Targa Florio PC Parameters Configuration

PAVAS requires two parameters allow the PC calculations to be performed during a stage. The menu is named Set Targa Florio Parameters.

Reaction Time

Reaction time is used to compensate for the time error introduced from when the operator sights the starting pneumatic tubes in a PC event. The navigator is then required to either press the Select Button either on the front panel or using the remote unit or press the Reliability button. When either the Select Button or the Reliability switch is use, the contacts making the contact bounce so instead of just a single change in eh voltage level, the actually level changes back and forth several times. This is called “contact bounce” and if not,compensated for, can cause operational errors. Typically total reaction time are made up of two components; the first is the delay in processing to overcome the contact bounce. This is called “debouncing”. The second is the time it takes the navigator to observe the pneumatic tube and the press the button. Debouncing the contact closure takes approximately 50 milliseconds and varies a small amount. The simple reaction time of the navigator varies and depends on an individuals style. Typical times are about 200 milliseconds to 600 milliseconds if the Select button is used, specialized code debounce PM's are commenced from a stationary position.

While PC's (Time Trials) can be commenced at any speed. In these stages, start time is measured by a pneumatic tube which activates a timer.

BUT Distance

The typical Targa Florio PC course is shaped like a U. The inbound and outbound legs are equal but the distance is move from one leg to another is dependent on the driver and dynamic of the vehicle. If the average speed is used to control the total time taken for the course, then the distance at the turn must be known. This is called the BUT (Bottom U Turn) distance. This distance will vary but it can be measured beforehand with the driver describing a circle at the approximate radius and speed that would be used in the event. It is the second Targa Florio parameter to be set. The method is to drive the vehicle in a number of circles while PAVAS measures the distance travelled. The turn direction should be in the same way as on the course because distance measurements are performed by the probe on one wheel and the distances travelled by the inner wheel and outer wheel on the turn will be different. After a number of circles is driven the vehicle is stopped and the Select button is pressed. PAVAS then request the number of circles and calculates the distance on half a full circle circumference. This is then stored as the BUT distance.

Edit/Measure

The above techniques, if used in isolation, force the operator to perform measurements. This is far from ideal in the field because it does not allow the provision to review the measurements some time after they have been performed. So both the Reaction Time and the BUT distance screen are prefaced by an Edit/Measure display. The selected mode is indicated by a cursor underline under each word. It can be changed with the left and right buttons. It is chosen with the Select button. In the Edit mode for either parameter, the Left and Right buttons select the digit of the value and the Up and Down buttons increment the value. The Select button saves the value. If the value is not edited, then it can be reviewed and simply saved, unaltered, by pressing the Select button. This technique allows the operator to edit,measure or review the Targa Florio parameters.

TF Stage Configuration

A second menu called Set Targa Florio Stage Values is used configure up 128 stages. It is used to set the Stage Mode, Time and Distance, where applicable. There are four different stage modes available.

PC Stages Mode 1

The Mode 1 in PC stages is basically a simple timer. The stage is started with a press of the Select button or Reliability switch and a preset countdown timer starts to run. No tones are sounded but a countdown clock is displayed for the navigator. When half the stage time has elapsed, PAVAS commences to emit tone indicating the time until the end. At the five second point a warble is sounded for one second and then the count down resumes.

PAVAS Techniques in PC stages Mode 2

PC stage timing is critical and is exacerbated by the short stage lengths that are used. There are two problems with using a mechanical switch in the vehicle to time the stage. The first of these is the operator's reaction time. This can be simply measured in a configuration parameter mode. The second problem, in mode 2, is the distance travelled during the reaction time. This is more complicated and depends on the vehicle speed. PAVAS corrects for this distance by logging the distance traveled from an arbitrary point every 100 milliseconds and stores it in memory. The memory structure rotates so that the First In memory value is the First Out memory value (FIFO). This memory is 6.4 seconds deep. When the switch contact is finally recognized, the software retrieves the distance value prior to the reaction time and uses this as the start distance reference.

The same method is used at the BUT when the operator presses the switch again. PAVAS uses the rotating memory to calculate the distance prior to the reaction time. Since the start distance is known, the outbound leg distance can be calculated. So the total distance of the stage can be calculated which is the outbound leg, plus the inbound leg and the BUT distance. Now the time prescribed for the stage is known so the required average speed can be calculated. This is then used as the requested speed for the TSD algorithm. PAVAS then uses Null Tone Guidance to direct the driver. To keep the driver aware of the navigators progress, a beep tone is sounded when the switch closure is recognized.

It should be noted that switch closures are subject to contact bounce, therefore the activation time is finite and typically 50 milliseconds. The PAVAS software debounces the contact closure to ensure a reliable signal and this time is accounted for in the reaction time measurements. If the Select button or Reliability switch is closed as the finish line is crossed, PAVAS indicates the time taken. This will not be the official stage time which is derived the the pneumatic tube based timing circuits

PAVAS Techniques in PC stage Mode 3

In Mode 3, the outbound distance is provided. The menu system allows for this value is to added after the mode is selected and prior to the start which is indicated by a Select button or a Reliability switch closure. The rotating memory is used as in the Mode 2 description above. The stage distance is immediately calculated and so the Null Tone Guidance commences immediately and provides feedback to the driver. The navigator only has to provide the start indication. At the five second time, a warble is sounded for one second. Then the tones revert to Null Guidance. If the Select button or Reliability switch is closed as the finish line is crossed, PAVAS indicates the time taken.