Add a bias term to interface spec.

src/LabProcesses.jl

-#__precompile__()
+__precompile__()
 
 module LabProcesses
 

src/controllers.jl

@@ -24,6 +24,7 @@ function run_control_2DOF(P::AbstractProcess,sysFB, sysFF=nothing; duration = 10
 		rf = sysFF == nothing ? r[i] : sysfilter!(stateFF, sysFF, r[i])
 		e  = rf-y[i]
 		ui = sysfilter!(stateFB, sysFB, e)[1]
+		ui + bias(P)
 	end
 
 	initialize(P)

src/interface.jl

@@ -24,6 +24,7 @@ inputrange(p::AbstractProcess)  = error("Function not implemented for $(typeof(p
 isstable(p::AbstractProcess)    = error("Function not implemented for $(typeof(p))")
 isasstable(p::AbstractProcess)  = error("Function not implemented for $(typeof(p))")
 sampletime(p::AbstractProcess)  = error("Function not implemented for $(typeof(p))")
+bias(p::AbstractProcess)        = error("Function not implemented for $(typeof(p))")
 
 control(p::AbstractProcess, u)  = error("Function not implemented for $(typeof(p))")
 measure(p::AbstractProcess)     = error("Function not implemented for $(typeof(p))")

src/interface_documentation.jl

@@ -62,6 +62,14 @@ Return the sample time of the process in seconds.
 """
 sampletime
 
+"""
+    b = bias(P::AbstractProcess)
+Return an input bias for the process. This could be, i.e., the constant input u₀ around which
+a nonlinear system is linearized, or whatever other bias might exist on the input.
+`length(b) = num_inputs(P)`
+"""
+bias
+
 """
     control(P::AbstractProcess, u)
 Send a control signal to the process. `u` must have dimension equal to `num_inputs(P)`

src/interface_implementations/ballandbeam.jl

@@ -22,6 +22,9 @@ inputrange(p::BallAndBeamType)  = [(-10,10)]
 isstable(p::BallAndBeamType)    = false
 isasstable(p::BallAndBeamType)  = false
 sampletime(p::BallAndBeamType)  = p.h
+bias(p::BallAndBeam)            = p.bias
+bias(p::BallAndBeamSimulator)   = 0
+
 
 control(p::BallAndBeam, u)  = ccall((:comedi_write, comedipath),Int32,
                                         (Int32,Int32,Int32,Int32),0,1,1,num2io(u[1]+p.bias))

src/interface_implementations/eth_helicopter.jl

@@ -4,11 +4,13 @@ export ETHHelicopter, ETHHelicopterSimulator, ETHHelicopterType
 
 struct ETHHelicopter <: PhysicalProcess
     h::Float64
+    bias::Float64
 end
 ETHHelicopter() = ETHHelicopter(0.050)
 
 struct ETHHelicopterSimulator <: SimulatedProcess
     h::Float64
+    bias::Float64
     state::Vector{Float64}
 end
 ETHHelicopterSimulator() = ETHHelicopterSimulator(0.01, zeros(4))
@@ -21,6 +23,8 @@ inputrange(p::ETHHelicopterType)  = [(-10,10)]
 isstable(p::ETHHelicopterType)    = false
 isasstable(p::ETHHelicopterType)  = false
 sampletime(p::ETHHelicopterType)  = p.h
+bias(p::ETHHelicopterType)        = p.bias
+
 
 function control(p::ETHHelicopter, u)
 	ccall((:comedi_write, comedipath),Int32,(Int32,Int32,Int32,Int32), 0,1,0,num2io(u[1]))