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Hi, the code is written in pybricks, so if you want to use it you have to install pybricks on your hub from https://pybricks.com/. Specifics of what each line means can be found in the documentation at https://docs.pybricks.com/en/latest/.

Looks good - infinite rotation on joints 4 & 6 and with all Lego parts . I've found a duty limit of around 40% to be the sweet spot most of the time. As long as the end stops are properly braced there are no problems. I don't detect in the program when they're out of sync. I save motor angles to be able to quickly test/use the robot in a reasonably accurate position without having to home it. Exactly - compensating for absolute position changes should make this more accurate, as long as the motors haven't moved by +/-180 degrees or more. This is probably worth trying :).

. The unfortunate truth. I too would go with the tap water. I guess there are a few places it could be placed - my thinking was to place it between joint 5 and joint 6 and determine the orientation error at that point. That is a great idea. Do you have any idea which camera and/or software you might use? For me, using the relative positions of the drive motors works very well to determine joint angles (and I think is more precise than direct joint encoders would be, because of the gearing down). I just save the motor positions to the hub every time I shut it down, and if they ever get out of sync with the joints I re-home the joints to the end-stops.

@Glaysche I was thinking of doing the same thing with the spike essentials hub on my robot arm (but decided not to mostly because the hub was too expensive). I think it's a good idea and not too heavy if you use the small motors (or just one motor and pass two functions through the turntable with a differential). The essentials hub would also give you orientation data for the end effector, which could be useful if you end up doing inverse kinematics. By the way, thanks for sharing the updates. That remote control setup is really nice!

