path following object

[NandanUmrikar]

I need to generate a scene where a moving object is being tracked. For that purpose, I need to generate a path and make an object (mostly just a spherical object) follow the generated path. In older versions of coppeliasim, there was an option in the path properties where we could directly set the path velocity, but it is no longer available in the latest updates, and now, the path is shown as a set of dummies instead of an object. How do I make the sphere follow the generated path? Do I need to associate a script to the path in order to set the velocity? Please help me with this and provide a sample code (if required) to tackle the issue.
Thank you!!!

[fferri]

https://manual.coppeliarobotics.com/en/paths.htm

[NandanUmrikar]

Thank you for the link. It is working well now.
In the objectTracking example, they have used a mobile robot as the target. I want to use this moving target instead of the mobile robot. I tried simply copying the UR5 model from the tutorial (along with the script and all) into my scene and running the simulation, but it is not tracking the sphere. The mobile robot script does not seem to contribute to the tracking algorithm.
How do I make it work?
Adding below the Robot manipulator script and the sensor script.
UR5:

Code: Select all

--lua

function sysCall_init()
    sim = require('sim')
    simIK = require('simIK')

    simBase = sim.getObject('.')
    simTip = sim.getObject('./tip')
    simTarget = sim.getObject('./target')
    simJoints = {}
    for i = 1, 6, 1 do
        simJoints[i] = sim.getObject('./joint', {index = i - 1})
    end

    ikEnv = simIK.createEnvironment()
    ikGroup = simIK.createGroup(ikEnv)
    simIK.setGroupCalculation(ikEnv, ikGroup, simIK.method_damped_least_squares, 1.5, 1)
    local ikElement = simIK.addElementFromScene(ikEnv, ikGroup, simBase, simTip, simTarget, simIK.constraint_position)
    
    visionSensor = sim.getObject('./Vision_sensor')
    centerX = 0
    centerY = 0
end

function setBoxCenter(cx, cy)
    centerX = cx
    centerY = cy
end

function sysCall_actuation()
    -- Get data computed by the Python image processing script:
    k = 0.15
    sim.setObjectPose(simTarget, {-k * centerX, k * centerY, 0, 0, 0, 0, 1}, simTip)
    simIK.handleGroup(ikEnv, ikGroup, {syncWorlds = true, allowError = true})
end

function sysCall_cleanup()
    simIK.eraseEnvironment(ikEnv)
end

Vision sensor:

Code: Select all

# python

import numpy as np
import cv2 as cv

def readFrame():
    sim.handleVisionSensor(self.handle)
    buf, res = sim.getVisionSensorImg(self.handle)
    return np.frombuffer(buf, dtype=np.uint8).reshape(*res, 3)

def showImage(k, img):
    sim.setVisionSensorImg(sim.getObject(f':/{k}'), img.tobytes())

def sysCall_init():
    sim = require('sim')
    self.handle = sim.getObject('.')
    robot = sim.getObject(':')
    script = sim.getScript(sim.scripttype_childscript, robot)
    self.robotScriptFuncs = sim.getScriptFunctions(script)

def sysCall_thread():
    while True:
        frame = readFrame()
        imgw, imgh, imgc = frame.shape
        blurred = cv.GaussianBlur(frame, (13, 13), 0)
        hsv = cv.cvtColor(blurred, cv.COLOR_RGB2HSV)
        # construct a mask for the color "red", then perform
        # a series of dilations and erosions to remove any small
        # blobs left in the mask
        mask = cv.inRange(hsv, (0, 200, 64), (80, 255, 200))
        n = 5
        mask = cv.dilate(mask, None, iterations=n)
        mask = cv.erode(mask, None, iterations=n)
        maskdbg = cv.cvtColor(mask, cv.COLOR_GRAY2RGB)
        
        contours, hierarchy = cv.findContours(mask.copy(), cv.RETR_EXTERNAL, cv.CHAIN_APPROX_SIMPLE)
        if contours:
            c = max(contours, key = cv.contourArea)
            x, y, w, h = cv.boundingRect(c)
            cv.rectangle(maskdbg, (x, y), (x+w, y+h), (0, 255, 0), 2)
            cv.arrowedLine(maskdbg, (x+w//2, y+h//2), (imgw//2, imgh//2), (255, 0, 0), 2)
            
            # normalize rect in -1 ... +1:
            normalize = lambda x: np.interp(x[0], (0, x[1]), (-1, 1))
            x, y, w, h = map(normalize, ((x, imgw), (y, imgh), (w, imgw), (h, imgh)))
            
            # box center:
            self.robotScriptFuncs.setBoxCenter(x + w/2, y + h/2)

        showImage('blurred', blurred)
        showImage('hsv', hsv)
        showImage('mask', maskdbg)

Please check and give me some solution.
Thank you!!!

[fferri]

Code: Select all

--lua
    sim.setObjectPose(simTarget, {-k * centerX, k * centerY, 0, 0, 0, 0, 1}, simTip)

you are setting position of simTarget relative to simTip's reference frame.

[coppelia]

Hello,

there is a demo scene that does exactly what you want, in various versions: scenes/movingAlongAPath-lua.ttt

Cheers