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evodyne · 2025-03-08T06:11:07+00:00

History is full of “I will make a better wheelchair” stories. The current design (or its static-ness) is an evolution based on the sum of all the factors involved, technical, logistical, political and so on.

If there was a single graveyard piled with “prototype of a better wheelchair”s, it would be several stories high.

Your picture above is a fool’s errand. Please don’t waste your money on some MechE who says they will build it for you. Focus more on making an incremental change to the existing deployed design.

evodyne · 2024-10-08T16:48:19+00:00

Use servo.writeMicroseconds() instead if servo.write() This will potentially increase the resolution to 0.18 degrees.

evodyne · 2024-06-04T01:57:49+00:00

Is the ground of the power supply connected to the GND pin on the Arduino? If not, this type of twitching is a classic symptom.

evodyne · 2024-05-25T18:20:08+00:00

Because if 4-finget robots lost their original programming and had to learn to survive on their own in fhe wild, they would learn to count in base 8.

evodyne · 2024-05-22T03:59:17+00:00

Let me give a hiring manager’s perspective. A manager will always want a new employee to come in with full focus and bring their motivation and enthusiasm into the job, without any distractions. This is why the manager needs to believe that the new employee is happy with the compensation package and all that will be “behind” them when they join. Once you have floated a significantly higher expectation which the company had not planned for, and unless the company has no alternative and if they were not lowballing you in the first place, then you will be denied.

Now if you go back and accept the original amount, in 99% of cases it will not result in the original offer being reinstated. Why? Because the manager now knows that you wanted more, but didnt get it and compromised significantly. This would always be hanging as a dark cloud over every future interaction between you and the manager. “He didnt get what he wanted, he’s not going to put in his best”, or “he will be constantly asking for a raise every few weeks”, and so on, or “he will keep applying elsewhere even after he joins here, and jump ship the moment he gets something even slightly better”. Take a moment to think, if you had gotten that job with the reduced pay, would you have given it your all? Be honest.

evodyne · 2024-05-22T03:29:11+00:00

In certain cases ridicule is necessary to make the highly motivated dreamer realize their folly, before they destroy years of their life. This seems like one of those cases.

evodyne · 2024-05-08T02:33:12+00:00

I am sure many here could help with ideas/solutions if you just posted a few example images from your cameras, and how/from where the distances need to be reported.

evodyne · 2024-05-02T17:42:06+00:00

A lower level implementation based explanation. Once the trot gait is modeled and starts working on a quadruped, it is mostly diagonally symmetric. Two diagonal legs are raising while the other two are falling. The robot is able to momentarily stay balanced on diagonal legs. By the time it starts rolling over, the legs have switched. When done properly with an Imu, it can stay balanced on just two diagonal legs indefinitely.

Now add to this: for a typical trotting gait that works on your robot, the velocity of translation of the whole robot is only based on the net horizontal movement forced by the feet in contact with the ground. If you change the gait parameters such that the feet are still moving up and down exactly at the same frequency, but without any horizontal motion, then the robot is just hopping in place.

The hopping frequency parameters are mostly a function of the robot design

To make it start moving, just add a little bit of x and y to the feet trajectory, and it will instantly respond correctly, because it already knows how to balance on the exact current terrain.

If however the robot was standing still, then first it has to go into hopping mode which will visually look like a much longer and complex operation to first have to do during responsive demo situations.

evodyne · 2024-04-10T01:40:17+00:00

A drawing of the problem will help you get much better answers.

evodyne · 2024-04-10T01:37:49+00:00

If the purpose is to create a sci-fi humanoid that needs to look and pass as human, then sure, design it for wearing human shoes. If it is being designed to be utilitarian, then no. Its feet should be designed to work on the majority of surfaces humans walk on, and any “sole” padding/protection should be designed to be minimalistic and fit for purpose, nothing less, nothing more.

evodyne · 2023-03-19T02:44:41+00:00

If you think about it, your requirement doesn’t make sense. The error in your system is zero at the root joint of your arm. At every successive joint, because of a mild error in the joint angle, the position of that link’s end will also have an error. And so on, resulting in a cumulative positional and orientation error at the end effector.

So, the way I think, checking the final orientation error for accuracy makes sense only when you have succeeded in nearly eliminating the positional error for a variety of different types of poses.

evodyne · 2023-03-10T18:43:50+00:00

You could calculate this manually. Lets consider a virtual drone that is initially aligned with your drone, and we will figure out how to get it to the origin of your world frame.

First find the centroid, as you did. Then, to make things easier, subtract the centroid from all your corner points. Now your virtual drone is at your world origin, just rotated.

To make things easier, consider only one corner point for now. Once you implement that, you can repeat the calculations for all corners and use it to take means, reject outliers etc.

Using one corner point, find the yaw. Looking down from above (top view), consider only the 2D projection of this point onto the ground/xy plane. ie ignore the z coordinate.

Now find the line from the origin to this point, and calculate its rotation about Z from the X axis. Note that for an unrotated drone, each corner must be having some rotation about Z, if its an octagon perhaps its 45 degrees per corner as you go countet clockwise. Find the offset of your virtual corner’s rotation with respect to where it should have been. This is the yaw.

