Add clamping to pid controller, make arguments more readable

2 files changed, 23 insertions, 11 deletions

diff --git a/src/core/lib/transport/pid_controller.c b/src/core/lib/transport/pid_controller.c
index ba56874503..3a4845d7ef 100644
--- a/src/core/lib/transport/pid_controller.c
+++ b/src/core/lib/transport/pid_controller.c
@@ -32,14 +32,12 @@
  */
 
 #include "src/core/lib/transport/pid_controller.h"
+#include <grpc/support/useful.h>
 
 void grpc_pid_controller_init(grpc_pid_controller *pid_controller,
-                              double initial_control_value, double gain_p,
-                              double gain_i, double gain_d) {
-  pid_controller->last_control_value = initial_control_value;
-  pid_controller->gain_p = gain_p;
-  pid_controller->gain_i = gain_i;
-  pid_controller->gain_d = gain_d;
+                              grpc_pid_controller_args args) {
+  pid_controller->args = args;
+  pid_controller->last_control_value = args.initial_control_value;
   grpc_pid_controller_reset(pid_controller);
 }
 
@@ -53,13 +51,20 @@ double grpc_pid_controller_update(grpc_pid_controller *pid_controller,
   /* integrate error using the trapezoid rule */
   pid_controller->error_integral +=
       dt * (pid_controller->last_error + error) * 0.5;
+  pid_controller->error_integral = GPR_CLAMP(
+      pid_controller->error_integral, -pid_controller->args.integral_range,
+      pid_controller->args.integral_range);
   double diff_error = (error - pid_controller->last_error) / dt;
   /* calculate derivative of control value vs time */
-  double dc_dt = pid_controller->gain_p * error +
-                 pid_controller->gain_i * pid_controller->error_integral +
-                 pid_controller->gain_d * diff_error;
+  double dc_dt = pid_controller->args.gain_p * error +
+                 pid_controller->args.gain_i * pid_controller->error_integral +
+                 pid_controller->args.gain_d * diff_error;
+  /* and perform trapezoidal integration */
   double new_control_value = pid_controller->last_control_value +
                              dt * (pid_controller->last_dc_dt + dc_dt) * 0.5;
+  new_control_value =
+      GPR_CLAMP(new_control_value, pid_controller->args.min_control_value,
+                pid_controller->args.max_control_value);
   pid_controller->last_error = error;
   pid_controller->last_dc_dt = dc_dt;
   pid_controller->last_control_value = new_control_value;
diff --git a/src/core/lib/transport/pid_controller.h b/src/core/lib/transport/pid_controller.h
index dd2b120052..1bf2fbc564 100644
--- a/src/core/lib/transport/pid_controller.h
+++ b/src/core/lib/transport/pid_controller.h
@@ -45,16 +45,23 @@ typedef struct {
   double gain_p;
   double gain_i;
   double gain_d;
+  double initial_control_value;
+  double min_control_value;
+  double max_control_value;
+  double integral_range;
+} grpc_pid_controller_args;
+
+typedef struct {
   double last_error;
   double error_integral;
   double last_control_value;
   double last_dc_dt;
+  grpc_pid_controller_args args;
 } grpc_pid_controller;
 
 /** Initialize the controller */
 void grpc_pid_controller_init(grpc_pid_controller *pid_controller,
-                              double initial_control_value, double gain_p,
-                              double gain_i, double gain_d);
+                              grpc_pid_controller_args args);
 
 /** Reset the controller: useful when things have changed significantly */
 void grpc_pid_controller_reset(grpc_pid_controller *pid_controller);