stjorthotic Chapter 15 Designing Mechs
Chapter 15 Designing Mechs
A little after eight o'clock in the evening, Lu Feng pushed open the dormitory door.
A burst of gunfire and explosions came rushing in; it wasn't a game, it was a movie.
Zhang Wei propped his laptop up on the small table on the bed, leaned against the pillows, and held a bag of potato chips in his hand, staring intently at the screen.
The movie playing on the screen is "The Avengers".
Lu Feng remembers this movie; it was released in May of this year and its global box office was phenomenal.
He had seen it in his previous life, but at that time he only thought the special effects were cool and forgot about it after watching it.
He tossed his backpack onto the chair and was about to sit down when he caught a glimpse of the screen and paused.
In the scene, Tony Stark stands on the platform at the top of the building, stepping on a conveyor belt-like armor assembly tunnel. Pieces of gold and red metal parts pop out from the ground and fit precisely onto his body.
The calf armor is fastened, the thigh armor is locked, the waist buckle is tightened, the chest armor is closed front and back, and the arms are wrapped in sequence.
Lu Feng stood there, staring at the scene for a full ten seconds.
He wasn't looking at the special effects.
He was looking at the structure.
The wearing logic of that mecha is actually very clear: modular assembly. Each part is an independent functional unit, and quick positioning and locking are achieved through buckles and guide rails.
The legs are the main load-bearing structure, the chest armor is the core protection area, and the arms integrate weapons and control interfaces.
If we remove the flight capabilities, the energy weapons, and anything beyond the limits of current materials science, retaining only the most basic exoskeleton support structure and modular wearable design…
This idea could definitely be designed as a project for a mechanical innovation competition.
It's not about making a real suit of armor, but a wearable mechanical exoskeleton demonstration device.
The chest armor, legs, and arms are three modules, using a lightweight aluminum alloy frame with a simple electric power assist mechanism integrated inside.
The head is too complex, involving sensor arrays and display systems, and it can't be solved in a short time.
However, the hinge deployment mechanism of the breastplate, the joint assist device of the legs, and the modular quick-release structure of the arms can all be achieved using existing mechanical principles.
Moreover, he also had the blueprint for the multi-scale perturbation method.
The joint actuation of exoskeletons involves nonlinear dynamics problems. We use perturbation methods for theoretical analysis, combined with physical demonstrations, to address both theory and practice.
"How about it, Lao Lu? Pretty cool, right?" Zhang Wei turned around and saw Lu Feng standing there staring blankly at the screen. He excitedly slapped the bed board.
"Look at this mecha, I really want to try it on. If I stood at the school gate, I guarantee all the girls in the school would scream."
Lu Feng smiled but did not answer.
He sat down at his desk, took out a blank sheet of paper, picked up a pencil, and began to draw.
First, a frontal outline of a human body is drawn, and then five independent modular areas are drawn at the positions of chest, upper arm, forearm, thigh, and calf.
Each module is marked with a dashed line indicating the connection method. The chest armor is a left-right split type, which is closed and locked by a center hinge; the arm part consists of upper and lower shell halves, which are fixed to the forearm with quick-release buckles; the leg part is a single-axis assist frame arranged along the outside of the thigh, with torsion springs at the knee joint for assistance.
The sketch was drawn quickly, with rough lines but accurate proportions.
Newton's keen observation skills came into play at this time.
He could clearly feel that when the pen tip glided across the paper, his mind had a clearer understanding of the kinematic relationships of each joint and the force analysis of each connection point than before.
Where should hinges be used, where should slides be used, and where is elastic preload required?
The front sketch was completed in 30 minutes.
Turn it over and draw a side view.
The side design primarily addresses ergonomic issues.
The center of gravity of the exoskeleton should coincide with the center of gravity of the human body as much as possible; otherwise, walking will be awkward after wearing it.
The leg frame is supported by the hip and ankle joints, with the knee joint serving only as an auxiliary point.
Lu Feng placed the two sketches side by side on the table and examined them for a while.
The framework is feasible; details will be added later.
"Holy crap, the class monitor just said in the group chat that we're collecting advanced math homework tomorrow!"
The sound came from the top bunk; it was the roommate in the bed closest to the door, the light from his phone screen reflecting on his face.
The people in the dormitory, who were all doing their own thing, suddenly erupted.
"What? You're collecting it tomorrow? Wasn't it supposed to be due on Friday?"
"Friday is Linear Algebra, and tomorrow is Advanced Mathematics."
