Synthesis of a Fuzzy Controller for an Adaptive Security System of Collaborative Robot Based on Computer Vision

Abstract

The article addresses the pressing scientific and technical problem of ensuring functional safety in conditions of close human-robot collaboration on modern automated lines. The research is conducted in the context of the global industrial transition to the Industry 5.0 paradigm, which requires the creation of flexible and human-centric production systems. The drawbacks of traditional safety safeguards (physical barriers, light curtains) are analyzed, the main of which is the rigid binary triggering logic. It initiates a complete emergency stop of the equipment upon any perimeter breach, leading to the interruption of technological cycles, increased downtime, and accelerated mechanical wear of the actuators.

As an alternative, a method of dynamic Speed and Separation Monitoring (SSM) based on contactless computer vision is proposed. The authors have developed a three-level architecture of an intelligent safety system. At the first (sensor) level, the MediaPipe neural network framework is used, which processes the video stream in real time and generates spatial 3D coordinates of the operator’s skeleton joints. At the data processing level, a software module calculates the minimum distance between the human and the hazardous parts of the robot, and also differentiates its change to determine the kinematics of movement.

The scientific novelty of the work lies in the synthesis of a Mamdani-type Fuzzy Controller for adaptive control of the manipulator’s speed, which, unlike existing solutions, implements a proactive strategy. Most known systems rely solely on static distance or actuator load (a reactive approach). The proposed system utilizes two linguistic variables: "Distance to the operator" and "Approach speed". This allows the controller to act preemptively: the system is capable of slowing down the robot in advance if a person approaches the zone with high acceleration. Such an approach ensures effective and safe dynamic scaling of virtual working zones (green, yellow, red).

To verify the developed algorithm, mathematical modeling was performed in the MATLAB environment using the Fuzzy Logic Toolbox package. The application of the defuzzification procedure using the Center of Gravity method made it possible to obtain a smooth response surface. The results of the comparative analysis confirm that the synthesized fuzzy controller guarantees a stepless, smooth change in speed, completely eliminating the "chattering" effect of the control signal at the boundaries of virtual barriers. The practical significance of the work lies in the possibility of integrating the proposed architecture into the control systems of industrial cobots to optimize the balance between productivity and occupational safety.