Merge pull request #183 from JuliaControl/simplify_diff_solvers

Changed: `RungeKutta` no longer uses `DiffCache`

Author: franckgaga

Project.toml

@@ -1,7 +1,7 @@
 name = "ModelPredictiveControl"
 uuid = "61f9bdb8-6ae4-484a-811f-bbf86720c31c"
 authors = ["Francis Gagnon"]
-version = "1.5.0"
+version = "1.5.1"
 
 [deps]
 ControlSystemsBase = "aaaaaaaa-a6ca-5380-bf3e-84a91bcd477e"
@@ -12,7 +12,6 @@ JuMP = "4076af6c-e467-56ae-b986-b466b2749572"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 Logging = "56ddb016-857b-54e1-b83d-db4d58db5568"
 OSQP = "ab2f91bb-94b4-55e3-9ba0-7f65df51de79"
-PreallocationTools = "d236fae5-4411-538c-8e31-a6e3d9e00b46"
 PrecompileTools = "aea7be01-6a6a-4083-8856-8a6e6704d82a"
 ProgressLogging = "33c8b6b6-d38a-422a-b730-caa89a2f386c"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
@@ -29,7 +28,6 @@ JuMP = "1.21"
 LinearAlgebra = "1.10"
 Logging = "1.10"
 OSQP = "0.8"
-PreallocationTools = "0.4.14"
 PrecompileTools = "1"
 ProgressLogging = "0.1"
 Random = "1.10"

src/ModelPredictiveControl.jl

@@ -25,8 +25,6 @@ import JuMP
 import JuMP: MOIU, MOI, GenericModel, Model, optimizer_with_attributes, register
 import JuMP: @variable, @operator, @constraint, @objective
 
-import PreallocationTools: DiffCache, get_tmp # TODO: remove this dep if possible (with Cache of DI.jl)
-
 import OSQP, Ipopt
 
