What combat role could a mech play on a real battlefield?

[Malleolus]

Quickly is a relative term. How fast you can sidestep depends on geometry. The mech will probably be optimized for one direction, unless it doesn't need to be very quick. In directions other than the primary, it will likely be slower. Mechs also need to deal with their inertia when turning while on the move. Runners turn like a vehicle do, gradually changing their direction of motion. Only when you're still or at low speed can you easily sidestep.

Only a portion. They may also give away their intentions when doing so.

 

 

This is no different than the mech. The wheeled vehicle has a potential advantage in being able to very finely control what does what while slowing down. The load on brakes con vary infinitely.

 

 

I don't agree with this. You are right in saying engineering isn't perfect, there are unknowns, and what is consider possible will change. This doesn't mean that you can go around and say that anything is possible though.

 

We don't have mini fusion reactors and high performance joints. You can't consider the argument without taking that into account. Why? Because how those systems work specifically will impact the mech and because how those system work will impact the mech competitions.

 

You could say that we may have technology advanced enough to allow mechs to fly supersonically in the future. This would allow mechs to dogfight, etc. Only jets will be better at it. Apply whatever raw power or drag reduction or advanced control systems to the plane instead of the mech and it would benefit more because it's better at the basics.

 

In short, we can't ask what we'll do with a mech unless we know how it will work. You can propose advantages, like saying it can jump over obstacles, etc, but then you have the problem of not knowing how well it can do this. That doesn't negate the point entirely, but it prevents you from saying it will be better than a wheeled vehicle with certainty.

 

Ultimately though I can agree with you in seeing potential in a infantry support mech.

 

Uh, just on a side note here, look up high-beta fusion reactors.

[Malleolus]

Aaaand, you just totally lost me.

 

Quoting fictional technologies from Battletech (a fictional game in a fictional world) does NOT help back up the science of why it would work. I may as well say "we can have battlemages, because once we invent mana...."

 

Please, explains, what exactly IS "endo steel" (internal steel?). Or "ferrofibrous" (iron fiber? What is that, iron filings?) They aren't real technologies, they are technobabble names given to a fictitious science in a GAME. You really lose credibility when you reference fictional games to back up your science, because (true or not) it makes you look like you're arguing from a stance of fanboy-ism instead of cold rationality.

 

...and yes, I am a huge fan of the Mechwarrior PC games (3 is still the best!) and have several battalions of miniatures for the Battletech tabletop game. It's a cool game, and has a lot of "badass" factor to it, but that doesn't mean it's practical

 

I can't speak for Endo steel per say, but I'd point you to stacked electro-active polymer actuators and iron matrix nickle-coated carbon fiber metal matrix plating.

[Exorcet]

Uh, just on a side note here, look up high-beta fusion reactors.

An interesting development I wasn't aware of, but we still don't have it and it will be ~10 years apparently before they even have a working model for energy production. That will need to be modified for vehicle use. You could say it would power a mech, but then you'd have no idea what effect it would have on the mech's design (and if it can power the mech, it can probably power a wheeled vehicle, who benefits more?).

 

Also fusion might be a good counter example to the whole mech thing. Fusion has some very clear advantages like huge energy output and less radiation risks than fission. We don't know how to produce useable fusion, but we have a good understanding of how it will benefit us and where we can use it. I don't think this is quite true for military mechs. Research in both fields is quite valid though.

[ShuRugal]

All your math is flawed, when applied to a walking system. <a whole lot of handwaving and techno-babble>

 

Mate, I really hate to break it to ya, but "Inverted pendulum" just means that it allows forward movement to continue in part on momentum... just like a wheel does. The biggest difference being that when the foot is planted on the forward step, a portion of that momentum is used to fight gravity and carry the body up on the leg. So, depending on stride depth, it's marginally less efficient than a wheel for maintaining forward motion.

 

If you want to accelerate your 20 ton mech forward at 3.5 m/s, you still need to produce exactly 132.3 kN of force between the mech and the ground. You can't get around this with fancy terminology and handwaving. You certainly can't get around it by saying "I don't like your numbers, modify them by percentages for reasons, so there."

 

You lean forward, inducing a momentum that builds the faster you throw your torso forward and the more you stand up

 

Law of Conservation of Momentum. If you want your mech to move away from the ground, you need to produce an acceleration greater than 9.8 m/s^2 vertically. This requires a minimum of 176.4 k/n of force transferred into the ground for your 20-ton example.

