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1 // turn_indicator.cxx - an electric-powered turn indicator.
2 // Written by David Megginson, started 2003.
3 //
4 // This file is in the Public Domain and comes with no warranty.
5
6 #include "turn_indicator.hxx"
7 #include <Main/fg_props.hxx>
8 #include <Main/util.hxx>
9
10
11 // Use a bigger number to be more responsive, or a smaller number
12 // to be more sluggish.
13 #define RESPONSIVENESS 0.5
14
15
16 TurnIndicator::TurnIndicator () :
17     _last_rate(0)
18 {
19 }
20
21 TurnIndicator::~TurnIndicator ()
22 {
23 }
24
25 void
26 TurnIndicator::init ()
27 {
28     _roll_rate_node = fgGetNode("/orientation/roll-rate-degps", true);
29     _yaw_rate_node = fgGetNode("/orientation/yaw-rate-degps", true);
30     _electric_current_node = 
31         fgGetNode("/systems/electrical/outputs/turn-coordinator", true);
32     _rate_out_node = 
33         fgGetNode("/instrumentation/turn-indicator/indicated-turn-rate", true);
34 }
35
36 void
37 TurnIndicator::bind ()
38 {
39     fgTie("/instrumentation/turn-indicator/serviceable",
40           &_gyro, &Gyro::is_serviceable, &Gyro::set_serviceable);
41     fgTie("/instrumentation/turn-indicator/spin",
42           &_gyro, &Gyro::get_spin_norm, &Gyro::set_spin_norm);
43 }
44
45 void
46 TurnIndicator::unbind ()
47 {
48     fgUntie("/instrumentation/turn-indicator/serviceable");
49     fgUntie("/instrumentation/turn-indicator/spin");
50 }
51
52 void
53 TurnIndicator::update (double dt)
54 {
55                                 // Get the spin from the gyro
56     _gyro.set_power_norm(_electric_current_node->getDoubleValue()/60.0);
57     _gyro.update(dt);
58     double spin = _gyro.get_spin_norm();
59
60                                 // Calculate the indicated rate
61     double factor = 1.0 - ((1.0 - spin) * (1.0 - spin) * (1.0 - spin));
62     double rate = ((_roll_rate_node->getDoubleValue() / 20.0) +
63                    (_yaw_rate_node->getDoubleValue() / 3.0));
64
65                                 // Clamp the rate
66     if (rate < -2.5)
67         rate = -2.5;
68     else if (rate > 2.5)
69         rate = 2.5;
70
71                                 // Lag left, based on gyro spin
72     rate = -2.5 + (factor * (rate + 2.5));
73     rate = fgGetLowPass(_last_rate, rate, dt*RESPONSIVENESS);
74     _last_rate = rate;
75     
76                                 // Publish the indicated rate
77     _rate_out_node->setDoubleValue(rate);
78 }
79
80 // end of turn_indicator.cxx