Rotary Racer Car Data

Rotary Racer - Car Performance

Goodwood National Final 2008-10-19

Results

The national final and we came second !

Car Computer Log

This shows the main items measured by the Rotary Racers car computer. They are:

Item Description
Throttle The position of the twist grip throttle from 0 to 100%
MotorCtl The motor power output setting. The Car computer sets the motor power based on the drivers throttle position, the speed of the car and the current being used. There is a software algorithm to implement this "drive by wire" system. The Car computer drives the PWM (Pulse Width Modulation) Motor Speed controller with a duty cycle proportional to this value. 0 - 100%
Speed The speed of the car in Km/H calculated from the magnetic read switch pulse generator by the Car Computer.
Voltage The batteries voltage under load.
Current The current being taken from the batteries.
Charge0 The charge left in the battery pack 0. This is calculated by the car computer using an algorithm that has been honed to match the battery discharge curves for the Yuassa batteries. It currently bases its results on the current being used from the battery.
Charge1 The charge left in the battery pack 1. This is calculated by the car computer using an algorithm that has been honed to match the battery discharge curves for the Yuassa batteries. It currently bases its results on the current being used from the battery.
BatPack The battery pack in use (0 or 1). We have changed the driver with each battery pack change.
Temp The Temperature of the motors casing in degrees C.


The graphs show the overall data, the actual ASCII data log files are also available, from the links below, for detailed analysis.

Car Data Log

Corrected Data

This is with the 18 minute stop for the ambulance removed.

Car Data Log

Practice Laps Data

Car Data

Battery Voltages

These are the battery voltages measured with a multimeter at the end of each change. The readings were taken as soon as possible after the batteries we placed back in the battery area.

Battery Pack BatA BatB
0 12.24 12.24
1 12.32 12.32
0 11.97 11.97
1 12.01 12.01
0
1

Notes

  • The Car Computers "Average Current" setting was 23.00 Amps, the Control Speed was 33 Km/Hour. The current setting and Control Speed parameters were changed later in the race to increase speed matching the battery charge state. The software was car12. The intention was to push the batteries nearer the limits in the race.
  • We had increased the low temperature cooling fan power by 10% to 60% and lowered the threshold for 75% power to 38 degrees C. After practice lap testing with a 19:57 (3.0) ratio, in the race we used a 20:57 (2.85) ratio on the chain drive.
  • The Goodwood circuit is 3.862Km long and is fairly flat with sweeping corners. There was a reasonable wind on the day (30Km/H ?).
  • There was an 18 minute stop for an ambulance during the race. Unfortunately we were one of the first cars stopped and just before our intended pit stop. We lost about 2 minutes 10 seconds over the lead car due to this.
  • Drivers were: Dan Isles, James Alington, Dan Dando, Gareth Barnaby, Tom Alington, Ben Millar.
  • The CarComputer and MotorSpeed controller worked very well although there was a glitch causing the battery charge calculations to go adrift during practice. We need to look at this. Otherwise it did its job and in the windy conditions of the day managed our battery useage excellently.
  • The experimental telemetry system worked far better than expected. We could acquire data from the car almost all of the time the car was visible. There were quite a lot of buildings in the way as well as trees, but we could probably acquire data for about 25% of the circuit. This allowed us to monitor our current usage and know we were doing Ok throughout the race. The bi-directional telemetry ability allowed us to up the car power in the later stages of the race to get our second position. We have not done any real testing with the telemetry system or really thought about how best to use it yet. However, it proved its worth. We now need to think about what we want from it and develop the software to improve information available.
  • The Motor cooling system worked fine. The temperature graph shows the motor slowly heating up through the race and reaching a top temperature of about 36 degrees C. The Car computer would have been running the fans at 60%. We could run the motor slightly cooler by modifying the Car Computers fan control algorithm to increase cooling fan speed a bit.
  • The drivers behaved and drove excellently again. There was a slight issue with noting the pit board though !
  • Pit changes were very well done and completely handled by the lads. We timed one at 41 seconds which with the new rules on harness tightness and marshal checking was superb and no doubt helped us get to second place.
  • The race log clearly shows the CarComputer limiting the current once the car was up to speed. Generally is was restricting the motor to about 90% when going into the wind early in the race when the car computer current was being controlled to average 23 amps. The average over the race was 23.1 Amps which is almost exactly what we were aiming for.
  • We made a tactical error in leaving Tom out too long as the batteries were dropping off rapidly. This with the missed pit stop meant that battery pack 0 was falling rapidly, car computer stated 2% charge left while there was around 12% left in battery pack 1. Caused us a few hairy moments ! We limited the power when the batteries were low, but we will have to see if the batteries have been damaged from this.
  • As discussed during the race, we could do with better driver/pits communication and better software for the telemetry data including simpler information on how the batteries are doing with respect to the race length.
  • The average speed was 45.68Km/H and the peak 58.68Km/H. We managed about 113 miles which was excellent considering the windy conditions.
  • All in all a very successful years Greenpower !