| /* |
| * |
| * Copyright 2016 gRPC authors. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| * |
| */ |
| |
| #include "src/core/lib/transport/pid_controller.h" |
| #include <grpc/support/useful.h> |
| |
| void grpc_pid_controller_init(grpc_pid_controller *pid_controller, |
| grpc_pid_controller_args args) { |
| pid_controller->args = args; |
| pid_controller->last_control_value = args.initial_control_value; |
| grpc_pid_controller_reset(pid_controller); |
| } |
| |
| void grpc_pid_controller_reset(grpc_pid_controller *pid_controller) { |
| pid_controller->last_error = 0.0; |
| pid_controller->last_dc_dt = 0.0; |
| pid_controller->error_integral = 0.0; |
| } |
| |
| double grpc_pid_controller_update(grpc_pid_controller *pid_controller, |
| double error, double dt) { |
| if (dt == 0) return pid_controller->last_control_value; |
| /* 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->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; |
| return new_control_value; |
| } |
| |
| double grpc_pid_controller_last(grpc_pid_controller *pid_controller) { |
| return pid_controller->last_control_value; |
| } |