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[wpimath] Add direction to slew rate limiter (#4377)

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This commit is contained in:
ohowe
2022-09-01 15:46:46 -06:00
committed by GitHub
parent fafc81ed1a
commit b5a17f762c
4 changed files with 94 additions and 16 deletions
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49
wpimath/src/main/native/include/frc/filter/SlewRateLimiter.h
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@@ -6,6 +6,7 @@
#include <algorithm>
#include <wpi/deprecated.h>
#include <wpi/timestamp.h>
#include "units/time.h"
@@ -28,15 +29,45 @@ class SlewRateLimiter {
using Rate_t = units::unit_t<Rate>;
/**
* Creates a new SlewRateLimiter with the given rate limit and initial value.
* Creates a new SlewRateLimiter with the given positive and negative rate
* limits and initial value.
*
* @param positiveRateLimit The rate-of-change limit in the positive
* direction, in units per second. This is expected
* to be positive.
* @param negativeRateLimit The rate-of-change limit in the negative
* direction, in units per second. This is expected
* to be negative.
* @param initialValue The initial value of the input.
*/
SlewRateLimiter(Rate_t positiveRateLimit, Rate_t negativeRateLimit,
Unit_t initialValue = Unit_t{0})
: m_positiveRateLimit{positiveRateLimit},
m_negativeRateLimit{negativeRateLimit},
m_prevVal{initialValue},
m_prevTime{units::microsecond_t(wpi::Now())} {}
/**
* Creates a new SlewRateLimiter with the given positive rate limit and
* negative rate limit of -rateLimit.
*
* @param rateLimit The rate-of-change limit.
*/
explicit SlewRateLimiter(Rate_t rateLimit)
: SlewRateLimiter(rateLimit, -rateLimit) {}
/**
* Creates a new SlewRateLimiter with the given positive rate limit and
* negative rate limit of -rateLimit and initial value.
*
* @param rateLimit The rate-of-change limit.
* @param initialValue The initial value of the input.
*/
explicit SlewRateLimiter(Rate_t rateLimit, Unit_t initialValue = Unit_t{0})
: m_rateLimit{rateLimit},
m_prevVal{initialValue},
m_prevTime{units::microsecond_t(wpi::Now())} {}
WPI_DEPRECATED(
"Use SlewRateLimiter(Rate_t positiveRateLimit, Rate_t negativeRateLimit, "
"Unit_t initalValue) instead")
SlewRateLimiter(Rate_t rateLimit, Unit_t initialValue)
: SlewRateLimiter(rateLimit, -rateLimit, initialValue) {}
/**
* Filters the input to limit its slew rate.
@@ -48,8 +79,9 @@ class SlewRateLimiter {
Unit_t Calculate(Unit_t input) {
units::second_t currentTime = units::microsecond_t(wpi::Now());
units::second_t elapsedTime = currentTime - m_prevTime;
m_prevVal += std::clamp(input - m_prevVal, -m_rateLimit * elapsedTime,
m_rateLimit * elapsedTime);
m_prevVal +=
std::clamp(input - m_prevVal, m_negativeRateLimit * elapsedTime,
m_positiveRateLimit * elapsedTime);
m_prevTime = currentTime;
return m_prevVal;
}
@@ -66,7 +98,8 @@ class SlewRateLimiter {
}
private:
Rate_t m_rateLimit;
Rate_t m_positiveRateLimit;
Rate_t m_negativeRateLimit;
Unit_t m_prevVal;
units::second_t m_prevTime;
};