Documentation User defined element

[asraelis]

Hey,

Great package! I am really glad that I found your package. I want to simulate nonlinear devices and their transient behaviour. Therefore, I would need two types of elements CCVS and VCVS. If I understand it correct the CCVS and VCVS are linear elements which cannot be changed (easily).
I thought that a user defined element would be perfect. Unfortunately the documentation is very little so far
" """
Adds a user defined element.

    In order for this to work, you should write a module that supplies the
    elem class.

    XXX WRITE DOC

"
Could you tell me what exactly is meant by elem class? or could you give an example of a user defined element.

Thanks a lot!

BR Stephan

[itdaniher]

Stephan - I'll make time to look into this, see if I can't point you in the right direction. Rgds!

[itdaniher]

Stephan - I believe the documentation you're searching for may be found at http://ahkab.readthedocs.org/en/latest/devices.html. The "elem class" should, as best I can tell, be the "Component" class.

You will need to define a subclass of "Component" and implement a small set of builtin methods.

[asraelis]

Many thanks,
I 'll try to create such an element according to the document asap.

BR Stephan

[itdaniher]

@asraelis Any luck?

[asraelis]

Not yet - Although I think i got a working dummy class, but I could not test it yet since the circuit.add_user_defined() method makes some problems. Tryed to make some changes but I just run into other issues, which seem to be linked with the "imp" module. At the moment i do not know if it is a issue of ahkab or of my coding skill.
I am planning to prepare a better description of the issues but this week I am really busy. I hope I can post a more straight forward report at the end of this week.

BR Stephan

[itdaniher]

Great, I'll keep an eye out for your update, looking forward to helping you work through this!

BR,
Ian

[asraelis]

Hello again,

here is my short report:

I have saved my classfile own_ahkab_classes.py in my actual wd and I tried to add a userdefined element with:

 mycircuit.add_user_defined(own_ahkab_classes,Butler_Volmer,{'p1':1})

then python says " name 'module_name' is not defined".

As mentioned above I tried to make some little changes to "circuit.py" since "module_name" is used within circuit.py (see below) but I just managed it to get other errors within the imp.py file (after importing it) on my system:

Error:

File "C:\Anaconda3\lib\site-packages\ahkab\circuit.py", line 995, in add_user_defined
fp, pathname, description = imp.find_module(module_name)

File "C:\Anaconda3\lib\imp.py", line 297, in find_module
raise ImportError(_ERR_MSG.format(name), name=name)

ImportError: No module named "<module 'own_ahkab_classes' from 'F:\\Python Scripts\\own_ahkab_classes.py'>

File:

#part of circuit.py including "module_name"

def add_user_defined(self, module, label, param_dict):
    """Adds a user defined element.

    In order for this to work, you should write a module that supplies the
    elem class.

    XXX WRITE DOC
    """
    """
    changed part
    """
    self.user_defined_modules_dict = {"own_ahkab_classes" : own_ahkab_classes}
    module_name = str(module)
    circuit = self
    """
    end of changed part
    """
    if module_name in circuit.user_defined_modules_dict:
        module = circuit.user_defined_modules_dict[module_name]
    else:
        fp, pathname, description = imp.find_module(module_name)
        module = imp.load_module(module_name, fp, pathname, description)
        circuit.user_defined_modules_dict.update({module_name: module})

    elem_class = getattr(module, label)

    param_dict.update({"convert_units": convert_units})
    param_dict.update({"circuit_node": self.add_node})

    elem = elem_class(**param_dict)
    elem.part_id = "y%s" % part_id[1:]

    # call check() if supported
    if hasattr(elem, "check"):
        selfcheck_result, error_msg = elem.check()
        if not selfcheck_result:
            raise NetlistParseError("module: " + module_name + \
                                    " elem type: " + elem_type_name + \
                                    " error: " + error_msg)

    self.append(elem)

APPENDIX:

own_ahkab_classes.py is basically a capacitor elem with little changes to test "add_user_defined()" and has no special purpose yet. It looks like this right now:

DEBUG = True

import ahkab

class Butler_Volmer(ahkab.devices.Component):
    """
    see
    http://ahkab.readthedocs.org/en/latest/devices.html#ahkab.devices.Component
    """
    """A capacitor.

    .. image:: images/elem/capacitor.svg

    **Parameters:**

    part_id : string
        The unique identifier of this element. The first letter should be
        ``'C'``.
    n1 : int
        *Internal* node to be connected to the anode.
   n2 : int
        *Internal* node to be connected to the cathode.
    value : float
        The capacitance in Farads.
    ic : float
        The initial condition (IC) to be used for time-based simulations,
        such as TRAN analyses, when requested, expressed in Volt.

    """
    #
    def __init__(self, part_id, n1, n2, value, ic=None):
        self.part_id = part_id
        self.value = value
        self.n1 = n1
        self.n2 = n2
        self.ic = ic
        self.is_nonlinear = True
        self.is_symbolic = False


    def get_ports(self):
        return ((self.n1,self.n2))


    def g(self, v, time=0):
        return 0


    def i(self, v, time=0):
        return 3*self.value**v


    def d(self, v, time=0):
        return self.value


    def get_op_info(self, ports_v):
        """Information regarding the Operating Point (OP)

        **Parameters:**

        ports_v : list of lists
            The parameter is to be set to ``[[v]]``, where ``v`` is the voltage
            applied to the capacitor terminals.

        **Returns:**

        op_keys : list of strings
            The labels corresponding to the numeric values in ``op_info``.
        op_info : list of floats
            The values corresponding to ``op_keys``.
        """
        vn1n2 = float(ports_v[0][0])
        qn1n2 = float(ports_v[0][0] * self.value)
        energy = float(.5 * ports_v[0][0] ** 2 * self.value)

        op_keys = ['Part ID', "V(n1-n2) [V]", "Q [C]", "E [J]"]
        op_info = [self.part_id.upper(), vn1n2, qn1n2, energy]
        return op_keys, op_info

if DEBUG:
    """
    First Test of class
    """
    bv1 = Butler_Volmer('BV1', 'n1', 'n2', 2)
    print ("DEBUG = True line 98 of DLSEC.py ==> str(bv1.d(1)) = " 
            + str(bv1.d(1)) + "\n")  
"""

BR Stephan

[AnthonyFraser]

Not sure whether this is still open, but I was successful in adding my own element using the original method, e.g. below I add the element ant.ant to the circuit.

cir = ahkab.Circuit('testbench_ant_device')
n1=cir.add_node('n1')
n2=cir.add_node('n2')
gnd=cir.add_node(cir.gnd)
elem1 = ahkab.devices.Resistor(part_id='R1',n1=n1,n2=n2,value=100)
cir.append(elem1)
elem2 = ant.ant(part_id='R2',n1=n2,n2=gnd,value=100)
cir.append(elem2)

cir.add_vsource('Vref','n1',cir.gnd,dc_value=10)
op = ahkab.new_op()
res = ahkab.run(cir,op)

Cheers,
Anthony

[asraelis]

Yes it is still open for me altough i found a workaround by means of ltspice.

I am testing your solution at the moment hopefully figuring out how it works

BR stephan