From this section, we'll start to investigate force control in robotic manipulators.
We have learned position control schemes until now.
But force control is at least as important as position control also.
There are different kind of task tasks in robotic manipulation.
These tasks can be without interruption and without interruption.
Interaction tasks that do not contain interaction can be pick and place wielding, painting, controlling
orientation of an object such as camera and so on.
In these kind of applications, we can use pure position and orientation control schemes.
However, the tasks that contain interactions such as assembly, polishing, cleaning, cutting and
so on requires control of interaction forces.
So we need in these kind of applications either pure force control or generally hybrid control, namely
both position and force control, as we have said.
These kind of tasks require our control interaction forces or contact forces.
Now you can ask why we need to have separate control mechanisms to control interaction forces, why
we can't apply position controllers to control forces, also to control forces also.
Let's investigate this issue a little bit.
Let's assume that we have given task of inserting some object in the hall as a control mechanism.
We use simple idea control.
Let's say that a robot model and environment models have some inaccuracies, which is quite normal in
practical applications because we cannot model everything precisely.
So then inserting object into the whole.
There are small misalignment and objects stuck near Holt and defectors.
Current position is X and the desired position is indicated as X.
The error is difference of these to these two quantities.
As error is non-zero, proportional control tries to increase input force in order to decrease the error.
But both environment and the robot is stiff, so huge interaction forces arise between robot and the
environment.
This can cause either breaking down of object or robot, which are not desired at all.
As you can see, not taking into consideration interaction forces and applying purely position control
blindly can cause huge problems.
In order to avoid these kind of issues, either the robot or the environment has to be made compliant,
so stiffness has to be controlled.
Additionally, contact control contact forces also have to be controlled.
OK, we now have a bit of idea about force control and its importance.
Force control can be indirect, in which case it is achieved through motion control without using force
torque sensors.
So without force feedback, loop stiffness, compliance control, impedance control belongs to this
category.
However, this kind of control requires proper model of the environment, which is not always easy to
obtain.
Interrupt Force Control Force is controlled up to desired value by utilizing force torque sensors.
So through force feedback, loop force control, hybrid force, motion control belong to this category.
This kind of control requires force torque sensors, which are quite expensive.
That's all about introduction to force control.