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In modern robotics, ensuring safe operation is paramount. Unintended collisions can lead to equipment damage, operational downtime, and, most critically, pose a risk to human personnel. While non-contact methods like vision systems and proximity sensors are effective for avoidance, force sensing technology provides a definitive, contact-based method for immediate collision detection. It serves as a critical layer of safety and control, enabling robots to react instantly to physical contact.
SOUSHINE develops and manufactures advanced force sensing resistors (FSRs) engineered for direct integration into robotic systems, providing the reliable data needed for robust collision detection protocols.
What is Force-Based Collision Detection?
Force-based collision detection is a method that uses sensors to identify and react to unexpected physical forces exerted on a robot’s structure or end-effector. Unlike predictive, non-contact systems that work to avoid obstacles, this technology detects the moment a collision actually occurs. By measuring the force of an impact, the system can trigger an immediate and appropriate safety response, such as a complete stop, a reversal of movement, or a switch to a low-power, safe mode.
This direct measurement provides a reliable fail-safe, particularly in complex or unpredictable environments where vision or proximity sensors may have limitations.
How It Works: The Mechanism of Force Sensing Detection
The implementation of force-based collision detection is a straightforward and effective process rooted in precise sensor technology. At SOUSHINE, we utilize our specialized Force Sensing Resistors (FSRs) for this application.
- Safety Protocol Execution: The controller instantly executes a pre-programmed safety protocol. This action is typically to halt all motion in milliseconds, effectively minimizing the force and potential damage from the impact.
- Integration: Thin, flexible FSRs are integrated directly onto the robot’s external surfaces, joints, or end-of-arm tooling (EOAT). Their low profile allows them to be applied to both flat and curved surfaces without altering the robot’s fundamental design.
- Baseline Calibration: During normal operation, the robot’s control system establishes a baseline of expected forces associated with its movements, acceleration, and payload handling.
- Impact Detection: When the robot collides with an object—be it a piece of equipment, a misplaced component, or a human operator—the object exerts a force on the FSR.
- Signal Generation: This applied force causes a predictable and instantaneous change in the FSR’s electrical resistance.
- Controller Response: This change in resistance is immediately detected by the robot’s central controller. If the force exceeds a pre-defined safety threshold, it is registered as a collision event.
Why Use Force Sensing for Collision Detection?
Integrating force sensing technology for collision detection offers distinct and measurable advantages for robotic systems.
- Enhanced Safety: It provides a fundamental safety layer, especially for collaborative robots (cobots) designed to work alongside humans. It ensures that any unintended contact results in an immediate cessation of movement, mitigating the risk of injury.
- Equipment Protection: By detecting collisions instantly, the system prevents damage to the robot arm, its end-effector, and other machinery or parts in the workspace. This reduces repair costs and minimizes production downtime.
- High Reliability: Force sensing offers a high-fidelity, direct measurement of physical contact. It is not susceptible to environmental factors that can interfere with optical or proximity sensors, such as dust, debris, ambient light changes, or transparent/reflective surfaces.
- Simplified Implementation: FSRs are a component-level solution that can be easily added to existing designs. Their thin, durable, and flexible nature allows for seamless integration onto the “skin” of a robot.
- Cost-Effectiveness: Compared to the high computational and hardware costs of some complex 3D vision systems, force sensing can be a more direct and economical solution specifically for contact detection.
Primary Applications
- Collaborative Robots (Cobots): Essential for ensuring the safety of human workers in a shared workspace.
- Industrial Automation: Protects high-value equipment during pick-and-place, assembly, and material handling operations.
- Autonomous Mobile Robots (AMRs): Provides physical bump detection to supplement navigation and avoidance systems.
- Medical and Surgical Robotics: Offers a critical safety measure to prevent excessive force application during delicate procedures.
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FAQ
How does force sensing for collision detection differ from a vision system?
A vision system is a non-contact, preventative solution that attempts to identify and navigate around obstacles before contact. Force sensing is a contact-based, reactive solution that detects a collision the moment it physically occurs, serving as a critical safety response system when avoidance fails. The two systems are often used in conjunction for comprehensive safety.
Can SOUSHINE’s force sensors be retrofitted onto an existing robot?
Yes. Due to their thin, flexible, and adhesive-backed form factor, our FSRs are well-suited for retrofitting onto the existing surfaces of robot arms and manipulators.
What is the typical response time of a force sensing system?
The Force Sensing Resistor itself responds in microseconds. The total system response time is primarily determined by the robot’s control system and its ability to process the sensor signal and execute a motor command, but it is typically in the range of milliseconds.
Are the sensors sensitive enough to detect light contact with a person?
Absolutely. Our FSRs can be designed with a wide range of force sensitivities. For collaborative robot applications, they are calibrated to detect very low forces, ensuring a rapid and safe stop upon gentle contact with a person.
How do I select the right sensor for my specific robotic application?
The selection process depends on factors such as the required force detection range, the surface area you need to cover, and the operational environment. We recommend contacting our technical support team through our website to discuss your specific requirements. We can provide data sheets and guide you to the optimal solution or a custom design.