Here's the code. Note that it's raw and a bit messy - I never intended to publish it. from pybricks.hubs import TechnicHub from pybricks.pupdevices import Motor from pybricks.parameters import Port, Stop, Color, Direction from pybricks.tools import wait from math import sin, pi, fabs, sqrt print("START") # Initialize the hub hub = TechnicHub() # Initialize the motors motor_x = Motor(Port.A, Direction.COUNTERCLOCKWISE, [20, 75]) motor_y = Motor(Port.B, Direction.COUNTERCLOCKWISE, [20, 75]) motor_z = Motor(Port.C, Direction.COUNTERCLOCKWISE, [20, 75]) #motor_suction = Motor(Port.D, Direction.CLOCKWISE, [12, 36]) # Initialize variables old_x = 0.0 old_y = 0.0 old_z = 0.0 # Flash light def flash(): hub.light.on(Color.GREEN) wait(100) hub.light.off() # Find zero def reset_motors(): print("Finding origin...") motor_x.run_until_stalled(-100, duty_limit=30) print("x zero set.") #flash() motor_y.run_until_stalled(-100, duty_limit=30) print("y zero set.") #flash() motor_z.run_until_stalled(-100, duty_limit=30) print("z zero set.") #flash() motor_x.reset_angle(0) motor_y.reset_angle(0) motor_z.reset_angle(0) #motor_suction.reset_angle(0) # Move end effector def move(x, y, z, speed): global old_x global old_y global old_z rel_x = x - old_x rel_y = y - old_y rel_z = z - old_z segment_length = sqrt(pow(rel_x,2) + pow(rel_y,2) + pow(rel_z,2)) time = segment_length / speed if time == 0: time = 0.01 x_speed = fabs(rel_x) / time y_speed = fabs(rel_y) / time z_speed = fabs(rel_z) / time #print("Time = " + str(time) + "; Segment length = " + str(segment_length) + "; Speed = " + str(x_speed) + ", " + str(y_speed) + ", " + str(z_speed) + "; Move to " + str(x) + ", " + str(y) + ", " + str(z)) if x_speed > 1: motor_x.run_target(x_speed, x*10, then=Stop.COAST, wait=False) if y_speed > 1: motor_y.run_target(y_speed, y*10, then=Stop.COAST, wait=False) if z_speed > 1: motor_z.run_target(z_speed, z*10, then=Stop.COAST, wait=False) wait(time * 12000) old_x = x old_y = y old_z = z # Move each axis +/- def axes_demo(speed): move(7,7,0,speed) move(0,7,0,speed) move(0,0,0,speed) move(0,7,0,speed) move(0,7,5,speed) move(0,7,0,speed) # Circle (diagonal) def circle(speed): move(6.0,5.3,4.3,speed) move(4.9,6.5,3.5,speed) move(3.7,7.0,2.5,speed) move(2.1,6.5,1.5,speed) move(1.0,5.3,0.7,speed) move(0.7,3.5,0.5,speed) move(1.0,1.7,0.7,speed) move(2.1,0.5,1.5,speed) move(3.5,0.0,2.5,speed) move(4.9,0.5,3.5,speed) move(6.0,1.8,4.3,speed) move(6.3,3.5,4.5,speed) # Circle (diagonal reverse) def circle2(speed): move(6.0,1.8,4.3,speed) move(4.9,0.5,3.5,speed) move(3.7,0.0,2.5,speed) move(2.1,0.5,1.5,speed) move(1.0,1.7,0.7,speed) move(0.7,3.5,0.5,speed) move(1.0,5.3,0.7,speed) move(2.1,6.5,1.5,speed) move(3.5,7.0,2.5,speed) move(4.9,6.5,3.5,speed) move(6.0,5.3,4.3,speed) move(6.3,3.5,4.5,speed) # Circle (diagonal reverse raised) def circle3(speed): move(6.7,1.8,4.8,speed) move(5.6,0.5,4.0,speed) move(4.2,0.0,3.0,speed) move(2.8,0.5,2.0,speed) move(1.7,1.7,1.2,speed) move(1.4,3.5,1.0,speed) move(1.7,5.3,1.2,speed) move(2.8,6.5,2.0,speed) move(4.2,7.0,3.0,speed) move(5.6,6.5,4.0,speed) move(6.7,5.3,4.8,speed) move(7.0,3.5,5.0,speed) # Circle (top plane) def circle4(speed): move(7,3.5,5,speed) move(6.96,4,5,speed) move(6.85,4.5,5,speed) move(6.66,5,5,speed) move(6.37,5.5,5,speed) move(5.95,6,5,speed) move(5.46,6.4,5,speed) move(4.92,6.7,5,speed) move(4.33,6.9,5,speed) move(3.5,7,5,speed) move(2.67,6.9,5,speed) move(2.08,6.7,5,speed) move(1.54,6.4,5,speed) move(1.05,6,5,speed) move(0.63,5.5,5,speed) move(0.34,5,5,speed) move(0.15,4.5,5,speed) move(0.04,4,5,speed) move(0,3.5,5,speed) move(0.04,3,5,speed) move(0.15,2.5,5,speed) move(0.34,2,5,speed) move(0.63,1.5,5,speed) move(1.05,1,5,speed) move(1.54,0.6,5,speed) move(2.08,0.3,5,speed) move(2.67,0.1,5,speed) move(3.5,0,5,speed) move(4.33,0.1,5,speed) move(4.92,0.3,5,speed) move(5.46,0.6,5,speed) move(5.95,1,5,speed) move(6.37,1.5,5,speed) move(6.66,2,5,speed) move(6.85,2.5,5,speed) move(6.96,3,5,speed) move(7,3.5,5,speed) # Suction movement def suction_move(x,y,z): move(6.8,1.2,5,100) #wait(500) move(6.8,1.2,z,100) wait(200) # Suction on motor_suction.run_target(500, 180, then=Stop.BRAKE, wait=False) wait(1000) move(6.8,1.2,5.3,100) #wait(500) move(x,y,5.3,150) #wait(500) move(x,y,1.5,150) #wait(500) # Suction off motor_suction.run_target(500, 0, then=Stop.BRAKE, wait=True) wait(100) # Video part 1a def part_1a(): # Bottom square move(0,7,0,60) wait(500) move(7,7,0,60) wait(500) move(7,0,0,60) wait(500) move(0,0,0,60) wait(1000) # Move z move(0,0,5,300) wait(500) #move(0,0,5,300) #wait(500) #move(7,0,0,300) #wait(500) #move(0,7,5,300) #wait(500) #move(0,7,0,300) #wait(500) move(7,0,5,300) wait(1000) # Two circles then home move(6.3,3.5,4.5,250) circle(140) circle(140) wait(500) move(0,0,0,100) # Video part 1b def part_1b(): move(0,7,0,100) wait(3000) axes_demo(70) wait(1000) # Top circle move(7,0,5,100) wait(1000) circle4(100) wait(2000) move(6.3,3.5,4.5,100) circle(130) circle(130) wait(600) move(0,0,0,140) # Video part 2 def part_2(): move(0,0,5,300) wait(500) suction_move(0,2.8,3.0) move(0,2.8,5,150) suction_move(3,2.8,2.0) move(3,2.8,5,150) suction_move(0,4.8,1.0) move(0,4.8,5,150) suction_move(3,4.8,0.0) # Push tray wait(1000) move(1.5,7,1.5,80) move(1.5,7,0,80) move(1.5,0,0,50) wait(200) # Back right top corner move(7,7,5,400) wait(500) # PROGRAM HERE reset_motors() hub.light.on(Color.WHITE * 0.8) wait(5000) part_1b() #part_1b or part_2 here print("END")