 export SimModel, LinModel, NonLinModel

src/controller/execute.jl

@@ -113,24 +113,27 @@ julia> round.(getinfo(mpc)[:Ŷ], digits=3)
 ```
 """
 function getinfo(mpc::PredictiveController{NT}) where NT<:Real
-    model, transcription = mpc.estim.model, mpc.transcription
-    nΔŨ      = mpc.Hc*model.nu + mpc.nϵ
+    model, buffer, transcription = mpc.estim.model, mpc.buffer, mpc.transcription
+    nΔŨ, nK = mpc.Hc*model.nu + mpc.nϵ, mpc.Hp*model.nk
     nŶe, nUe = (mpc.Hp+1)*model.ny, (mpc.Hp+1)*model.nu
     nX̂0, nÛ0 = mpc.estim.nx̂*mpc.Hp, model.nu*mpc.Hp 
     Z̃ = mpc.Z̃
     info = Dict{Symbol, Any}()
-    ΔŨ = Vector{NT}(undef, nΔŨ)
-    x̂0end = similar(mpc.estim.x̂0)
+    ΔŨ     = Vector{NT}(undef, nΔŨ)
+    x̂0end  = similar(mpc.estim.x̂0)
+    K0     = Vector{NT}(undef, nK) 
     Ue, Ŷe = Vector{NT}(undef, nUe), Vector{NT}(undef, nŶe)
     U0, Ŷ0 = similar(mpc.Uop), similar(mpc.Yop)
     Û0, X̂0 = Vector{NT}(undef, nÛ0), Vector{NT}(undef, nX̂0)
-    U,  Ŷ  = similar(mpc.Uop), similar(mpc.Yop)
+    U,  Ŷ  = buffer.U, buffer.Ŷ
+    D̂      = buffer.D̂
     U0 = getU0!(U0, mpc, Z̃)
     ΔŨ = getΔŨ!(ΔŨ, mpc, transcription, Z̃)
-    Ŷ0, x̂0end  = predict!(Ŷ0, x̂0end, X̂0, Û0, mpc, model, transcription, U0, Z̃)
+    Ŷ0, x̂0end  = predict!(Ŷ0, x̂0end, X̂0, Û0, K0, mpc, model, transcription, U0, Z̃)
     Ue, Ŷe = extended_vectors!(Ue, Ŷe, mpc, U0, Ŷ0)
     U .= U0 .+ mpc.Uop
     Ŷ .= Ŷ0 .+ mpc.Yop
+    D̂ .= mpc.D̂0 + mpc.Dop
     J = obj_nonlinprog!(Ŷ0, U0, mpc, model, Ue, Ŷe, ΔŨ)
     Ŷs = similar(mpc.Yop)
     predictstoch!(Ŷs, mpc, mpc.estim)
@@ -140,7 +143,7 @@ function getinfo(mpc::PredictiveController{NT}) where NT<:Real
     info[:U]    = U
     info[:u]    = info[:U][1:model.nu]
     info[:d]    = mpc.d0 + model.dop
-    info[:D̂]    = mpc.D̂0 + mpc.Dop
+    info[:D̂]    = D̂
     info[:ŷ]    = mpc.ŷ
     info[:Ŷ]    = Ŷ
     info[:x̂end] = x̂0end + mpc.estim.x̂op

src/controller/explicitmpc.jl

@@ -195,7 +195,7 @@ optim_objective!(mpc::ExplicitMPC) = lmul!(-1, ldiv!(mpc.Z̃, mpc.H̃_chol, mpc.
 
 "Compute the predictions but not the terminal states if `mpc` is an [`ExplicitMPC`](@ref)."
 function predict!(
-    Ŷ0, x̂0end, _ , _ , mpc::ExplicitMPC, ::LinModel, ::TranscriptionMethod, _ , Z̃
+    Ŷ0, x̂0end, _ , _ , _ , mpc::ExplicitMPC, ::LinModel, ::TranscriptionMethod, _ , Z̃
 )
     # in-place operations to reduce allocations :
     Ŷ0    .= mul!(Ŷ0, mpc.Ẽ, Z̃) .+ mpc.F

src/controller/nonlinmpc.jl

@@ -578,15 +578,17 @@ Inspired from: [User-defined operators with vector outputs](@extref JuMP User-de
 function get_optim_functions(mpc::NonLinMPC, ::JuMP.GenericModel{JNT}) where JNT<:Real
     # ----- common cache for Jfunc, gfuncs, geqfuncs called with floats -------------------
     model = mpc.estim.model
-    nu, ny, nx̂, nϵ, Hp, Hc = model.nu, model.ny, mpc.estim.nx̂, mpc.nϵ, mpc.Hp, mpc.Hc
+    nu, ny, nx̂, nϵ, nk = model.nu, model.ny, mpc.estim.nx̂, mpc.nϵ, model.nk
+    Hp, Hc = mpc.Hp, mpc.Hc
     ng, nc, neq = length(mpc.con.i_g), mpc.con.nc, mpc.con.neq
-    nZ̃, nU, nŶ, nX̂ = length(mpc.Z̃), Hp*nu, Hp*ny, Hp*nx̂
