Update, still (forever) working on the legs. Broke hip a couple of days ago, now the knee. Reprinting knee joint at 45% fill was 35% fill in ABS (all parts going to 45% fill or alum.). Would appreciate any advise or ideas. All designs are in Autodesk Inventor 3D, so could move to most 3d formats if any interest. Thinking someone could add covers to make it look like legs if I could get it to work. It is amazing the stress on a leg to take a step. Hip has 3 degrees of freedom, knee one, and ankles 2. If I could get this to work would still like to add some sort of toes. Software currently for an Arduino Mega in C++ but would want to move it MRL.

Video at https://youtu.be/l_8YHEU9zG0

as always the Inmoov is a great project,  thanks Gael

Harland

 

calamity

4 years 9 months ago

Great work harland, it's really amazing to see legs working.

some times ago, I have made a model and algorythm to have the to have an inMoov upper body try to keep it's balance. I would very like to add your legs design to the model to see how it goes. To be able to do that I will need some additional info.

  • the size of each part (preferably in XYZ format) and the distance (in the same format) between pivot point.
  • how many degree and direction of each pivot point can go
  • the approximate weight of each part
  • the angular velocity (degree/s) of each joint.

With those info, I could make a 3d model to simulate what will happen when you raise a leg or when any part of the robot moves.

With a model that could 'manage' balance, robot will move in a more natural way and will be less prone to falling. It can also help reduce the stress on some parts.

I will be very interrested in testing this.

 

harland

4 years 9 months ago

Info for calamity, lengths from the ground up:

bottom of foot to ankle pivot point 77.72mm (3.06 in)

lower leg from ankle pivot to knee pivot point 366.78mm (14.44 in)

upper leg from knee pivot point to hip pivot point 358.26 mm (14.105 in)

hip assembly from hip pivot point to top of platform where Inmoov robot would attach 172.98mm (6.81 in)

total height 975.74mm (38.415 in)

foot (sole) width 152.4mm (6 in.), length 279.4 mm (11 in.)

Ankle 2 degrees of freedom: rotates side to side (roll) 27 deg in both directions

moves up from flat (pitch) +45 deg, down from flat -25 deg. from flat (flat anlke is 90 deg to lower leg)

knee one degree of freedom: moves back from straight (pitch) bends 40 deg

Hip has 3 degrees of freedom: back and forward (pitch) 46 deg from hoizonal platform

rotates left and right (yaw) looking down at top it turns 20 deg CW and 20 deg CCW (limited by wires),

rotates in and out from center (roll) plus and minus 10 deg

The above degrees of movement are constrained by the location of the motors and linkage placement. I measured the above angles.

In my CAD assembly I do not have the linkage connected, so my CAD drawings can move more.

I am using 4 motors RoboShop 12 volts, 251 rpms, 7 amps max, stall torque 150 oz-in for the ankles up/down and hips up/down. The motors for the knees are from ServoCity 12 volts, 313 rpms, 20 amps max, stall torque 416 oz-in.

Weight of parts I am working on. The CAD data does not have fasteners, wire, motor weights, and electronics so it will not give me the correct weights

I have no idea on the velocities and not sure how to come up with it.  Any ideas?


 

Thanks Harland

I will analyze that and see if I have everything

for the velocity, it can be calculated by timing approximatly how much time it take to move between two know position. ie if it take about 5 sec to move 20 degrees, then the velocity is 20 / 5 = 4 degree/second. 

But don't worry if you don't have the data or if it's hard to compute. I can put default value to start. It's just some details to help have a model close to the reality

I understand that it may be hard to weight part when it's all monted. but again an approximate will do. Weight from the CAD + weight of the motor from the datasheet should gives a close approximation of the weight, we add a bit for the other stuff and that will be good. 

No urgency for those data, there is quite a lot of work to build up the model 

a first try at adding legs that resemble to the one Harland created. 

I know it's just basic shape right now. but i'm currently more interrested on the way it move than how it look.

Harland, can you confirm that I got your joint placement and the way they move correctly?

 

 

 

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