The second one is a Robobuilder that is capable of self balancing but has NO gyros and NO acceleration sensor, simply using feedback from his servos to keep himself stable.
As a personal note, I must say I got this information from the manufacturer (Robobuilder) but I don't know how they confirmed the technical solution in the above video.
In any case, after some thought, I think the robot is evaluating the impact by analysing if there are deviations in the target position of the arm servos and leg servos.
I think that if you tweak teh PID settings to allow for more elasticity you can more easily detect these movements. I am not sure if this is what he did though. In any case it seems very ingenious.
While it is still pretty clever stuff, in the second video it looks like most (if not all) of the impacts are not hard enough to knock the robot over and it is more or less stable again by the time it reacts. Just my two cents though!
Is the first one using an acceleration sensor or is it using the cameras?
Felix: the first one is using an IMU (which is a combination of Accelerometer and Gyro). I believe the first one is NOT using the RBC controller.
They probably replaced it with a more powerful controller (I think ARM but I am not sure) to able to run the Inverse Kinematics solution.
As I mentioned the sensors are a 6 axis IMU I think (3 axis gyro, 3 axis accelerometer).
The standard RBC controller box will not let you use an IMU unless you use on with a microprocessor, reprogramed to be able to sit on the bus an emulate itself as a device.
This is a 6 axis IMU with a re programmable ARM Cortex running at 64Mhz (it comes with a bootloader for easy programming).
The IMU is accessed via a UART TTL connection so you may actually be able to connect this one to a Robobuilder bus provided you modify the software to understand the protocol and act as a bus device.
We are waiting for a new revision of the Open Source software for this IMU that implements a Kalman Filter which is likely the best filtering you can have for stability processing.
For those who are really ambitious, you can actually use the ARM7 on the IMU to control the whole robot and just leave the RBC in place to offer battery, the bus breakout connectors and the Direct Control mode to have the PC talk to the bus and the IMU on the bus (but doing no LOGIC work).
I could go on and on about this solution which is a very cool one btw but I'll stop here.
It is actually a very clean and small solution for Robobuilder and I believe ti may fit in the chest of the robot.
It works by obtaining feedback information from the ankle servos. If a force is applied in one of four directions, it will move with the force to avoid falling over. Thesevideos probably show it better.
I've even made the source code available on my blog if you want to have a look.
I'm glad there are people out there who appreciate my hard work! I will try to make some more for you to enjoy.
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