/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2017, Jeffrey Roberson <jeff@freebsd.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/sysctl.h>
#include <sys/pidctrl.h>
void
pidctrl_init(struct pidctrl *pc, int interval, int setpoint, int bound,
int Kpd, int Kid, int Kdd)
{
bzero(pc, sizeof(*pc));
pc->pc_setpoint = setpoint;
pc->pc_interval = interval;
pc->pc_bound = bound * setpoint * Kid;
pc->pc_Kpd = Kpd;
pc->pc_Kid = Kid;
pc->pc_Kdd = Kdd;
}
void
pidctrl_init_sysctl(struct pidctrl *pc, struct sysctl_oid_list *parent)
{
SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "error", CTLFLAG_RD,
&pc->pc_error, 0, "Current difference from setpoint value (P)");
SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "olderror", CTLFLAG_RD,
&pc->pc_olderror, 0, "Error value from last interval");
SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "integral", CTLFLAG_RD,
&pc->pc_integral, 0, "Accumulated error integral (I)");
SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "derivative", CTLFLAG_RD,
&pc->pc_derivative, 0, "Error derivative (D)");
SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "input", CTLFLAG_RD,
&pc->pc_input, 0, "Last controller process variable input");
SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "output", CTLFLAG_RD,
&pc->pc_output, 0, "Last controller output");
SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "ticks", CTLFLAG_RD,
&pc->pc_ticks, 0, "Last controller runtime");
SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "setpoint", CTLFLAG_RW,
&pc->pc_setpoint, 0, "Desired level for process variable");
SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "interval", CTLFLAG_RD,
&pc->pc_interval, 0, "Interval between calculations (ticks)");
SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "bound", CTLFLAG_RW,
&pc->pc_bound, 0, "Integral wind-up limit");
SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "kpd", CTLFLAG_RW,
&pc->pc_Kpd, 0, "Inverse of proportional gain");
SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "kid", CTLFLAG_RW,
&pc->pc_Kid, 0, "Inverse of integral gain");
SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "kdd", CTLFLAG_RW,
&pc->pc_Kdd, 0, "Inverse of derivative gain");
}
int
pidctrl_classic(struct pidctrl *pc, int input)
{
int output, error;
int Kpd, Kid, Kdd;
error = pc->pc_setpoint - input;
pc->pc_ticks = ticks;
pc->pc_olderror = pc->pc_error;
/* Fetch gains and prevent divide by zero. */
Kpd = MAX(pc->pc_Kpd, 1);
Kid = MAX(pc->pc_Kid, 1);
Kdd = MAX(pc->pc_Kdd, 1);
/* Compute P (proportional error), I (integral), D (derivative). */
pc->pc_error = error;
pc->pc_integral =
MAX(MIN(pc->pc_integral + error, pc->pc_bound), -pc->pc_bound);
pc->pc_derivative = error - pc->pc_olderror;
/* Divide by inverse gain values to produce output. */
output = (pc->pc_error / Kpd) + (pc->pc_integral / Kid) +
(pc->pc_derivative / Kdd);
/* Save for sysctl. */
pc->pc_output = output;
pc->pc_input = input;
return (output);
}
int
pidctrl_daemon(struct pidctrl *pc, int input)
{
int output, error;
int Kpd, Kid, Kdd;
error = pc->pc_setpoint - input;
/*
* When ticks expires we reset our variables and start a new
* interval. If we're called multiple times during one interval
* we attempt to report a target as if the entire error came at
* the interval boundary.
*/
if ((u_int)ticks - pc->pc_ticks >= pc->pc_interval) {
pc->pc_ticks = ticks;
pc->pc_olderror = pc->pc_error;
pc->pc_output = pc->pc_error = 0;
} else {
/* Calculate the error relative to the last call. */
error -= pc->pc_error - pc->pc_output;
}
/* Fetch gains and prevent divide by zero. */
Kpd = MAX(pc->pc_Kpd, 1);
Kid = MAX(pc->pc_Kid, 1);
Kdd = MAX(pc->pc_Kdd, 1);
/* Compute P (proportional error), I (integral), D (derivative). */
pc->pc_error += error;
pc->pc_integral =
MAX(MIN(pc->pc_integral + error, pc->pc_bound), 0);
pc->pc_derivative = pc->pc_error - pc->pc_olderror;
/* Divide by inverse gain values to produce output. */
output = (pc->pc_error / Kpd) + (pc->pc_integral / Kid) +
(pc->pc_derivative / Kdd);
output = MAX(output - pc->pc_output, 0);
/* Save for sysctl. */
pc->pc_output += output;
pc->pc_input = input;
return (output);
}
