This article aims to introduce the application of EP3E servo drive in SCARA robots, and provide customers with a complete set of robot electronic control system solutions based on POWERLINK bus.

1. Overview

In recent years, China's industrial robots have shown rapid growth in new installations and ownership, the current overall ownership is about 10W, and according to research institutions, the future robot market will continue to develop at an annual growth rate of 25%.

SCARA robot is a desktop type 4-joint robot model, which is widely used in the metal processing industry for loading and unloading, dispensing, gluing and handling in the electronics industry, and handling and assembly in the glass industry. Although domestic robots are in rapid development, most of the domestic SCARA robots are controlled by pulse, and a motion control unit can only complete the control of a single SCARA robot, and cannot complete the status monitoring and control of each axis of the SCARA robot.

EP3E servo drive is the latest domestic first servo drive based on POWERLINK bus launched by Wuhan Meixin Electric Technology Co., Ltd., which can be connected to singleturn or multiturn absolute encoder, real-time bus jitter online synchronous adjustment and other innovative technologies, providing customers with higher performance, more flexible and safer servo system.

EP3E servo drive from the product size, connection mode is very suitable for multi-robot industrial field production, its POWERLINK bus network to the end of the connection mode, wiring method is more convenient, can provide more convenience for the customer's SCARA robot automated assembly line, can provide customers with more cost-effective solutions.

2. SCARA robot control

The SCARA robot used in this project is the latest domestic equipment, which has the characteristics of compact structure, high production efficiency, high precision and strong overload capacity. This project is used for automatic dispensing production line, suitable for dispensing process, laser cutting, soldering and other occasions. The product is shown in Figure 1:

Figure 1 Photo of the SCARA robot solution

3. System design

3.1 Customer Needs

The customer required the SCARA robot to have a high processing speed, as well as a very high automation, which can automatically complete the loading and unloading functions of the production line, and at the same time require very high stability. In addition, the customer requested the ability to view the working status of the robot through remote access in real time.

3.2 System design

Through in-depth analysis of customer needs, we designed an electronic control solution of "B&R's X20 controller + EP3E servo drive" for customers, as shown in Figure 2.

Figure 2 Electrical scheme diagram of SCARA robot

The advantages of this system are:

(1) X20 motion control system integrating MC, CNC, robotics

The X20-based motion control solution is a design platform using universal motion control technology, which combines robot, CNC, multi-axis motion and single-axis positioning into a system through POWERLINK bus technology. Complex path information can be applied to machine tools and production machinery, and multi-axis joint robot control can also be realized to carry out complex 3D diagram CNC machining. With the real-time operating system, the motion control cycle time can reach 400μs, CNC, PLC, I/O and drivers can be synchronized with high precision down to microseconds, the same processor handles motion control and logic control, and CNC and PLC run tasks synchronously.

The software framework of the X20 is shown in Figure 3, and the supported CNC technologies include:

1. Support the standard language of standard DIN66025, support customer-defined interpretation language;
2. Each system has 8 CNC channels, each CNC channel interpolates up to 15 axes to participate, and each CNC channel is non-interpolated without limiting the number of axes;
3. Each path segment has the function of "program segment pre-reading", which optimizes the motion trajectory and can change the speed magnification in real time;
4. Automatic tangent cutter wizard, widely used in leather cutting, glass cutting and other industries;
5. Reverse movement along the wheel gallery, widely used in laser cutting, water cutting and other industries;
6. More than 20 kinds of multi-axis motion conversion, support customer-defined coordinate transformation;
7. Unidirectional and bidirectional pitch error compensation and backlash compensation, support axis offset compensation of Cartesian coordinate system;
8. All technical functions: milling, grinding, cutting, welding, handling, packaging, woodworking, mahogany, stone, marble, glass cutting and other industries;

(2) EP3E high-performance servo drive

EP3E is the first product in China to pass the compliance test organized by EPSG, so it can cooperate well with the X20 controller; At the same time, the control cycle of EP3E's built-in current loop, speed loop, and position loop is 50us, 100us, 100us, respectively, which can support 17-bit singleturn and multiturn encoders, or 20-bit singleturn and multiturn encoders, and supports real-time Ethernet bus jitter synchronization adjustment technology, which can fully meet the requirements of MC, CNC, robotics for dynamic response and synchronization.

3.3 System Software Framework

Figure 4 System software framework

The system software is composed of Configuration, System, Cnc and Axes modules, the Configuration module is responsible for the configuration of the entire system, System is responsible for the system state machine, and CNC and Axes are responsible for interpolating channel state machine and axis state machine respectively. In order to achieve complete robot software functions, the system software also includes functions such as coordinate transformation, servo communication and human-machine interface communication.

4. System performance test

During the actual test, the system was successfully commissioned in a short time.

Figure 5 Trace data of motor current in each axis of SCARA robot

5. Concluding remarks

Wuhan Meixin Electric is committed to providing POWERLINK bus servo drives for domestic automation equipment manufacturers, which can meet the requirements of MC, CNC, robotics and various industries for servo systems in terms of performance and function, and at the same time, the price is not as high as foreign servo drives, so as to realize the POWERLINK busification of domestic SCARA robots, reduce the overall cost of domestic robots, and improve the competitiveness of domestic robots.