"Damn it, I didn't answer a single question."
"I don't even know where I put my homework."
The sound of a ping-pong ball rang out, and the student on the upper bunk rolled over to get out of bed to look for their homework, while the student playing video games paused their game and started rummaging through their schoolbag.
Zhang Wei turned off the movie, pulled out a crumpled workbook, opened it, and found it blank.
"Oh no, oh no, oh no," Zhang Wei muttered, flipping to the homework page and looking at the questions with a blank expression.
Lu Feng glanced at it.
There are eight limit problems in total.
The first four questions are basic ε-δ proofs and applications of the squeeze theorem, while the last four questions are calculations of function limits, involving equivalent infinitesimal substitutions and L'Hopital's rule.
To be honest, these questions are not much different from doing one plus one for him now.
The dormitory started to get lively.
Five people huddled together, their homework books spread all over the table, discussing amongst themselves.
"For the third question, how do we choose ε? We can choose any ε greater than zero, and then what?"
"Then find δ."
"How do I find δ?"
"If I knew how to find δ, would I be asking you?"
"What is the limit for question 5? I spent ages calculating it and got a negative number, which doesn't feel right."
"You used the equivalent substitution incorrectly. The equivalent infinitesimal of sinx is x, not the square of x."
"The same, right?"
"Same my foot, they're just one tier apart."
After discussing for about ten minutes, they still hadn't figured out the complete solution for any of the eight questions.
Zhang Wei turned to look at Lu Feng, who was sitting at his desk, marking the dimensions of the two mecha sketches with a pencil.
"Old Lu, Old Lu!" Zhang Wei came over with his homework book, poking his arm with his pen. "Could you help me with question three? How do I figure out this ε-δ part?"
Lu Feng put down his pencil, took the workbook, and glanced at it.
Question 3: Prove lim(x→2)(3x-1)=5 using the definition of ε-δ.
"This question is very simple." Lu Feng took Zhang Wei's pen and started writing directly in the blank space next to him.
「对任意ε>0，取δ=ε/3，当0<|x-2|<δ时，|(3x-1)-5|=|3x-6|=3|x-2|<3δ=ε。」
Three lines, done.
Zhang Wei stared at the three lines of text for five seconds.
"this one?"
"That's it."
"You don't even need to think about it?"
Lu Feng didn't answer the question, but handed the workbook back to him and casually pointed to question five.
"The answer to this question, the one you were discussing for so long, is one-half. Just expand the numerator to the second order using Taylor expansion, and factor out the common factor in the denominator and cancel it out."
Before Zhang Wei could react, the other people who had been listening intently immediately gathered around.
"Old Lu, what about the fourth question?"
"For the fourth question, take δ equal to min(1, ε/7). Choose the smaller of the two values because you need to restrict the range of x before you can estimate the upper bound."
"The sixth question?"
"L'Hôpital's rule, by taking the derivative twice, gives the answer as 1."
"The seventh question?"
Lu Feng took one of the students' workbooks and started writing from the third question, one by one.
He could come up with the answer to almost every question as soon as he finished reading it; writing out the process was just a formality.
He wrote very quickly, and although his handwriting wasn't beautiful, every step was clear and precise. For the ε-δ proof problem, he even marked out how to draw the auxiliary lines; for the limit calculation problem, he specified which formula to use for equivalent substitution, and to what order the numerator and denominator were expanded.
He finished all eight questions in five minutes.
The dormitory was completely quiet.
Five people sat around the table in Lu Feng's room, staring at the notebook filled with the process instructions, speechless.
Zhang Wei was the first to break the silence, his voice carrying a sense of weakness born from the crushing blows of reality.
"Old Lu, you were copying the class representative's homework with me just a couple of days ago, and now you've just easily surpassed it yourself?"
"I've been studying on my own for two days," Lu Feng said, handing the pen back to him.
"Two days?" another roommate's voice rose. "You learned this much in just two days? I've been studying ε-δ for a month and I still don't understand it."
"This thing isn't difficult once you understand it."
Zhang Wei had already begun frantically copying Lu Feng's account of the process, shaking his head as he copied.
"He's a monster, utterly a monster. Just two days ago he was my best buddy who skipped class and played cards with me, and now he's a test-taking monster."
He copied without looking up, muttering to himself.
"I'm counting on you for my advanced math assignments from now on."
"Dream on." Lu Feng picked up his pencil again and turned his attention back to the mecha sketches on the table.