+    nZ̃, nU, nŶ, nX̂, nK = length(mpc.Z̃), Hp*nu, Hp*ny, Hp*nx̂, Hp*nk
     nΔŨ, nUe, nŶe = nu*Hc + nϵ, nU + nu, nŶ + ny  
     strict = Val(true)
     myNaN  = convert(JNT, NaN)  # NaN to force update_simulations! at first call:
     Z̃ ::Vector{JNT}                  = fill(myNaN, nZ̃)
     ΔŨ::Vector{JNT}                  = zeros(JNT, nΔŨ)
     x̂0end::Vector{JNT}               = zeros(JNT, nx̂)
+    K0::Vector{JNT}                  = zeros(JNT, nK)
     Ue::Vector{JNT}, Ŷe::Vector{JNT} = zeros(JNT, nUe), zeros(JNT, nŶe)
     U0::Vector{JNT}, Ŷ0::Vector{JNT} = zeros(JNT, nU),  zeros(JNT, nŶ)
     Û0::Vector{JNT}, X̂0::Vector{JNT} = zeros(JNT, nU),  zeros(JNT, nX̂)
@@ -596,18 +598,18 @@ function get_optim_functions(mpc::NonLinMPC, ::JuMP.GenericModel{JNT}) where JNT
     function Jfunc(Z̃arg::Vararg{T, N}) where {N, T<:Real}
         if isdifferent(Z̃arg, Z̃)
             Z̃ .= Z̃arg
-            update_predictions!(ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, X̂0, gc, g, geq, mpc, Z̃)
+            update_predictions!(ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, K0, X̂0, gc, g, geq, mpc, Z̃)
         end
         return obj_nonlinprog!(Ŷ0, U0, mpc, model, Ue, Ŷe, ΔŨ)::T
     end
-    function Jfunc!(Z̃, ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, X̂0, gc, g, geq)
-        update_predictions!(ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, X̂0, gc, g, geq, mpc, Z̃)
+    function Jfunc!(Z̃, ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, K0, X̂0, gc, g, geq)
+        update_predictions!(ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, K0, X̂0, gc, g, geq, mpc, Z̃)
         return obj_nonlinprog!(Ŷ0, U0, mpc, model, Ue, Ŷe, ΔŨ)
     end
     Z̃_∇J = fill(myNaN, nZ̃) 
     ∇J_context = (
         Cache(ΔŨ), Cache(x̂0end), Cache(Ue), Cache(Ŷe), Cache(U0), Cache(Ŷ0), 
-        Cache(Û0), Cache(X̂0), 
+        Cache(Û0), Cache(K0), Cache(X̂0), 
         Cache(gc), Cache(g), Cache(geq),
     )
     ∇J_prep = prepare_gradient(Jfunc!, mpc.gradient, Z̃_∇J, ∇J_context...; strict)
@@ -631,19 +633,23 @@ function get_optim_functions(mpc::NonLinMPC, ::JuMP.GenericModel{JNT}) where JNT
         gfunc_i = function (Z̃arg::Vararg{T, N}) where {N, T<:Real}
             if isdifferent(Z̃arg, Z̃)
                 Z̃ .= Z̃arg
-                update_predictions!(ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, X̂0, gc, g, geq, mpc, Z̃)
+                update_predictions!(
+                    ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, K0, X̂0, gc, g, geq, mpc, Z̃
+                )
             end
             return g[i]::T
         end
         gfuncs[i] = gfunc_i
     end
-    function gfunc!(g, Z̃, ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, X̂0, gc, geq)
-        return update_predictions!(ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, X̂0, gc, g, geq, mpc, Z̃)
+    function gfunc!(g, Z̃, ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, K0, X̂0, gc, geq)
+        return update_predictions!(
+            ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, K0, X̂0, gc, g, geq, mpc, Z̃
