Market Application Background
As the size of products such as flat panel displays (including TFT/LCD, PDP, and OLED) increases, and the demand for compatibility with miniaturized, high-precision products intensifies, major manufacturers are placing higher demands on the load capacity, moving platform range, efficiency, and accuracy of vision alignment processes. Therefore, UVW alignment platforms have become the ideal choice for users who need to meet these requirements.
The UVW alignment platform, also known as the XXY alignment platform, is a three-axis parallel motion mechanism. Through the coordinated control of three linear motion axes, it can achieve rotation around any point on a plane and translation in any direction. Combined with a CCD vision system, the platform performs precise fine-tuning in the XY plane and at the θ angle, achieving high-precision visual alignment with an accuracy of ±0.001mm.
The UVW vision alignment platform is widely used in intelligent equipment that requires high-speed and high-precision positioning alignment, including exposure machines, bonding machines, screen printing machines, wafer alignment machines, PCB drilling machines, laminating machines (LCD/FPC), vision die-cutting machines, lithium battery stacking machines, etc.
Limitations of traditional XYθ platform solutions:
The XYθ platform has a relatively simple structure, mainly consisting of two X and Y linear axes and one rotation axis. It mainly performs displacement and central rotation in the XY plane, but cannot perform central rotation based on the coordinates of any point, which affects its application in high-precision vision alignment and reduces its flexibility.
The vertical stacking structure of the XYθ platform makes the worktable relatively bulky, hindering rapid movement or adjustment and making it difficult to integrate with other motion axes, thus reducing the efficiency of automated equipment development. Compared with the UVW platform, the XYθ platform is also inferior in terms of rigidity, load capacity, and repeatability, limiting its application in high-speed, high-precision vision alignment applications.
Positive motion technology solutions:
To address current market demands, Zhengdong Technology has developed a UVW vision alignment solution based on the VPLC7 series machine vision motion control integrated machine. Users can select the axis list for the corresponding model and use the corresponding instructions to establish the forward and inverse kinematics of the robot, converting this into the movement distance of each linked axis. Combined with a high-precision CCD vision system, this enables rapid and high-speed, high-precision binocular or quad-eye UVW vision alignment applications.
The UVW platform motion control algorithm of positive motion technology is compatible with three common models: FRAME33, FRAME34, and FRAME37, which correspond to two mechanical structures (PRP and PPR) and two coordinate system directions (XYY and XXY), respectively. It can realize complex motions such as single-axis linear motion, two-axis linear interpolation, two-axis circular interpolation, and spatial circular arc.
The VPLC7 series machine vision and motion control all-in-one machine integrates vision and motion control, replacing the traditional PC industrial computer + vision software + motion control solution. Hardware wiring is more convenient and costs are lower. Equipped with the MotionRT7 real-time motion control kernel, it features in-core interaction and command call speeds down to the microsecond level, improving processing and inspection efficiency.
01. Application of VPLC7 Machine Vision Motion Control All-in-One Machine in UVW Vision Alignment
UVW Vision Four-Eye Alignment Application Diagram
Traditional UVW visual alignment scheme
The combination of industrial PC, vision software, and motion control card involves many components, complex wiring, and requires data exchange between vision and motion control, making troubleshooting difficult. Furthermore, the cost and maintenance of multiple hardware sets are relatively high.
Design of UVW visual alignment scheme for positive motion technology
• Ethernet interface: Gigabit Ethernet port, supporting up to 8 cameras via a switch;
• EtherCAT interface: Connects to the EtherCAT bus driver to control the UVW drive motor;
• 20DI: Connects to origin, limit, and other sensors, as well as switch signals, etc.
• 20DO: Connects to the output switch signal, or a single-ended pulse output (500kHz);
• HDMI port: Connect to a display screen;
• USB interface: for connecting mouse, keyboard, etc.
Motion control and machine vision implementation process
(1) Machine vision
Depending on the specific application requirements, two or four area scan cameras are used to capture alignment marker points. Calibration can be completed in one step by configuring camera parameters and selecting marker points to create the target area, obtaining calibration coefficients, simplifying visual operation steps, and reducing the difficulty of field applications.
The system automatically calculates the deviation between the target position and the actual position (including the positional offset of the U, V, and W axes and the angular offset of the θ axis), thus realizing the UVW visual alignment function.
(2) Motion control
Select the corresponding model's axis list, set the joint axis parameters and virtual axis parameters, and determine the robot's zero-point position (RAME33 requires ensuring the VW axis is horizontal. Any point on the platform can be used as the zero point, as long as the structural parameters are correct). Then, use the corresponding instructions to establish the robot's forward and inverse kinematics solutions, and calculate the relationship between the original three-axis positions of the UVW platform and the relative coordinates obtained by two or four area scan cameras.
After determining ΔU, ΔV, and ΔW, the UVW platform can then perform rotational and translational movements linearly along the three axes to compensate for positional and angular deviations, enabling high-speed and high-precision vision alignment applications.
UVW visual alignment process flow
Core advantages of the solution
• Integrates machine vision, UVW control, and motion control into one unit, making hardware wiring more convenient and reducing costs;
• Real-time motion control kernel with intra-kernel interaction and instruction call speeds down to the microsecond level, improving processing efficiency;
• Built-in UVW platform algorithm, making it easier for customers to use and improving engineers' development efficiency;
• Improve cycle time by automatically calibrating to determine the positional relationship between the camera and the worktable;
• Built-in visual algorithm for high accuracy; dual-camera positioning accuracy within 2 pixels.
• A unified API function interface, applicable to various PC host computer languages, making it easy for customers to integrate into existing systems and create high-speed, high-precision vision alignment systems.
Solution Hardware Configuration
02. VPLC7 Series Machine Vision and Motion Control Integrated Machine
The VPLC7 series machine vision motion control all-in-one machine vision controller from Zheng Motion Technology is a high-performance EtherCAT motion controller based on the x86 platform and Windows operating system. It can operate offline, supports rich IO control, 30+ robot algorithms, and vision and motion control functions, greatly simplifying the configuration process of vision and motion control projects.
The VPLC7 series machine vision motion control integrated machine is easy to install and remove, occupies little space, and can be seamlessly integrated with other control unit components (such as servo drives, sensors, encoders, control valves, etc.) and MES systems, providing a complete end-to-end vision motion control solution.
• Optional 6-64 axis motion control (pulse + EtherCAT bus)
• Built-in real-time kernel MotionRT7, supporting third-party vision software
• Onboard 20 general purpose inputs (10 of which are high-speed inputs), 20 high-speed outputs
• Provides integrated vision and motion control solutions with real-time soft controllers/soft PLCs in an all-in-one open IPC form factor.
Multi-core parallel computing enables efficient processing of core tasks in automated equipment such as motion control and machine vision.
