PC-based control drives AGV advances

01 February 2021

A comprehensive PC-based control solution has enabled a Chinese technology company to develop better-performing products more efficiently and is also helping these products to meet the requirements of Industry 4.0 and the Made in China 2025 initiative.

As the industrial sector continues to evolve rapidly, the need for flexible and intelligent logistics systems is on the rise. Driverless transport systems have an important role to play in this arena. Suzhou i-Cow Intelligent Logistics Technology Co has addressed this market with the development of a range of driverless forklifts equipped with a laser-based navigation system, designed to meet the needs of automated warehouse logistics across a wide range of industries. The company also offers custom solutions, which enable automated guided vehicle (AGV) manufacturers and integrators custom solutions to incorporates i-Cow’s core technology into their own hardware.

Laser navigation
The core challenge for advanced AGV systems used in warehouse logistics is to navigate flexibly and efficiently through the racks of inventory. One solution is computer-aided vehicle control based on laser technology, which enables vehicles to navigate freely within the warehouse space and also offers cost advantages, because it does not rely on fixtures embedded in the floor. i-Cow’s laser-guided AGVs can automatically pick up and deposit goods on warehouse shelves. The laser navigation system works with just a single vehicle, but it is capable of supporting multiple vehicles when combined with a traffic management system.

To meet the tough technical challenges involved in this type of navigation, i-Cow’s system relies on PC-based control technology from Beckhoff. The system is controlled by an embedded PC with a dual-core Intel Atom CPU running TwinCAT 3 software and incorporates a control panel with 5.7in h touchscreen for visualisation and operator interaction. The TwinCAT 3 PLC HMI provides a user interface for easy configuration of AGV parameters, AGV positioning, and troubleshooting problems occurring at rack locations in the warehouse. To achieve the levels of speed and precision needed for laser-based navigation, the system employs oversampling terminals that benefit from Beckhoff’s eXtreme Fast Control (XFC) technology. A TwinSAFE solution that integrates safety features seamlessly into the overall system was also supplied.

The compact embedded PC handles all the control functions required for laser navigation. It replaces a conventional navigation-control system and communication module reduced both space requirements and costs. The software functionality includes a laser navigation algorithm and a control loop for AGV drive and steering axes, both written in C++ code, plus control logic for a single AGV, the PLC/HMI for visualisation, planning software, and a TCP/IP communication program for the automatic charging station.

“We chose the CX5130 for its performance, range of interfaces and compact design. As a DIN rail-mounted embedded PC, it takes up less space than the previous control systems. Another advantage is that the Beckhoff bus terminal system supports a variety of fieldbuses, including CANopen and PROFIBUS, so it is compatible with our existing peripheral devices,” said Yongping Pan, head of Research and Development at i-Cow. “In addition, the embedded PC has Ethernet ports and supports a variety of protocols, making it easier for us to implement wireless communication.” 

When an AGV is navigating by laser, a built-in laser scanner performs rapid rotating sweeps to capture reflective markers located around the operating area. The exact position of the AGV can only be computed once a sufficient number of markers have been scanned. Precise, high-speed, scanning is vital. To achieve this, i-Cow uses an XFC EtherCAT digital input terminal with oversampling. This solution enables up to 1,000 sampling operations in 1 ms – which corresponds to a sampling cycle of 1 µs – it supports exceptionally high-resolution target-value and actual-value acquisition that meets the high-speed requirements of laser navigation.

Higher performance
The ability to programme in C++ and e to call up modules has simplified both the development process in general and migration of the navigation control algorithm in particular. In addition, due to its flexibility and modular design, TwinCAT 3 offers an efficient development environment suited to creating a range of software components and enables i-Cow engineers to work collaboratively as a team.

“The ability to work with C/C++ as a programming language is valuable for us because we’ve gained a lot of experience with it over the years and it allows us to implement complex function blocks. If a process lets us code in C++, we can embed the function blocks quickly and easily in TwinCAT 3, as is the case with the laser navigation code, which is written in C++. TwinCAT 3 also allows individual program tasks to be distributed across multiple CPU cores. This means that the computing power of multi-core CPUs can be leveraged to enable programs to execute faster,” explained. Zhifei Yu, head of i-Cow’s development department.

Saving time and money 
Although AGVs with laser navigation can take on much of the workload in a warehouse, they still need to work alongside people, so collision protection is crucial. Here, i-Cow has opted to deploy a comprehensive solution using Beckhoff’s TwinSAFE open and scalable safety technology. 

The AGV chassis is fitted with safety sensors all the way round that are scanned via the input terminal. If the sensors detect an obstacle in an AGV’s safety zone while it is moving, the TwinSAFE system responds immediately, first engaging the emergency brake on the AGV’s drive axis, then cutting the power to the drive after a preset delay. “Using TwinSAFE to fully integrate a safety solution into the control technology eliminates the need for a separate safety system and all the extra effort it would have involved. Our solution reduces cabling costs and development time,” said Haixia Wang, i-Cow’s safety officer.

Since i-Cow began using Beckhoff components to implement laser-based navigation on its forklift AGVs in early 2016, collaboration between the two companies has widened and intensified. Beckfoff automation solutions are now also being implemented in magnetically guided shuttles and in vehicles for smart rack systems, both currently under development. “The PC-based automation platform’s openness and flexibility give us the latitude to solve a wide range of application problems,” concluded Wang Ping, i-Cow’s Chief Executive Officer. 

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