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[wpilib] Fix timestamp slew in SlewRateLimiter (#2627)

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Fixes #2626.
This commit is contained in:
Tyler Veness
2020-08-02 00:06:52 -07:00
committed by GitHub
parent aba035eb3d
commit 2f81f2b78a
2 changed files with 20 additions and 16 deletions
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18
wpilibc/src/main/native/include/frc/SlewRateLimiter.h
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@@ -37,9 +37,9 @@ class SlewRateLimiter {
* @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_timer.Start();
}
: m_rateLimit{rateLimit},
m_prevVal{initialValue},
m_prevTime{frc2::Timer::GetFPGATimestamp()} {}
/**
* Filters the input to limit its slew rate.
@@ -49,9 +49,11 @@ class SlewRateLimiter {
* rate.
*/
Unit_t Calculate(Unit_t input) {
m_prevVal += std::clamp(input - m_prevVal, -m_rateLimit * m_timer.Get(),
m_rateLimit * m_timer.Get());
m_timer.Reset();
units::second_t currentTime = frc2::Timer::GetFPGATimestamp();
units::second_t elapsedTime = currentTime - m_prevTime;
m_prevVal += std::clamp(input - m_prevVal, -m_rateLimit * elapsedTime,
m_rateLimit * elapsedTime);
m_prevTime = currentTime;
return m_prevVal;
}
@@ -62,13 +64,13 @@ class SlewRateLimiter {
* @param value The value to reset to.
*/
void Reset(Unit_t value) {
m_timer.Reset();
m_prevVal = value;
m_prevTime = frc2::Timer::GetFPGATimestamp();
}
private:
frc2::Timer m_timer;
Rate_t m_rateLimit;
Unit_t m_prevVal;
units::second_t m_prevTime;
};
} // namespace frc