d330d7874a
The First Order Plus Delay Time module is a model of a controlled system that is useful in modelling and simulating process control systems. The Proportional Integral Differential module is a control system that is useful in controlling process control systems. This is not fully functional yet.
124 lines
3.6 KiB
Python
124 lines
3.6 KiB
Python
#!/usr/bin/env python
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# vim: ft=python ts=8 sts=4 sw=4 expandtab autoindent smartindent nocindent
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# Classes for device simulation using: First Order Plus Delay Time (FOPDT)
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#
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# Author: Unknown
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# Finder: Douglas Clowes
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"""
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The class fopdt is a container for one or more fopdt_sink objects.
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I am guessing that an fopdt_sink is a FOPDT source such as a heater element
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or FOPDT sink such as a heat leak to the environment.
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TODO:
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* look into the isinstance block in getAbsolute
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because there doesn't seem to be a 'current_value' anywhere
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"""
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from math import exp
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class fopdt_sink:
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def __init__(self, value, Kp, Tp, Td, absolute=False):
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self.value = value
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self.absolute = absolute
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self.Kp = Kp
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self.Tp = Tp
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self.Td = Td
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self.vmap = dict()
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def getAbsolute(self):
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if isinstance(self.value, fopdt):
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result = self.value.current_value
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else:
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result = self.value
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return result
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def getValue(self, tm, current):
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result = self.getAbsolute()
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# Do the timeshifting implied by Td
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t2 = round(tm)
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t1 = round(tm - self.Td)
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if not t2 in self.vmap:
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self.vmap[t2] = result
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for key in sorted(self.vmap.keys()):
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if key < t1:
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del self.vmap[key]
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else:
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break
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if t1 in self.vmap:
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result = self.vmap[t1]
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else:
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result = self.vmap[sorted(self.vmap.keys())[0]]
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# TODO should this go before timeshifting?
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if not self.absolute:
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result = result - current
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return result
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def getDelta(self, tm, current):
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value = self.getValue(tm, current)
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return (1 - exp(-1.0/self.Tp)) * self.Kp * value
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class fopdt:
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def __init__(self, pv):
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self.pv = pv
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self.sources = []
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self.sinks = []
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def AddSource(self, source):
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self.sources.append(source)
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def RemSource(self, source):
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if source in self.sources:
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self.sources.remove(source)
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def AddSink(self, sink):
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self.sinks.append(sink)
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def RemSink(self, sink):
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if sink in self.sinks:
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self.sinks.remove(sink)
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def iterate(self, tm):
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self.source_delta = 0.0
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self.sink_delta = 0.0
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for sink in self.sources:
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self.source_delta = self.source_delta + sink.getDelta(tm, self.pv)
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for sink in self.sinks:
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self.sink_delta = self.sink_delta + sink.getDelta(tm, self.pv)
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self.old_value = self.pv
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self.new_value = self.pv + self.source_delta + self.sink_delta
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self.pv = self.new_value
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if __name__ == "__main__":
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dev = fopdt(20)
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source = fopdt_sink(20, 2, 13, 10, False)
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dev.AddSource(source)
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dev.AddSource(source)
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dev.AddSource(source)
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dev.AddSource(source)
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sink = fopdt_sink(20, 1, 30, 1, False)
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dev.AddSink(sink)
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dev.AddSink(sink)
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min = max = dev.pv
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fd = open("test.csv", "w")
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fd.write("Time,value,source,source_v,sink,sink_v\n")
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for i in range(0,300+ 1):
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if i == 15:
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source.value = 30
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elif i == 45:
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source.value = 10
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dev.iterate(i)
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current = dev.pv
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if current > max:
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max = current
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if current < min:
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min = current
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#print "%3d: %6.3f = %6.3f + %6.3f + %6.3f" % ( i, current, prev, delta_in, delta_out )
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line = "%d,%.3f,%.3f,%.3f,%.3f,%.3f" % (i, current, source.value, dev.source_delta, sink.value, dev.sink_delta)
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fd.write(line + "\n")
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fd.close()
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print "Now: %6.3f, Min: %6.3f, Max: %6.3f" % (current, min, max)
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