They seem to be exactly the same thing

I am interested in calculating the inverse kinematics of the robot illustrated below. The robot has 2DoF with two revolute joints. Without the cylinder which physically connecting the two links, the problem might be ideal: δq= J^(−1) δx. Since the cylinder movement is caused by the rotation of J1, the relationship between J1 and J2 can be described as follow: δq_2_additional= =scalefactor* δq_1

By simply extending the output from δq= J^(−1) δx by (δq_1,δq_2+scalefactor∗δq_1)the problem could be solved, but it seems to be rather ad-hoc. Is there a way to consider this extra movement of the cylinder already during calculating the Jacobian matrix?

https://preview.redd.it/ist9r3kxtx861.png?width=1088&format=png&auto=webp&s=d2d5f18310352eaee0c541ec01a29b38ccec91cb

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Edit:

https://preview.redd.it/6cmworytjy861.png?width=385&format=png&auto=webp&s=9daaacb786de54bd85fb57230d9c3db557661f29

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Edit2:

https://preview.redd.it/qblixy2cvy861.png?width=485&format=png&auto=webp&s=6b357bf3d468dff59310490a5cdc5fc487fd5604

I was simulating 4 bar mechanism for practice and ran into a problem and can't really understand the reason behind it. Initially I performed the simulation by using rigid transforms on default frames of links to define revolute joints and it worked perfectly fine. Then I tried defining custom frames from inside the solid body's definition block at the edges of links. The links assemble perfectly as long as assembly is an open chain but as soon as I join the last link with first link to form a closed chain, the assembly gives error on compiling that the position constraints cannot be met. How can I use the custom frames to make 4 bar linkage?

Actually I need custom frames for another project and it was causing issues too so I tried a basic problem to understand underlying mechanics better but i can't work it out.

*Revolut

Hi, I wanted to get some advice regarding robot arm inverse kinematics.

I created a robot arm in a 3D game engine with 7 revolute joints and want the end effector to go to a certain location at a certain orientation. I calculated the forward kinematic equations for position and quaternion for the end effector and was able to get the partial derivatives of each joint rotation against position and the quaternion to form the Jacobian. Solving for this in real time leads to an adequate control system.

What I've found however is that the Jacobian control system gets the arm stuck in certain orientations and positions because it needs to temporarily get further away from its goal to get unstuck.

1. What are some available strategies to use so I can more reliably get to the target?

2. What are ways to determine if it possible to reach the target in the first place?

3. Is it possible to directly solve for the joint angles against for a target? I took an initial look at this and it seemed extremely complicated.

Thanks!

Hello,

I wanna to make revolute joints to a many instance, not just one. I have a "core" object and this one must be connect to a "base" object, but it would be a many instance. When I have only one instance of these two object (a pair of it) its works properly. However, when I create one more instance of "base" its not connect to the "core" as the first one.

I use this line of code in the create event of obj_core: physics_joint_revolute_create(obj_core, obj_base, x, y, 0, 0, 1, 0, 0, 0, 1);

I tried to use the code in the obj_base but the result still same...

Thanks!

https://preview.redd.it/l15iywl525z71.png?width=904&format=png&auto=webp&s=3a781003a360944c27e36625d90ea2ff8550ca5e

• Both of them laughed that their old tag team attire could be too tight to wear. It actually was. But at the same time they missed each other as a team so much the felt as if their attires gave a bit of power;
• Sera said that even though they didn't team up for more than 18 months, Yuki didn't even want to rewatch their previous matches to remind their tag moves. Why? Because, one, they improved as a wrestlers so much they already knew what each of them want to do, and two, their body complexion is different from even 2019;
• "I have nothing to be afraid of now that I'm doing death matches. I don't care what anyone says about me. In professional wrestling, if you mess up, you might die. When you're in a death match, you're very aware of that. You always feel like you're on the verge of death. That's why I feel more strongly that I have to do what I want to do before I die. There's no time to be afraid of being criticised. It's better to do something and be criticised than not to do it." - Risa about her path during the AR timeout;

https://preview.redd.it/rvdobgfo25z71.png?width=765&format=png&auto=webp&s=69bdc7dd9ecadd04d1e7989670833058445ad3dc

