OK.
In the previous lesson, we have seen general information about force control in this lesson, we will
see RCC or Remote Center of Compliance, which is used in robotics to provide artificial compliance
to the robot arm on premise less than we have seen the importance of compliance in robotic applications.
The issue is that generally the robots and environment are stiff, especially the environment can be
very stiff.
So we have to control the stiffness in order to control interaction forces, by some way.
We can provide compliance in two ways, namely passive compliance and active compliance.
Passive compliance is generated through mechanical devices.
RCC or remote sensing of compliance is one of these mechanical devices.
The advantage of this method of providing compliance is that it doesn't require sophisticated control
algorithms or sensors.
You will have to just connect it to your robot manipulator.
But the problem is that the robots are not standard.
Also, robotic tasks are not standard.
So depending on task and robot, this device has to be changed.
This means additional cost and low flexibility.
Active compliance in opposite provide compliance through control algorithms so you can provide specific
level of stiffness or compliance by algorithm.
You may need for stored sensors to achieve this level of control.
By this method, you will get high operational flexibility because there is no robot or task dependent
device, but you will need sophisticated algorithms, which includes computational complexity.
Additionally, you may need the model of environment, which can be difficult to obtain.
So what is the center of compliance?
Let's assume below situation the apply force being in blue.
We apply purely horizontal force in red.
We apply pure torque.
However, as you can see from second stage, even we apply pure the horizontal force on pure torque.
We get combination of rotational and translational motions, so transnational motion and rotational
motion are coupled.
You want to decouple them because of the reasons you will see in the minute.
In the third stage, you see that we get only translational motion due to horizontal force and rotational
motion due to pure torque.
This point is called centre of compliance, so centre of compliance is the point in which translation
and motion and rotational motion are decoupled.
So what is a remote centre of compliance?
As we have said before, it's a mechanical device to provide passive compliance, as you can see from
the picture.
It consists of springs that provides six degrees of freedom.
In this picture, you can see the functionality of our CC upper.
Part of our CC is connected to the rest of the robot arm, and this is the gripper of the robot arm.
RCC provides centre of compliance in that point.
As you can see, it is not inside of CC, but outside.
So that's why this device is called a remote symbol of compliance.
It's obvious from picture that we have lateral and cooking's alignment during assembly if we don't provide
compliance to the robot arm.
These misalignments can cause serious issues, however, due to the centre of compliance created by
our CC, single point control forces create translational motion only, while two point contact forces
create rotational motion.
So, by this way, misalignments have been compensated for.
In this video, you can see RTC in action.
From the video, it is obvious how misalignments are compensated for due to the provided compliance.
So all in all, RCC, which provides passive compliance, is a simple and moderately cheap solution.
However, it is not very flexible and application dependent.
Based on some parameter requirements change, and for this reason, RCC has to be changed.
Also, in the next few lessons, we will see other methods that are better than RCC in terms of flexibility
and providing compliance.