+        )
     end
     Z̃_∇g = fill(myNaN, nZ̃)
     ∇g_context = (
         Cache(ΔŨ), Cache(x̂0end), Cache(Ue), Cache(Ŷe), Cache(U0), Cache(Ŷ0), 
-        Cache(Û0), Cache(X̂0), 
+        Cache(Û0), Cache(K0),   Cache(X̂0), 
         Cache(gc), Cache(geq),
     )
     # temporarily enable all the inequality constraints for sparsity detection:
@@ -678,19 +684,23 @@ function get_optim_functions(mpc::NonLinMPC, ::JuMP.GenericModel{JNT}) where JNT
         geqfunc_i = function (Z̃arg::Vararg{T, N}) where {N, T<:Real}
             if isdifferent(Z̃arg, Z̃)
                 Z̃ .= Z̃arg
-                update_predictions!(ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, X̂0, gc, g, geq, mpc, Z̃)
+                update_predictions!(
+                    ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, K0, X̂0, gc, g, geq, mpc, Z̃
+                )
             end
             return geq[i]::T
         end
         geqfuncs[i] = geqfunc_i          
     end
-    function geqfunc!(geq, Z̃, ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, X̂0, gc, g) 
-        return update_predictions!(ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, X̂0, gc, g, geq, mpc, Z̃)
+    function geqfunc!(geq, Z̃, ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, K0, X̂0, gc, g) 
+        return update_predictions!(
+            ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, K0, X̂0, gc, g, geq, mpc, Z̃
+        )
     end
     Z̃_∇geq = fill(myNaN, nZ̃)
     ∇geq_context = (
         Cache(ΔŨ), Cache(x̂0end), Cache(Ue), Cache(Ŷe), Cache(U0), Cache(Ŷ0),
-        Cache(Û0), Cache(X̂0),
+        Cache(Û0), Cache(K0),   Cache(X̂0),
         Cache(gc), Cache(g)
     )
     ∇geq_prep = prepare_jacobian(geqfunc!, geq, mpc.jacobian, Z̃_∇geq, ∇geq_context...; strict)
@@ -716,7 +726,7 @@ end
 
 """
     update_predictions!(
-        ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, X̂0, gc, g, geq, 
+        ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, K0, X̂0, gc, g, geq, 
         mpc::PredictiveController, Z̃
     ) -> nothing
 
@@ -725,17 +735,17 @@ Update in-place all vectors for the predictions of `mpc` controller at decision
 The method mutates all the arguments before the `mpc` argument.
 """
 function update_predictions!(
-    ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, X̂0, gc, g, geq, mpc::PredictiveController, Z̃
+    ΔŨ, x̂0end, Ue, Ŷe, U0, Ŷ0, Û0, K0, X̂0, gc, g, geq, mpc::PredictiveController, Z̃
 )
     model, transcription = mpc.estim.model, mpc.transcription
     U0 = getU0!(U0, mpc, Z̃)
     ΔŨ = getΔŨ!(ΔŨ, mpc, transcription, Z̃)
-    Ŷ0, x̂0end  = predict!(Ŷ0, x̂0end, X̂0, Û0, mpc, model, transcription, U0, Z̃)
+    Ŷ0, x̂0end  = predict!(Ŷ0, x̂0end, X̂0, Û0, K0, mpc, model, transcription, U0, Z̃)
     Ue, Ŷe = extended_vectors!(Ue, Ŷe, mpc, U0, Ŷ0)
     ϵ = getϵ(mpc, Z̃)
     gc  = con_custom!(gc, mpc, Ue, Ŷe, ϵ)
     g   = con_nonlinprog!(g, mpc, model, transcription, x̂0end, Ŷ0, gc, ϵ)
-    geq = con_nonlinprogeq!(geq, X̂0, Û0, mpc, model, transcription, U0, Z̃)
