Author Topic: Bipedal locomotion  (Read 272 times)

Online Small brown dog

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Bipedal locomotion
« on: August 28, 2019, 08:37:19 PM »
AFV’s and large commercial/industrial vehicles began to benefit from EMFEM weight reduction just prior to the First World War. However, these vehicles still relied upon traction drive in the form of wheel or track.  Experiments with bipedal locomotion initially showed little hope of serious application until the development of gyroscopic field focusing which ushered in a new age of fighting vehicles.

The development of the first world war Mechanical men or “Mech’s” was rapid from lightly armed tottering early designs through to the towering Russian giant of the Second World war, the T-334 Svyatogor.



Some Background on the Russian T-334:
Russia remained as the sole champion of Bipedal AFV’s after WW1.  This was not by choice but rather a matter of practicality owing to Russia’s own inner turmoil during the period and the years following the conflict. By the early 1930’s all other nations had ceased operating the type completely or had relegated it to secondary non-combatant duties. Russia had been in a technological state of flux and had lagged behind the west in all the Tesla based technologies. However they had taken bipedal AFV technology to an advanced state. 

The German push towards Moscow in late 1941 were among the darkest days for Russia but it is strongly believed  that without the T-134 Moscow may well have fallen. The Machine was outclassed in almost every way but was numerous and operated by committed, almost fanatical crews.  In the late spring of 1942 the T- 234 began to appear in greater numbers and fought well during the new German offensive during July.

In 1943 the final variant, the T-334 Svyatogor, entered service being the largest, most heavily armed and powerful Bipedel AFV to be developed anywhere. The whole series had been big and always prey to air attack particularly from the ME626 Donnervogel. The T334 was almost three stories high but incorporated a heavy machine gun turret which was initially a huge surprise to the Germans and many unsuspecting ME626 fell to the T-334

Flack variants were produced having their entire weapon points devoted to 20 & 30mm AA cannon and were dispersed among standard armoured variants causing huge casualties to attacking aircraft.  However, the Achilles heal was the height of the machine especially the T-334 which was easily targeted from concealed vantage points.

By 1944 the T-344 could no longer depend upon its armour once the Luftpanzer Jaguar 2 came into service and, although a risky business, leg sweeping was accounting for more and more of the vehicles. The LP Jaguar 2 was perfect for leg sweeping if timed correctly with the forefoot fall during the step. Once down the machine was down for good.

By the end of the war new technologies had overtaken the T-334 such as the Volkosob but Russia has forever had a soft spot for the BAFV and the mighty Svyatogor.



Background to the above image
The problem with the very early Luftpanzer, and in particular the Jaguar 1-A, was its frequent need to recharge its shields. The armour was not as thick as would have been preferred in order to save weight but this was considered to be acceptable as the lack of thickness was made up for by shielding which was fine until the shield efficiency dropped which it did rapidly.

Of course, later variants and especially the Jaguar MK2, were in another class altogether owing to vastly superior power generation.  However, the early power units should perhaps have never gone into production as the above image shows. The Russian T-334 crews loved to happen upon a recharging Jag 1, they blew up in a most satisfying way if you got them in the capacitor.



I'm not so clued up on AFV's so apologies for stupidity beyond the obvious in the above.


Its not that its not real but it could be that its not true.

Offline Old Wombat

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Re: Bipedal locomotion
« Reply #1 on: August 28, 2019, 08:48:19 PM »
 :D :smiley:
"This is the Captain. We have a little problem with our engine sequence, so we may experience some slight turbulence and, ah, explode."

Offline tankmodeler

  • Wisely picking parts of the real universe 2 ignore
Re: Bipedal locomotion
« Reply #2 on: August 29, 2019, 01:17:29 AM »
I'm not at all sure you care, however...

One issue with these sorts of mechs, including the Star Wars AT-ST, is that they actually can't walk, at least not as depicted. They aren't balanced correctly to allow the wide stance of the legs to manage the balance of the vehicle when perched on one leg while the other leg advances. The human body manages this by having the distance between the hip joints and the centre of mass be a small fraction of the length of the leg, that small offset of the joint meaning that the moment arm between the body's centre of mass and the vertical position of one foot is small meaning that the torque looking to pitch the body off to one side is also small. The body starts to pitch over, nonetheless, but with a small torque, it doesn't do so very quickly and then the other foot touches the ground and balance is restored until the other foot leaves the ground and the process reverses. This provides the rolling gait of a normal human walk. When running, when the downward forces are greater due to the higher vertical accelerations experienced, you notice that people's feet start to hit the ground ever closer to the body centreline, reducing the moment arm further and, again, we don't pitch over.

