In human-machine collaborative environments, ensuring operator safety is paramount. Six-dimensional force sensors, with their precise sensing capabilities and efficient feedback mechanisms, play a crucial role in this process.
I. Real-time force sensing
Multi-dimensional force detection
A six-dimensional force sensor can simultaneously detect three forces (Fx, Fy, Fz) and three torques (Mx, My, Mz) in three-dimensional space. In human-robot collaboration scenarios, this means it can sense the contact between the robot and the operator.
For example, when an operator's hand accidentally touches a working robot arm, sensors can detect the forces generated by this contact in various directions. Whether it's a side collision (Fx, Fy directions), a collision along the arm's direction (Fz direction), or the possible torsional torques (Mx, My, Mz), none of these can escape the sensors' "perception".
High sensitivity detection
The six-dimensional force sensor has high sensitivity and can detect minute changes in force. During human-computer interaction, even slight contact can be detected promptly.
For example, in medical surgery scenarios, the collaboration between surgical robots and medical staff requires a high degree of precision. If a medical staff member's finger lightly touches the robot's instruments, the sensors can sensitively detect this minute force, thus providing a basis for subsequent safety measures.
II. Setting and Determining Safety Thresholds
Threshold setting based on human tolerance limits
Based on human physiological structure and the limits of external forces that the human body can withstand, reasonable safety thresholds are set for the six-dimensional force sensor. These thresholds are determined through extensive human biomechanics research and safety standards.
For example, the maximum pressure a human arm can typically withstand may be within a certain range (e.g., less than 100N). This data can be used to set the safety threshold for the six-dimensional force sensor in the corresponding direction. When the force detected by the sensor approaches or exceeds this threshold, the safety mechanism will be triggered.
Intelligent judgment of contact intent
The sensor can not only detect the magnitude of the force, but also combine factors such as the trend of force change and duration to determine whether the contact is an accidental collision or an intentional interaction.
For example, if the change in force is instantaneous and large in magnitude, it may be judged as a collision; while if the force changes gradually and fluctuates within a small range, it may be that the operator is performing some slight guidance or adjustment operations. In this case, the robot can make a corresponding gentle response according to the preset program, instead of stopping directly.
III. Security Response Strategy
Emergency stop mechanism
When the force detected by the six-dimensional force sensor exceeds the safety threshold, the most direct safety response strategy is to immediately stop the robot. This can effectively prevent the robot from causing further injury to the operator.
In industrial manufacturing workshops, when a worker accidentally collides with a collaborative robot, sensors will quickly send a signal to immediately stop the robot's power system, preventing the robot's robotic arm and other components from continuing to move and crush or collide with the operator.
Speed and trajectory adjustment
In addition to emergency stops, robots can also adjust their speed and trajectory based on force information from sensors. This response method can provide more flexible safety assurance in some situations.
For example, in a logistics warehouse, when an operator has slight contact with a robot that is moving goods, the robot can appropriately reduce its speed and change its direction of movement based on the direction and magnitude of the force detected by its sensors, in order to avoid causing injury to the operator and to minimize disruption to the workflow.
Force feedback warning
The six-dimensional force sensor can also issue warnings to operators through force feedback. When the contact force approaches the safety threshold, the robot can generate slight resistance or vibration to alert the operator.
In some collaborative assembly tasks, the robot can alert the operator when their hand is about to approach the robot's high-speed movement area, reducing the possibility of a collision.
IV. System Integration and Security Standards Compliance
Integration with robot control systems
Six-dimensional force sensors can be well integrated with robot control systems. The sensors transmit the detected force and torque information to the control system in real time, and the control system executes corresponding safety strategies based on this information.
This integration is achieved through standard communication interfaces (such as Ethernet, CAN bus, etc.), ensuring fast and accurate information transmission. For example, in robot programming, a dedicated interrupt routine can be set to immediately execute the corresponding safety operation upon receiving a safety signal from a sensor.
Meets safety standards
Using six-dimensional force sensors ensures safety in human-robot collaboration, complying with various industry safety standards. For example, the ISO/TS 15066 standard specifies the force and energy limits for collaborative robots during human-robot contact.
The application of six-dimensional force sensors can help robot systems meet these standards, making the use of robots in human-robot collaborative environments safer and more reliable, thereby promoting the widespread application of human-robot collaborative technology.
