tek-tonic

Walker robot

Finally got most of the parts to start making my biped walker robot. At first I am going to try and construct a robot that can walk on 2 legs by itself. After that is accomplished I will try and do something more with it. This page will contain information on my progress.

It all started with a few sketches in my note book. I just had an idea to try and create a 2 leg walker that uses 4 servos to move. It will have a servo on each leg to control the ankle movement on that leg. Both ankles will be able to pivot left and right on a hinge mounted to the bottom of the leg posts. The next servo will be mounted to the bottom of the body and control the "shoulders". Basically it will allow the legs pivot apart from each other on the back of the body. The fourth and final servo will be mounted on the back and will lift the legs up and down. The combination of these 4 pivot points should allow the robot to walk.

The first step was to figure out how I was going to control the robot and what I was going to use for motors. After some research I decided on the basic stamp from Parallax and a few of their hobby servos.

I went with the Parallax basic stamp for a couple of reasons. This is my first time ever using a micro controller and the BASIC Stamp Discovery Kit (USB) seemed to be the best all around kit to get me started. I know that their are other much less expensive and more powerful micro controllers out there but I thought that this would be the best way for me to start. The kit came with everything listed below and I got started. I flipped through the book and did some of the projects and after about an hour got the hang of it. Since I was able to get the servos moving I decided to move on to building the mechanics for the robot.

I started first by building the body of the robot. This is where the micro controller, 2 of the servos, battery pack, and the legs will be mounted. I went to SkyCraft and looked around some of the scrap metal bins and walked out with most of what I needed for a couple of dollars. I bent up some of the metal scraps into the shape you see to the side. Don't know why but it just turned out looking that way. On the front of it I mounted the Parallax board of education. This is what the basic stamp chip mounts to and gives you a bread board to add more sensors. The battery pack will probably mount some where on the top behind the board of education.

Here you can see the side and bottom views of the body unit. Inside are 2 of the servos mounted. You can see in the bottom picture where the servo horns are located. In the side view picture you can also see one of the shoulder hinges. This is where the leg posts will be mounted. The servo mounted on the bottom and these shoulder hinges are what will allow the robot to pivot its legs. The rear mounted servo will lift the legs. It will accomplish this by pushing down on one while lifting up on the other.

The images to the right are of the leg posts that I have bent and one of the foot pads. All the parts are made out of aluminum and are pretty light. I am not sure why they are gold colored but if you file or cut them they are aluminum colored inside. The image below is a mock up of how the legs and foot pad will mount to the body. The ankle servos will mount some where on the leg bend.

Below are pics of how the legs are mounted to the body on the shoulder hinges. There is an image also of the ankle joint. The ankle joint uses another hinge to connect the leg posts to the foot pad. With the addition of the ankle servos it will make the foot pads more stable. The last image on the bottom right shows the back servo and how it is mounted to the legs to move them up and down. This set up is likely to change...

Here is a quick video of the first steps the walker has taken. Definitely needs some work....

In the pictures above you can seen the modifications I had to make to the back servo horn. This is the servo that controls the lifting of the legs. I need to get over to the hobby store and get a few more linkages. The other picture above is of the # 2 servo mounted. This will control the inward and outward motion of the legs. I had to mount it a little differently than it was originally because of clearance issues.

I have attached the control linkage to the hip motor. Below is a movie of the hip and leg movement.