Robust looking switching - it seems to lock into positions nicely. Can't wait to see the full video.

Nice work! Congratulations on getting it so accurate.

Ah, I now see that this is apparently what you had in the first version. I had similar problems when building my XY plotter. It seems like the increased friction is happening in the same position vertically... perhaps the ball chain is catching on something...

Wow, interesting project. I hope you can get it working. If the up/down mechanism is what's inadvertently triggering the clutch, could you just decouple the up/down so it's directly powered by the motor?

Impressive! It seems like you have achieved your goal of less than 1% error .

Nice! How is the performance of the bearings? It looks like you've kept a 2L space between both the inner and outer rings?

The year is selected first then the red carriage will move to one of two positions depending if it's a leap year or not, if I understand correctly? Maybe you could use the 14-tooth sprocket with treads with tiles attached:

Wow, another interesting entry. Curious to see how you handle leap years and the '400 year rule'.

I have a feeling that it can. The joints appear to be able to attach in series using 2x 2L axles, and a friction pin would make that connection even more robust. I was thinking that too. Interestingly, the joint that part is designed for has a very similar function to this joint - 2 articulations with 15 degree increments.

Fascinating and creative use of Lego. Following closely .

It is essentially the method that Glaysche mentioned of using two parallel gear trains. It is explained in this thread: I am looking forward to this!

There was some discussion recently in this topic: This is the smoothest ball bearing design I've seen:

In some sets they come in grey, I guess for aesthetics.

Have you considered this? Someone posted it in a MOC recently and I thought it was smart. Not sure about it's real world performance.

Wow, that's great! I especially like the conveyor design but there are lots of things to like here.

An almost perfect fit that is new for me: The width of three stacked beams (red dimension) is 8 x 3 = 24mm. According to The Unofficial Lego Technic Builder's Guide, beams are 7mm wide on the thin side, which would make the sides of the yellow triangle (2.5 x 8) - (7 / 2) = 16.5 and the hypotenuse sqrt(16.5² + 16.5²) = 23.33mm. 0.67mm undersize might seem like a lot, but in reality the three stacked beams are held rather snugly at 45°. This can be tested easily inside a 5x7 frame. Edit: like this...

Again, I learnt from the great Akiyuki: I was looking into this last night. The train wheels don't stand up on their own so I think they need a carrier ring connecting them together. Maybe only four wheels could fit on such a ring, which might compromise performance. Also, the 1x1 tiles do a surprisingly good job at providing radial support, but the train wheels not as much, so the bearing might require extra support if using the train wheels. I will build one and see...

I built a bearing based on Akiyuki's design but with the smaller banana gears and it works well: I even managed to pass two axles through it. I think I'll be incorporating this into my robot arm as it seems very rigid.

It's an interesting problem @sammypants and one I have been scratching my head at too. Having built Akiyuki's design (first video), I think it's possibly the best solution - it runs smoothly and is the most rigid design that I've built. The design in the second video is easier to build and remains in-grid, but doesn't have the upper gear form-locked below the lower gear, so is less rigid. I'm not sure how either design would go with the smaller banana gears, but would be interested to see!

Making a video is too much work so I don't plan to do that. Yes the subject is complicated but all of the information is available if you follow the installation instructions on the vpype github - this is how I learnt how to do it. The mechanics of my plotter are fundamentally pretty simple. It's the coding of complex plots, I would say, that make it a complex system.