As the modern industry gradually moves towards the Industry 4.0 era, the performance requirements of automation equipment are getting higher and higher. Due to some of its drawbacks, the traditional AC servo system is gradually unable to meet customer needs. To overcome the various disadvantages of traditional pulse-type servos, many servo manufacturers on the market are actively developing Fieldbus-type servo drives. At present, there are dozens of more mature Fieldbus technologies in the market. EtherCAT Fieldbus has been favored by most servo manufacturers in the world due to its excellent performance and open communication protocol. This article will briefly explain the development status of EtherCAT Fieldbus technology and the application experience in the actual field based on the application case of EtherCAT Fieldbus technology on the high-speed tape slitting machine.
Keywords: VEICHI bus type servo, EtherCAT, ultra-high-speed slitting machine,
EtherCAT Fieldbus has been widely used in the world since its introduction. At the end of last year, Beckhoff further introduced the second generation of EtherCAT Fieldbus technology-EtherCAT G. EtherCAT G adopts Gigabit Ethernet communication technology, which brings EtherCAT performance to a whole new level. EtherCAT G is not only fully compatible with the previous generation of 100M EtherCAT technology, which enables customers to communicate reliably without modifying the parameters of the master station but also has the same advantages of simplicity and ease of use. Also, the branch controller mode of EtherCAT G can realize the efficient operation of multiple subnet segments in parallel. When Beckhoff launched EtherCAT G Gigabit EtherCAT, it also proposed the design concept of 10 Gigabit EtherCAT 10G. The 10 Gigabit EtherCAT 10G has a higher communication rate (100Gbit/s). Therefore supports high-density data-intensive applications.
The slitting machine is mainly to complete the last process of the tape production process. The customer's traditional plan is to use the frequency converter and ordinary pulse-type servo to complete the tension control and labeling during the tape slitting process. The traditional scheme has shortcomings such as low efficiency and poor accuracy, and a lot of static electricity will be generated during the winding and unwinding of the tape, which easily interferes with the pulse received by the servo drive, thereby reducing the product qualification rate.
In response to the shortcomings of the customer’s old plan, the VEICHI application development team formulated a new set of automatic slitting machine solutions through discussion and analysis. Through the cooperation of VEICHI AC200T tension professional inverter and SD700 EtherCAT bus-type servo, the problem of low efficiency and poor anti-interference of the old solution is perfectly solved.
The last step of the tape production process is to use a slitting machine to divide the produced mother roll tape into finished tapes. The high-speed slitting machine designed in the case of this article is the automated equipment to complete this step. The entire control system can be roughly divided into three parts for separate design, namely: 1. Manipulator synchronous interpolation movement part 2. Inverter tension controls part 3. Labeling movement part.
To solve the problem of low efficiency of the old scheme, we added a manipulator to the new scheme to complete the loading and unloading actions, which increased the production efficiency by nearly 50%.
The manipulator part is composed of two articulated manipulators, which are driven by four VEICHI SD700 EtherCAT bus-type servos to drive the joint movement of the machine. The important and difficult point of this part of the control is that the synchronization of the left and right manipulators must be ensured during the movement. The synchronization time error must not exceed 2 microseconds, and the movement of the two joints of a single manipulator must also have interpolation algorithms. Therefore, it is very difficult to ensure the synchronization between the two axes while ensuring the interpolation trajectory. VEICHI SD700 EtherCAT bus-type servo drive adopts the principle of distributed clock synchronization to control the position loop. The time synchronization cycle is as short as 125 microseconds, and the position synchronization error between the two axes is about 1 microsecond, so the performance can fully meet the process requirements.
The old scheme uses ordinary Frequency converters because the slitting machine needs to be started and stopped continuously during the operation of the slitting machine, and the fluctuation of tension often occurs in the start and stop phase. Therefore, the system has very strict requirements for tension control, and the precision of the tension control of the ordinary inverter is too poor. In the new plan, we use the latest AC200T tension special inverter from VEICHI to complete the tension control of the system. VEICHI AC200-T tension control frequency converter is specially designed for places with strict tension control. Even in places with frequent start and stop, the precision of tension control can be guaranteed within the fluctuation range of 1.5%. It also provides tension taper control, making the processed products more perfect.
The labeling part of the system requires the EtherCAT clock synchronization function. The VEICHI SD700 EtherCAT bus-type servo drive adopts the distributed clock synchronization algorithm to make the slave axis more follow-up. In the labeling process, it can perfectly link with the spindle to complete the labeling action. The labeling accuracy has reached plus or minus 0.1mm through testing.
The more complicated part of the whole system is the manipulator. Since the design of the manipulator is not the traditional XYZ rectangular coordinate manipulator design, but the double-joint manipulator design, the coordinates of the end position of the manipulator need to be determined by the positive and negative solution algorithm. Because the entire system program is too large, here I only share the positive solution algorithm of the double-joint manipulator and how to control the manipulator to run to the specified position by interpolation.
Determine the relational expression of (X, Y) by (θ, α):
c=[a cos(θi)+a sin(θj)+[b cos(α+θ)j+b sin(α+θ)j]
c=[[a cos(θ)+b cos(θ+α)i+[a sinθ+b sin(θ+α)j]
Solved by the above formula:
x=a cosθ+b cos(θ+α)
y=a sinθ+b sin(θ+α)
The following is part of the algorithm program for manipulator control:
By switching to VEICHI bus-type servo and tension control inverters, the performance of the customer's equipment has been greatly improved, and both the production efficiency and accuracy of the equipment are at the leading level in the industry.
VEICHI has been committed to the research and development of more advantageous bus-type servo drives. At present, it has successfully developed a variety of high-performance bus-type servo drives including CANopen, EtherCAT, M-II, M-III, etc. and it has been obtained in the market. Lots of applications. Through practical tests, the VEICHI bus-type servo drive has reached a new height in terms of performance and stability.