How to build a cable with robot

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ringo
Posts: 4
Joined: 12 Nov 2019, 08:39

How to build a cable with robot

Post by ringo » 13 Nov 2019, 10:04

Dear all,

I am trying to create cables with robot like a sample video on Youtube :https://www.youtube.com/watch?v=VS8Vctoxguo and I am making them from this sample rope : http://www.coppeliarobotics.com/scenesA ... peTest.ttt

I have already read this thread : viewtopic.php?t=2665

But still now I don't understand how to make cables.
Could you show me an example or let me know how to create cables?

This is what I made up to now : https://drive.google.com/file/d/1NiteSP ... sp=sharing

coppelia
Site Admin
Posts: 7441
Joined: 14 Dec 2012, 00:25

Re: How to build a cable with robot

Post by coppelia » 14 Nov 2019, 09:37

Hello,

you have two ways of creating a cable as in the video: you can do this kinematically, or dynamically.

With the dynamic approach, it is similar to a rope. But instead of using spherical joints, use revolute joints that operate in spring-damper mode, otherwise your cable won't have any rigidity. So something like:

Code: Select all

base --> revJoint1a --> auxMass --> revJoint1b --> link --> revJoint2a --> auxMass --> revJoint2b --> .. revJointRot
Consecutive joints should be perpendicular to each other. The last joint should be along the cable direction, and free, to allow a rotation along the cable. Then use a loop closure construction.

Cheers

ringo
Posts: 4
Joined: 12 Nov 2019, 08:39

Re: How to build a cable with robot

Post by ringo » 14 Nov 2019, 14:30

Dear coppelia

Thank you very much.
I'm trying to make the cables.
https://drive.google.com/file/d/1ZMg2bb ... sp=sharing

I made 3 types of cable.
One is that as you wrote here, which I named IK-Hybrid, this doesn't work well.
another is

Code: Select all

dummy --> revJointA1 --> Sphere1 --> revJointB1 --> Cylinder1 --> revJointA2 ... --> Cylinder --> SphericalJoint --> EndPoint(Small static object) --> Dummy
, I named IK because I added IK function on top of the cable
the other is like

Code: Select all

dummy --> revJointA1 --> revJointB1 --> Cylinder --> revJointA2 --> revJointB2 ... --> Cylinder --> SphericalJoint --> EndPoint(Small static object) 
, which I named J_J_C and I used IK function too.

I have other questions.
1. Do you mean that auxMass is like small sphere, link means cylinder?

2. All objects except base should be respondable and dynamic?

3. All joints should be "inverses-kinematics" mode with Hybrid operation in order to operate in spring-damper mode like this picture?
Image

ringo
Posts: 4
Joined: 12 Nov 2019, 08:39

Re: How to build a cable with robot

Post by ringo » 15 Nov 2019, 08:50

Dear coppelia,

Actually my colleague found a sample file which I saw on Youtube. I use them.
I'm not sure that I can upload this file here for others who don't have and don't have any idea.

If you let me do that, I will renew this post.

Anyway really thank you for your advices. These help me a lot!!

RobAtLab
Posts: 74
Joined: 10 Jan 2018, 17:49

Re: How to build a cable with robot

Post by RobAtLab » 16 Nov 2019, 22:37

You could upload to a dropbox, google drive or other such cloud storage platform, then put a link to it here.

ringo
Posts: 4
Joined: 12 Nov 2019, 08:39

Re: How to build a cable with robot

Post by ringo » 19 Nov 2019, 12:32

OK! Thank you.

Same robot and cable on Youtube, https://drive.google.com/file/d/1xO7M6L ... sp=sharing

I added Custom UI and you can change joint and lengths as you want, https://drive.google.com/file/d/1HiFUvo ... sp=sharing

Code: Select all

function sysCall_init()
    h=sim.getObjectAssociatedWithScript(sim.handle_self)
    hTip = sim.getObjectHandle("cable_tip")
    hTarget = sim.getObjectHandle("cable_target")
    child = sim.getObjectsInTree(h,sim.object_joint_type,0)

    xml = readXML()
    ui=simUI.create(xml)
    simUI.setPosition(ui,1077,85,true)
    child = sim.getObjectsInTree(h,sim.object_joint_type,0)
    num = table.getn(child)*0.5
    for i= 1,num,1 do
        InitsetSliderValue(1000+i)
        InitsetSliderValue(2000+i)
    end
    makeIK()
end

function InitsetSliderValue(id)
    hJoint = HandleFromID(id)
    val = sim.getJointPosition(hJoint)
    simUI.setSliderValue(ui,id,val*180/math.pi,true)
end

sliderChange_callback=function(ui,id,value)
    hJoint = HandleFromID(id)
    sim.setJointPosition(hJoint,value*math.pi/180)

