INDEX
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THE GENERAL PROBLEM
CURRENT
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PROBLEMS
- Car 2 is noticeably slower than the other cars. I think the same problem affects also the performance over time. The dynamics seen in car1 and 3 caused by the capacitor does not seem to reach a steady state with car 2.
- Both cars 1 and 3 (I couldn't check car 2) have biased steer. When the steer input signal is 0 they turn left (in car1 this problem is very evident).
- Cameras should be screwd to the metal support. Now everytime they move, the calibration must be done again. An extrinsic calibration (at least) should probably be performed again after this job.
- Sometimes the two chargers close to the whiteboard display the green light when cars are connected (i.e. they're done charging) but when I move the wires the light turns red.
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- ca2: grouped utility functions in a separate folder that is shared with the simulator.
- CPS: fixed a bug that affected the initial target dectection for cars that were not tracked by computer 0.
- CPS: implemented linear error correction for the computation of camera position.
- CPS: now compute and send also the 2D speed of the cars. This makes Andrea CPS not compatible to previous ca2 versions and my ca2 not compatible with previous version of CPS.
CAR MODEL
h7. EFFECT OF PWM AND STEER INPUT ON THE SPEED DYNAMICS
I made car1 run on circles for 50 seconds with fixed PWM and steer input for a total of 16 runs. Every run was performed starting from the same battery voltage of 16.7V. The full data gathered and the detailed description of how the experiments were performed can be found in my folder on Dropbox in "../backup/data/circle_7-27-2013". All the images below are obtained by filtering the encoder signal with a moving average window to discard the large part of the noise. The oscillation of the speed is largely due to the fact that the test-bed is not perfectly flat but inclined in some areas.
Figure pwm.png shows the speed of the car obtained by keep the steer constant and varying the PWM. The relationship between PWM and velocity is quite linear. For some reason, when the steer input is high, the speed observed with PWM 140 is slightly lower than I would expect. On the other hand, the steer effect seems to be a little bit more complicated (see steer.png). Velocities observed for steer 92 and 120 are always very close. This may be due to the fact that curvature radius for the two steer input are very similar (the curvature radius is not linear with respect to the steer signal). Still the speed is not linear w.r.t. the curvature radius because the discrepancy between the speed for steer 36 and 64 (which I measured to have respectively a curvature radius of roughly 200cm and 100cm) tends to be reduced by decreasing the PWM.
h7. EFFECT OF THE BATTERY AND THE POWER FILTER CAPACITOR ON THE SPEED DYNAMICS
I made an investigation on the effect that the battery has on the car speed. Data has been acquired by running car1 on a circle with constant steer and engine input. The steer has always been set to -64. The starting position of the car has always been about (3000, 3600) in global coordinates (this if you want to make considerations connected to the test-bed slope). The voltage of the battery was measured both before turning on the car (while off) and just before run ca2 (while on). The full data gathered and the detailed description of how the experiments were performed can be found in my folder on Dropbox in "../backup/data/battery_7-30-2013".
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