beneficial and takes you in a full power mode operation into a range of 10 2% efficiency Improvement on the right hand side we have more or less the same data
As it was uh uh confirmed by our test bench testing where we in the end we’re working on the same pressure and flow levels and working with real components to see if the results that we achieved in the simulation are uh let’s say uh correct now as a conclusion based on the
Machine usage you can achieve between two up to even 9% for low load conditions with optimized control and I think this makes it quite interesting and why is it so interesting because in the end we have talking here about software this has no impact on uh the selected uh components this has no
Impact uh on the system costs yeah of course uh the software functionality uh needs to be developed needs to be implemented there are efforts related to this um but it’s from my perspective quite a smart way to take out uh all the efficiency of the system that you can
Achieve now let’s see what this means uh on the complete Machine level then if we now take this into consideration again so what did I do I uh have an average value of about 3% efficiency Improvement for the subsystem inverter motor and pump with the optimum control but 1.5% of this were already
Considered in our systems measurement that the colleagues have done so in the 46% consump reduction we were already working with the nmin strategy that’s why here in this uh let’s say calculation I’m not considering the 3% I’m only considering about let’s say 1.5 2% that you can see at the bottom and
This takes us overall to an increased battery runtime for the complete machine of nearly twice the time so when you ask me again how to increase battery operation time I can tell you we have the different levs that we need to consider on the complete machine looking into the selection of optimum
Components looking into Potentials in the system and of course understanding what is the impact that we can have with software functions at the same time we need to consider the impact of the operator and probably react with assistance functions to uh compensate for let’s say negative impact that can
Be caused by untrained operators so in the end with our Eli solution in total it’s possible to increase the machine operation time significantly thank you okay thank you stepan for your very nice presentation so I think um we have time for some questions so the first question I see
Here is when is the new A10 V CDs 60 available the first nominal size 45cc is already in serious production and we will continue with the sizes let’s say this year and the following years okay thank you so next question um the battery run time increase increase
You show is impressive so yeah do you think it is possible to get in any machine type yeah that’s a very good question because in fact uh merco the topic is that I have selected here use case of a machine where the hydraulic portion of the energy consumption is very high yeah
If you look into other applications or other use cases where you have a high portion of travel driving for example then the Implement system does not have such a high impact yeah however what we do always is to look at the overall system to understand where we have uh
Let’s say the biggest levels to improve the overall efficiency mhm yeah okay so next question U thanks for sharing this example but how can I ensure to select the best solution for my machine I think is a little bit connected to the previous question in a way yes yes yes exactly so basically
What we do is that we look together with the customer into his machine application understand together what are the Duty Cycles and uh based on that we have a simulation tool so basically the customer can provide to us flow and pressure requirements and with these requirements we can run simulations to
Understand which electric motor is the best which pump selection is the best one does it make sense to use a variable displacement pump or should we rather use a fixed displacement pump yeah so in this way together with a customer looking at the application we always working to find the best
Solution okay yeah and this may be is answering also the next question regarding if the algorithm that you have inside the electronics are standard or can be in some way customized based on the vehicle type or the customer request but basically I think you have already answered yeah maybe I can say something
About this so basically uh with the development of the citronic solution we have a very long experience in the field of industrial applications so uh we started about 15 20 years ago already to work on these algorithms and with that experience yeah it was a task let’s say
To transfer uh the algorithms from industrial applications where you have a lot of computing power uh to mobile applications yeah okay and for sure this was one of the major tasks and uh of course we can adapt the software always let’s say to the hydraulic system and to
The electric machines that we applying okay I have a very interesting question now um in conjunction with electrification to increase the electric motor power density will be a benefit to run high speed as much as possible yes so are you working in higher speed Solutions I guess for the Hydraulics
Like 5,000 RPM or more this is an information that I cannot yet talk about today okay you will see in the future what is happening yeah and I mean personally I am really interested in this question because you know who wants to develop Motors they want to go higher and higher
In speed so yes yeah so generally this is possible but of course you have to take certain measures to make it possible yeah yeah in the pump technology and also in the system so many questions are coming I tell you so uh um this is is asking if
There are some impact in these new technologies these new Solutions on the after sales and field service so maintenance or other stuff like that what is the impact H that’s a challenging question I believe the biggest impact here is that uh in the field of service we need to
