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120.9 - 0 = 0 ?

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  • #1

    120.9 - 0 = 0 ?

    Code:
    '''''Find slip angles of tires based on rotation and translation
#COMPILE EXE
DEFSNG a-z

FUNCTION PBMAIN() AS LONG
LOCAL TEXT AS STRING
LOCAL TEXT2 AS STRING
LOCAL TEXT3 AS STRING
LOCAL TEXT4 AS STRING
PI=3.141593
YAW=0
WHEELBASE=10'108/12
REAR_WEIGHT_PERCENT=.5
LEFT_WEIGHT_PERCENT=.5
FRONT_TRACK_WIDTH=6
REAR_TRACK_WIDTH=6

DIST_CG_FRONT_AXLE = WHEELBASE * REAR_WEIGHT_PERCENT
DIST_CG_REAR_AXLE = WHEELBASE * (1-REAR_WEIGHT_PERCENT)

DIST_CG_FRONT_RIGHT_WHEEL=SQR(DIST_CG_FRONT_AXLE^2-(FRONT_TRACK_WIDTH*LEFT_WEIGHT_PERCENT)^2)
DIST_CG_FRONT_LEFT_WHEEL=SQR(DIST_CG_FRONT_AXLE^2-(FRONT_TRACK_WIDTH*(1-LEFT_WEIGHT_PERCENT))^2)
DIST_CG_REAR_RIGHT_WHEEL=SQR(DIST_CG_REAR_AXLE^2-(REAR_TRACK_WIDTH*LEFT_WEIGHT_PERCENT)^2)
DIST_CG_REAR_LEFT_WHEEL=SQR(DIST_CG_FRONT_AXLE^2-(REAR_TRACK_WIDTH*(1-LEFT_WEIGHT_PERCENT))^2)
CIRCUM_FRONT_RIGHT=2 * DIST_CG_FRONT_RIGHT_WHEEL * PI
CIRCUM_FRONT_LEFT=2 * DIST_CG_FRONT_LEFT_WHEEL * PI
CIRCUM_REAR_RIGHT=2 * DIST_CG_REAR_RIGHT_WHEEL * PI
CIRCUM_REAR_LEFT=2 * DIST_CG_REAR_LEFT_WHEEL * PI
D1 = FRONT_TRACK_WIDTH * LEFT_WEIGHT_PERCENT  'FRONT RIGHT
D2 = REAR_TRACK_WIDTH * LEFT_WEIGHT_PERCENT   'REAR RIGHT
D3 = REAR_TRACK_WIDTH * (1-LEFT_WEIGHT_PERCENT) 'REAR LEFT
D4 = FRONT_TRACK_WIDTH * (1-LEFT_WEIGHT_PERCENT)'FRONT LEFT
ANGLE_TO_WHEEL_FRONT_RIGHT=ATN(D1/DIST_CG_FRONT_AXLE)*180/PI
ANGLE_TO_WHEEL_REAR_RIGHT=180-ATN(D2/DIST_CG_REAR_AXLE)*180/PI
ANGLE_TO_WHEEL_REAR_LEFT=180+ATN(D3/DIST_CG_REAR_AXLE)*180/PI
ANGLE_TO_WHEEL_FRONT_LEFT=360-ATN(D4/DIST_CG_FRONT_AXLE)*180/PI
TEXT$= "Angle to front right wheel:"+STR$ (ANGLE_TO_WHEEL_FRONT_RIGHT)
TEXT2$= "Angle to rear right wheel:"+STR$ (ANGLE_TO_WHEEL_REAR_RIGHT)
TEXT3$= "Angle to rear left wheel:"+STR$ (ANGLE_TO_WHEEL_REAR_LEFT)
TEXT4$= "Angle to front left wheel:"+STR$ (ANGLE_TO_WHEEL_FRONT_LEFT)
DIRECTION_VEL_FRONT_RIGHT= (ANGLE_TO_WHEEL_FRONT_RIGHT + YAW + 90) MOD 360
DIRECTION_VEL_REAR_RIGHT= (ANGLE_TO_WHEEL_REAR_RIGHT + YAW + 90) MOD 360
DIRECTION_VEL_REAR_LEFT= (ANGLE_TO_WHEEL_REAR_LEFT + YAW + 90) MOD 360
DIRECTION_VEL_FRONT_LEFT= (ANGLE_TO_WHEEL_FRONT_LEFT + YAW + 90) MOD 360
TEXT$="Velocity direction: Front right:"+STR$(DIRECTION_VEL_FRONT_RIGHT)
TEXT2$="Rear right:"+STR$(DIRECTION_VEL_REAR_RIGHT)
TEXT3$="Rear left:"+STR$(DIRECTION_VEL_REAR_LEFT)
TEXT4$="Front left:"+STR$(DIRECTION_VEL_FRONT_LEFT)
TRUE_VELOCITY=10
X_COMPONENT = SIN (DIRECTION_VEL*PI/180) * TRUE_VELOCITY
Y_COMPONENT = COS (DIRECTION_VEL*PI/180) * TRUE_VELOCITY
CAR_X_VEL=0
CAR_Y_VEL=0
IF CAR_X_VEL>=0 AND CAR_Y_VEL>=0 THEN CAR_DIRECTION=(ATN(CAR_X_VEL/CAR_Y_VEL)*180/PI)
IF CAR_X_VEL<0 AND CAR_Y_VEL>=0 THEN CAR_DIRECTION=(ATN(CAR_X_VEL/CAR_Y_VEL)*180/PI)+360
IF CAR_Y_VEL<0 THEN CAR_DIRECTION=(ATN(CAR_X_VEL/CAR_Y_VEL)*180/PI)+180
'----Here is problem area:
MSGBOX STR$(DIRECTION_VEL_FRONT_RIGHT )+"    "+STR$(CAR_DIRECTION)
SLIP_FRONT_RIGHT = DIRECTION_VEL_FRONT_RIGHT-CAR_DIRECTION
MSGBOX STR$(SLIP_FRONT_RIGHT)

