studywolf / blog

for code created as part of http://studywolf.wordpress.com

Studywolf code blog

This repository serves to hold projects that I'm both working on and have completed and presented on http://www.studywolf.com.

The Control folder has been moved to its own repo, at studywolf/control.

The DMPs folder has been moved to its own repo, at studywolf/pydmps and can be installed with pip.

blog's Issues

Problem with V-REP two-link arm example

I am so sorry for opening yet another of these. This really must be the issue at my end, but just in case it is not; the two-link arm example is not running out of the box either:

The second link, top, is continuously reflecting about the top joint, suggesting there is a sign that's gone wrong somewhere.

RL - Cat vs Mouse seems not to run out of the box

You might want to make egoMouseLook.py executable and remove the executable flag from the others.

You could make this a its own repository and add it here as a subrepository.

I've also just "forked" this part of your repository: https://github.com/MartinThoma/cat-vs-mouse

Your Code Explain is lacking

I read your posts in your blog. It is exciting, but you rarely explain your code and I cannot understand absolutely

Your blog theme is very good

Your blog theme is very good, very simple and regular, people like to read. Is your blog theme open source? I like it very much and want to use your blog. thank you.

Funny error with UR5 arm

Hi Travis,

Excellent blog as always.

I was playing around with your ur5_ctrl.py example and I am running into this funny error where I can run the code from outside an IDE like so:

[90] → python ur5_ctrl.py
Connected to remote API server
Generating transform function for EE
connection closed...
Traceback (most recent call last):
  File "ur5_ctrl.py", line 364, in <module>
    ax.plot([track_hand[0, 0]],
IndexError: too many indices for array

If I then run it inside and IDE like sublime or a notebook, I get the same error above once, but then if I try to run it again I get this rather worrying chunk of stuff:

Connected to remote API server
Generating transform function for EE
connection closed...
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-2-d8786628c253> in <module>()
    149             # calculate position of the end-effector
    150             # derived in the ur5 calc_TnJ class
--> 151             xyz = robot_config.Tx('EE', q)
    152 
    153             # calculate the Jacobian for the end effector

/Users/nd/cloud/control/src/vrep/ur5.pyc in Tx(self, name, q, x)
    213             # both have their own transform calculated with this check
    214             self._Tx[name] = self._calc_Tx(
--> 215                 name, x=x)
    216         parameters = tuple(q) + tuple(x)
    217         return self._Tx[name](*parameters)[:-1].flatten()

/Users/nd/cloud/control/src/vrep/ur5.pyc in _calc_Tx(self, name, x, lambdify)
    384         if (os.path.isfile('%s/%s.T' % (self.config_folder, name))):
    385             Tx = cloudpickle.load(open('%s/%s.T' %
--> 386                                        (self.config_folder, name), 'rb'))
    387         else:
    388             T = self._calc_T(name=name)

/Users/nd/anaconda2/lib/python2.7/pickle.pyc in load(file)
   1382 
   1383 def load(file):
-> 1384     return Unpickler(file).load()
   1385 
   1386 def loads(str):

/Users/nd/anaconda2/lib/python2.7/pickle.pyc in load(self)
    862             while 1:
    863                 key = read(1)
--> 864                 dispatch[key](self)
    865         except _Stop, stopinst:
    866             return stopinst.value

/Users/nd/anaconda2/lib/python2.7/pickle.pyc in load_reduce(self)
   1137         args = stack.pop()
   1138         func = stack[-1]
-> 1139         value = func(*args)
   1140         stack[-1] = value
   1141     dispatch[REDUCE] = load_reduce

/Users/nd/anaconda2/lib/python2.7/site-packages/sympy/core/numbers.pyc in __new__(cls, num, prec)
    823                 else:
    824                     _mpf_ = mpmath.mpf(
--> 825                         S.NegativeOne**num[0]*num[1]*2**num[2])._mpf_
    826         elif isinstance(num, Float):
    827             _mpf_ = num._mpf_

TypeError: can't multiply sequence by non-int of type 'float'

Do you know why it might be doing that?

EDIT:

The issue seems to be with cloudpickle

If I do

Tx = cloudpickle.load((open('%s/%s.T' % ('ur5_config', 'EE'), 'rb')))

I get

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-5-d19e02c244b8> in <module>()
----> 1 Tx = cloudpickle.load((open('%s/%s.T' % ('ur5_config', 'EE'), 'rb')))

/usr/local/Cellar/python/2.7.13/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.pyc in load(file)
   1382 
   1383 def load(file):
-> 1384     return Unpickler(file).load()
   1385 
   1386 def loads(str):

/usr/local/Cellar/python/2.7.13/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.pyc in load(self)
    862             while 1:
    863                 key = read(1)
--> 864                 dispatch[key](self)
    865         except _Stop, stopinst:
    866             return stopinst.value

/usr/local/Cellar/python/2.7.13/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.pyc in load_reduce(self)
   1137         args = stack.pop()
   1138         func = stack[-1]
-> 1139         value = func(*args)
   1140         stack[-1] = value
   1141     dispatch[REDUCE] = load_reduce

/usr/local/lib/python2.7/site-packages/sympy/core/numbers.pyc in __new__(cls, num, prec)
    823                 else:
    824                     _mpf_ = mpmath.mpf(
--> 825                         S.NegativeOne**num[0]*num[1]*2**num[2])._mpf_
    826         elif isinstance(num, Float):
    827             _mpf_ = num._mpf_

TypeError: can't multiply sequence by non-int of type 'float'

I think, possibly, maybe, there is an issue with the files in ur5_config/ - surely I should be able to use the ones on this repo and not process them myself (it takes a few hours as you have noted :)

having issues in understanding of code vrep two link arm example

sir i have read your code. i have certain issues

1. how did you make M , C matrices of two link manipulator (that represent the dynamics of your 2 link manipulator)
2. i have read that vrep joints required velocity and torque for simulation. my question is that how I can give the output of PID to our manipulator joints

UR5 arm unused variable

In the ur5.py code, the following methods have x as an unused argument:

def _calc_Tx(self, name, x, lambdify=True)
def _calc_T_inv(self, name, x, lambdify=True)

Also, thanks for all the excellent educational material!

Typo within self.J_orientation

self.J_orientation = [[0, 0, 10],  # joint 0 rotates around z axis
                          [10, 0, 0],  # joint 1 rotates around x axis
                          [10, 0, 0],  # joint 2 rotates around x axis
                          [10, 0, 0],  # joint 3 rotates around x axis
                          [0, 0, 10],  # joint 4 rotates around z axis
                          [1, 0, 0]]  # joint 5 rotates around x axis

I guess the orientation axis should be normed, so 10 ->1 .

MapleSim Example Model

Could you please upload the corresponding MapleSim Model to reproduce the presented workflow? Thx in advance