added: tips about ManualEstimator in error message

Author: franckgaga

src/controller/construct.jl

@@ -1,3 +1,6 @@
+const MSG_LINMODEL_ERR = "estim.model type must be a LinModel, see ManualEstimator docstring "*
+                         "to use a nonlinear state estimator with a linear controller"
+
 struct PredictiveControllerBuffer{NT<:Real}
     u ::Vector{NT}
     Z̃ ::Vector{NT}

src/controller/explicitmpc.jl

@@ -157,7 +157,7 @@ function ExplicitMPC(
     N_Hc = Diagonal(repeat(Nwt, Hc)),
     L_Hp = Diagonal(repeat(Lwt, Hp)),
 ) where {NT<:Real, SE<:StateEstimator{NT}}
-    isa(estim.model, LinModel) || error("estim.model type must be a LinModel") 
+    isa(estim.model, LinModel) || error(MSG_LINMODEL_ERR) 
     nk = estimate_delays(estim.model)
     if Hp ≤ nk
         @warn("prediction horizon Hp ($Hp) ≤ estimated number of delays in model "*

src/controller/linmpc.jl

@@ -256,7 +256,7 @@ function LinMPC(
     transcription::TranscriptionMethod = DEFAULT_LINMPC_TRANSCRIPTION,
     optim::JM = JuMP.Model(DEFAULT_LINMPC_OPTIMIZER, add_bridges=false),
 ) where {NT<:Real, SE<:StateEstimator{NT}, JM<:JuMP.GenericModel}
-    isa(estim.model, LinModel) || error("estim.model type must be a LinModel") 
+    isa(estim.model, LinModel) || error(MSG_LINMODEL_ERR) 
     nk = estimate_delays(estim.model)
     if Hp ≤ nk
         @warn("prediction horizon Hp ($Hp) ≤ estimated number of delays in model "*