    --set Tip and Target
    child = sim.getObjectsInTree(sim_handle_scene,sim.handle_all,0)
    for i=1,table.getn(child) do
        -- hLastBody_bef = hLastBody
        if string.match(sim.getObjectName(child[i]), "cable_body") == "cable_body" then
            hLastBody = child[i]
        end
        if string.match(sim.getObjectName(child[i]), "cable_orientTarget") == "cable_orientTarget" then
            hLastTarget = child[i]
        end
        if string.match(sim.getObjectName(child[i]), "cable_orientTip") == "cable_orientTip" then
            hLastTip = child[i]
        end
    end
    -- print(sim.getObjectName(hLastBody))
    pBody = sim.getObjectPosition(hLastBody,-1)
    oBody = sim.getObjectOrientation(hLastBody,-1)
    sim.setObjectPosition(hTip,-1,pBody)
    sim.setObjectOrientation(hTip,-1,oBody)
    sim.setObjectPosition(hTarget,-1,pBody)
    sim.setObjectOrientation(hTarget,-1,oBody)
end

function renewUI()
    x,y=simUI.getPosition(ui)
    simUI.destroy(ui)
    xml = readXML()
    ui=simUI.create(xml)
    child = sim.getObjectsInTree(h,sim.object_joint_type,0)
    num = table.getn(child)*0.5
    for i= 1,num,1 do
        InitsetSliderValue(1000+i)
        InitsetSliderValue(2000+i)
    end
    simUI.setPosition(ui,x,y,true)
end

function readXML()
    xml = [[
        <ui closeable="true" on-close="closeEventHandler" resizable="true">
            <tabs>
                <tab title="CABLE" layout="grid">
                    <button text="Add cable" on-click="addCable" />
                    <button text="Delete cable" on-click="delCable" />
                    <button text="Renew UI" on-click="renewUI" />
                    <br />
                    '<label text="Joint Name" />'
                    '<label text="Joint A" />'
                    '<label text="Joint B" />'
                    <br />
        ]]
        child = sim.getObjectsInTree(h,sim.object_joint_type,0)
        num = table.getn(child)*0.5
        for i= 1,num,1 do
            if i == 1 then
                xml = xml .. '<label text="Joint Ori" />'
            else
                xml = xml .. '<label text="Joint '..-2 + i..'" />'
            end
            
            xml = xml .. '<hslider minimum="-180" maximum="180" on-change="sliderChange_callback" id="'..1000+i..'"/>'
            xml = xml .. '<hslider minimum="-180" maximum="180" on-change="sliderChange_callback" id="'..2000+i..'"/>'
            xml = xml .. '<br />'
        end
        xml = xml .. '</tab></tabs></ui>'
    return xml
end 

function HandleFromID(id)
    if id == 1001 then
        hJoint = sim.getObjectHandle("cable_jointA")
    elseif id == 2001 then
        hJoint = sim.getObjectHandle("cable_jointB")
    elseif id > 2000 then
        num = id - 2002
        hJoint = sim.getObjectHandle("cable_jointB" .. num)
    elseif id > 1000 then
        num = id - 1002
        hJoint = sim.getObjectHandle("cable_jointA" .. num)
    end
    return hJoint
end

function closeEventHandler(h)
    sim.addStatusbarMessage('Window '..h..' is closing...')
    simUI.hide(h)
end

function makeIK()
    if sim.getIkGroupHandle("cable_straight@silentError") ~= -1 then
        hIKgroup = sim.getIkGroupHandle("cable_straight")
        sim.removeIkGroup(hIKgroup)
    end
    if sim.getIkGroupHandle("IK_Group@silentError") ~= -1 then
        hIKgroup = sim.getIkGroupHandle("IK_Group")
        sim.removeIkGroup(hIKgroup)
    end
    hIKgroup = sim.createIkGroup(0,{sim.ik_damped_least_squares_method,3})
    hBody = sim.getObjectHandle("cable_body")
    hOrientTip = sim.getObjectHandle("cable_orientTip")
    sim.createIkElement(hIKgroup,0,{hOrientTip,hBody,-1,sim.ik_alpha_beta_constraint})
    child = sim.getObjectsInTree(h,sim.object_joint_type,0)
    num = table.getn(child)*0.5
    for i=0,num-2 do
        hBody = sim.getObjectHandle("cable_body"..i)
        hOrientTip = sim.getObjectHandle("cable_orientTip"..i)
        sim.createIkElement(hIKgroup,0,{hOrientTip,hBody,-1,sim.ik_alpha_beta_constraint})
    end
end

