Understanding Collaborative Robots: Safety and Functionality

Cobot (Collaborative Robot)

Definition

A cobot (short for collaborative robot) is a category of industrial robot designed to work directly alongside human operators in shared workspaces, without the need for physical safety barriers (e.g., cages, light curtains) required by traditional industrial robots. Engineered for safe, intuitive human-robot interaction (HRI), cobots prioritize flexibility, ease of use, and risk mitigation, making them suitable for low-volume, high-mix production, repetitive tasks, and applications requiring human-robot teamwork.

Cobots comply with ISO/TS 15066 (the global standard for collaborative robot safety) and are distinguished from traditional industrial robots by built-in safety features, adaptive behavior, and user-friendly programming interfaces.

Core Characteristics of Cobots

1. Intrinsic Safety Design

Cobots are engineered to minimize injury risk during human contact:

Power and Force Limiting (PFL): Joints with torque/force sensors that detect collisions and immediately stop or slow movement (force limits typically <150 N for upper-body contact, per ISO/TS 15066).
Rounded Edges & Lightweight Construction: Smooth, non-abrasive surfaces and low-mass arms reduce impact severity if contact occurs.
Speed Restriction: Operates at reduced speeds (typically <250 mm/s) when humans are in the workspace, with faster motion allowed only in unoccupied areas (via Speed and Separation Monitoring, SSM).

2. Intuitive Programming

Cobots eliminate the need for specialized coding skills, enabling rapid deployment:

Lead-Through Teaching: Operators physically guide the robot arm to teach waypoints and sequences (teach-by-demonstration).
Graphical User Interfaces (GUIs): Touchscreen controls with drag-and-drop logic, pre-built task templates (e.g., pick-and-place, assembly), and real-time status feedback.
Handheld Teach Pendants: Portable controllers for fine-tuning movements, adjusting parameters (speed, force), and testing tasks.

3. Flexibility & Adaptability

Cobots are optimized for dynamic production environments:

Quick Reconfiguration: Tool changers (e.g., grippers, sensors) allow switching between tasks (e.g., assembly → packaging) in minutes.
Compact Footprint: Lightweight arms (10–50 kg) and modular design enable mounting on tables, mobile carts, or existing machinery.
Payload Versatility: Payloads range from 0.5 kg (precision tasks, e.g., electronics assembly) to 50 kg (heavy lifting, e.g., palletizing), with reach up to 1.5 meters.

4. Collaborative Operation Modes

Per ISO/TS 15066, cobots support four key modes of collaboration:

Mode	Description	Use Case Example
Power/Force Limiting	Torque/speed-limited joints stop on contact; no external sensors required.	Manual assembly assistance (hand-over tasks).
Speed/Separation Monitoring	External sensors (cameras/lasers) track human position; robot slows/stops as humans approach.	High-speed pick-and-place with occasional human intervention.
Hand Guidance	Operator controls robot via a handle/teach pendant; robot provides assistive force.	Guiding heavy tools (e.g., sanders, welders) for precision work.
Safety-Rated Monitored Stop	Robot stops completely when humans enter the workspace; resumes after clearance.	Semi-collaborative CNC machine loading/unloading.

Key Components of a Cobot System

1. Robot Arm

Axes of Motion: 4–7 degrees of freedom (DoF) for dexterity (e.g., 6-axis arms for 3D positioning, 7-axis arms for obstacle avoidance).
Actuators: Servo motors with integrated torque sensors for precise motion and collision detection.
End Effectors: Interchangeable tools including:
- Grippers (pneumatic, electric, vacuum) for part handling.
- Tools (screwdrivers, sanders, welders) for processing tasks.
- Sensors (vision systems, force/torque sensors) for quality control.

2. Control System

Main Controller: A compact unit running motion control software, safety algorithms, and task logic (e.g., Universal Robots Polyscope, ABB RobotStudio).
Safety Controller: Monitors all safety functions (force limits, speed, emergency stops) and communicates with factory safety systems (e.g., PLCs, E-stops).
User Interface: Touchscreen HMI or teach pendant for programming, monitoring, and troubleshooting.

