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/**
* Copyright (c) 2012 Precise Path Robotics, Inc
* Copyright (c) 2017 Luke Shumaker
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* @author Luke Shumaker <lukeshu@sbcglobal.net>
*/
package org.usfirst.frc.team4272.robotlib;
import edu.wpi.first.wpilibj.PIDOutput;
import edu.wpi.first.wpilibj.Timer;
/**
* RateLimitedPIDOutput wraps a {@link PIDOutput}, unsuring that the
* set value does not change too quickly.
*
* If the writer attempts to call {@link pidWrite(double)} with a
* value that is too different than the previous value; it will
* instead write a value that is closer to the previous value.
*/
public class RateLimitedPIDOutput implements PIDOutput {
PIDOutput o;
double m;
double prev_rate = 0;
double prev_time = 0;
/**
* @param out The actual PIDOutput to write to.
* @param maxChange the maximum amount that the setpoint can
* change by per second.
*/
public RateLimitedPIDOutput(PIDOutput out, double maxChange) {
o = out;
m = maxChange;
}
public void pidWrite(double rate) {
double time = Timer.getFPGATimestamp();
double dTime = time-prev_time;
double dRate = rate-prev_rate;
if (Math.abs(dRate/dTime)>m) {
int sign = (dRate<0?-1:1);
rate = prev_rate+(m*dTime*sign);
}
o.pidWrite(rate);
}
}
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