 

As a side note: all of my numbers so far have been without specifying a specific power delivery method (geared, hydraulic, chain drive, etc) and factoring in the losses inherent to one of those systems (mostly because I really don't feel like doing that much math just to be able to say "Ha! you're even more wrong!"). So if you really want to break out the technobabble and handwaving, I do still have more things for you to wave away. At the rate this is going, you'll be flying under your own power soon.

 

 

Uh, just on a side note here, look up high-beta fusion reactors.

oh, now there's room for a steam engine inside your mech? We just barely fit a gas turbine, where are you going to put a steam turbine, heat exchanger, coolant supply, and 2x2x4 meter reactor vessel? the reactor itself is the same height as your proposed 14' foot mech!
Edited June 15, 2014 by ShuRugal

[Jona33]

A fine (if actually quite interesting) display of testiculation here gentlemen. (Waving your arms around and tallking bollocks. :D)

 

On a more related note I genuinely don't see a mech being significantly more useful, less armour and less speed, and less fuel, and less weapons that are less accurate.

 

To address a specific point one of the arguments was

And how long does it take to exchange a package for another? A mech can theoretically do this on the order of minutes.

 

What makes a mech so special here, how is a mech going to switch weapons instantly, replace the arms, the entire torso? Doesn't sound like a few minutes.

Edited August 16, 2014 by Jona33

[SimFreak]

I can't speak for Endo steel per say, but I'd point you to stacked electro-active polymer actuators and iron matrix nickle-coated carbon fiber metal matrix plating.

 

Somehow people do not realize that with invention of "new" armor, now that armor can apply to other vehicles, not just mechs. So if M1A is 70 Tonns...suddenly it's lighter with same protection and much reduced loading on the ground. Oh my...

[shagrat]

If you want to accelerate your 20 ton mech forward at 3.5 m/s, you still need to produce exactly 132.3 kN of force between the mech and the ground.

Only a walking system let the 9.8m/sec^2 .generate a good deal of it. Since you don't need "accelerate" the mass into the sky, but simply stabilize it, and store plus generate enough energy to heave it up the distance it was accelerated towards the ground (a few inch?) That is where muscles and sinews do a pretty good job. They store a very high portion of that energy. So in the end you need to generate the initial "push" in the direction you want to walk, and constantly add a little to put the leg in front of you. Now the power from the downward acceleration is stored and used to push you up again. You just need to add a little bit to go "over the pinnacle" and start again... it is a complete different way of movement than rolling/accelerating a mass horizontally.

If you generate enough power to overcome inertia to let a vehicle roll, gain speed and then have to decellerate, you would need to store the energy usually wasted through friction/heat. Without a hybrid drive, very difficult. So to accelerate again you need to burn fuel aka produce energy.

I doubt a car/vehicle/tank is better in using it's energy for acceleration than a walking "thing".

Consider you let a car roll down a ramp (think of a soap box derby) gravity accelerates the car. Wheels reduce the friction in the ground. Now if the next hill is low enough you can get over it without applying additional energy. If you could just add a little engine powered acceleration you can even pass a hill of the same height. The less energy you lose while rolling, the less you need to apply... that kind of vehicle is more close to a walker than Tank when thinking about energy usage.

[ShuRugal]

Only a walking system let the 9.8m/sec^2 .generate a good deal of it. Since you don't need "accelerate" the mass into the sky, but simply stabilize it, and store plus generate enough energy to heave it up the distance it was accelerated towards the ground (a few inch?)

 

are mechs now perpetual motion machines? Just add a little gravity, and they magically amplify that gravity without expending any energy to move forward???

[shagrat]

Somehow people do not realize that with invention of "new" armor, now that armor can apply to other vehicles, not just mechs. So if M1A is 70 Tonns...suddenly it's lighter with same protection and much reduced loading on the ground. Oh my...

 

And it still won't drive through woods or over Tank ditches or climb rough hillsides... it is just better armored and yet can't go where a small Mech could walk.

[shagrat]

@Shu Rugal

 

Nope!

 

(...)So in the end you need to generate the initial "push" in the direction you want to walk, and constantly add a little to put the leg in front of you."(...)

[ShuRugal]

And it still won't drive through woods or over Tank ditches or climb rough hillsides... it is just better armored and yet can't go where a small Mech could walk.

