Mobile AGVs (Automated Guided Vehicles) can efficiently, accurately, and flexibly complete material handling tasks, and their applications have become increasingly widespread in recent years. However, as a type of mobile object carrying a load, while AGVs bring convenience, they may also cause injury from collisions with people.
Relevant safety standards
• EN ISO 13849-1:2015 Safety of machinery—Safety-related components of control systems—Part 1: General design principles
Design Principles
• EN 1175-1 Safety of industrial vehicles – Electrical requirements – General requirements for battery-powered vehicles
• EN 1525 Safety of industrial vehicles – Unmanned vehicles and their systems (may be replaced by EN ISO 3691-4 in the future)
• VDI 2510 Automated Guided Vehicle System (AGVS)
Speed control requirements
Depending on the size and purpose of the AGV, common safety features include emergency stop buttons, safety scanners, safety edges, and safety position switches. These external safety sensors are "add-ons," readily visible, and easily considered when configuring AGV safety features. However, a point often overlooked is that uncontrolled AGV speeds can also pose a hazard to personnel. EN 1525 sets forth mandatory requirements for AGV speed control.
Security level assessment
The safety-related parts of a control system are called (SRP/CS). The safety level needs to be determined by considering the "input-logic-output" of the safety loop SRP/CS as a whole.
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The modular safety solution PNOZmulti 2 provides comprehensive protection for AGVs. The motion monitoring module PNOZ m EF 1MM or PNOZ m EF 2MM (selectable based on model, monitoring one or two axes) detects the speed signal of the moving axes to monitor the AGV's running speed in real time. To achieve the highest requirements of EN1525 (Cat 3 or PL d) for speed monitoring of a single axis, the following input signal method can be used.
logic
In the logic section, users can open the graphical operating software PNOZmulti configurator and use proven motion monitoring function blocks to implement a rich set of safety functions compliant with EN 61800-5-2:
• Safe Stop 1: SS1
• Safe Stop 2: SS2
• Safe Speed Range: SSR
• Safe Speed Monitoring: SSM
• Safe Direction: SDI
• Safe Operating Stop: SOS
These functions can reach a safety level of PLe/Cat 4, ensuring that the AGV's operating speed meets the design safety requirements in real time, and greatly reducing unnecessary downtime.
Output
In the output section, once the speed exceeds the limit, the corresponding signal of the safety output cut-off driver is triggered in the system. This completes the SRP/CS implementation for the speed control safety-related components.
The software's rich logic elements enable perfect coordination between speed control functions and external sensor signals.
The PNOZmulti2 programmable safety controller can integrate multiple safety functions into a single system. Its modular and scalable design offers great flexibility, and its graphical programming software is very simple and easy to use.
Pilz, as one of the few suppliers in the market that can provide complete safety solutions for AGVs, has mature solutions in the logistics and handling industry. With its accurate understanding of safety standards, it helps users achieve safe and efficient operation of AGVs.
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