Patrick Venture | d801218 | 2018-03-08 08:21:38 -0800 | [diff] [blame] | 1 | /** |
| 2 | * Copyright 2017 Google Inc. |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | #include "pid.hpp" |
| 18 | |
| 19 | namespace ec |
| 20 | { |
| 21 | |
| 22 | /******************************** |
| 23 | * clamp |
| 24 | * |
| 25 | */ |
Patrick Venture | 5f59c0f | 2018-11-11 12:55:14 -0800 | [diff] [blame] | 26 | static double clamp(double x, double min, double max) |
Patrick Venture | d801218 | 2018-03-08 08:21:38 -0800 | [diff] [blame] | 27 | { |
| 28 | if (x < min) |
| 29 | { |
| 30 | return min; |
| 31 | } |
| 32 | else if (x > max) |
| 33 | { |
| 34 | return max; |
| 35 | } |
| 36 | return x; |
| 37 | } |
| 38 | |
| 39 | /******************************** |
| 40 | * pid code |
| 41 | * Note: Codes assumes the ts field is non-zero |
| 42 | */ |
Patrick Venture | 5f59c0f | 2018-11-11 12:55:14 -0800 | [diff] [blame] | 43 | double pid(pid_info_t* pidinfoptr, double input, double setpoint) |
Patrick Venture | d801218 | 2018-03-08 08:21:38 -0800 | [diff] [blame] | 44 | { |
Patrick Venture | 5f59c0f | 2018-11-11 12:55:14 -0800 | [diff] [blame] | 45 | double error; |
Patrick Venture | d801218 | 2018-03-08 08:21:38 -0800 | [diff] [blame] | 46 | |
Patrick Venture | 5f59c0f | 2018-11-11 12:55:14 -0800 | [diff] [blame] | 47 | double p_term; |
| 48 | double i_term = 0.0f; |
| 49 | double ff_term = 0.0f; |
Patrick Venture | d801218 | 2018-03-08 08:21:38 -0800 | [diff] [blame] | 50 | |
Patrick Venture | 5f59c0f | 2018-11-11 12:55:14 -0800 | [diff] [blame] | 51 | double output; |
Patrick Venture | d801218 | 2018-03-08 08:21:38 -0800 | [diff] [blame] | 52 | |
| 53 | // calculate P, I, D, FF |
| 54 | |
| 55 | // Pid |
Patrick Venture | da4a5dd | 2018-08-31 09:42:48 -0700 | [diff] [blame] | 56 | error = setpoint - input; |
| 57 | p_term = pidinfoptr->p_c * error; |
Patrick Venture | d801218 | 2018-03-08 08:21:38 -0800 | [diff] [blame] | 58 | |
| 59 | // pId |
| 60 | if (0.0f != pidinfoptr->i_c) |
| 61 | { |
Patrick Venture | da4a5dd | 2018-08-31 09:42:48 -0700 | [diff] [blame] | 62 | i_term = pidinfoptr->integral; |
| 63 | i_term += error * pidinfoptr->i_c * pidinfoptr->ts; |
| 64 | i_term = clamp(i_term, pidinfoptr->i_lim.min, pidinfoptr->i_lim.max); |
Patrick Venture | d801218 | 2018-03-08 08:21:38 -0800 | [diff] [blame] | 65 | } |
| 66 | |
| 67 | // FF |
| 68 | ff_term = (setpoint + pidinfoptr->ff_off) * pidinfoptr->ff_gain; |
| 69 | |
| 70 | output = p_term + i_term + ff_term; |
| 71 | output = clamp(output, pidinfoptr->out_lim.min, pidinfoptr->out_lim.max); |
| 72 | |
| 73 | // slew rate |
| 74 | // TODO(aarena) - Simplify logic as Andy suggested by creating dynamic |
| 75 | // out_lim_min/max that are affected by slew rate control and just clamping |
| 76 | // to those instead of effectively clamping twice. |
| 77 | if (pidinfoptr->initialized) |
| 78 | { |
| 79 | if (pidinfoptr->slew_neg != 0.0f) |
| 80 | { |
| 81 | // Don't decrease too fast |
Patrick Venture | 5f59c0f | 2018-11-11 12:55:14 -0800 | [diff] [blame] | 82 | double min_out = |
Patrick Venture | da4a5dd | 2018-08-31 09:42:48 -0700 | [diff] [blame] | 83 | pidinfoptr->last_output + pidinfoptr->slew_neg * pidinfoptr->ts; |
Patrick Venture | d801218 | 2018-03-08 08:21:38 -0800 | [diff] [blame] | 84 | if (output < min_out) |
| 85 | { |
| 86 | output = min_out; |
| 87 | } |
| 88 | } |
| 89 | if (pidinfoptr->slew_pos != 0.0f) |
| 90 | { |
| 91 | // Don't increase too fast |
Patrick Venture | 5f59c0f | 2018-11-11 12:55:14 -0800 | [diff] [blame] | 92 | double max_out = |
Patrick Venture | da4a5dd | 2018-08-31 09:42:48 -0700 | [diff] [blame] | 93 | pidinfoptr->last_output + pidinfoptr->slew_pos * pidinfoptr->ts; |
Patrick Venture | d801218 | 2018-03-08 08:21:38 -0800 | [diff] [blame] | 94 | if (output > max_out) |
| 95 | { |
| 96 | output = max_out; |
| 97 | } |
| 98 | } |
| 99 | |
| 100 | if (pidinfoptr->slew_neg != 0.0f || pidinfoptr->slew_pos != 0.0f) |
| 101 | { |
| 102 | // Back calculate integral term for the cases where we limited the |
| 103 | // output |
| 104 | i_term = output - p_term; |
| 105 | } |
| 106 | } |
| 107 | |
| 108 | // Clamp again because having limited the output may result in a |
| 109 | // larger integral term |
Patrick Venture | da4a5dd | 2018-08-31 09:42:48 -0700 | [diff] [blame] | 110 | i_term = clamp(i_term, pidinfoptr->i_lim.min, pidinfoptr->i_lim.max); |
Patrick Venture | d801218 | 2018-03-08 08:21:38 -0800 | [diff] [blame] | 111 | pidinfoptr->integral = i_term; |
Patrick Venture | da4a5dd | 2018-08-31 09:42:48 -0700 | [diff] [blame] | 112 | pidinfoptr->initialized = true; |
| 113 | pidinfoptr->last_output = output; |
Patrick Venture | d801218 | 2018-03-08 08:21:38 -0800 | [diff] [blame] | 114 | |
| 115 | return output; |
| 116 | } |
| 117 | |
Patrick Venture | da4a5dd | 2018-08-31 09:42:48 -0700 | [diff] [blame] | 118 | } // namespace ec |