END FUNCTION

    Problem is in the last few lines.
    DIRECTION_VEL_FRONT_RIGHT = about 120.9
    CAR_DIRECTION=0. These show up ok in the first MSGBOX. SLIP_FRONT_RIGHT is the difference between the two, it should be 120.9, but comes up as 0 for some reason. What's happening?

    Todd Wasson
    Todd Wasson
    http://PerformanceSimulations.Com
    PowerBasic Racing Simulator (October 2007 clip - 15.1MB wmv file) http:http://www.performancesimulations.co...m-GenIV-12.wmv
    Tags: None
  • #2
    Code:
    #COMPILE EXE
DEFSNG a-z

FUNCTION PBMAIN() AS LONG
LOCAL TEXT AS STRING
LOCAL TEXT2 AS STRING
LOCAL TEXT3 AS STRING
LOCAL TEXT4 AS STRING
PI=3.141593
YAW=0
WHEELBASE=10 '108/12
REAR_WEIGHT_PERCENT=.5
LEFT_WEIGHT_PERCENT=.5
FRONT_TRACK_WIDTH=6
REAR_TRACK_WIDTH=6
DIST_CG_FRONT_AXLE = WHEELBASE * REAR_WEIGHT_PERCENT
DIST_CG_REAR_AXLE = WHEELBASE * (1-REAR_WEIGHT_PERCENT)
DIST_CG_FRONT_RIGHT_WHEEL=SQR(DIST_CG_FRONT_AXLE^2-(FRONT_TRACK_WIDTH*LEFT_WEIGHT_PERCENT)^2)
DIST_CG_FRONT_LEFT_WHEEL=SQR(DIST_CG_FRONT_AXLE^2-(FRONT_TRACK_WIDTH*(1-LEFT_WEIGHT_PERCENT))^2)
DIST_CG_REAR_RIGHT_WHEEL=SQR(DIST_CG_REAR_AXLE^2-(REAR_TRACK_WIDTH*LEFT_WEIGHT_PERCENT)^2)
DIST_CG_REAR_LEFT_WHEEL=SQR(DIST_CG_FRONT_AXLE^2-(REAR_TRACK_WIDTH*(1-LEFT_WEIGHT_PERCENT))^2)
CIRCUM_FRONT_RIGHT=2 * DIST_CG_FRONT_RIGHT_WHEEL * PICIRCUM_FRONT_LEFT=2 * DIST_CG_FRONT_LEFT_WHEEL * PI
CIRCUM_REAR_RIGHT=2 * DIST_CG_REAR_RIGHT_WHEEL * PICIRCUM_REAR_LEFT=2 * DIST_CG_REAR_LEFT_WHEEL * PI
D1 = FRONT_TRACK_WIDTH * LEFT_WEIGHT_PERCENT  'FRONT RIGHT
D2 = REAR_TRACK_WIDTH * LEFT_WEIGHT_PERCENT   'REAR RIGHT
D3 = REAR_TRACK_WIDTH * (1-LEFT_WEIGHT_PERCENT) 'REAR LEFT
D4 = FRONT_TRACK_WIDTH * (1-LEFT_WEIGHT_PERCENT)'FRONT LEFT
ANGLE_TO_WHEEL_FRONT_RIGHT=ATN(D1/DIST_CG_FRONT_AXLE)*180/PI
ANGLE_TO_WHEEL_REAR_RIGHT=180-ATN(D2/DIST_CG_REAR_AXLE)*180/PI
ANGLE_TO_WHEEL_REAR_LEFT=180+ATN(D3/DIST_CG_REAR_AXLE)*180/PI
ANGLE_TO_WHEEL_FRONT_LEFT=360-ATN(D4/DIST_CG_FRONT_AXLE)*180/PI
TEXT$= "Angle to front right wheel:"+STR$ (ANGLE_TO_WHEEL_FRONT_RIGHT)
TEXT2$= "Angle to rear right wheel:"+STR$ (ANGLE_TO_WHEEL_REAR_RIGHT)
TEXT3$= "Angle to rear left wheel:"+STR$ (ANGLE_TO_WHEEL_REAR_LEFT)
TEXT4$= "Angle to front left wheel:"+STR$ (ANGLE_TO_WHEEL_FRONT_LEFT)