These mechs, pretty much all of them, have wide spread hips and relatively short legs and move those legs relatively slowly. By the time one leg manages to lift, advance and return to contact, the mech will have angled over considerably. The only gait that works for these mechs (as depicted virtually everywhere) is the rather hopping gait of someone walking on two older style prosthetic legs. They have to virtually hop their mass up as their legs move between steps to prevent tipping over and the usual pattern mech would have to be at least as bad or worse as the legs get shorter and the hips further apart.

To remain upright in your tech world probably requires some sort of lift generator to offset the toppling torque such that the mech would remain upright. Note, of course, that this also means that the traction on the legs gets less as the weight is offset, so it might want to be a variable lift force and maybe something coupled to the walking control system to provide for the right amount of weight offset depending on what the mech is doing.

If you don't want to do that, then with the usual wider hips and short legs you probably need foot pads that cross over the centreline of the vehicle, like some of the old, win-up, tin toy robots.

But, like I say, this may be faaaaar too much engineering thought being put into this. All I can plead is that I'm an aerospace engineer and I can't help m'self.

Paul

Offline Old Wombat

  • "We'll see when I've finished whether I'm showing off or simply embarrassing myself."
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Re: Bipedal locomotion
« Reply #3 on: August 29, 2019, 01:20:41 AM »
Just hit me! ED43, ED209's grandfather! ;D
"This is the Captain. We have a little problem with our engine sequence, so we may experience some slight turbulence and, ah, explode."

Online Small brown dog

  • Dwelling too long on the practicalities of such things can drive you mad.
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Re: Bipedal locomotion
« Reply #4 on: August 29, 2019, 01:40:01 AM »
I'm not at all sure you care, however...

One issue with these sorts of mechs, including the Star Wars AT-ST, is that they actually can't walk, at least not as depicted. They aren't balanced correctly to allow the wide stance of the legs to manage the balance of the vehicle when perched on one leg while the other leg advances. The human body manages this by having the distance between the hip joints and the centre of mass be a small fraction of the length of the leg, that small offset of the joint meaning that the moment arm between the body's centre of mass and the vertical position of one foot is small meaning that the torque looking to pitch the body off to one side is also small. The body starts to pitch over, nonetheless, but with a small torque, it doesn't do so very quickly and then the other foot touches the ground and balance is restored until the other foot leaves the ground and the process reverses. This provides the rolling gait of a normal human walk. When running, when the downward forces are greater due to the higher vertical accelerations experienced, you notice that people's feet start to hit the ground ever closer to the body centreline, reducing the moment arm further and, again, we don't pitch over.

These mechs, pretty much all of them, have wide spread hips and relatively short legs and move those legs relatively slowly. By the time one leg manages to lift, advance and return to contact, the mech will have angled over considerably. The only gait that works for these mechs (as depicted virtually everywhere) is the rather hopping gait of someone walking on two older style prosthetic legs. They have to virtually hop their mass up as their legs move between steps to prevent tipping over and the usual pattern mech would have to be at least as bad or worse as the legs get shorter and the hips further apart.

To remain upright in your tech world probably requires some sort of lift generator to offset the toppling torque such that the mech would remain upright. Note, of course, that this also means that the traction on the legs gets less as the weight is offset, so it might want to be a variable lift force and maybe something coupled to the walking control system to provide for the right amount of weight offset depending on what the mech is doing.

If you don't want to do that, then with the usual wider hips and short legs you probably need foot pads that cross over the centreline of the vehicle, like some of the old, win-up, tin toy robots.

But, like I say, this may be faaaaar too much engineering thought being put into this. All I can plead is that I'm an aerospace engineer and I can't help m'self.

Paul

I love the feedback and believe me I wrestle all the time with this sort of thing.
You are of course totally correct and to be honest I have never been happy with mechs largely for those very reasons. I  also think that the development  may never have taken place in my universe but I had this half finished mech idea I started about 3 years ago and it was one of those scrap it or finish decisions.
The Russians did away with their mechs anyway as alternatives like the Solokov Volkosob which is much more in keeping with my universe.which I could post if you like.
Its not that its not real but it could be that its not true.