+    geq = con_nonlinprogeq!(geq, X̂0, Û0, K0, mpc, model, transcription, U0, Z̃)
     return nothing
 end
 

src/controller/transcription.jl

@@ -1028,7 +1028,7 @@ getU0!(U0, mpc::PredictiveController, Z̃) = (mul!(U0, mpc.P̃u, Z̃) .+ mpc.Tu_
 
 @doc raw"""
     predict!(
-        Ŷ0, x̂0end, _ , _ ,
+        Ŷ0, x̂0end, _ , _ , _ ,
         mpc::PredictiveController, model::LinModel, transcription::TranscriptionMethod, 
         _ , Z̃
     ) -> Ŷ0, x̂0end
@@ -1040,7 +1040,7 @@ the terminal constraints applied on ``\mathbf{x̂}_{k-1}(k+H_p)``. The computati
 identical for any [`TranscriptionMethod`](@ref) if the model is linear.
 """
 function predict!(
-    Ŷ0, x̂0end, _ , _ , 
+    Ŷ0, x̂0end, _, _, _,
     mpc::PredictiveController, ::LinModel, ::TranscriptionMethod, 
     _ , Z̃
 )
@@ -1052,29 +1052,31 @@ end
 
 @doc raw"""
     predict!(
-        Ŷ0, x̂0end, X̂0, Û0, 
+        Ŷ0, x̂0end, X̂0, Û0, K0,
         mpc::PredictiveController, model::NonLinModel, transcription::SingleShooting,
         U0, _
     ) -> Ŷ0, x̂0end
 
 Compute vectors if `model` is a [`NonLinModel`](@ref) and for [`SingleShooting`](@ref).
     
-The method mutates `Ŷ0`, `x̂0end`, `X̂0` and `Û0` arguments.
+The method mutates `Ŷ0`, `x̂0end`, `X̂0`, `Û0` and `K0` arguments.
 """
 function predict!(
-    Ŷ0, x̂0end, X̂0, Û0,
+    Ŷ0, x̂0end, X̂0, Û0, K0,
     mpc::PredictiveController, model::NonLinModel, ::SingleShooting,
     U0, _
 )
-    nu, nx̂, ny, nd, Hp, Hc = model.nu, mpc.estim.nx̂, model.ny, model.nd, mpc.Hp, mpc.Hc
+    nu, nx̂, ny, nd, nk = model.nu, mpc.estim.nx̂, model.ny, model.nd, model.nk
+    Hp, Hc = mpc.Hp, mpc.Hc
     D̂0 = mpc.D̂0
     x̂0 = @views mpc.estim.x̂0[1:nx̂]
     d0 = @views mpc.d0[1:nd]
     for j=1:Hp
         u0     = @views U0[(1 + nu*(j-1)):(nu*j)]
         û0     = @views Û0[(1 + nu*(j-1)):(nu*j)]
+        k0     = @views K0[(1 + nk*(j-1)):(nk*j)]
         x̂0next = @views X̂0[(1 + nx̂*(j-1)):(nx̂*j)]
-        f̂!(x̂0next, û0, mpc.estim, model, x̂0, u0, d0)
+        f̂!(x̂0next, û0, k0, mpc.estim, model, x̂0, u0, d0)
         x̂0next .+= mpc.estim.f̂op .- mpc.estim.x̂op
         x̂0 = @views X̂0[(1 + nx̂*(j-1)):(nx̂*j)]
         d0 = @views D̂0[(1 + nd*(j-1)):(nd*j)]
@@ -1088,7 +1090,7 @@ end
 
 @doc raw"""
     predict!(
-        Ŷ0, x̂0end, _ , _ , 
+        Ŷ0, x̂0end, _ , _ , _ , 
         mpc::PredictiveController, model::NonLinModel, transcription::MultipleShooting,
         U0, Z̃
     ) -> Ŷ0, x̂0end
@@ -1098,7 +1100,7 @@ Compute vectors if `model` is a [`NonLinModel`](@ref) and for [`MultipleShooting
 The method mutates `Ŷ0` and `x̂0end` arguments.
 """
 function predict!(
-    Ŷ0, x̂0end, _, _,
+    Ŷ0, x̂0end, _, _, _,
     mpc::PredictiveController, model::NonLinModel, ::MultipleShooting,
     U0, Z̃
 )
@@ -1204,17 +1206,20 @@ end
 
 """
     con_nonlinprogeq!(
-        geq, X̂0, Û0, mpc::PredictiveController, model::NonLinModel, ::MultipleShooting, U0, Z̃
+        geq, X̂0, Û0, K0
+        mpc::PredictiveController, model::NonLinModel, ::MultipleShooting, U0, Z̃
     )
 