• One of the reasons why Yuki decided to form Rebel x Enemy is that Ice Ribbon can't be a promotion of "Tsukasa Fujimoto and her friends" and that it's not only about Tsukka;
• At the beginning of her wrestling career, Yuki never thought she'd be the top star and main champion, and started to really aim for it when she realised people have expectations about her;
• At first, Sera thought that Yuki was a bit "reserved" and a step back compared to her. Now it's not the case anymore. She admires Yuki for her willingness to encourage younger members of IR roster to step up and be more brave. It even helped Risa;

https://preview.redd.it/e9zjln0u45z71.png?width=765&format=png&auto=webp&s=1805cc9fd9bbef3d9576be78d3992d2503f2c71b

• In Ice Ribbon, usually when a wrestler wants to perform a double move, they should shout "double!", but it needs to be coordinated between wrestlers. For Yuki and Sera, it's almost at subconscious, and Yuki elaborates that an eye contact is enough for them to know what to do next;
• Yuki reveals that Sera supported her during "rebel" period in 2020. If she'd say "What the hell are you doing?", it might not be possible for them to reun

Revolut Bank account is optional, but as decribed on support page "From version 8.5 of the Revolut app, when joining Revolut, you will have a bank deposit account and an EMI (Electronic Money Institution) account." can I register without creating bank account, just to old revolut? When I've tried it, app pushes me to create bank account.

I’m contemplating order a second card for my wife on my account. We want to have an account which we can both use for household expenses etc. and this seems like the best option.

Is anyone currently using their Revolut in this way, and it yes, do you have any feedback or advice?

While I know she won’t be able to see the balance as it will linked to my phone, everything else should be okay it seems.

Any feedback is appreciated, thanks.

My partner and I both use revolut and plan on getting our salaries paid into it. As far as I can see there is no option to setup a joint account which is a fairly big negative. Is that correct?

One year ago I was watching in horror just like most of you, as sore losers decided to do what they could to larp a revolution and topple our democratic process. How fun!

Being a bit of a psycho myself, and feeling personally attacked, I went to work. I started backing up videos that showed individuals committing coordinated acts of violence. I focused primarily on the West Tunnel brawl for the first week.

By January 15th I had submitted over 50 separate profiles to the FBI. They all included clean shots of faces, timestamped acts of violence, and I cross referenced those against other videos.

When an assault on an officer occurred, I’d work to establish their name and badge number, as well as a timestamp so they could quickly find the footage on their own body cameras.

I admit that I became a bit obsessed, in an unhealthy fashion. But it really felt like the bottom was falling out of the whole country and I wanted to do whatever I could.

I’ve had over a dozen calls with members of the Joint Terrorism Task Force, the Capitol Police, and a few Special Agents around the country. Each have expressed what seemed like genuine gratitude for my efforts. Some have told me “you have literally built the case for me and done my job.”

During the second week after the attack I focused on a two hour long uncut raw video of a man who entered the capitol. I mapped his movements, timestamped his video, and built a model where I could jump to other videos taken in the capitol at the same time to see other angles.

I’m not going to say much about that because I suspect much bigger things to come from that work that involve groups of former military guys with a plan.

I am so saddened, though not shocked, by the tone change from the political right. The night of the 6th I had a moment of hope thinking we might finally come together to root out this rising tide of fascist tendencies. Wrong.

All in all I keep tabs on the cases that are pending and read all the court documents. I sit in anticipation about folks I really want to see have the book thrown at them. I work hard to share updates with my networks, and to keep the conversation about this event alive.

Things to consider:

We’re getting more and more answers by the day about the planning that went into this, the cogs of the machine. It seems to be becoming clear that this was intended as a reichtags fire and that the Trump team wanted to us the national guard to justify invoking the insurrection act.

T

I am in the beginning stages of a project where I am going to make a robotic arm play chess against a human autonomously. The chess engine integration and computer vision are already in progress or done. My biggest challenge is finding/building an arm to do the job and handling the inverse kinematics to control it.

I need the arm to pick up chess pieces and move them around on a board. The end effector (a gripper) should always be vertical to avoid knocking over pieces. I assume that this will require an additional DOF because each orientation of the arm will change the angle of the end effector.

Originally I was playing around with the idea of buying and using a 6DOF arm, but now that seems way overkill. I only need the arm to pick up pieces vertically and move them around. I don't need to rotate or otherwise re-orient the pieces. Ideally, I would like to design this arm myself as it would get me some much-needed CAD experience.

I'm sure this could be done with a 2-axis 3d printer type of system, but want to make this an arm for several reasons. Firstly I don't want anything to permanently be obstructing the board. It should be comfortable for a human to play on. Secondly, controlling an arm with inverse kinematics will be an excellent learning experience. Thirdly, for the cool factor. Who doesn't love robotic arms?

