This section describes Comet's walking system. First of all, I want to say that I used a few other versions of the legs and gearing, but this worked the best of all. The two NXT motors are attached to a wequence of gears. Six gears on ech side are attached to the four legs, two for each leg. The legs are almost rigid, only moving slightly to absorb some of the weight. When the motors rotate, the legs move up and down in a circular motion. After each rotation, the legs take a tep. This causes Comet to move forward slowly but surely. Unfortunately Comet is very heavy, making his legs have a tendency to bend outwards. I solved this problem by connecting some steering links on Comet's belly. The links are attached to some pivoting beams which are held together by rubber bands. When Comet moves, the links pull the legs inwards regulate a steady motion. The legs are very sturdy and are capable of lifting a heavy load.
Picture 1 The legs
Picture 2 The inner side of the leg
Picture 3 The outer side of the leg
Picture 4 The steering links for stabilization
Picture 5 The gears
This section describes Comets head. I designed Comet's head to look as much like a Chameleons as I could and I think it turned out well. The head uses one motor to open and close its mouth, and extend and retract its tongu, just like a real chameleon. The motor is attached to some beames wich pull the tongue out of the mout. The tongue is connected to two rubber bands for security, extends upon the motor's movement. Asmall wheel keeps the tongue from moving out of place. The bottom jaw is attached to the side of the motor and it pivots vertically. When the mouth opens the tongue slides forwards and falls into the small tilted beam on top of the motor. This keeps the tong from retracting. When the motor turns backwards, the tongue pops back inside of the mouth.
Comets scales are one of my faavorite features. In order to make comet look as real as possible, I added scales onto COmet's sides. Each scale is a small, circular lego stud peice. The scales are attched to plates wich are connected to Comet's body by studded pegs.
Picture 1 The head
Picture 2 The tongue extended
Picture 3 The tongue mechanism
Picture 4 The tongue mechanism after extension
Picture 5 The scales
One of the most important tasks in building an animal is to make it behave like an animal. Chameleons cannot hear well, so Comet does not have a sound sensor. Also, since chameleons are coldblooded, they need to be warmed by the sun or other source of heat. I made Comet have a light sensor to determine his mood. When there is bright light (sun) Comet is very happy. When there is little light, Comet is rather grumpy. Most chameleons do not like being petted, but there are a few who love being petted. For Comet, it depends on his mood. If he is happy, he will tolerate your petting, but if he is grumpy, he will run away from you (not quickly) and stick out his tongue. To detect your touch, COmet has a touch sensor mounted beneath his spines. The ultrasonic sensor is mounted under Comet's chin, and it detects Comets surrondings. If Comet finds an object, he will walk to it and sniff it, and then (depending on his mood) taste it (if grumpy) and turn away, or just turn away. One of the main problems that I had with Comet was his motors becoming unsynchronized. To combat this, I stuck another touch sensor on Comet's tail to detect the ground if the motors become uneven. If the sensor registers the ground, one of the motors moves half a rotation.
Picture 1 ???
Picture 2 The light sensor
Picture 3 The spine sensor
Picture 4 The ultrasonic sensor
Picture 5 The tail sensor.
Well, I already explained most of what the program does, so I will not say any more about it. The Green chameleon in the picture came in a Designer set that came out in 2004 (I think that is the rigth year). The program uses no myblocks, so simply download it if you want to see it. Also, I used two variables to determine the mood and the motor for synchronization.
Of course when designing an animal robot, you have to make it look like the animal. Chameleons have very curly tails, so I had to make comets replicate this. You can see in picture 2 Comets coiled tail. Also, chameleons have interesting feet. Of the four toes on each foot, two are on each side for grasping the branches that it climbs on. The four toes are visible in picture 2 in the right back. Chameleon's eyes bulge out to see objects, and each one is independently moving. I made comet have white eyes instead of yellow sense I did not have the right peices, and I wanted him to be more expresive. (more because I did not have the peices. :-} You may notice hat chameleons have a sort of crown in the back of their heads, and I made comet have a dark red and orange crown. Also, chameleons have many different colors and scale patterns, and I chose to make Comet have a striped pattern. Chmaeleons have very long tongues that are twice the length of their body. I could not make this tongue that long, but hey, it does extend. ;-} There are a few more facts that I could go into, but I think that this is enough.
When I was building Comet, I had many problems. I tried six or more walking mechanisms, and finally came up with this one. Also, I need to give some credit to some of the people who helped my make this project. My sister helped me make the scales and also gave me many suggestions. There are many people who I do not know that posted onlin information about chameleons, and I thank them for all there articles and info.
Now here is something fun: Trivia Which of my project(s) did the last two pictures come from? Please answer in comments :-}
Thank you all for reading, and hopefully rating.
Once again. MySnailEatsPizza- over and out. :-} :-}