 Nonlinear equality constrains for [`NonLinModel`](@ref) and [`MultipleShooting`](@ref).
 
-The method mutates the `geq`, `X̂0` and `Û0` vectors in argument.
+The method mutates the `geq`, `X̂0`, `Û0` and `K0` vectors in argument.
 """
 function con_nonlinprogeq!(
-    geq, X̂0, Û0, mpc::PredictiveController, model::NonLinModel, ::MultipleShooting, U0, Z̃
+    geq, X̂0, Û0, K0, 
+    mpc::PredictiveController, model::NonLinModel, ::MultipleShooting, U0, Z̃
 )
-    nx̂, nu, nd, Hp, Hc = mpc.estim.nx̂, model.nu, model.nd, mpc.Hp, mpc.Hc
+    nu, nx̂, ny, nd, nk = model.nu, mpc.estim.nx̂, model.ny, model.nd, model.nk
+    Hp, Hc = mpc.Hp, mpc.Hc
     nΔU, nX̂ = nu*Hc, nx̂*Hp
     D̂0 = mpc.D̂0
     X̂0_Z̃ = @views Z̃[(nΔU+1):(nΔU+nX̂)]
@@ -1225,7 +1230,8 @@ function con_nonlinprogeq!(
         u0     = @views U0[(1 + nu*(j-1)):(nu*j)]
         û0     = @views Û0[(1 + nu*(j-1)):(nu*j)]
         x̂0next = @views X̂0[(1 + nx̂*(j-1)):(nx̂*j)]
-        f̂!(x̂0next, û0, mpc.estim, model, x̂0, u0, d0)
+        k0     = @views K0[(1 + nk*(j-1)):(nk*j)]
+        f̂!(x̂0next, û0, k0, mpc.estim, model, x̂0, u0, d0)
         x̂0next .+= mpc.estim.f̂op .- mpc.estim.x̂op
         x̂0next_Z̃ = @views X̂0_Z̃[(1 + nx̂*(j-1)):(nx̂*j)]       
         ŝnext    = @views  geq[(1 + nx̂*(j-1)):(nx̂*j)]
@@ -1235,5 +1241,5 @@ function con_nonlinprogeq!(
     end
     return geq
 end
-con_nonlinprogeq!(geq,_,_,::PredictiveController,::NonLinModel,::SingleShooting,  _,_) = geq
-con_nonlinprogeq!(geq,_,_,::PredictiveController,::LinModel,::TranscriptionMethod,_,_) = geq
+con_nonlinprogeq!(geq,_,_,_,::PredictiveController,::NonLinModel,::SingleShooting,  _,_)=geq
+con_nonlinprogeq!(geq,_,_,_,::PredictiveController,::LinModel,::TranscriptionMethod,_,_)=geq

src/estimator/construct.jl

@@ -1,6 +1,7 @@
 struct StateEstimatorBuffer{NT<:Real}
     u ::Vector{NT}
     û ::Vector{NT}
+    k::Vector{NT}
     x̂ ::Vector{NT}
     P̂ ::Matrix{NT}
     Q̂ ::Matrix{NT}
@@ -13,17 +14,18 @@ struct StateEstimatorBuffer{NT<:Real}
 end
 
 @doc raw"""
-    StateEstimatorBuffer{NT}(nu::Int, nx̂::Int, nym::Int, ny::Int, nd::Int)
+    StateEstimatorBuffer{NT}(nu::Int, nx̂::Int, nym::Int, ny::Int, nd::Int, nk::Int=0)
 
 Create a buffer for `StateEstimator` objects for estimated states and measured outputs.
 
 The buffer is used to store intermediate results during estimation without allocating.
 """
 function StateEstimatorBuffer{NT}(
-    nu::Int, nx̂::Int, nym::Int, ny::Int, nd::Int
+    nu::Int, nx̂::Int, nym::Int, ny::Int, nd::Int, nk::Int=0
 ) where NT <: Real
     u  = Vector{NT}(undef, nu)
     û  = Vector{NT}(undef, nu)
+    k  = Vector{NT}(undef, nk)
     x̂  = Vector{NT}(undef, nx̂)
     P̂  = Matrix{NT}(undef, nx̂, nx̂)
     Q̂  = Matrix{NT}(undef, nx̂, nx̂)
@@ -33,7 +35,7 @@ function StateEstimatorBuffer{NT}(
     ŷ  = Vector{NT}(undef, ny)
     d  = Vector{NT}(undef, nd)
     empty = Vector{NT}(undef, 0)
-    return StateEstimatorBuffer{NT}(u, û, x̂, P̂, Q̂, R̂, K̂, ym, ŷ, d, empty)
+    return StateEstimatorBuffer{NT}(u, û, k, x̂, P̂, Q̂, R̂, K̂, ym, ŷ, d, empty)
 end
 
 @doc raw"""