3. Safety & Sensing

Force/Torque Sensors: Embedded in joints or end effectors to detect contact and trigger safe stops.
Vision Systems: 2D/3D cameras for part recognition, quality inspection, or human tracking (SSM mode).
Emergency Stop (E-Stop): Physical/software E-stop buttons for immediate shutdown in hazardous situations.

Real-World Applications

1. Manufacturing & Assembly

Electronics Assembly: Inserting components onto PCBs, soldering, or testing devices (e.g., smartphones).
Automotive Component Handling: Loading/unloading parts onto CNC machines, assembling dashboard components, or applying adhesives.
Medical Device Production: Assembling syringes, pacemakers, or surgical tools with micron-level precision.

2. Packaging & Logistics

Case Packing/Unpacking: Loading products into shipping boxes or unpacking raw materials from pallets.
Labeling & Coding: Applying barcodes, expiration dates, or branding to packages/products.
Palletizing: Stacking boxes/bags onto pallets (collaborative palletizers reduce human lifting strain).

3. Healthcare & Laboratories

Sample Handling: Moving test tubes, petri dishes, or labware to/from analyzers (reduces human exposure to hazardous materials).
Pharmaceutical Packaging: Counting pills into blister packs or bottles, ensuring dosage accuracy and compliance.
Rehabilitation Robotics: Assisting patients with physical therapy (e.g., robotic exoskeletons for mobility training).

4. Food & Beverage

Food Processing: Sorting fruits/vegetables, packaging ready-to-eat meals, or loading products into sterilization equipment (using food-grade materials).
Quality Control: Inspecting products for defects (e.g., missing toppings on pizzas) or verifying seal integrity on packages.

5. Education & Research

STEM Training: Teaching robotics, programming, and automation in universities/vocational schools (e.g., Universal Robots UR3 for classrooms).
HRI Research: Testing human-robot interaction algorithms (e.g., gesture control, voice commands) for future cobot designs.

Safety Standards & Compliance

Cobots must adhere to strict global standards to ensure safe operation:

ISO 10218-1/-2: Base standards for industrial robot safety (design, installation, operation).
ISO/TS 15066: Technical specification for collaborative robots (force limits, speed, risk assessment).
ANSI/RIA R15.06: U.S. standard for industrial robots, including collaborative operation requirements.
OSHA 29 CFR 1910: U.S. occupational safety regulations mandating risk assessments for human-robot workspaces.

Critical Risk Assessment Steps (per ISO/TS 15066)

Identify hazards (e.g., pinching, impact, entanglement).
Evaluate risk severity (injury level) and likelihood (frequency of contact).
Implement risk reduction measures (e.g., adjust force limits, add SSM sensors).
Validate safety via testing (e.g., simulated collision force measurements).

Advantages vs. Traditional Industrial Robots

Feature	Cobots	Traditional Industrial Robots
Safety	Built-in PFL/SSM; no physical barriers	Requires cages/light curtains
Programming	Intuitive lead-through/GUI; no coding	Complex programming (C++, ladder logic)
Flexibility	Quick reconfiguration for low-volume production	Optimized for high-volume, repetitive tasks
Cost	Lower upfront cost ($20k–$100k); fast ROI (6–18 months)	Higher cost ($50k–$500k); longer ROI
Speed/Payload	Slower (<1 m/s); smaller payloads (<50 kg)	Faster (>3 m/s); larger payloads (>1000 kg)

Leading Cobot Manufacturers & Models

Manufacturer	Popular Models	Key Strengths
Universal Robots	UR3, UR5, UR10, UR20	Lightweight, easy programming, wide payload range
ABB	YuMi, GoFa, SWIFTI	Dual-arm collaboration (YuMi), high speed (SWIFTI)
Fanuc	CR-3iA, CRX Series	Dust/water resistance (IP67), precision
KUKA	LBR iiwa, KR AGILUS cobot	7-axis redundancy, high force sensitivity
Doosan Robotics	A Series, M Series	Compact design, IoT integration