Diff: Steering.cpp

Revision:

0:a3b128cdb78b

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Steering.cpp	Wed Apr 27 18:55:38 2011 +0000
@@ -0,0 +1,42 @@
+#include "Steering.h"
+#include "math.h"
+
+/** create a new steering calculator for a particular vehicle
+ *
+ */
+Steering::Steering(float wheelbase, float track)
+    : _wheelbase(wheelbase)
+    , _track(track)
+    , _intercept(2.0)
+{
+}
+
+void Steering::setIntercept(float intercept)
+{
+    _intercept = intercept;
+}
+
+/** Calculate a steering angle based on relative bearing
+ *
+ */
+float Steering::calcSA(float theta) {
+    float radius;
+    float SA;
+    bool neg = (theta < 0);
+
+    // I haven't had time to work out why the equation is slightly offset such
+    // that negative angle produces slightly less steering angle
+    //
+    if (neg) theta *= -1.0;    
+    
+    // The equation peaks out at 90* so clamp theta artifically to 90, so that
+    // if theta is actually > 90, we select max steering
+    if (theta > 90.0) theta = 90.0;
+    
+    radius = _intercept/(2*sin(angle_radians(theta)));
+    SA = angle_degrees(asin(_wheelbase / (radius - _track/2)));
+
+    if (neg) SA *= -1.0;
+
+    return SA;
+}