Left Wheel

Right, repetitive iterative testing sort of completed on the left wheel, although I do have some questions need answering about it.

Here is the data:

13, 752, 0.20
13, 746, 0.15
13, 753, 0.25
13, 745, 0.2
13, 754, 0.33
13, 744, 0.30
13, 755, 0.45
13, 743, 0.40
13, 756, 0.55
13, 742, 0.55
13, 757, 0.66
13, 741, 0.66
13, 758, 0.75
13, 740, 0.75
13, 759, 0.91
13, 739, 0.91
13, 760, 1.03
13, 738, 1.03
13, 765, 1.6
13, 733, 1.6
13, 770, 2.25
13, 728, 2.25
13, 775, 2.75
13, 723, 2.75
13, 780, 3.25
13, 718, 3.25
13, 785, 3.6
13, 713, 3.6
13, 790, 3.9
13, 790, 3.85
13, 790, 3.9
13, 790, 3.85
13, 708, 3.75
13, 795, 4.1
13, 703, 4.05
13, 800, 4.25
13, 698, 4.2
13, 805, 4.25
13, 693, 4.25
13, 810, 4.3
13, 688, 4.3
13, 820, 4.3
13, 683, 4.3

There is a slight difference in the way this servo reverses direction. It goes further forwards than it does in reverse. In order to get the same distance backwards as well as forwards in the file TestServoSpeed.bs2, it was necessary to change the value of the counter variable from 244 x 2 microseconds to 238 x 2 microseconds, a difference of 12 microseconds.

If you think back to the previous post about the right wheel, the top speed that servo seemed capable of was 47.5 rpm.


As you can see, the top speed the left servo appears capable of is around 43 rpm, which is pretty significant really. Its enough to make a difference in dead reckoning navigation anyway.


Given that I tested the right wheel with absolutely fresh batteries and that I'm testing the left wheel with the same batteries as I used for the right wheel, I initially thought the difference may be down to the batteries not putting out as much power for the left wheel as for the right.


That seems to have some effect, but it isn't the whole answer. I tested the right wheel with a pulse width of both 820 and 679, which in the previous test were widths which managed to achieve the top speed of 4.75 and in this battery of tests, those widths only gave the wheel an rpm of 46. So, while the freshness of the battery may have had some effect, it isn't as pronounced as 4 rpm.


I wonder if there is a way to tune servos?