Offline Old Wombat

  • "We'll see when I've finished whether I'm showing off or simply embarrassing myself."
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Re: Bipedal locomotion
« Reply #5 on: August 29, 2019, 10:01:18 AM »
... which I could post if you like.

Duh! Yeah! Of course we want you to! Quit asking & DO, fer cryin' out loud! ;D
"This is the Captain. We have a little problem with our engine sequence, so we may experience some slight turbulence and, ah, explode."

Offline tankmodeler

  • Wisely picking parts of the real universe 2 ignore
Re: Bipedal locomotion
« Reply #6 on: August 29, 2019, 10:58:41 PM »
and it was one of those scrap it or finish decisions.
;D ;)

Quote
The Russians did away with their mechs anyway as alternatives like the Solokov Volkosob which is much more in keeping with my universe.which I could post if you like.
Absolutely!

Offline apophenia

  • Patterns? What patterns?
Re: Bipedal locomotion
« Reply #7 on: August 30, 2019, 07:24:51 AM »
Love this mech!

I'm not too sure about using humans as a model for walkers, though. We are naturally unbalanced - like an F-16 - some other bipedal creatures are more stable and require far less brainpower to maintain balance while walking. The comment about wide hips made me think of extinct 'terror birds' like Gastornithiformes.

As birds go, the Gastornithiformes had relatively short legs and quite wide hips. Obviously they were smaller and more gracile than the average mech and scaling up changes things. But, generally I think, the Gastornithiformes make a better locomotion model than Homo sapiens.

As an example of the Gastornithiforme order, see Dromornis stirtoni from Late Miocene Oz:
https://www.abc.net.au/news/image/9868842-3x2-940x627.jpg
"Could be the elves ... But it's probably the werewolf"

Offline kerick

  • Responsible for all surrendered booty....Arrrr!!!!
Re: Bipedal locomotion
« Reply #8 on: August 30, 2019, 07:57:33 AM »
I'm not at all sure you care, however...

One issue with these sorts of mechs, including the Star Wars AT-ST, is that they actually can't walk, at least not as depicted. They aren't balanced correctly to allow the wide stance of the legs to manage the balance of the vehicle when perched on one leg while the other leg advances. The human body manages this by having the distance between the hip joints and the centre of mass be a small fraction of the length of the leg, that small offset of the joint meaning that the moment arm between the body's centre of mass and the vertical position of one foot is small meaning that the torque looking to pitch the body off to one side is also small. The body starts to pitch over, nonetheless, but with a small torque, it doesn't do so very quickly and then the other foot touches the ground and balance is restored until the other foot leaves the ground and the process reverses. This provides the rolling gait of a normal human walk. When running, when the downward forces are greater due to the higher vertical accelerations experienced, you notice that people's feet start to hit the ground ever closer to the body centreline, reducing the moment arm further and, again, we don't pitch over.

These mechs, pretty much all of them, have wide spread hips and relatively short legs and move those legs relatively slowly. By the time one leg manages to lift, advance and return to contact, the mech will have angled over considerably. The only gait that works for these mechs (as depicted virtually everywhere) is the rather hopping gait of someone walking on two older style prosthetic legs. They have to virtually hop their mass up as their legs move between steps to prevent tipping over and the usual pattern mech would have to be at least as bad or worse as the legs get shorter and the hips further apart.

To remain upright in your tech world probably requires some sort of lift generator to offset the toppling torque such that the mech would remain upright. Note, of course, that this also means that the traction on the legs gets less as the weight is offset, so it might want to be a variable lift force and maybe something coupled to the walking control system to provide for the right amount of weight offset depending on what the mech is doing.

If you don't want to do that, then with the usual wider hips and short legs you probably need foot pads that cross over the centreline of the vehicle, like some of the old, win-up, tin toy robots.

But, like I say, this may be faaaaar too much engineering thought being put into this. All I can plead is that I'm an aerospace engineer and I can't help m'self.

Paul

I love the feedback and believe me I wrestle all the time with this sort of thing.
You are of course totally correct and to be honest I have never been happy with mechs largely for those very reasons. I  also think that the development  may never have taken place in my universe but I had this half finished mech idea I started about 3 years ago and it was one of those scrap it or finish decisions.
The Russians did away with their mechs anyway as alternatives like the Solokov Volkosob which is much more in keeping with my universe.which I could post if you like.

