What Is Force Control? How Robots Handle Physical Contact.

What Is Force Control?

Force control is a robotics control method that regulates the force a robot applies to an object or surface.

Instead of controlling only where a robot moves, force control helps determine how strongly it pushes, pulls, presses, or otherwise interacts with its environment.

For example, a robotic arm polishing a metal surface may need to maintain a consistent contact force as it moves across the workpiece.

Too little force could produce an incomplete finish. Too much could damage the surface or tool.

Key Takeaways

• Force control regulates physical interaction forces rather than relying exclusively on position commands.
• It is useful for assembly, polishing, grinding, testing, and delicate manipulation.
• Force control may use dedicated force-torque sensors, joint torque measurements, or suitable force-estimation methods.

How Does Force Control Work?

Imagine a robotic arm pressing a polishing tool against a curved metal component.

If the robot follows a fixed position trajectory, variations in the surface may cause the contact force to change.

A force controller uses measurements or estimates to determine whether the tool is pressing too strongly or too gently.

The controller adjusts the robot's movement or actuator commands to maintain the desired interaction.

For example, if the measured force exceeds the target, the robot may reduce the pressure by adjusting its position or commanded torque.

The specific response depends on the control strategy.

Force Control vs. Position Control

Position control regulates where a robot moves.

Force control regulates physical interaction forces.

Consider a robot inserting a component into a tight opening.

Position control helps the robot approach the intended location.

Force control can help it respond when the component contacts the surrounding surfaces.

In practice, these methods are often combined.

A robot may control its position in some directions while regulating force in another.

What Is Hybrid Force-Position Control?

Hybrid force-position control combines the two objectives.

For example, a robot polishing a flat surface might control its movement along the surface while maintaining a specified force perpendicular to it.

This allows the robot to follow the desired path while responding to variations in contact.

Other methods, such as impedance and admittance control, can also provide controlled mechanical interaction.

What Are the Challenges of Force Control?

Force measurements can contain noise and may be influenced by tool weight, robot acceleration, and sensor calibration.

Contact conditions can also change abruptly.

For example, a polishing tool may transition from a smooth region to an edge.

Poor controller settings can cause oscillation, excessive force, or unstable behavior.

Force-control applications therefore require appropriate tuning, equipment selection, and validation.

Frequently Asked Questions

Does force control require a dedicated force sensor?

Not always. Some robots estimate external forces from motor torque or other measurements, although accuracy and capabilities vary.

Does force control make a robot safe around people?

Not automatically. Safe interaction requires appropriate risk assessment, protective functions, and operating limits.

The Bottom Line

Force control allows robots to regulate how strongly they interact with physical objects. It is essential for applications where successful operation depends on controlled contact rather than position alone.