A Stair Climbing Robot

I am building a stair climbing vehicle. I want to use a four wheeled chassis with a high area between the front and rear wheels. The chassis looks something like this:

To help the robot get on to a step, I am planning to use a servo powered U shaped piece attached on the rear which will lift up the robot's rear side while the front is climbing on to a step.

Someone has done something similar before, except with a tracked chassis.

Is my plan of doing the same with a wheeled chassis viable? I want to climb 5" Inch stairs.

How do you want to achieve enough friction, so that the fore wheels will climb up the vertical part of the step?

The rear support only prevents the chassis from falling on its back, when it reaches its most vertical inclination, just before toppling into horizontal orientation on the next stair.

Hi @Lithiuminc,

I have such robot in mind .

The challenge is to have the robot not blocked in the stair between 2 steps.
What is the size of the robot and the wheels ?

DrDiettrich:
How do you want to achieve enough friction, so that the fore wheels will climb up the vertical part of the step?

The rear support only prevents the chassis from falling on its back, when it reaches its most vertical inclination, just before toppling into horizontal orientation on the next stair.

I fixed some old 6V geared motors to a piece of cardboard, put an Arduino, a battery, and a breadboard on it, and let the thing run towards a wall. It did climb up and fell on its back. See here.

However, I'm afraid it might get stuck on the nose of step. How about front arms to lift up the front wheels up to the step? Something like this.

gerardosamara:
Hi @Lithiuminc,

I have such robot in mind .

The challenge is to have the robot not blocked in the stair between 2 steps.
What is the size of the robot and the wheels ?

Good to know I have some company here. If I can, I will use the same motors and wheels as in the gif above linked above. If I remember correctly, the wheels are 65mm. For the size of the base, I would want a small size, somewhere around a 8 inches in length.

Right now I am totally open to ideas. If there is a better approach than the one I posted in the original post, I would gladly go for it. I'm even thinking of RHex like legs that spring into action when the robot has to climb stairs, 2 in the front and 2 on the rear.

Just stumbled across this Mindstorms robot. See it in action here.

The rear support moves straight downwards to level the robot. Any ideas on how I could implement a similar mechanism with a high torque servo?

lithiuminc:
I fixed some old 6V geared motors to a piece of cardboard, put an Arduino, a battery, and a breadboard on it, and let the thing run towards a wall. It did climb up and fell on its back.

However, I'm afraid it might get stuck on the nose of step. How about front arms to lift up the front wheels up to the step?

If I can, I will use the same motors and wheels as in the gif above linked above. If I remember correctly, the wheels are 65mm. For the size of the base, I would want a small size, somewhere around a 8 inches in length.

For sure with such small wheels you will be unable to pass the nose of the first stair , you need to the diameter of the wheel equal to twice the height of the step of the stair ... about 42 cm if the height of the step is 20 cm .

The chassis must be also at least the intervall betwen 2 steps in order to do not be blocked by the nose of the step. A good area to work is to have a high area between the front and rear wheels , as shown in your post#1.

The robot architecture with wheels ( 3 or 4 ) seems to perform much less then the tank one .. as per numerous video available.

However i do not want to use tank architecture , only wheels and without arms to lift the robot ..... i started to build a first version of my mobile robot with 2x80 mm wheels , a 3rd free wheel and a high area between the front wheels and the free wheel .

When it will work , i will try to build a much bigger one as an attempt solution for stair climbing robot.

I know tracks perform far better than wheels but I have to use wheels. I will be attempting to recreate something like this Lego Mindstorms stair climber robot. The rear mechanism is probably hard to implement but I can give it a shot.

Google Scotch and Yoke mechanism to turn circular motion into a linear motion, use it to have your rear leg push up.
https://www.google.com/#q=scotch+and+yoke+mechanism

CrossRoads:
Google Scotch and Yoke mechanism to turn circular motion into a linear motion, use it to have your rear leg push up.
Google

Thanks. I had been pondering over the slider crank mechanism, but scotch and yoke appears to be far simpler to implement.