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 _configDisengageStep = 0;
43 _configMaxDecel = 11; // ft-sec-sec
44 _configRTODecel = 11; // ft-sec-sec
45 _configRTOSpeed = 85; // kts
48 FGAutoBrake::~FGAutoBrake()
52 void FGAutoBrake::init()
54 _root = fgGetNode("/autopilot/autobrake", true);
56 _root->tie("armed", SGRawValueMethods<FGAutoBrake, bool>
57 (*this, &FGAutoBrake::getArmed, &FGAutoBrake::setArmed));
59 _root->tie("step", SGRawValueMethods<FGAutoBrake, int>
60 (*this, &FGAutoBrake::getStep, &FGAutoBrake::setStep));
62 _root->tie("rto", SGRawValueMethods<FGAutoBrake, bool>
63 (*this, &FGAutoBrake::getRTO, &FGAutoBrake::setRTO));
65 _engineControlsNode = fgGetNode("/controls/engines");
67 // brake position nodes
68 _brakeInputs[0] = fgGetNode("/controls/gear/brake-left");
69 _brakeInputs[1] = fgGetNode("/controls/gear/brake-right");
70 _brakeInputs[2] = fgGetNode("/controls/gear/copilot-brake-left");
71 _brakeInputs[3] = fgGetNode("/controls/gear/copilot-brake-right");
74 SGPropertyNode_ptr config = _root->getChild("config", 0, true);
75 config->tie("num-steps", SGRawValuePointer<int>(&_configNumSteps));
76 config->tie("rto-step", SGRawValuePointer<int>(&_configRTOStep));
77 config->tie("disengage-step", SGRawValuePointer<int>(&_configDisengageStep));
78 config->tie("rto-decel-fts-sec", SGRawValuePointer<double>(&_configRTODecel));
79 config->tie("max-decel-fts-sec", SGRawValuePointer<double>(&_configMaxDecel));
80 config->tie("rto-engage-kts", SGRawValuePointer<double>(&_configRTOSpeed));
84 _root->tie("target-decel-fts-sec",
85 SGRawValueMethods<FGAutoBrake,double>(*this, &FGAutoBrake::getTargetDecel));
86 _root->tie("actual-decel-fts-sec",
87 SGRawValueMethods<FGAutoBrake,double>(*this, &FGAutoBrake::getActualDecel));
88 _root->tie("fcs-brake", SGRawValuePointer<double>(&_fcsBrakeControl));
89 _root->tie("brake-left-output", SGRawValuePointer<double>(&_leftBrakeOutput));
90 _root->tie("brake-right-output", SGRawValuePointer<double>(&_rightBrakeOutput));
92 _root->tie("engaged", SGRawValueMethods<FGAutoBrake, bool>(*this, &FGAutoBrake::getEngaged));
95 void FGAutoBrake::postinit()
97 _weightOnWheelsNode = fgGetNode("/gear/gear/wow");
98 _groundspeedNode = fgGetNode("/velocities/groundspeed-kt");
99 _lastWoW = _weightOnWheelsNode->getBoolValue();
103 void FGAutoBrake::bind()
107 void FGAutoBrake::unbind()
111 void FGAutoBrake::update(double dt)
113 _leftBrakeInput = SGMiscd::max(_brakeInputs[0]->getDoubleValue(),
114 _brakeInputs[2]->getDoubleValue());
115 _rightBrakeInput = SGMiscd::max(_brakeInputs[1]->getDoubleValue(),
116 _brakeInputs[3]->getDoubleValue());
118 // various FDMs don't supply sufficent information for us to work,
119 // so just be passive in those cases.
120 if (!_weightOnWheelsNode || !_groundspeedNode || !_engineControlsNode) {
121 // pass the values straight through
122 _leftBrakeOutput = _leftBrakeInput;
123 _rightBrakeOutput = _rightBrakeInput;
131 double gs = _groundspeedNode->getDoubleValue();
132 _actualDecel = (_lastGroundspeedKts - gs) / dt;
133 _lastGroundspeedKts = gs;
135 if (!_armed || (_step == 0)) {
136 // even if we're off or disarmed, the physical valve system must pass
137 // pilot control values through.