You have described what I instinctively felt was a problem for walking mechs for a long time. I'm glade someone was able to finally explain it properly.

Offline Old Wombat

  • "We'll see when I've finished whether I'm showing off or simply embarrassing myself."
  • "Define 'interesting'?"
Re: Bipedal locomotion
« Reply #9 on: August 30, 2019, 08:51:21 AM »
The "walker" designs I enjoy the best are those like ED-209 & the T-334, here. They have what I call "chicken legs".

The fault with most of them is the designers put the mass too high or too far forward. If you look at a chicken (or any other (semi-)flightless bird, for that matter) you'll see that their hip joints are way up near their ribs & spine, that their body mass is pretty evenly distributed fore-&-aft, & that most of their body mass is of a height with or below their hips.

"Chicken leg" designs were amongst the first successful walking robot designs (for a given level of "successful") & it's only the desire to create android robots that really pushes the research into mammalian, specifically hominid-gaited robot walkers.

Spiders, to my mind, are the best model for walking robots.
« Last Edit: August 30, 2019, 08:55:52 AM by Old Wombat »
"This is the Captain. We have a little problem with our engine sequence, so we may experience some slight turbulence and, ah, explode."

Online Small brown dog

  • Dwelling too long on the practicalities of such things can drive you mad.
  • Woof!
Re: Bipedal locomotion
« Reply #10 on: August 30, 2019, 05:32:04 PM »
I'm not at all sure you care, however...

One issue with these sorts of mechs, including the Star Wars AT-ST, is that they actually can't walk, at least not as depicted. They aren't balanced correctly to allow the wide stance of the legs to manage the balance of the vehicle when perched on one leg while the other leg advances. The human body manages this by having the distance between the hip joints and the centre of mass be a small fraction of the length of the leg, that small offset of the joint meaning that the moment arm between the body's centre of mass and the vertical position of one foot is small meaning that the torque looking to pitch the body off to one side is also small. The body starts to pitch over, nonetheless, but with a small torque, it doesn't do so very quickly and then the other foot touches the ground and balance is restored until the other foot leaves the ground and the process reverses. This provides the rolling gait of a normal human walk. When running, when the downward forces are greater due to the higher vertical accelerations experienced, you notice that people's feet start to hit the ground ever closer to the body centreline, reducing the moment arm further and, again, we don't pitch over.

These mechs, pretty much all of them, have wide spread hips and relatively short legs and move those legs relatively slowly. By the time one leg manages to lift, advance and return to contact, the mech will have angled over considerably. The only gait that works for these mechs (as depicted virtually everywhere) is the rather hopping gait of someone walking on two older style prosthetic legs. They have to virtually hop their mass up as their legs move between steps to prevent tipping over and the usual pattern mech would have to be at least as bad or worse as the legs get shorter and the hips further apart.

To remain upright in your tech world probably requires some sort of lift generator to offset the toppling torque such that the mech would remain upright. Note, of course, that this also means that the traction on the legs gets less as the weight is offset, so it might want to be a variable lift force and maybe something coupled to the walking control system to provide for the right amount of weight offset depending on what the mech is doing.

If you don't want to do that, then with the usual wider hips and short legs you probably need foot pads that cross over the centreline of the vehicle, like some of the old, win-up, tin toy robots.

But, like I say, this may be faaaaar too much engineering thought being put into this. All I can plead is that I'm an aerospace engineer and I can't help m'self.

Paul


I love the feedback and believe me I wrestle all the time with this sort of thing.
You are of course totally correct and to be honest I have never been happy with mechs largely for those very reasons. I  also think that the development  may never have taken place in my universe but I had this half finished mech idea I started about 3 years ago and it was one of those scrap it or finish decisions.
The Russians did away with their mechs anyway as alternatives like the Solokov Volkosob which is much more in keeping with my universe.which I could post if you like.


You have described what I instinctively felt was a problem for walking mechs for a long time. I'm glade someone was able to finally explain it properly.


I like the look of mechs I must admit but the tech required to keep them upright. balanced and under control seems even more crazy than the crap I come up with.
Quads just look wrong to me  .. Star Wars ATAT for instance and Spider types too leave me cold as do the real ones. Tripods as per WoW can look pretty awesome.

I have only ever done one other mech thing which is called Steel Raptor
« Last Edit: August 30, 2019, 05:42:17 PM by Small brown dog »
Its not that its not real but it could be that its not true.