 

Sure, a small mech, say, 2m tall, even that is going to have to duck through most doors (assuming its narrow enough). Your 4m high platform is still going to have a time of it in trees, though. Oh, and guess what, in addition to being able to climb a 60% grade and negotiate an 850mm obstacle, exist tanks can also cross a 2.8m wide trench!

 

 

 

 

@Shu Rugal

 

Nope!

 

(...)So in the end you need to generate the initial "push" in the direction you want to walk, and constantly add a little to put the leg in front of you."(...)

 

right, walking. Check my post again, I wasn't talking about walking. Malleolus claims that a legged tank at 4m high weighing 20 tons would be able to accelerate as fast as a sprinter in order to dodge bullets at long range.

 

Walking is analogous to rolling on a wheel, it requires slightly more energy because there is vertical displacement with each step, but the difference is fairly small (I won't say negligible, because it isn't).

 

A sprinting start, on the other hand, is all about power through the legs. You don't start a sprint standing up and "Fall forward" into it. You start a sprint low and forward, and you move forwards and up. There is no "inverted pendulum action" at play for this maneuver. Your body must generate 100% of the energy involved in that kind of acceleration.

 

A full-speed run also does not benefit from the "inverted pendulum effect": the stride length is long enough that relying on momentum to carry the body over its leg robs too much forward speed. In running configuration, again, the legs must generate a portion of the force to bear up against gravity (how much depends on stride depth). The wheel has a significant advantage in this regard.

 

Hell, for a direct comparison: bicycle vs runner. In all areas, the bicycle outperforms the walker/runner, but don't take my word for it.

Edited June 15, 2014 by ShuRugal

[shagrat]

right, walking. Check my post again, I wasn't talking about walking. Malleolus claims that a legged tank at 4m high weighing 20 tons would be able to accelerate as fast as a sprinter in order to dodge bullets at long range.

 

Walking is analogous to rolling on a wheel, it requires slightly more energy because there is vertical displacement with each step, but the difference is fairly small (I won't say negligible, because it isn't).

 

A sprinting start, on the other hand, is all about power through the legs. You don't start a sprint standing up and "Fall forward" into it. You start a sprint low and forward, and you move forwards and up. There is no "inverted pendulum action" at play for this maneuver. Your body must generate 100% of the energy involved in that kind of acceleration.

 

A full-speed run also does not benefit from the "inverted pendulum effect": the stride length is long enough that relying on momentum to carry the body over its leg robs too much forward speed. In running configuration, again, the legs must generate a portion of the force to bear up against gravity (how much depends on stride depth). The wheel has a significant advantage in this regard.

 

Hell, for a direct comparison: bicycle vs runner. In all areas, the bicycle outperforms the walker/runner, but don't take my word for it.

Yeah, acceleration is more depending on overcoming inertia, so 20tons is 20tons!

Sorry, misunderstood.

Still the important difference is, a leg with muscles and sinews stores and reuses the energy from gravity to push the mass up again. Similar to a hybrid car with batteries or electric trains. That means it actually needs not that much energy to start walking. Sprinting etc. is an extreme acceleration, force fully wasting energy to speed up as fast as possible. Well, a burn rubber in a car is the same :D

Sprinters use the low start position to get as much energy transferred in the direction they want to run. Standing motionless, upright, as a human, compared to a bike or a car and now tasked to accelerate in any given direction over 4 times its body length there are about 2 directions a car or bike may be better directly ahead and may be backwards. All other directions the human wins.

Edited June 15, 2014 by shagrat

[ShuRugal]

Still the important difference is, a leg with muscles and sinews stores and reuses the energy from gravity to push the mass up again. Similar to a hybrid car with batteries or electric trains. That means it actually needs not that much energy to start walking.

 

I'm sorry, but this directly contradicts everything every biology class I have taken has ever taught me about how biomechanics work. Muscles are not energy storage devices, they are energy-conversion devices, and they work one-way. They convert chemical energy into mechanical energy and heat (at a rather appallingly inefficient rate, I might add).

 

The only "storage" available to muscles is glucose and glycogen. When a muscle contracts, it consumes glucose (which can be stored internally to the muscle cells in the form of glycogen). When a muscle is extended, it does NOT magically regenerate glycogen or glucose. There is no biological regenerative braking that I am aware of. If you are aware of such a system, please cite some references so the rest of us may be so enlightened.

