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/*
*
* 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;
}
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