DIRECTION_VEL_FRONT_RIGHT= (ANGLE_TO_WHEEL_FRONT_RIGHT + YAW + 90) MOD 360
DIRECTION_VEL_REAR_RIGHT= (ANGLE_TO_WHEEL_REAR_RIGHT + YAW + 90) MOD 360
DIRECTION_VEL_REAR_LEFT= (ANGLE_TO_WHEEL_REAR_LEFT + YAW + 90) MOD 360
DIRECTION_VEL_FRONT_LEFT= (ANGLE_TO_WHEEL_FRONT_LEFT + YAW + 90) MOD 360
TEXT$="Velocity direction: Front right:"+STR$(DIRECTION_VEL_FRONT_RIGHT)
TEXT2$="Rear right:"+STR$(DIRECTION_VEL_REAR_RIGHT)
TEXT3$="Rear left:"+STR$(DIRECTION_VEL_REAR_LEFT)
TEXT4$="Front left:"+STR$(DIRECTION_VEL_FRONT_LEFT)
TRUE_VELOCITY=10
X_COMPONENT = SIN (DIRECTION_VEL*PI/180) * TRUE_VELOCITY
Y_COMPONENT = COS (DIRECTION_VEL*PI/180) * TRUE_VELOCITY
CAR_X_VEL=0
CAR_Y_VEL=0
IF CAR_X_VEL>=0 AND CAR_Y_VEL>=0 THEN
   IF ABS(CAR_Y_VEL) < .000001 THEN
      CAR_DIRECTION = 0
   ELSE
      CAR_DIRECTION=(ATN(CAR_X_VEL/CAR_Y_VEL)*180/PI)
   END IF
END IF
IF CAR_X_VEL<0 AND CAR_Y_VEL>=0 THEN
   IF ABS(CAR_Y_VEL) < .000001 THEN
      CAR_DIRECTION = 0
   ELSE
      CAR_DIRECTION=(ATN(CAR_X_VEL/CAR_Y_VEL)*180/PI)+360
   END IF
END IF
IF CAR_Y_VEL<0 THEN
   IF ABS(CAR_Y_VEL) < .000001 THEN
      CAR_DIRECTION = 0
   ELSE
      CAR_DIRECTION=(ATN(CAR_X_VEL/CAR_Y_VEL)*180/PI)+180'----Here is problem area:
   END IF
END IF
MSGBOX STR$(DIRECTION_VEL_FRONT_RIGHT )+"    "+STR$(CAR_DIRECTION)
SLIP_FRONT_RIGHT = DIRECTION_VEL_FRONT_RIGHT-CAR_DIRECTION
MSGBOX STR$(SLIP_FRONT_RIGHT)
END FUNCTION
    You were dividing by zero and ending up with a number that prints out as zero but is really undefined. It acts like a very negative number. No matter what you add to or subtract from it you will get zero.

    Check for zero before you divide.

    Tim Wisseman



    [This message has been edited by Tim Wisseman (edited April 18, 2000).]

    Comment

    • #3
      Thanks, Tim. I didn't know that. Was curious as to why if I just put the value in the variables place in the equation, it would work, but the variable by itself wouldn't. Thanks!
      Todd Wasson


      ------------------
      Todd Wasson
      http://PerformanceSimulations.Com
      PowerBasic Racing Simulator (October 2007 clip - 15.1MB wmv file) http:http://www.performancesimulations.co...m-GenIV-12.wmv

      Comment

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