138 _leftBrakeOutput = _leftBrakeInput;
139 _rightBrakeOutput = _rightBrakeInput;
146 bool e = shouldEngage();
153 // sum pilot inpiuts with auto-brake FCS input
154 _leftBrakeOutput = SGMiscd::max(_leftBrakeInput, _fcsBrakeControl);
155 _rightBrakeOutput = SGMiscd::max(_rightBrakeInput, _fcsBrakeControl);
157 _lastWoW = _weightOnWheelsNode->getBoolValue();
160 void FGAutoBrake::engage()
162 SG_LOG(SG_AUTOPILOT, SG_INFO, "FGAutoBrake: engaging");
166 void FGAutoBrake::updateEngaged(double dt)
168 // check for pilot braking input cancelling engage
169 const double BRAKE_INPUT_THRESHOLD = 0.02; // 2% application triggers
170 if ((_leftBrakeInput > BRAKE_INPUT_THRESHOLD) || (_rightBrakeInput > BRAKE_INPUT_THRESHOLD)) {
171 SG_LOG(SG_AUTOPILOT, SG_INFO, "auto-brake, detected pilot brake input, disengaing");
176 if (!throttlesAtIdle()) {
177 SG_LOG(SG_AUTOPILOT, SG_INFO, "auto-brake, throttles not at idle, disengaing");
182 // update the target deceleration; note step can be changed while engaged
184 _targetDecel = _configRTODecel;
186 double f = (double) _step / _configNumSteps;
187 _targetDecel = _configMaxDecel * f;
191 bool FGAutoBrake::shouldEngage()
194 return shouldEngageRTO();
197 if (_lastWoW || !_weightOnWheelsNode->getBoolValue()) {
202 if (!throttlesAtIdle()) {
206 SG_LOG(SG_AUTOPILOT, SG_INFO, "Autobrake, should enage");
210 bool FGAutoBrake::shouldEngageRTO()
212 double speed = _groundspeedNode->getDoubleValue();
215 if (speed < _configRTOSpeed) {
216 SG_LOG(SG_AUTOPILOT, SG_INFO, "FGAutoBrake: RTO armed, but speed is now below arming speed");
221 if (!_weightOnWheelsNode->getBoolValue()) {
223 SG_LOG(SG_AUTOPILOT, SG_INFO, "FGAutoBrake: RTO, airbone, disengaging");
226 _step = _configDisengageStep;
232 if (throttlesAtIdle()) {
233 SG_LOG(SG_AUTOPILOT, SG_INFO, "FGAutoBrake: RTO, throttles at idle, will engage");
240 if (speed > _configRTOSpeed) {
241 SG_LOG(SG_AUTOPILOT, SG_INFO, "Autobrake RTO: passed " << _configRTOSpeed << " knots, arming RTO mode");
249 void FGAutoBrake::disengage()
255 SG_LOG(SG_AUTOPILOT, SG_INFO, "FGAutoBrake: disengage");
257 _fcsBrakeControl = 0.0;
261 _step = _configDisengageStep;
264 bool FGAutoBrake::airborne() const
266 return !_weightOnWheelsNode->getBoolValue();
269 bool FGAutoBrake::throttlesAtIdle() const
271 SGPropertyNode_ptr e;
272 const double IDLE_THROTTLE = 0.05; // 5% margin for idle setting
274 for (int index=0; (e = _engineControlsNode->getChild("engine", index)) != NULL; ++index) {
275 if ((e->getDoubleValue("throttle") > IDLE_THROTTLE) && !e->getBoolValue("reverser")) {
278 } // of engines iteration
283 void FGAutoBrake::setArmed(bool aArmed)
285 if (aArmed == _armed) {
293 void FGAutoBrake::setRTO(bool aRTO)
296 // ensure we meet RTO selection criteria:
297 if (!_weightOnWheelsNode->getBoolValue()) {
298 // some systems combine RTO with a standard step, selecting RTO if on
299 // the ground. Handle that case by setting _rto = false, and letting
300 // setStep() do the rest of the work as normal.
301 if ((_configRTOStep > 0) && (_configRTOStep <= _configNumSteps)) {
302 // RTO is combined with a normal step, select that
304 SG_LOG(SG_AUTOPILOT, SG_WARN, "auto-brake: cannot select RTO mode, no weight on wheels");
313 _step = _configRTOStep;
315 SG_LOG(SG_AUTOPILOT, SG_INFO, "RTO mode set");
319 // and if we're enaged?
324 void FGAutoBrake::setStep(int aStep)
326 if (aStep == _step) {
330 SG_LOG(SG_AUTOPILOT, SG_INFO, "Autobrake step now=" << aStep);
332 bool validStep = false;
334 if (aStep == _configRTOStep) {
339 validStep = (_step > 0) && (_step <= _configNumSteps);
342 setArmed(validStep); // selecting a valid step arms the system