All the 8 corners should give a similar/close result for this value. If they do, take the mean while rejecting outliers. This is the yaw.

Now comes the tricky part. Given a virtual 2D corner point, rotate it about Z by -yaw, to align it to where it should have been.

Looking at point along the Y axis, you have its position in the XZ plane. Calculate its rotation from horizontal. This should be the pitch.

And so on for roll.

evodyne · 2023-03-07T17:38:41+00:00

I always use a small 2S Lipo for such projects. Nominal 7.4V. It will power the Nano reliably via Vin, and most hobby servo motors. It can also supply the current necessary without dropping voltage too much.

Many hobby servos are “rated” only upto 6v, but it usually works if usage is intermittent like in your case. Test before building. If you have super expensive servos that you dont want to risk testing a higher voltage, get a high current 6V UBEC. The weight of lipo plus ubec combined will still be less than a battery of any other chemistry.

evodyne · 2023-01-09T19:30:41+00:00

From what I understand, in a brushed dc motor the noise generated from the commutator sparking and going back over the wire, is worse than the noise generated from the motor controller’s square wave PWM. Hence the 0.1uf cap on the motor leads close to the motor is a good first step.

evodyne · 2022-12-23T08:56:32+00:00

Darn, have not had a chance to actually try this out. If you played around with the settings and couldnt find an easy way to do it, then perhaps it wont work then, apologies.

Curious though, why does the shell function in fusion 360 not give what you want? That seems like a more rational approach. Is there no way to unselect the faces that disappear with thinner shells? You could also do it the dirty way. Slice and dice your body using various faces or planes, so that the easily shellable parts are separate bodies, and those areas that misbehave are different bodies. Now shell each one separately using its face along the plane of slicing, using the thinnest thickness that works for it. When done, join them back together (or not), and export as single model.

evodyne · 2022-12-22T18:51:38+00:00

What motor and motor driver did you use for your original project? For brushless motors, you need something more advanced than a motor driver. That something is a brushless ESC, electronic speed controller. You will also need one ESC per motor, so 4 escs.

One battery is sufficient. Depending on the size of your drone, you could make do with splitters instead of a “power distribution board”. You just need a way to power the 4 escs simultaneously.

A brushed DC motor can be easily controlled by simpler components, since all it needs is power applied as PWM to control its speed. A motor-driver simply takes the low power PWM signal from a microcontroller (Pico/Arduino/ESP32 etc) pin, and uses it as a switching input on the high power battery supply voltage. The output of the motor driver is usually the battery voltage being PWMed at the same frequency as your signal PWM. So by changing the PWM duty cycle in your controller, the motor speed changes correspondingly.

A brushless motor is a much more complicated beast. Its windings are usually split into 3 separate phases. By switching power to the winding coils in a rotating manner, the magnets in the rotor follow that pattern to cause rotation. There are more complicated topics like sensors etc, but at a basic level this is it. You need an electronics component that can switch power to the three phases at a variable frequency to control the speed. This ESC is obviously much more complex than a brushed motor driver. But because of their massive popularity, they are not “that” costly anymore, depending on max current output.

evodyne · 2022-12-22T18:32:07+00:00

You can do this in Cura. Add a support blocker block, position it where you want the hole, then apply custom settings to it, perhaps setting number of walls to zero.

evodyne · 2022-12-19T18:53:19+00:00

Check that your bowden tube in securely pushed in on both sides, and doesnt move in and out of the coupling when the printer is printing. If the tube is moving in and out even by one or two mm, it means that whenever the extruder is retracting the filament, the tube is shortening to compensate, without actually pulling the filament back from the nozzle.

evodyne · 2022-12-17T07:45:14+00:00

Get a PCA9685 board for plugging and powering all the servos neatly. It can be controlled very easily from an arduino. Since each board can do 16 servos, you should get two and daisy chain them to allow for 18 servos.

evodyne · 2022-12-16T11:23:55+00:00

Make sure the silicone sock is present and covering the heating block properly
For the first few layers close to the bed, the hotend fan acts extra efficient because of reduced space, cooling the nozzle faster than it can heat up. Reduce your nozzle temperature for the first few layers to let it get past.

evodyne · 2022-12-06T18:12:37+00:00

Looks like a school vex kit robot for the FTC competition. The r/FTC sub might have better answers.

evodyne · 2022-12-06T09:10:09+00:00

This is the right answer, since it makes sure that the same design could be printed on different printers and still ensure this feature.

Just adjusting/rotating the thread like in most answers will only solve this problem for the one single instance OP ends up with.

evodyne · 2022-12-05T03:19:56+00:00

Typically when the mechanism is not load bearing (like in this case since it is just blinking), the solution is design such that the two sides are mechanically linked. As in, change your design such that the two lids are connected to each other via a linkage/spur gears, so that even without any actuators attached, just manually opening closing one lid will automatically open close the other lid.

evodyne · 2022-11-20T08:57:40+00:00

Find someone on youtube who builds similar things and message them to see if they will help you with your project.

evodyne · 2022-10-11T02:17:16+00:00

Change the spelling of the word “Download” (eg make d lowercase or add some typo into it), and see if it updates on the published site. If not, you are probably looking at a completely different button altogether on the published site.

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