function addCable(ui, id)
    child = sim.getObjectsInTree(sim_handle_scene,sim.handle_all,0)
    for i=1,table.getn(child) do
        -- hLastBody_bef = hLastBody
        if string.match(sim.getObjectName(child[i]), "cable_body") == "cable_body" then
            hLastBody = child[i]
        end
        if string.match(sim.getObjectName(child[i]), "cable_jointA") == "cable_jointA" then
            hLastJointA = child[i]
        end
        if string.match(sim.getObjectName(child[i]), "cable_jointB") == "cable_jointB" then
            hLastJointB = child[i]
        end
        if string.match(sim.getObjectName(child[i]), "cable_orientTarget") == "cable_orientTarget" then
            hLastTarget = child[i]
        end
        if string.match(sim.getObjectName(child[i]), "cable_orientTip") == "cable_orientTip" then
            hLastTip = child[i]
        end
    end
    hNew = sim.copyPasteObjects({hLastTarget,hLastJointA,hLastJointB,hLastBody,hLastTip},0)
    sim.setObjectPosition(hNew[2],hNew[4],{0,0,0.01})
    sim.setObjectParent(hNew[1],hLastBody,true)
    sim.setObjectParent(hNew[2],hLastBody,true)
    pLastTip = sim.getObjectPosition(hLastTip,-1)
    oLastTip = sim.getObjectOrientation(hLastTip,-1)
    sim.setObjectPosition(hNew[1],-1,pLastTip)
    sim.setObjectOrientation(hNew[1],-1,oLastTip)
    -- sim.createIkElement(hIKgroup,0,{hLastTip,hLastBody,-1,sim.ik_alpha_beta_constraint})

    sim.setObjectParent(hTip,hNew[4],true)
    pNewTip = sim.getObjectPosition(hNew[5],-1)
    oNewTip = sim.getObjectOrientation(hNew[5],-1)
    sim.setObjectPosition(hTip,-1,pNewTip)
    sim.setObjectOrientation(hTip,-1,oNewTip)
    sim.setObjectPosition(hTarget,-1,pNewTip)
    sim.setObjectOrientation(hTarget,-1,oNewTip)

    makeIK()
end

function delCable(ui,id)
    child = sim.getObjectsInTree(sim_handle_scene,sim.handle_all,0)
    for i=1,table.getn(child) do
        -- hLastBody_bef = hLastBody
        if string.match(sim.getObjectName(child[i]), "cable_body") == "cable_body" then
            hLastBody = child[i]
        end
        if string.match(sim.getObjectName(child[i]), "cable_jointA") == "cable_jointA" then
            hLastJointA = child[i]
        end
        if string.match(sim.getObjectName(child[i]), "cable_jointB") == "cable_jointB" then
            hLastJointB = child[i]
        end
        if string.match(sim.getObjectName(child[i]), "cable_orientTarget") == "cable_orientTarget" then
            hLastTarget = child[i]
        end
        if string.match(sim.getObjectName(child[i]), "cable_orientTip") == "cable_orientTip" then
            hLastTip = child[i]
        end
    end
    pOldTarget = sim.getObjectPosition(hLastTarget,-1)
    oOldTarget = sim.getObjectOrientation(hLastTarget,-1)
    sim.removeObject(hLastBody)
    sim.removeObject(hLastJointA)
    sim.removeObject(hLastJointB)
    sim.removeObject(hLastTarget)
    sim.removeObject(hLastTip)

    sim.setObjectPosition(hTip,-1,pOldTarget)
    sim.setObjectOrientation(hTip,-1,oOldTarget)
    sim.setObjectPosition(hTarget,-1,pOldTarget)
    sim.setObjectOrientation(hTarget,-1,oOldTarget)

    makeIK()
end


function sysCall_nonSimulation()
    -- local selectedObjects=sim.getObjectSelection()
    -- if selectedObjects and (#selectedObjects==1) and (selectedObjects[1]==h) then
    --     if simUI.isVisible(ui) == false then
    --         simUI.show(ui)
    --     end
    -- else
    --     simUI.destroy(ui)
    --     print(ui)
    -- end
end

function sysCall_cleanup()
    simUI.destroy(ui)
    print("CLEAN UP")
end

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