1 // autobrake.cxx - generic, configurable autobrake system
3 // Written by James Turner, started September 2009.
5 // Copyright (C) 2009 Curtis L. Olson
7 // This program is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU General Public License as
9 // published by the Free Software Foundation; either version 2 of the
10 // License, or (at your option) any later version.
12 // This program is distributed in the hope that it will be useful, but
13 // WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 // General Public License for more details.
17 // You should have received a copy of the GNU General Public License
18 // along with this program; if not, write to the Free Software
19 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
23 #include "autobrake.hxx"
25 #include <Main/fg_props.hxx>
27 FGAutoBrake::FGAutoBrake() :
28 _lastGroundspeedKts(0.0),
35 _fcsBrakeControl(0.0),
36 _leftBrakeOutput(0.0),
37 _rightBrakeOutput(0.0)
39 // default config, close to Boeing 747-400 / 777 values
42 _configMaxDecel = 11; // ft-sec-sec
43 _configRTODecel = 11; // ft-sec-sec
44 _configRTOSpeed = 85; // kts
47 FGAutoBrake::~FGAutoBrake()
51 void FGAutoBrake::init()
53 _root = fgGetNode("/autopilot/autobrake", true);
55 _root->tie("armed", SGRawValueMethods<FGAutoBrake, bool>
56 (*this, &FGAutoBrake::getArmed, &FGAutoBrake::setArmed));
58 _root->tie("step", SGRawValueMethods<FGAutoBrake, int>
59 (*this, &FGAutoBrake::getStep, &FGAutoBrake::setStep));
61 _root->tie("rto", SGRawValueMethods<FGAutoBrake, bool>
62 (*this, &FGAutoBrake::getRTO, &FGAutoBrake::setRTO));
64 _engineControlsNode = fgGetNode("/controls/engines");
66 // brake position nodes
67 _brakeInputs[0] = fgGetNode("/controls/gear/brake-left");
68 _brakeInputs[1] = fgGetNode("/controls/gear/brake-right");
69 _brakeInputs[2] = fgGetNode("/controls/gear/copilot-brake-left");
70 _brakeInputs[3] = fgGetNode("/controls/gear/copilot-brake-right");
73 SGPropertyNode_ptr config = _root->getChild("config", 0, true);
74 config->tie("num-steps", SGRawValuePointer<int>(&_configNumSteps));
75 config->tie("rto-step", SGRawValuePointer<int>(&_configRTOStep));
76 config->tie("rto-decel-fts-sec", SGRawValuePointer<double>(&_configRTODecel));
77 config->tie("max-decel-fts-sec", SGRawValuePointer<double>(&_configMaxDecel));
78 config->tie("rto-engage-kts", SGRawValuePointer<double>(&_configRTOSpeed));
81 _root->tie("target-decel-fts-sec",
82 SGRawValueMethods<FGAutoBrake,double>(*this, &FGAutoBrake::getTargetDecel));
83 _root->tie("actual-decel-fts-sec",
84 SGRawValueMethods<FGAutoBrake,double>(*this, &FGAutoBrake::getActualDecel));
85 _root->tie("fcs-brake", SGRawValuePointer<double>(&_fcsBrakeControl));
86 _root->tie("brake-left-output", SGRawValuePointer<double>(&_leftBrakeOutput));
87 _root->tie("brake-right-output", SGRawValuePointer<double>(&_rightBrakeOutput));
89 _root->tie("engaged", SGRawValueMethods<FGAutoBrake, bool>(*this, &FGAutoBrake::getEngaged));
92 void FGAutoBrake::postinit()
94 _weightOnWheelsNode = fgGetNode("/gear/gear/wow");
95 _groundspeedNode = fgGetNode("/velocities/groundspeed-kt");
96 _lastWoW = _weightOnWheelsNode->getBoolValue();
100 void FGAutoBrake::bind()
104 void FGAutoBrake::unbind()
108 void FGAutoBrake::update(double dt)
110 _leftBrakeInput = SGMiscd::max(_brakeInputs[0]->getDoubleValue(),
111 _brakeInputs[2]->getDoubleValue());
112 _rightBrakeInput = SGMiscd::max(_brakeInputs[1]->getDoubleValue(),
113 _brakeInputs[3]->getDoubleValue());
115 // various FDMs don't supply sufficent information for us to work,
116 // so just be passive in those cases.