 

Standing motionless, upright, as a human, compared to a bike or a car and now tasked to accelerate in any given direction over 4 times its body length there are about 2 directions a car or bike may be better directly ahead and may be backwards. All other directions the human wins.

 

Of course a human can accelerate sideways better than something which is not capable of any sideways acceleration. But if you acknowledge that a wheeled/tracked vehicle is more efficient at forward acceleration, then you can't really say that you expect a human's sideways or backwards acceleration to fare any better. Lateral acceleration is something we are significantly worse at than forward and backwards acceleration...

[shagrat]

Muscles add the little energy, sinews store energy in there elastic part until they snap, releasing that energy when pushing up. The most important ones achilles-sinew and the ones in your lower back (cruciate ligament of atlas)... not much energy, but enough to be efficient.

 

When accelerating sideways it takes a human about one and a half steps to move and turn in the direction he runs, he immediately moves in that direction. Any tracked or wheeled vehicle will role forward or may be backward and turn or remain in place and turn (Tank).

[shagrat]

Think about an experiment...

 

You know the game "Burn ball" where runners dodge a ball thrown from around a field, by the other team?

 

Now place an agile little car (a mini rover?) in a field half the size of a football field. Let it try dodging a ball thrown by professional handball players.

 

Now do the same with a human, just to be fair, make the field half the size of the cars field. The human is smaller giving him an advantage otherwise. I still think the human will dodge more balls by side stepping or changing directions, than the car...

 

Now repeat that with arrows?

[Malleolus]

Shurugal, the dynamics of human gait cannot be compared in any but the most basic way. Inverted pendulum also accounts for the majority of the force that lifts the leg vertically. All the data is experimentally derived, theoretically the efficiency numbers are greater still. Like it or not, in actuator efficiency alone you can undersize your motors by over 30% over stiff actuators if you use antagonistically oriented variable inductance actuators.

[ShuRugal]

Shurugal, the dynamics of human gait cannot be compared in any but the most basic way. Inverted pendulum also accounts for the majority of the force that lifts the leg vertically. All the data is experimentally derived, theoretically the efficiency numbers are greater still. Like it or not, in actuator efficiency alone you can undersize your motors by over 30% over stiff actuators if you use antagonistically oriented variable inductance actuators.

 

what data? You have yet to produce a single scrap of real information. I, on the other hand, have cited multiple hard-documented sources, and all of my math is shown laid bare, step by step, in accordance with physics principals which everyone who graduated high school should be familiar with.

 

Start citing sources and showing hard data, or stop talking, I'm getting sick of arguing with a human wind tunnel.

[cichlidfan]

Also one thing that Mechs are way better at than just about any other military vechile -> coolness factor :)

 

Shhhh. There are professionals at work here. ;)

[Exorcet]

Think about an experiment...

 

You know the game "Burn ball" where runners dodge a ball thrown from around a field, by the other team?

 

Now place an agile little car (a mini rover?) in a field half the size of a football field. Let it try dodging a ball thrown by professional handball players.

 

Now do the same with a human, just to be fair, make the field half the size of the cars field. The human is smaller giving him an advantage otherwise. I still think the human will dodge more balls by side stepping or changing directions, than the car...

 

Now repeat that with arrows?

I don't think this comparison really works. It's not just about wheels vs legs, but the specific design of each. You could make a wheeled vehicle really, really hard to hit in that case if you wanted to. It wouldn't be an average car though unless the field was really large and the car would "dodge" the balls by speed alone (where it would be much, much more effective than the person).

 

Something like this at human size might make a good challenge:

[Malleolus]

what data? You have yet to produce a single scrap of real information. I, on the other hand, have cited multiple hard-documented sources, and all of my math is shown laid bare, step by step, in accordance with physics principals which everyone who graduated high school should be familiar with.

 

Start citing sources and showing hard data, or stop talking, I'm getting sick of arguing with a human wind tunnel.

 

Hmmmm... ok. Let's just get this out of the way, since you intend on being an ass rather than being at least partially respectful: you are comparing a single body linear force flow to a multi-bodied nonlinear force flow. This is, well, stupid as hell. Where you did the most basic force calculations, which out of respect I didn't pick apart because you didn't show your work on single order levers, but I couldn't do a decent force flow diagram of human gait on three pages of this forum. But, why don't we just go ahead and do a little citing, as requested.