Increase the competencies for software and high voltage technology yeah I think this is one of the major impacts that we see currently that uh with any new development in this direction we have to take care to train our service teams uh to make it possible for them to analyze
The machine on site and to take the right measures to help the customers yeah okay so next question if we increase the motor speed for better efficiency do you think that the system noise level will increase too because it is a serious matter yes and that is of
Course always let’s say the uh uh different optimization goals that you have right so uh if you have a need for a really silent machine maximum speed is probably not the right uh approach to realize this okay so next question uh which which recuperation Vector did you choose
To reach 6% with z and 8% with boom simply hydraulic or also electric um this was done on the hydraulic machine this was without the electric SL MH okay uh and and maybe maybe here’s one interesting point if you recover energy or recuperate energy hydraulically then you can reuse it in the hydraulic
System and this is sometimes even more efficient then trans uh Ferring it to electric energy first and then bringing it back to hydraulic energy so we had quite some interesting finding here yeah that it’s not always the best to use electric drives for energy recuperation because of transferring it
From the different uh let’s say regimes from hydraulic to mechanic to and back again yeah yeah um since hydraulic savings shown uh were around 40% and then after electric Drive the savings were 46% MH would you say that to achieve Energy savings focusing on Hydraulics is better approach than looking to at
El I think I think it’s more or less what you were saying yeah I can I can add something to this so basically it depends always on the machine function when you’re talking about the hydraulic system of the machine Implement Hydraulics for example then there’s a huge lever in the hydraulic system when
You’re talking about a travel Drive application of course it makes sense to look into the efficiency benefit of an electric solution and the SLO Drive is something in the middle yeah so you really can look into the application to understand the duty cycle what is the best solution
Here M but we have some indications that the hydraulic solution with energy recuperation from the SL Drive is also not so bad in compar okay so next question says simulation seems to be very precise today so are there in your opinion still improvements possible in the end this is
All about model validations so basically if you have a a good uh knowledge of the product and you can make a very good physical model of the product at the same time you have the real product available uh to do a let’s say a parameter study to to understand which
Is the right parameter setting for your model then you can achieve a really very good level on component uh side and combining uh very good component models to a system model typically then leads to a good result yeah sure uh another question what changes in
H size do we need to do and uh how significant the effect is that yes so at this point it depends of course always on the application which flow you have yeah how you uh select the hoses based on that and it’s the best to optimize this with a hydraulic host supplier to
See together where you have the optimum for the application uh does your control box operate with the E mechanical PTO supplied by the track manufacturer generally this is possible yeah uh a calculation was made to understand what difference there is between a traditional system and this one in term
Of energy cost in 8 hours of work what is the cost of the standard fuel solution and how much is the energy cost with electric so for this I don’t have the calculation here on hand but there’s there’s one impact that is quite interesting from my point of view that
Is the impact of where you operate the machine so today in Germany electricity is very expensive and also fuel is quite expensive if you go to France you have different relationships between the costs yeah and if you go to Saudi Arabia it looks again different yeah so so that would be a
First uh step to talk about which uh uh Fuel and energy prices we are talking about and of course it makes sense to consider this complete uh calculation for a return of invest approach in the case you do not really need zero emission for your side but you look for the most economic
Machine solution MH okay I have the last question here uh what do you think about having same pressure at every function of the machine in order to reduce the losses when multiple functions are used yes so I like this approach as a let’s say provider for Valves and uh pumps but uh
We are here in a conflict uh with the suppliers of the cylinders and typically the customer is using for looking for the most costeffective solution yeah and here we have in the end a clear contradiction okay uh now another questions came now so do you see the market moving to voltages above 1,000
Volt when MCS replaces CCs in charging infrastructure if yes then are the Elon products available for it um that’s an interesting point so for the mobile Machinery I do not yet have any indications to go to voltages above 1,000 volt we see it sometimes in the requests for the truck Market though
Yeah so whenever we are close to onroad Applications uh we see that this can be for sure a future Trend um are the Eline products available for it our maximum voltage for the inverter is 850 volt so today uh the Eline products are not the right solution to go above 1,000
V okay okay thank you for answer also these questions we had a lot of questions today good that it means that you have stimulated the audience and um yeah as I said in the beginning it’s possible to watch also on demand this session and uh at this point I will
Thank you again stepan for today and see you soon very you good M it was a pleasure see you soon byebye yeah bye