thesis rover perseverance

[ACX]

Hi, guys, I'm struggling with my three-year degree thesis, and I've been having a lot of problems and doubts lately. I write in hope that some experienced users can help me move forward by giving me a few tips/suggestion.
I am working on the rocker-bogie system adopted by the nose on the rover perseverance for the space mission Mars 2020.
the purpose of this work is to optimize the structure by reducing the weight (producing with a fem analysis on the inventor software), to dimensional the 6 electric motors for the rotation of the six wheels, and the 4 electric motors mounted on the front and rear wheels necessary to steer the wheels to the rover, identifying the optimal transmission ratio to reduce the power absorbed by the 4 engines.
3d screenshoot allego made by me:I played the rover based on the information on the nasa site and started designing the engines to move the wheels from this data:
6 moving wheels
total mass 1250 kg
v=152 m/h progress speed
d=0,526 m diameter wheels
(I omitted system mass center calculations on xy plane)I will not have to study any transitory and the speed of advancement is constant.
Therefore starting from the speed of advance I calculated the angle speed of the single wheel and subsequently I obtained the number of turns of the wheel and the motor.
I then went to isolate the single wheel and calculated the torque that the electric motor will have to provide to the wheel.here begin doubts, I hypothesized n equal to the total weight divided the six wheels, so each wheel holds 1/6 of the weight of the rover. then the static friction coefficient exist tables to estimate it? same speech for and (on the design is indicated with u). I am considering that the contact between a titanium wheel and Martian soil (predominantly rocky).
following my procedure then I identified an electric motor with a pair of about 60 nm and a number of laps previously calculated in the excel sheet.
I therefore wanted to verify the maximum slope that the rover manages to overcome by installing these engines, so I studied the system on a sloped plane.solving the system I got a maximum inclination of 30,85° quite consistent with what also stated by the information on the nasa site.However the doubt that I have in this part of the sizing is relative to the value of the forces, I used the same values of the normal reaction and the tangential one calculated previously on the excel sheet and I assumed the values of the two equal reactions for each wheel.
once calculated the 6 engines remain the 4 engines for the front and rear wheels and I have already thought of a temporary solution (see picture below).dimensionalized the 4 motors for steering and the 6 motors for each single wheel, I will transfer the efforts (on the knots where the wheels are mounted) to the structure that I schematized in a fictitious way on ftool. In this way I will be able to calculate the characteristics of the stress and dimension the "tubes" and calculate the efforts on the internal hinges that in reality represent the bearings. Sorry if I was prolisso, I hope I was clear in the description of the various phases of the sizing, and thank you for the attention! :

 

[meccanicamg]

Bye. for the speech coefficient of static friction we do not find in literature anything written. the onlyode is to take a piece of rocky soil and let it slide on a tilted plane of titanium. the tangent of the angle represents the coefficient of static friction.
Unfortunately, the coefficient of friction is also experimental and depends on speed. There's something in literature about wagons even though it's almost a secret.
Please note that you did not consider any accidentality in the calculation due to the irregular path.
basic, as university execution the speech can work. Actually, the wheels will be more loaded if you work tilted side.
the direct rotation system on the rotation pin I see little stable and little precise.

 

[ACX]

Bye. for the speech coefficient of static friction we do not find in literature anything written. the onlyode is to take a piece of rocky soil and let it slide on a tilted plane of titanium. the tangent of the angle represents the coefficient of static friction.
Unfortunately, the coefficient of friction is also experimental and depends on speed. There's something in literature about wagons even though it's almost a secret.
Please note that you did not consider any accidentality in the calculation due to the irregular path.
basic, as university execution the speech can work. Actually, the wheels will be more loaded if you work tilted side.
the direct rotation system on the rotation pin I see little stable and little precise.

I thank you for the answer, let's say that at the moment since I reported the calculations on excel, friction coefficients are "the lesser evil" I can therefore replace them without big problems. Of course, the steering system needs to be reviewed, I posted that photo just to make the idea. Thanks again, I will continue to post to show you the evolution of work.

 

[TETRASTORE]

here begin doubts, I hypothesized n equal to the total weight divided the six wheels, so each wheel holds 1/6 of the weight of the rover. then the static friction coefficient exist tables to estimate it? same speech for and (on the design is indicated with u). I am considering that the contact between a titanium wheel and Martian soil (predominantly rocky).

in a rough soil, it is difficult for weight to be distributed evenly on the six wheels; in this regard it is necessary to carry out simulations to evaluate the worst conditions in which one or more wheels must support the greater part of the load, this because the system is equipped with encoders, load cells and sensors that through algorithms allow to make the appropriate corrections (see here).
for friction coefficient look qui.
the evaluation of the movement on the sloping plane is very simplistic; qui, qui, qui e qui see studies and simulations on motion and force agents on the articulated system.

However, there is a wide range of documentation and studies on this.

 

[ACX]

in a rough soil, it is difficult for weight to be distributed evenly on the six wheels; in this regard it is necessary to carry out simulations to evaluate the worst conditions in which one or more wheels must support the greater part of the load, this because the system is equipped with encoders, load cells and sensors that through algorithms allow to make the appropriate corrections (see here).
for friction coefficient look qui.
the evaluation of the movement on the sloping plane is very simplistic; qui, qui, qui e qui see studies and simulations on motion and force agents on the articulated system.

However, there is a wide range of documentation and studies on this.

Thank you so much!

 

[ACX]

the appropriate corrections (see here).

I can't open this link, could you send it back?

 

[TETRASTORE]

There he is.