Lag.java

/*
 * JaamSim Discrete Event Simulation
 * Copyright (C) 2013 Ausenco Engineering Canada Inc.
 * Copyright (C) 2016 JaamSim Software Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.jaamsim.CalculationObjects;

import com.jaamsim.input.Keyword;
import com.jaamsim.input.Output;
import com.jaamsim.input.ValueInput;
import com.jaamsim.units.TimeUnit;
import com.jaamsim.units.UserSpecifiedUnit;

/**
 * The Lag block is a standard control system component whose output is equal to integral(input - output) / LagTime.
 * This operation has the effect of delaying and smoothing the input signal over the time scale given by LagTime.
 * @author Harry King
 *
 */
public class Lag extends DoubleCalculation {

	@Keyword(description = "The time constant for this operation: "
	                     + "output = integral(input - output) / LagTime.",
	         exampleList = {"15 s"})
	private final ValueInput lagTime;

	{
		lagTime = new ValueInput("LagTime", "Key Inputs", 1.0d);
		lagTime.setValidRange(1.0e-10, Double.POSITIVE_INFINITY);
		lagTime.setUnitType(TimeUnit.class);
		this.addInput(lagTime);
	}

	public Lag() {}

	@Override
	public double calculateValue(double simTime, double inputVal, double lastTime, double lastInputVal, double lastVal) {
		double dt = simTime - lastTime;
		double error = inputVal - lastVal;
		return lastVal + dt*error/lagTime.getValue();
	}

	@Output(name = "Error",
	 description = "The value for InputValue - Value.",
	    unitType = UserSpecifiedUnit.class)
	public double getError(double simTime) {
		return this.getInputValue(simTime) - this.getLastValue();
	}

}