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Topic: 12 Servo Quadruped - Servo Shield selection discussion (Read 8 times) previous topic - next topic

DuaneB

Hi, I measured the standard servo libaray as using aroung 1% Of available processing to control 12 servos.

http://rcarduino.blogspot.com/2012/02/can-i-control-more-than-x-servos-with_03.html

Using the RCArduino serial servos library will be even lower because it only has a clock pin to deal with so no pin mapping or masking is required - all of the decoding is done by the simple 4017 counter.

Duane B
rcarduino.blogspot.com


zoomkat

Some reading material on multilegged bots. Study up on how others have built their successful bots.

http://www.lynxmotion.net/viewforum.php?f=8
Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

oric_dan

Another reason to use a dedicated servo chip/board is because they usually do servo
velocity computation, which is very useful for controlling the speed of a walker. The
Arduino servo library does not do this. To compute velocity, you have to interpolate
points inbetween the servo initial and target positions, and this isn't difficult, but it
takes some processor overhead.

http://arduino.cc/en/Reference/Servo

CasperH

Hi,

I made a Quadropod with 8 servo's for walking (2 x 4 additional ones for steering and driving) using an arduino. I combined the following:



From the Arduino I send a group move to the SSC-32 and that takes care of the servo movements. Looks something like:

Code: [Select]

#15 P1500 #3 P1500 #31 P1500 #19 P1500
#12 P1844 #13 P1855 #14 P911 #0 P1155 #1 P1033 #2 P1866 #28 P888 #29 P1355 #30 P2133 #16 P1755 #17 P1644 #18 P700 T72
#15 P1500 #3 P1500 #31 P1500 #19 P1500
#12 P1833 #13 P1855 #14 P911 #0 P1155 #1 P1022 #2 P1855 #28 P888 #29 P1322 #30 P2100 #16 P1755 #17 P1644 #18 P700 T72
#15 P1500 #3 P1500 #31 P1500 #19 P1500
#12 P1833 #13 P1844 #14 P900 #0 P1144 #1 P1011 #2 P1844 #28 P888 #29 P1288 #30 P2066 #16 P1755 #17 P1655 #18 P711 T72
#15 P1500 #3 P1500 #31 P1500 #19 P1500
#12 P1833 #13 P1833 #14 P888 #0 P1144 #1 P1000 #2 P1833 #28 P888 #29 P1255 #30 P2033 #16 P1766 #17 P1666 #18 P722 T72
#15 P1500 #3 P1500 #31 P1500 #19 P1500


The longer line of the two is the walking gait, the shorter is for the continues rotation servos to stay non moving (otherwise they become 'unpowered').

For pictures, a video of the walking gait and source code, go here: http://www.cmhofstede.nl/eigen-projecten-vrije-tijd/project-tachikoma-prototype-ii-2/ Note that this was actually my first time coding an Arduino so its really beginner level stuff.  ;) Its been a few months since then and I made a ton of improvements for speed and IK. Did'nt post the code for that cause its getting very long.

Echalon

Thanks for the tremendous support and input. Any comments: SSC-32 servo controller (http://www.bizoner.com/arduino-usb-ssc32-servo-motors-controller-with-bluetooth-apc220-p-215.html) VS. Spider Controller (http://www.netram.co.za/Electronics/Dev-Boards/Arduino/Spider-Controller-Atmega-1280.html) in terms of ease of use, performance and features? I would prefer the SSC-32, but it is rather difficult to source locally (South Africa).

Thanks again


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