50 lines
1.3 KiB
C++
50 lines
1.3 KiB
C++
#pragma once
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/* slew rate limiting filter. This is used to prevent oscillation of a
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* controller by modifying the controllers output based on a maximum
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* slew rate
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*/
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#include <stdint.h>
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#include "LowPassFilter.h"
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#define SLEWLIMITER_N_EVENTS 2 // number of positive and negative consecutive slew rate exceedance events recorded where a value of 2 corresponds to a complete cycle
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class SlewLimiter {
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public:
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SlewLimiter(const float &slew_rate_max, const float &slew_rate_tau);
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CLASS_NO_COPY(SlewLimiter);
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/*
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apply filter to sample, returning multiplier between 0 and 1 to keep
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output within slew rate
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*/
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float modifier(float sample, float dt);
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/*
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get last oscillation slew rate
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*/
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float get_slew_rate(void) const {
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return _output_slew_rate;
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}
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private:
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const float &slew_rate_max;
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const float &slew_rate_tau;
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LowPassFilterFloat slew_filter;
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float _output_slew_rate;
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float _modifier_slew_rate;
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float last_sample;
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float _max_pos_slew_rate;
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float _max_neg_slew_rate;
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uint32_t _max_pos_slew_event_ms;
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uint32_t _max_neg_slew_event_ms;
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uint8_t _pos_event_index;
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uint8_t _neg_event_index;
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uint32_t _pos_event_ms[SLEWLIMITER_N_EVENTS];
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uint32_t _neg_event_ms[SLEWLIMITER_N_EVENTS];
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bool _pos_event_stored;
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bool _neg_event_stored;
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};
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