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The
Robots
Tricycle
One of the more developed of the walking robots is this
8 legged spider robot. (Remember spider=8legs, beetle=insect=6
legs). Each leg is actuated by 3 servos (Futaba S3003
and S9450)which makes 24 servos total. Because the robot
has 3dof legs then it is capable of being omni-directional
. Omni-directional means that it can move sideways, forwards,
backwards and turn left and right, ie translate and rotate.
An array of sensors that is located below its body is
used to follow a track but this array will be replaced
soon by a computer vision system. The beetle is controlled
by a Basic Stamp2SX (turbo-charged BS2) for each leg and
another which synchronises them and yet another BS2 for
the sensor array. (Total 10 Basic Stamps). A plurality
of polynomial fit equations (order=2) is used to compute
the leg-end positions. As an example, one of the polynomial
equations represents a sufficiently accurate simplified
Jacobian equivalent which produces vertical motion (z-axis)
of the leg-end that is independent of motion in the x
and y axes.Six inputs are sent to each leg every 20msecs.
The BS2SX is an easy-to-program, and fast enough, integer
calculator which carries out these polynomial equations
safely inside 20msecs. I find it's not necessary to require
floating point calculations. I find simplicity and ingenuity
in developing algorithms is more important. The Basic
Stamp is easy to program and rapidly prototypes and tests
out your algorithms. Yes there are faster processors but
the BS is so easy to program. Once you've proven an algorithm
using Stamps then you can think how to implement the algorithm
in a better way. For example I now realise that the 8
BS2SX's can be replaced by one processor but you must
write in assembler.
You can view the movie of Tricycle competition on track
without obstacle here.
This robot converts reciprocating motion into continuous
rotary motion similar to a steam engine. Integrated servos
oscillate back and forth through four-bar linkages. The
cranks attached to the drive wheel are set at a 90degree
phase difference so the two four-bar linkages cannot become
locked up. Students wrote the software during a problem
based learning 36hr tutorial session over 12 weeks. For
the complete list of movies available for viewing and
downloading please go to the movies
section
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