Programming a basic walking gait using servo.write(angle) and then a delay is very easy. Then you get something like this: https://vimeo.com/61460555
I'm not much of a programmer, the challenge for me was to program it using inverse kinematics and using a timer. That's a lot harder for someone that is new to programming. A couple of months later I ended up with this: https://vimeo.com/67994924 I can now remote control (by using another Arduino as a remote and 2 nRF24L01 modules) it, and make it walk in every direction. With the remote I can let it do preprogrammed "moves". Also has an autonomous obstacle avoiding mode using ultrasonic sensors and with the WiiCamera sensor it can track IR light. I also added 18 leds, 16 of them controlled by 2 shift registers. Mixing all those things in one sketch took me a lot of time to get right. My last sketch is over 1500 lines of code. But I'm sure someone with better programming skills could do it a lot simpler.
I recently built a hexapod, well it took me many months to program it I used inverse kinematics, I found the following site helpful -> http://www.engineer-this.com/IK.shtml The IK wasn't that hard to figure out. The biggest problem for me was coding the whole walking gait based on a timer (millis). I didn't want to use the delay function as I wanted to let the micro controller do lots of other things. You can read about my hexapod on my blog: http://www.bajdi.com/category/bajdupod-996r/
Yes the Lynxmotion servo controller is good solution. I actually have a Chinese (Torobot) 32 channel servo controller. I plan on rewriting my code one day using it. It should be much easier to make the servos move smoothly with those controllers.
The only code I had was the math for the inverse kinematics. Which actually is not that hard, there are lots of websites that explain how it works. My biggest problem was coding the walking gait. I first wrote a sketch using a for loop and the delay function to move the servos. That was pretty easy. But when you want the micro controller to do a bunch of other things you're in trouble. So I tried dozens of ways to code the gait using the millis timer, after a dozen revisions of my code I finally got it right. I did look at the Lynxmotion code before I built my hexapod, but it's pretty complex. I can't understand much of it. I name it a monster because it uses so much current. I once tried to power it without the UBECs, and connected the servos directly to my lab power supply. I saw the current shoot up to almost 20A. I'm using very cheap metal geared servos (standard size), Towardpro MG996r servos. They cost less then 5€ a piece and have +10kg/cm torque.
My hexapod has an autonomous mode and a remote controlled mode. In the autonomous mode it can track an IR light source using the WiiCamera sensor and avoid obstacles which it detects with 2 ultrasonic sensors. In the remote controlled mode I can let it walk in every direction. I also have a mode to move the body without moving the tips of the legs, this is where inverse kinematic comes in very handy. I also programmed a “fitness mode” where the hexapod lift 3 legs of the ground and moves them up. In the last mode I can control each leg individually, you can see this in the last part of the video. My code is far from perfect, but it works It was not easy to program all these things and let it all work together.
This is a list of parts that I have used in my hexapod:
Hexapod chassis kit (bought on Ebay) 3x laser cut acrylic plates (made by local shop) 6x bearings (to mount the underside of the servo brackets) Acrylic ultrasonic sensor bracket (bought from Rocket brand studios) Pan/tilt kit (for WiiCamera sensor, bought from Rocket brand studios) 18 metal servo horns Lots of M3 nuts and bolts
18x MG996R servos (bought on Ebay) 3x SG90 servo (to move the sensors, bought on Ebay)
3x 8A UBECs (bought from Hobbyking) 3S 3000mAh Lipo battery (powers the 18 MG996R servos) 2S 1000mAh Lipo battery (powers the 3 SG90 servo and sensors) 20A automotive blade fuse (protects 3S Lipo battery, bought on Ebay) In line fuse holder + 1A fuse (protects 2S Lipo battery) Servo power distribution PCB (own design, made by Seeedstudio) Seeeduino Mega2560 ATmega328 board (own design, made by Seeedstudio) nRF24L01 module (wireless control, bought on Ebay) 2x HC-SR04 ultrasonic sensors WiiCamera sensor (bought from Rocket brand studios) 2 x 74HC595 shift registers (to control the 16 leds) 18 blue leds 18 220 Ohm resistors 4 resistors for 2 voltage dividers (analog reading of the 2 Lipo batteries) Perfboard, lots of wires LM2596 PCB (powers the 3 small servos, leds and sensors, bought on Ebay)
I reused the remote control (based on an Uno, joystick shield and nRF24L01 module) from previous projects. This project cost me quite a bit of money. During the building of Bajdupod 996R one servo burned up. Yes only one, I can assure you these servos have had a very hard time. So I am quite surprised that I did not burn up more servos.
Quite a bit of time and money was spent on powering this hungry beast. I initially used 2 8A UBECs and killed them pretty fast. Then I bought 3 more 8A UBECs and designed a new power servo PCB. Then I destroyed a 3S 3000mAh Lipo battery. I had to recharge the battery so many times that the Lipo charger died on me. Luckily I had 2. The hexapod eats Lipo’s for breakfast, lunch and dinner. The battery lasts less then 10 minutes.
Coding this beast has taken up most of my free time the last couple of months. I would have never thought I would be able to program such a complex project one year ago. I have only been playing with Arduino for one year and a halve, before that I had never written a line of code. I’ve never taken any programming courses, everything I’ve learned comes mainly from lots of trying and testing. I can assure you it took me lots of dedication and hard work to accomplish what you see in the above video