 

http://reedlab.eng.usf.edu/publications/handzic2013validation.pdf

 

Just to save you the trouble:

 

"The PDW model and human horizontal reaction forces

switch from resisting to assisting forward progression at

the same time during stance. However, the maximum forces

are slightly different. The PDW model’s horizontal reaction

forces have a maximum backward force of 48 % of the

walker mass at heel contact and a maximum forward force

of 37 % of the walker mass at toe off. The human data shows

smaller forces: maximum backward force is 23 % of the body

mass at 8 % of the gait cycle and the forward force is 26 %

of the body mass at 53 % of the gait cycle."

 

And, btw, there's this too:

 

http://jeb.biologists.org/content/213/5/790.full

 

Saving the trouble, again, is:

 

Recovery of potential and kinetic energy

Walking is characterized by a pendular exchange of gravitational potential and forward kinetic energy during each step (Cavagna et al., 1977). We suspected that walking digitigrade might in some way decrease the transfer of kinetic and potential energy. We found that the mean percentage recovery was 70.8±6.1% (mean ± s.d.) when the subjects walked with plantigrade posture and 64.8±6.4% when they walked with low-digitigrade posture. The mean difference in percentage recovery for the eight subjects was 6.0±5.8% (P=0.025, one-tailed). Thus, walking with low-digitigrade posture appears to reduce the pendular transfer of kinetic and potential energy.

 

and

 

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=12&cad=rja&uact=8&ved=0CG8QFjAL&url=http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F22475510_Joint_torque_and_energy_patterns_in_normal_gait%2Ffile%2F79e4150de3fb249715.pdf&ei=qHaeU5X7OqTJsQTbyILYDA&usg=AFQjCNFew8bG96aiEjLerGLDNeasb5WOIg&sig2=GAcVEwKfuUrASiUqnnN43w&bvm=bv.68911936,d.cWc

 

Explicitly, out of the second citation:

 

"...driving moment. In this particular case the muscle's

contribution is the least of the three. The forward

deceleration of the knee joint (caused by extensor

deceleration at the hip) and the gravitational forces

contribute about 80% of the moment required to

accelerate the shank forward. This will explain the

limited EMG activity of the knee extensors (quadri-

ceps) at this time. During the latter half of swing the

inertial load reverses; and also do the three com-

ponents. They all contribute in varying degrees to the

deceleration of the shank. However, in this case the

muscle moment contributes about 80% of that re-

quired. This is in agreement, in normals, with the

considerable hamstring activity seen during the latter

half of swing, and also explains why an above-knee

amputee requires a shock absorber in his knee mecha-

nism to decelerate his prosthetic limb..."

 

So, 20% conservation of energy during walking is understated, but I chose this for the running torque because this can be, theoretically, considered the "running peak" torque.

 

Now, on to the efficiency of compliant actuators vs. stiff actuators

 

ftp://xsee.ene.unb.br/Projects/rleg/protese/materiais/variable%20stiffness%20actuators/compliant%20actuator%20designs.pdf

 

"Walking and running robots: an actuator with adaptable

compliance extends the capabilities of these devices.

The setting of the compliance can be used to maximize

the amount of energy, which can be stored during

touchdown of the feet and released during push-off. In

addition, by varying the stiffness of the joints, the natural

The equilibrium position of a

compliant actuator is defined as the

position of the actuator where the

actuator generates zero force

or zero torque.

82 IEEE Robotics & Automation Magazine SEPTEMBER2009"

 

This simple statement alone says the greatest benefit of compliant actuation. Tuneable compliance, and with more elaborate schemes than SEA, offer higher fidelity. So, again, one can either downsize the motor to running torque with the compliance in mind, or have extremely extended peak powers, and still save on energy.

 

I cannot legally post information that I have purchased, nor my own work. These tidbits should be enough to sate your thirst, however.

 

Just for shits and giggles, high beta fusion reactor from lockheed martin:

 

"Public reactions describe the announcement of their activities on nuclear fusion remarkable, because Lockheed Martin doesn't usually make public announcements about Skunkwork projects unless they have a high degree of confidence in their chances of success. The developement timeline indicates plans to have a prototype 100-megawatt nuclear fusion machine of Lockheed Martin tested in 2017, and that a fully operational machine should be grid-ready ten years from now."

