Diff: Actuators/Steering/Steering.h

Revision:

0:a6a169de725f

Child:

2:fbc6e3cf3ed8

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Actuators/Steering/Steering.h	Mon May 27 13:26:03 2013 +0000
@@ -0,0 +1,70 @@
+
+#define PI 3.141592653589
+
+/** A class for managing steering angle calculations based on current and desired heading
+ *  and specified intercept distance along the new path.  
+ *
+ *  See Notebook entry: http://mbed.org/users/shimniok/notebook/smooth-steering-for-rc-car/
+ */
+class Steering
+{
+  public:
+    /** create a new steering calculator
+     *
+     * @param wheelbase vehicle wheelbase
+     * @param track vehicle track width
+     * @param intercept new course intercept distance
+     */
+    Steering(float wheelbase, float track);
+
+    /** set intercept distance
+     * @param intercept distance along new course at which turn arc will intercept
+     */
+    void setIntercept(float intercept);
+
+    /** convert course change to average steering angle
+     * assumes Ackerman steering, with track and wheelbase
+     * and course intercept distance specified.
+     *
+     * See notebook: http://mbed.org/users/shimniok/notebook/smooth-steering-for-rc-car/
+     *
+     * @param theta relative bearing of the new course
+     * @returns steering angle in degrees
+     */ 
+    float calcSA(float theta);
+
+    /** convert course change to average steering angle
+     * assumes Ackerman steering, with track and wheelbase
+     * and course intercept distance specified. Also, |radius| of turn is limited to limit
+     *
+     * See notebook: http://mbed.org/users/shimniok/notebook/smooth-steering-for-rc-car/
+     *
+     * @param theta relative bearing of the new course
+     * @param limit is the limit of the turn circle radius (absolute value)
+     * @returns steering angle in degrees
+     */ 
+    float calcSA(float theta, float limit);
+
+    /** compute steering angle based on pure pursuit algorithm
+     */
+    float purePursuitSA(float hdg, float Bx, float By, float Ax, float Ay, float Cx, float Cy);
+    
+    /** compute steering angle based on a simpler path pursuit variant of pure pursuit
+     */
+    float pathPursuitSA(float hdg, float Bx, float By, float Ax, float Ay, float Cx, float Cy);
+
+    /** Compute cross track error given last waypoint, next waypoint, and robot coordinates
+     * @returns cross track error
+     */
+    float crossTrack(float Bx, float By, float Ax, float Ay, float Cx, float Cy);
+    
+  private:
+
+    inline static float angle_radians(float deg) {return (PI/180.0)*deg;}
+
+    inline static float angle_degrees(float rad) {return (180/PI)*rad;}
+
+    float _wheelbase;
+    float _track;
+    float _intercept;
+};
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