As I understand, the inverse kinematics of a 2/3 DOF arm can be done with a little bit of trig, but when another revolute joint is added to the 'waist' of the robot, it seems like things are going to get complicated. I have made myself vaguely familiar with the Denavit Hartenburg convention, I'm not sure if that will be relevant.

So I have two questions:

1. What is the minimum amount of degrees of freedom (not including the motor that contracts the gripper) required to accomplish this task
2. Where should I start in terms of handling inverse kinematics for the arm?

Disclaimer

This is a long read (4k+ words). Just a heads up.

None of the information in this report should be constituted as near/mid/long term financial advice OR financial advice for that matter, cryptocurrency investing is highly risky and speculative and there is a chance you may lose most of your initial investment.

I won't provide any TLDR for this post because it is worth reading all of it, since it is a good idea to know what you are investing into.

Also DON'T give me awards.

I hold a significant Loopring investment, thus this may be a biased analysis.

(Edit 1: Added an extra section analyzing market cap of NFT)

Introduction

Loopring is an open protocol for building decentralized exchanges initiated by Daniel Wang. The protocol is free, extensible, and serves as a standardized building block for decentralized applications (dApps) that incorporate exchange functionality. It is operable on Ethereum and Qtum while NEO is also under construction. (Reference: Bitcoin Wiki).

Loopring is a no-brainer investment at these price levels and here is why:

Loopring is an engineering first team

Probably the most important thing that gets overlooked in an initial investment thesis, is the management. Good management is absolutely pivotal to a business/technologies success.

Loopring is an engineering first development team, meaning they are made up of mostly engineers(95% of the team are engineers). Now you may be asking, isn't this a problem… it's not, you always want a team that is as technical as possible, a good product will always sell itself, look at Tesla, mostly engineers and 0 marketing. Good management, is the cornerstone of a company and the value it will deliver to its investors. (Source: Loopring Medium Article, Finestone's parting words)

Some of the most successful companies on the planet, are engineering first companies, with a rich focus in R&D (Research and Development). I can list many but here is a few

- Palantir

- Google

- Amazon

- Tesla

Loopring's lack of media presence, may seem bearish to outside investors or on a short time frame, BUT to me, it is a sign that they are focused on delivering industry changing products that will accelerate mass adoption to cryptocurrencies, metaverse and NFTs. There is no need to endlessly hype your products, there is no need

Hi everyone, my robot model will collapse to the ground in Gazebo when setting <transmission> tag EffortJointInterface. The <inertial> parameters are calculated by Solidworks.

https://preview.redd.it/ky5fqllpmw781.png?width=2268&format=png&auto=webp&s=58ba735d6fe494688831a8b545654fdcce213c90

https://i.redd.it/ml4i404rmw781.gif

And the robot will start shaking once I launch the ros controller(effort_controllers/JointTrajectoryController). What am I supposed to do to fix this? Any advice will be appreciated.

P.S. Here's the content of the urdf file:

<!-- This URDF was automatically created by SolidWorks to URDF Exporter! Originally created by Stephen Brawner (brawner@gmail.com) 
     Commit Version: 1.6.0-1-g15f4949  Build Version: 1.6.7594.29634
     For more information, please see http://wiki.ros.org/sw_urdf_exporter -->

<robot name="arm">

  <link name="world" />

  <link name="base_link">
    <visual>
      <origin xyz="0 0 0" rpy="0 0 0" />
      <geometry>
        <mesh filename="package://arm_description/meshes/base_link.STL" />
      </geometry>
      <material name="3143">
        <color rgba="0.79216 0.81961 0.93333 1" />
      </material>
    </visual>
    <collision>
      <origin xyz="0 0 0" rpy="0 0 0" />
      <geometry>
        <mesh filename="package://arm_description/meshes/base_link.STL" />
      </geometry>
    </collision>
    <inertial>
      <origin xyz="-0.52E-03 -0.01E-03 20.01E-03" rpy="0 0 0" />
      <mass value="1.25" />
      <inertia ixx="3000.53E-06"    ixy="-2.36E-06"    ixz="-15.68E-06"
                                    iyy="3039.39E-06"  iyz="0.05E-06"
                                                       izz="5609.85E-06" />
    </inertial>
  </link>

  <joint name="joint_0" type="fixed">
    <origin xyz="0 0 0" rpy="0 0 0" />
    <parent link="world" />
    <child link="base_link" />
  </joint>

  <link name="J1_link">
    <visual>
      <origin xyz="0 0 0" rpy="0 0 0" />
      <geometry>
        <mesh filename="package://arm_description/meshes/J1_link.STL" />
      </geometry>