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/*
*
* Copyright 2016, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#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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