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feat(thermocycler-gen2): add filtering to peltier output (#435)
* Added a PeltierFilter class to constrain peltier outputs during closed loop control
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stm32-modules/include/thermocycler-gen2/thermocycler-gen2/peltier_filter.hpp
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| /** | ||
| * @file peltier_filter.hpp | ||
| * @brief Implements a simple filter on the output power of a peltier to | ||
| * enforce a maximum ∆power/sec limit. | ||
| */ | ||
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| #pragma once | ||
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| #include "systemwide.h" | ||
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| namespace peltier_filter { | ||
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| using PowerPerSec = double; | ||
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| /** Number of seconds in 100ms */ | ||
| static constexpr double ONE_HUNDRED_MS = 0.1; | ||
| /** | ||
| * Maximum rate of change is -100% to 100% in one hundred milliseconds. | ||
| * This effectively means that changing from max cooling to max heating | ||
| * will take 100ms. | ||
| */ | ||
| static constexpr PowerPerSec MAX_DELTA = (2.0 / ONE_HUNDRED_MS); | ||
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| /** | ||
| * Provides a simple filter on Peltier power values to ease the stress on | ||
| * on the peltiers over their lifetime. | ||
| */ | ||
| class PeltierFilter { | ||
| public: | ||
| /** | ||
| * @brief Reset the filter. This should be called whenever a peltier is | ||
| * disabled. | ||
| */ | ||
| auto reset() -> void; | ||
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| /** | ||
| * @brief Set a new peltier power value and filter it based on the | ||
| * last value that was set. | ||
| * | ||
| * @param setting The desired power, in the range [-1.0, 1.0] | ||
| * @param delta_sec The number of seconds that have elapsed since the | ||
| * last setting. | ||
| * @return The power that should be set on the peltier. | ||
| */ | ||
| [[nodiscard]] auto set_filtered(double setting, double delta_sec) -> double; | ||
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| /** | ||
| * @brief Get the last filtered setting for this peltier. | ||
| * | ||
| * @return The most recent filtered setting | ||
| */ | ||
| [[nodiscard]] auto get_last() const -> double; | ||
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| private: | ||
| /** The last setting for this peltier.*/ | ||
| double _last = 0.0; | ||
| }; | ||
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| } // namespace peltier_filter |
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| #include "thermocycler-gen2/peltier_filter.hpp" | ||
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| #include <algorithm> | ||
| #include <cstdlib> | ||
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| using namespace peltier_filter; | ||
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| auto PeltierFilter::reset() -> void { _last = 0.0F; } | ||
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| [[nodiscard]] auto PeltierFilter::set_filtered(double setting, double delta_sec) | ||
| -> double { | ||
| setting = std::clamp(setting, -1.0, 1.0); | ||
| const auto max_change = delta_sec * MAX_DELTA; | ||
| if (std::abs(setting - _last) > max_change) { | ||
| // Just change by the max change for this tick | ||
| auto change = (setting > _last) ? max_change : -max_change; | ||
| setting = _last + change; | ||
| } | ||
| _last = setting; | ||
| return _last; | ||
| } | ||
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| [[nodiscard]] auto PeltierFilter::get_last() const -> double { return _last; } |
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stm32-modules/thermocycler-gen2/tests/test_peltier_filter.cpp
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| #include <vector> | ||
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| #include "catch2/catch.hpp" | ||
| #include "thermocycler-gen2/peltier_filter.hpp" | ||
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| TEST_CASE("peltier filter functionality") { | ||
| using namespace peltier_filter; | ||
| auto subject = PeltierFilter(); | ||
| REQUIRE(subject.get_last() == 0.0F); | ||
| WHEN("setting power outside of the filter limits") { | ||
| const auto TIME_DELTA = GENERATE(0.01, 0.02); | ||
| const auto SETTING = GENERATE(1.0, -1.0); | ||
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| auto result = subject.set_filtered(SETTING, TIME_DELTA); | ||
| THEN("the result is filtered") { | ||
| auto expected = MAX_DELTA * TIME_DELTA * (SETTING > 0 ? 1 : -1); | ||
| REQUIRE_THAT(result, Catch::Matchers::WithinAbs(expected, 0.01)); | ||
| AND_WHEN("doing it again") { | ||
| result = subject.set_filtered(SETTING, TIME_DELTA); | ||
| THEN("the result is doubled") { | ||
| REQUIRE_THAT( | ||
| result, Catch::Matchers::WithinAbs(expected * 2, 0.01)); | ||
| } | ||
| } | ||
| } | ||
| THEN("getting the last result matches expected") { | ||
| REQUIRE(subject.get_last() == result); | ||
| } | ||
| } | ||
| WHEN("setting power within filter limits") { | ||
| const auto TIME_DELTA = GENERATE(0.1, 0.5, 1.0); | ||
| const auto SETTING = GENERATE(1.0, -1.0, -0.245, 0.64); | ||
| auto result = subject.set_filtered(SETTING, TIME_DELTA); | ||
| THEN("the result is not filtered at all") { | ||
| REQUIRE_THAT(result, Catch::Matchers::WithinAbs(SETTING, 0.01)); | ||
| } | ||
| } | ||
| WHEN("setting power at 10ms intervals") { | ||
| const auto TIME_DELTA = 0.01; | ||
| THEN("it increments as expected") { | ||
| std::vector<double> expected = {0.2, 0.4, 0.6, 0.8, 1.0, 1.0}; | ||
| std::vector<double> result; | ||
| for (auto i = 0; i < 6; ++i) { | ||
| result.push_back(subject.set_filtered(1.0, TIME_DELTA)); | ||
| } | ||
| REQUIRE_THAT(result, Catch::Matchers::Approx(expected)); | ||
| } | ||
| } | ||
| } |