How Collaborative Robots and Grippers Work: Force Limits, End Effectors and Shared Workspaces

The short answer

A collaborative robot, often called a cobot, is a robot arm designed for applications where people and the robot share a workspace. Typical features are joint torque or force sensing, limits on speed and force, and configurable safety functions that stop or slow the arm. A gripper or other tool at the end of the arm, called the end effector, does the actual holding. [1] [2]

The word “collaborative” describes an application, not a robot. The 2025 revision of the US industrial robot safety standard, adapted from ISO 10218:2025, replaced the term “collaborative robot” with “collaborative application”, because the safety of collaboration depends on the whole application: the arm, the tool, the part, the speed, the layout and the people nearby. [3] [4]

A simple picture: carrying a tray through a busy kitchen

A waiter carrying a tray through a busy kitchen moves slowly near people, keeps the tray steady and stops if someone steps in front. A cook with a sharp knife works more carefully again. The same person is safer or riskier depending on what they carry and where they move.

A cobot is similar. An arm that is gentle enough to bump into someone while holding a foam block can be dangerous when holding a blade or a hot part. The comparison has a limit: the waiter notices danger by looking and thinking, while the robot only reacts to what its sensors and safety settings detect.

Cobot or traditional industrial robot?

[3] [4]

The R15.06-2025 announcement names three collaborative technologies: hand-guiding controls, speed and separation monitoring, and power and force limiting. Power and force limiting is intended to keep contact forces and pressures low enough that an accidental contact does not injure a person, according to limits the application must justify. Speed and separation monitoring slows or stops the robot as a person approaches. [3] [5]

The distance calculation behind speed and separation monitoring is worked through in why an edge vision model cannot set the safe speed.

Inside a collaborative arm

Two documented examples show the common building blocks. Universal Robots lists six rotating joints, a 5 kg payload, an 850 mm reach and a built-in force/torque sensor with 4 N accuracy for the UR5e, along with 23 configurable safety functions rated PL d Category 3 under EN ISO 13849-1. Kinova offers its Gen3 with six or seven degrees of freedom, torque sensors integrated in each actuator, reaches of 891 mm and 902 mm, and support for ROS 2 Humble through its Kortex software. [1] [2]

Payload figures need reading carefully. Kinova lists 2.0 kg continuous across the full range and 4.0 kg in the middle of the range, both excluding the gripper. The gripper’s own mass, and the distance of the load from the wrist, come out of the payload budget. [2]

The motors, gearboxes and encoders inside these joints are described in how robot joints and actuators work.

Types of gripper

[6] [7] [8]

Robotiq’s 2F-85 is a concrete example of a two-finger gripper with adjustable behaviour: an 85 mm stroke, grip force adjustable from 20 to 235 N, closing speed from 20 to 150 mm/s, and support for both pinch and encompassing grips. [8]

The tool connects to the arm in two ways. A mechanical interface, usually a bolted flange at the wrist, carries the load. An electrical interface supplies power and signals, either through a tool connector on the arm or through separate cables. Both must match before a gripper can be used with a given arm.

Three objects, three grips

Holding a metal component with two fingers

With a friction grip, the fingers press with force F, and friction between each finger and the part provides at most μ × F, where μ is the friction coefficient. Two fingers must hold the part’s weight plus the extra force needed to accelerate it, with a margin: 2μF ≥ m × (g + a) × S.

Picking a box with suction

A suction cup’s theoretical holding force is the pressure difference times the effective cup area, F = Δp × A. Schmalz recommends a safety factor of at least 2, notes that German accident-prevention rules prescribe 1.5, and advises 2.5 or more when a part is swiveled. [7]

Handling something that breaks easily

A paper cup, a ripe fruit or a thin plastic part can be crushed by the force needed for a secure friction grip. Options include closing slowly with a low force limit, using soft pads or fingers that wrap around the object, holding it by its shape instead of by squeezing, or switching to suction on a smooth face. Tactile sensing can help the robot notice slip before squeezing harder. [8] [9]

How robots detect slip and choose contacts is explained in how humanoid robots pick up objects.

How the arm and gripper work together

A pick is a coordinated sequence. The arm moves the open gripper to a pre-grasp pose above the object, approaches slowly, and the gripper closes. The gripper reports that it has stopped closing, which suggests contact, or a vacuum sensor reports that pressure has dropped. A wrist force/torque sensor or joint torque sensors measure the added weight when the arm lifts. If the measured load is wrong, the controller treats the pick as failed. [6] [1]

Force sensing also protects people. Collision detection compares expected joint torques with measured ones; a sudden unexplained difference means the arm has hit something, and the configured reaction is to stop or move back. How hard the arm may press before reacting is part of the power and force limiting settings that the application’s risk assessment must justify. [4] [3]

Risk assessment and shared workspaces

Every application needs its own risk assessment. The general method is set out in ISO 12100, and the robot-specific requirements in ISO 10218-1 and ISO 10218-2, which were revised in 2025; Part 2 now incorporates collaborative application content drawn from ISO/TS 15066. In the EU, a Commission decision published in September 2026 lists EN ISO 10218-1:2025 and EN ISO 10218-2:2025 under the Machinery Directive; in the US, they are adopted as ANSI/A3 R15.06-2025. Check which edition applies in your jurisdiction and for your application. [10] [4] [11] [3]

[3] [5] [7]

What a safety certificate does and does not cover is explained in humanoid robot safety standards and certification.