1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2017, Jeffrey Roberson <[email protected]>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <sys/cdefs.h>
30 #include <sys/param.h>
31 #include <sys/kernel.h>
32 #include <sys/systm.h>
33 #include <sys/sysctl.h>
34 #include <sys/pidctrl.h>
35
36 void
pidctrl_init(struct pidctrl * pc,int interval,int setpoint,int bound,int Kpd,int Kid,int Kdd)37 pidctrl_init(struct pidctrl *pc, int interval, int setpoint, int bound,
38 int Kpd, int Kid, int Kdd)
39 {
40
41 bzero(pc, sizeof(*pc));
42 pc->pc_setpoint = setpoint;
43 pc->pc_interval = interval;
44 pc->pc_bound = bound * setpoint * Kid;
45 pc->pc_Kpd = Kpd;
46 pc->pc_Kid = Kid;
47 pc->pc_Kdd = Kdd;
48 }
49
50 void
pidctrl_init_sysctl(struct pidctrl * pc,struct sysctl_oid_list * parent)51 pidctrl_init_sysctl(struct pidctrl *pc, struct sysctl_oid_list *parent)
52 {
53
54 SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "error", CTLFLAG_RD,
55 &pc->pc_error, 0, "Current difference from setpoint value (P)");
56 SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "olderror", CTLFLAG_RD,
57 &pc->pc_olderror, 0, "Error value from last interval");
58 SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "integral", CTLFLAG_RD,
59 &pc->pc_integral, 0, "Accumulated error integral (I)");
60 SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "derivative", CTLFLAG_RD,
61 &pc->pc_derivative, 0, "Error derivative (D)");
62 SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "input", CTLFLAG_RD,
63 &pc->pc_input, 0, "Last controller process variable input");
64 SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "output", CTLFLAG_RD,
65 &pc->pc_output, 0, "Last controller output");
66 SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "ticks", CTLFLAG_RD,
67 &pc->pc_ticks, 0, "Last controller runtime");
68 SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "setpoint", CTLFLAG_RW,
69 &pc->pc_setpoint, 0, "Desired level for process variable");
70 SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "interval", CTLFLAG_RD,
71 &pc->pc_interval, 0, "Interval between calculations (ticks)");
72 SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "bound", CTLFLAG_RW,
73 &pc->pc_bound, 0, "Integral wind-up limit");
74 SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "kpd", CTLFLAG_RW,
75 &pc->pc_Kpd, 0, "Inverse of proportional gain");
76 SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "kid", CTLFLAG_RW,
77 &pc->pc_Kid, 0, "Inverse of integral gain");
78 SYSCTL_ADD_INT(NULL, parent, OID_AUTO, "kdd", CTLFLAG_RW,
79 &pc->pc_Kdd, 0, "Inverse of derivative gain");
80 }
81
82 int
pidctrl_classic(struct pidctrl * pc,int input)83 pidctrl_classic(struct pidctrl *pc, int input)
84 {
85 int output, error;
86 int Kpd, Kid, Kdd;
87
88 error = pc->pc_setpoint - input;
89 pc->pc_ticks = ticks;
90 pc->pc_olderror = pc->pc_error;
91
92 /* Fetch gains and prevent divide by zero. */
93 Kpd = MAX(pc->pc_Kpd, 1);
94 Kid = MAX(pc->pc_Kid, 1);
95 Kdd = MAX(pc->pc_Kdd, 1);
96
97 /* Compute P (proportional error), I (integral), D (derivative). */
98 pc->pc_error = error;
99 pc->pc_integral =
100 MAX(MIN(pc->pc_integral + error, pc->pc_bound), -pc->pc_bound);
101 pc->pc_derivative = error - pc->pc_olderror;
102
103 /* Divide by inverse gain values to produce output. */
104 output = (pc->pc_error / Kpd) + (pc->pc_integral / Kid) +
105 (pc->pc_derivative / Kdd);
106 /* Save for sysctl. */
107 pc->pc_output = output;
108 pc->pc_input = input;
109
110 return (output);
111 }
112
113 int
pidctrl_daemon(struct pidctrl * pc,int input)114 pidctrl_daemon(struct pidctrl *pc, int input)
115 {
116 int output, error;
117 int Kpd, Kid, Kdd;
118
119 error = pc->pc_setpoint - input;
120 /*
121 * When ticks expires we reset our variables and start a new
122 * interval. If we're called multiple times during one interval
123 * we attempt to report a target as if the entire error came at
124 * the interval boundary.
125 */
126 if ((u_int)ticks - pc->pc_ticks >= pc->pc_interval) {
127 pc->pc_ticks = ticks;
128 pc->pc_olderror = pc->pc_error;
129 pc->pc_output = pc->pc_error = 0;
130 } else {
131 /* Calculate the error relative to the last call. */
132 error -= pc->pc_error - pc->pc_output;
133 }
134
135 /* Fetch gains and prevent divide by zero. */
136 Kpd = MAX(pc->pc_Kpd, 1);
137 Kid = MAX(pc->pc_Kid, 1);
138 Kdd = MAX(pc->pc_Kdd, 1);
139
140 /* Compute P (proportional error), I (integral), D (derivative). */
141 pc->pc_error += error;
142 pc->pc_integral =
143 MAX(MIN(pc->pc_integral + error, pc->pc_bound), 0);
144 pc->pc_derivative = pc->pc_error - pc->pc_olderror;
145
146 /* Divide by inverse gain values to produce output. */
147 output = (pc->pc_error / Kpd) + (pc->pc_integral / Kid) +
148 (pc->pc_derivative / Kdd);
149 output = MAX(output - pc->pc_output, 0);
150 /* Save for sysctl. */
151 pc->pc_output += output;
152 pc->pc_input = input;
153
154 return (output);
155 }
156