1 /*
2 *
3 * Copyright 2016 gRPC authors.
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 */
18
19 #include <grpc/support/port_platform.h>
20
21 #include "src/core/lib/transport/pid_controller.h"
22
23 #include "src/core/lib/gpr/useful.h"
24
25 namespace grpc_core {
26
PidController(const Args & args)27 PidController::PidController(const Args& args)
28 : last_control_value_(args.initial_control_value()), args_(args) {}
29
Update(double error,double dt)30 double PidController::Update(double error, double dt) {
31 if (dt <= 0) return last_control_value_;
32 /* integrate error using the trapezoid rule */
33 error_integral_ += dt * (last_error_ + error) * 0.5;
34 error_integral_ = GPR_CLAMP(error_integral_, -args_.integral_range(),
35 args_.integral_range());
36 double diff_error = (error - last_error_) / dt;
37 /* calculate derivative of control value vs time */
38 double dc_dt = args_.gain_p() * error + args_.gain_i() * error_integral_ +
39 args_.gain_d() * diff_error;
40 /* and perform trapezoidal integration */
41 double new_control_value =
42 last_control_value_ + dt * (last_dc_dt_ + dc_dt) * 0.5;
43 new_control_value = GPR_CLAMP(new_control_value, args_.min_control_value(),
44 args_.max_control_value());
45 last_error_ = error;
46 last_dc_dt_ = dc_dt;
47 last_control_value_ = new_control_value;
48 return new_control_value;
49 }
50
51 } // namespace grpc_core
52