Edited June 16, 2014 by Malleolus

[shagrat]

Hmmmm... ok. Let's just get this out of the way, since you intend on being an ass rather than being at least partially respectful: you are comparing a single body linear force flow to a multi-bodied nonlinear force flow. This is, well, stupid as hell. Where you did the most basic force calculations, which out of respect I didn't pick apart because you didn't show your work on single order levers, but I couldn't do a decent force flow diagram of human gait on three pages of this forum. But, why don't we just go ahead and do a little citing, as requested.

 

http://reedlab.eng.usf.edu/publications/handzic2013validation.pdf

 

Just to save you the trouble:

 

"The PDW model and human horizontal reaction forces

switch from resisting to assisting forward progression at

the same time during stance. However, the maximum forces

are slightly different. The PDW model’s horizontal reaction

forces have a maximum backward force of 48 % of the

walker mass at heel contact and a maximum forward force

of 37 % of the walker mass at toe off. The human data shows

smaller forces: maximum backward force is 23 % of the body

mass at 8 % of the gait cycle and the forward force is 26 %

of the body mass at 53 % of the gait cycle."

 

And, btw, there's this too:

 

http://jeb.biologists.org/content/213/5/790.full

 

Saving the trouble, again, is:

 

Recovery of potential and kinetic energy

Walking is characterized by a pendular exchange of gravitational potential and forward kinetic energy during each step (Cavagna et al., 1977). We suspected that walking digitigrade might in some way decrease the transfer of kinetic and potential energy. We found that the mean percentage recovery was 70.8±6.1% (mean ± s.d.) when the subjects walked with plantigrade posture and 64.8±6.4% when they walked with low-digitigrade posture. The mean difference in percentage recovery for the eight subjects was 6.0±5.8% (P=0.025, one-tailed). Thus, walking with low-digitigrade posture appears to reduce the pendular transfer of kinetic and potential energy.

 

and

 

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=12&cad=rja&uact=8&ved=0CG8QFjAL&url=http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F22475510_Joint_torque_and_energy_patterns_in_normal_gait%2Ffile%2F79e4150de3fb249715.pdf&ei=qHaeU5X7OqTJsQTbyILYDA&usg=AFQjCNFew8bG96aiEjLerGLDNeasb5WOIg&sig2=GAcVEwKfuUrASiUqnnN43w&bvm=bv.68911936,d.cWc

 

Explicitly, out of the second citation:

 

"...driving moment. In this particular case the muscle's

contribution is the least of the three. The forward

deceleration of the knee joint (caused by extensor

deceleration at the hip) and the gravitational forces

contribute about 80% of the moment required to

accelerate the shank forward. This will explain the

limited EMG activity of the knee extensors (quadri-

ceps) at this time. During the latter half of swing the

inertial load reverses; and also do the three com-

ponents. They all contribute in varying degrees to the

deceleration of the shank. However, in this case the

muscle moment contributes about 80% of that re-

quired. This is in agreement, in normals, with the

considerable hamstring activity seen during the latter

half of swing, and also explains why an above-knee

amputee requires a shock absorber in his knee mecha-

nism to decelerate his prosthetic limb..."

 

So, 20% conservation of energy during walking is understated, but I chose this for the running torque because this can be, theoretically, considered the "running peak" torque.

 

Now, on to the efficiency of compliant actuators vs. stiff actuators

 

ftp://xsee.ene.unb.br/Projects/rleg/protese/materiais/variable%20stiffness%20actuators/compliant%20actuator%20designs.pdf

 

"Walking and running robots: an actuator with adaptable

compliance extends the capabilities of these devices.

The setting of the compliance can be used to maximize

the amount of energy, which can be stored during

touchdown of the feet and released during push-off. In

addition, by varying the stiffness of the joints, the natural

The equilibrium position of a

compliant actuator is defined as the

position of the actuator where the

actuator generates zero force

or zero torque.

82 IEEE Robotics & Automation Magazine SEPTEMBER2009"

 

This simple statement alone says the greatest benefit of compliant actuation. Tuneable compliance, and with more elaborate schemes than SEA, offer higher fidelity. So, again, one can either downsize the motor to running torque with the compliance in mind, or have extremely extended peak powers, and still save on energy.

 

I cannot legally post information that I have purchased, nor my own work. These tidbits should be enough to sate your thirst, however.

