From 9ac4d039a591c273a3dd6bc8ed67fa6da78a1077 Mon Sep 17 00:00:00 2001
From: Cas Bex <cas.bex@kuleuven.be>
Date: Thu, 29 Jun 2023 10:03:06 +0200
Subject: [PATCH 1/2] Add zero-integral test for P controller with saturation

---
 test/runtests.jl | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/test/runtests.jl b/test/runtests.jl
index 59d4adc..2edb274 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -134,9 +134,10 @@ res2 = lsim(P, ctrl, 3)
 
 # plot([res, res2], plotu=true)
 @test maximum(res2.u) == umax
+@test pid.I == 0.0
 
 
 @test DiscretePID(Ts=1f0) isa DiscretePID{Float32}
 @test DiscretePID(Ts=1.0) isa DiscretePID{Float64}
 
-end
\ No newline at end of file
+end

From 211ac8ba328475ef61e8148b140940f0db686d7b Mon Sep 17 00:00:00 2001
From: Cas Bex <cas.bex@kuleuven.be>
Date: Thu, 29 Jun 2023 10:04:48 +0200
Subject: [PATCH 2/2] Fix anti-windup for P controller

---
 src/DiscretePIDs.jl | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/DiscretePIDs.jl b/src/DiscretePIDs.jl
index 487bd0e..d3c9680 100644
--- a/src/DiscretePIDs.jl
+++ b/src/DiscretePIDs.jl
@@ -75,7 +75,11 @@ function DiscretePID(;
     0 ≤ b ≤ 1 || throw(ArgumentError("b must be ∈ [0, 1]"))
     umax > umin || throw(ArgumentError("umax must be greater than umin"))
 
-    ar = Ts / Tt
+    if Ti > 0
+        ar = Ts / Tt
+    else
+        ar = zero(Ts / Tt)
+    end
     ad = Td / (Td + N * Ts)
     bd = K * N * ad