RoboSavvy Forum

The time has come...

2006-11-26T22:55:37+01:00

OK cool, thx for the replies. Spider was just to test everything and get used to the software basics. Haven't started any own code yet.
I've already taken the spider apart and right now building the humanoid which looks awesome! Will post some more news laterz.

Statistics: Posted by Dimitris — Sun Nov 26, 2006 10:55 pm

The time has come...

2006-11-26T17:39:57+01:00

Dimitris. In my experience when the battery is completely charged the POWER led blinks sloooowly while PLAY led still blinks fast. I cannot remember the MANAGE led flashing after charging.

Pepperm. Actually if you set the margins wider the noise vanishes. Even when the PWM signal from the servo circuit is still working. So the noise definitely comes from the circuit trying to reach the goal position again and again without success. You can solve it by making margins wider. A margin of 2 is enough, although I checked that a margin of zero solves the problem too. By default margin is set to 1.

Statistics: Posted by inaki — Sun Nov 26, 2006 5:39 pm

The time has come...

2006-11-26T14:19:01+01:00

Isn't the sound just the result of driving the motors with a 2KHz (ish) PWM drive signal?

My Robot Wars robot, The Stag makes exactly the same whine and that is because I chose a 2KHz PWM signal to switch the drive to the motors. The 2KHz whine is produced in the same way as a speaker does, the vibrations being at an audible frequency. Indeed, when I worked for a printer manufacturer, we used this feature to save money on buzzers. We just "buzzed" the motor that drove the platten roller to give user feedback.

Mark

Statistics: Posted by pepperm — Sun Nov 26, 2006 2:19 pm

The time has come...

2006-11-26T13:01:45+01:00

Hi Dimitris,

About the high pitch sound;

The AX12 servos expose speed and position control parameters.
Speed control has only one configurable variable - desired speed
Position control has some 6 variables.

You can view and change servo parameters using the bootloader console (in the robot terminal connect 57600 to COM1, press the '#' key while turning on the bioloid - see manual).
the default values for the "Compliance" parameters.
CW_MARGIN : 0
CCW_MARGIN : 0
CW_ANGLE : 32
CCW_ANGLE : 32
PUNCH : 32
MAXIUMUM_TORQUE : 1023

Each servo has a microcontroler that updates the motor position few hundred times per second making sure that the current position complies with the compliance formula.

These default values are quite aggressive so the servos tend to make high pitched noise if they cant reach the desired position even by a fraction of an angle.

As an experiment you can change the PUNCH value to 0 and the CW_MARGIN & CCW_MARGIN to 30. what you will get is an spring effect if you try to force the servo from its center position clockwise and counterclockwise, it will feel like there is a spring inside.

Statistics: Posted by limor — Sun Nov 26, 2006 1:01 pm

The time has come...

2006-11-25T22:15:09+01:00

At last it's here!
Got the bioloid yesterday, I have to say it's pretty amazing! Bigger than I thought too. Built the spider, might start on the humanoid tomo.
Just a couple of questions:
Sometimes the kit starts making a high pitched sound. Is that due to the servos not going to the exact position ? I think it was mentioned somewhere on the forum but can't remember where.
Also, I'm now charging it for the first time. Instructions say the play button starts flashing at the start then the manage button starts. I've had it charging for about an hour but the manage button hasn't started flashing yet, only the play one and power are still flashing. How long does recharging take then?

That's all. Hope to post more soon!

Statistics: Posted by Dimitris — Sat Nov 25, 2006 10:15 pm

The time has come...

2006-11-15T01:41:06+01:00

Finally! I have ordered a Bioloid! Can't wait to join the community, and provide as much input as possible in the future.

Laterz
Dimitris

Statistics: Posted by Dimitris — Wed Nov 15, 2006 1:41 am