 

Just for shits and giggles, high beta fusion reactor from lockheed martin:

 

"Public reactions describe the announcement of their activities on nuclear fusion remarkable, because Lockheed Martin doesn't usually make public announcements about Skunkwork projects unless they have a high degree of confidence in their chances of success. The developement timeline indicates plans to have a prototype 100-megawatt nuclear fusion machine of Lockheed Martin tested in 2017, and that a fully operational machine should be grid-ready ten years from now."

 

^this

...and sorry I don't have the time to search all that on the web, but I remember learning some things about the human movement and how walking or running works. Biology and sports class in the highschool (? Different system in Germany, about 8th or 9th grade). It was all about letting gravity do the work. Of course walking is way more efficient than running, still it is mostly about moving the leg into the direction of "fall" and induce enough energy to counter the 2-3 inches lost by our center of mass. A good portion stored in the system during the last step... and human accelerates better, than a bike, at least until the bike overcame the momentum giving the human at least a few inches advantage. Which is maybe enough to move away from the incoming RPG, at least to prevent a critical hit... from what I've read on RPG attacks (firestrike 7/9, Sgt. Paul Grahame & Damien Lewis) for example they "see the RPG being fired and flying in their direction" it hits "seconds" later. So let assume 2-2.5 sec, after launch for 500m. Reaction after 1 sec, now move 50 cm a sec with a 1-1.5m torso... would mean a near miss?

Edited June 16, 2014 by shagrat

[ShuRugal]

I cannot legally post information that I have purchased, nor my own work. These tidbits should be enough to sate your thirst, however.

 

They very well may, this is exactly the sort of information I have been asking for this whole time. I'll review it more thoroughly and get back to you later today, but it looks like a good read at a glance.

 

 

Just for shits and giggles, high beta fusion reactor from lockheed martin:

 

"Public reactions describe the announcement of their activities on nuclear fusion remarkable, because Lockheed Martin doesn't usually make public announcements about Skunkwork projects unless they have a high degree of confidence in their chances of success. The developement timeline indicates plans to have a prototype 100-megawatt nuclear fusion machine of Lockheed Martin tested in 2017, and that a fully operational machine should be grid-ready ten years from now."

 

right, but at 2x2x4 meters for just the reactor vessel, you still won't be fitting it inside anything mobile smaller than a ship.

[Malleolus]

They very well may, this is exactly the sort of information I have been asking for this whole time. I'll review it more thoroughly and get back to you later today, but it looks like a good read at a glance.

 

 

 

 

right, but at 2x2x4 meters for just the reactor vessel, you still won't be fitting it inside anything mobile smaller than a ship.

 

It's actually a very fun read, and yeah, but I did say shits and giggles.

[OutOnTheOP]

I can't speak for Endo steel per say, but I'd point you to stacked electro-active polymer actuators and iron matrix nickle-coated carbon fiber metal matrix plating.

 

...which would have nothing to do with ferrofibrous ARMOUR, would it? The point is that it doesn't help one's argument to introduce fantasy terms into a scientific argument.

 

Also, your point about how the torso and head can be "thrown" to provide assistance inertia to a mech: just like moving the legs, that TOO takes energy.

 

Secondly, the point that the legs only are providing propulsion half the time each (because the other half, they're moving up for the next step): also bad. A wheeled or tracked system is using all it's energy to provide forward movement; the mech is wasting energy on picking up legs and moving them up to the next step.

 

Look, the "compliance action" tendons and all are just helping to recover lost energy to make the walking action a bit less inefficient. The tracks and wheels just don't lose that energy in the first place.

[OutOnTheOP]

H\

Recovery of potential and kinetic energy

Walking is characterized by a pendular exchange of gravitational potential and forward kinetic energy during each step (Cavagna et al., 1977). We suspected that walking digitigrade might in some way decrease the transfer of kinetic and potential energy. We found that the mean percentage recovery was 70.8±6.1% (mean ± s.d.) when the subjects walked with plantigrade posture and 64.8±6.4% when they walked with low-digitigrade posture. The mean difference in percentage recovery for the eight subjects was 6.0±5.8% (P=0.025, one-tailed). Thus, walking with low-digitigrade posture appears to reduce the pendular transfer of kinetic and potential energy.

 

Ok, so the walking gait wastes a bunch of energy, but out of that energy wasted, 70.8% is recovered. And? That's still a bunch of energy wasted.