117 if (!_weightOnWheelsNode || !_groundspeedNode || !_engineControlsNode) {
118 // pass the values straight through
119 _leftBrakeOutput = _leftBrakeInput;
120 _rightBrakeOutput = _rightBrakeInput;
128 double gs = _groundspeedNode->getDoubleValue();
129 _actualDecel = (_lastGroundspeedKts - gs) / dt;
130 _lastGroundspeedKts = gs;
132 if (!_armed || (_step == 0)) {
133 // even if we're off or disarmed, the physical valve system must pass
134 // pilot control values through.
135 _leftBrakeOutput = _leftBrakeInput;
136 _rightBrakeOutput = _rightBrakeInput;
143 bool e = shouldEngage();
150 // sum pilot inpiuts with auto-brake FCS input
151 _leftBrakeOutput = SGMiscd::max(_leftBrakeInput, _fcsBrakeControl);
152 _rightBrakeOutput = SGMiscd::max(_rightBrakeInput, _fcsBrakeControl);
154 _lastWoW = _weightOnWheelsNode->getBoolValue();
157 void FGAutoBrake::engage()
159 SG_LOG(SG_AUTOPILOT, SG_INFO, "FGAutoBrake: engaging");
163 void FGAutoBrake::updateEngaged(double dt)
165 // check for pilot braking input cancelling engage
166 const double BRAKE_INPUT_THRESHOLD = 0.02; // 2% application triggers
167 if ((_leftBrakeInput > BRAKE_INPUT_THRESHOLD) || (_rightBrakeInput > BRAKE_INPUT_THRESHOLD)) {
168 SG_LOG(SG_AUTOPILOT, SG_INFO, "auto-brake, detected pilot brake input, disengaing");
173 // update the target deceleration; note step can be changed while engaged
175 _targetDecel = _configRTODecel;
177 double f = (double) _step / _configNumSteps;
178 _targetDecel = _configMaxDecel * f;
182 bool FGAutoBrake::shouldEngage()
185 return shouldEngageRTO();
188 if (_lastWoW || !_weightOnWheelsNode->getBoolValue()) {
192 SG_LOG(SG_AUTOPILOT, SG_INFO, "Autobrake, should enage");
196 bool FGAutoBrake::shouldEngageRTO()
198 double speed = _groundspeedNode->getDoubleValue();
201 if (speed < _configRTOSpeed) {
202 SG_LOG(SG_AUTOPILOT, SG_INFO, "FGAutoBrake: RTO armed, but speed is now below arming speed");
207 if (!_weightOnWheelsNode->getBoolValue()) {
211 return throttlesAtIdle();
214 if (speed > _configRTOSpeed) {
215 SG_LOG(SG_AUTOPILOT, SG_INFO, "Autobrake RTO: passed " << _configRTOSpeed << " knots, arming RTO mode");
223 void FGAutoBrake::disengage()
229 SG_LOG(SG_AUTOPILOT, SG_INFO, "FGAutoBrake: disengage");
236 bool FGAutoBrake::throttlesAtIdle()
238 SGPropertyNode_ptr e;
239 const double IDLE_THROTTLE = 0.05; // 5% margin for idle setting
241 for (int index=0; (e = _engineControlsNode->getChild("engine", index)) != NULL; ++index) {
242 if ((e->getDoubleValue("throttle") > IDLE_THROTTLE) && !e->getBoolValue("reverser")) {
245 } // of engines iteration
247 SG_LOG(SG_AUTOPILOT, SG_INFO, "FGAutoBrake: throttles at idle");
251 void FGAutoBrake::setArmed(bool aArmed)
253 if (aArmed == _armed) {
261 void FGAutoBrake::setRTO(bool aRTO)
264 // ensure we meet RTO selection criteria:
265 if (!_weightOnWheelsNode->getBoolValue()) {
266 SG_LOG(SG_AUTOPILOT, SG_WARN, "auto-brake: cannot select RTO mode, no weight on wheels");
272 _step = _configRTOStep;
274 SG_LOG(SG_AUTOPILOT, SG_INFO, "RTO mode set");
278 // and if we're enaged?
283 void FGAutoBrake::setStep(int aStep)
285 if (aStep == _step) {
289 SG_LOG(SG_AUTOPILOT, SG_INFO, "Autobrake step now=" << aStep);
291 bool validStep = false;
293 if (aStep == _configRTOStep) {
298 validStep = (_step > 0) && (_step <= _configNumSteps);
301 setArmed(validStep); // selecting a valid step arms the system