Design of Machine Tool Testing System Based on Computer

This paper uses a computer as the main controller and adopts Windows-style interface software. It has fast calculation and testing speed, strong information processing ability, high system integration, friendly working interface, easy operation, realizes the automation of multi-parameter test process, and improves test efficiency and accuracy.

Main functions and features of the system

The system is mainly aimed at integrated testing of parameters that have a great impact on machine tool performance, and has the following functions and features:

(1) The system can measure the load of the reducer, and perform no-load test, load test, inertia load test, clutch on-off test, hysteresis test, etc. It can test the three axes of X, Y1 and Y2 at the same time;

(2) The system has online measurement for the automatic height adjustment system; the height adjustment precision function can test up to 8 heads at the same time, and the feed distance has automatic setting and user setting functions. The error value is calculated and displayed in real time as the head feeds;

(3) It has the functions of automatic test time setting, adding virtual load and load adjustment;

(4) The control system has a high temperature aging test function and automatically monitors and records the system status;

(5) Dynamic display of measurement data, if the data exceeds the standard, alarm will be given immediately or the experiment will be stopped;

(6) The test results are automatically analyzed and printed, and related file operations can be performed to facilitate in-depth analysis and statistics of the test results.

System hardware structure and composition

The system adopts a modular structure, with a computer as the main controller. The computer has rich software and hardware resources and powerful system functions, high computing and control speed, and good control performance in field control. The other parts of the system are connected to the computer through an interface card, controlled by it and providing test data for it. By executing the interface software on the computer, the hardware structure block diagram of the system is shown in Figure 1. It mainly consists of the following parts:

Figure 1 System structure diagram

Main Controller

The main controller of the system consists of an industrial computer, a standard keyboard, a mouse, a CRT color display and a printer. As the main controller of the system, the computer controls the actions of other parts through the interface card, collects test data, and performs complex calculations and analyses on these data to complete various test functions integrated by the system. At the same time, during the test process, the test results are displayed in real time and dynamically. If it is found that the standard is exceeded, an alarm will be issued and the fault time will be automatically recorded so that the operator can take relevant measures. The operator can perform human-machine operations through the display, keyboard and mouse, select the corresponding test items, enter the necessary test parameters, monitor the entire test process, perform corresponding file operations, and print the test results through the printer.

Interface modules

The interface module mainly includes the isolation driver card and the input/output interface card. The input/output interface card is responsible for the computer control of the test device and data acquisition, and is divided into a digital signal interface and an analog signal interface. The analog input (AI) uses Advantech PCI-726, the analog output (AO) uses Advantech PCI-1710, and the isolation driver card digital input (DI) and digital output (DO) use Advantech PCI-734. The specific number of channels is determined as follows:

Digital Input (DI):

Torque sensor 3-way

Code disk 18 way

Fault alarm 3 channels

Analog Input (AI):

Proximity sensor 8-way

Digital output (DO):

Clutch 3-way

Pulse inhibit 3-way

SV-ON 3-way

Pulse train 3 channels

Symbol 3 way

C-MODE 3-way

Analog Output (AO):

Servo command: 3 channels[page]

Loading control: 3-way

Total DI: 24 channels, AI: 8 channels, DO: 18 channels, AO: 6 channels.

The input and output interface cards used in this system are all PCI buses. Due to the large amount of testing and control, three interface cards are used. Through hardware adjustment, the base addresses are set to 300H and 330H respectively. The analog signal input and output channels are independent of each other, with a resolution of 12 bits, and the signal range is as follows:

Input range: -10V～+10V

Output range: -10V～+10V

The digital input and output signals of the interface card are compatible with TTL level and are easy to connect with other parts. The characteristics are as follows:

Input low level VIL≤0.8V

Input high level VIH ≥ 2.0V

Output low level VOL≤0.5V

Output high level VOH ≥ 2.4V

In order to ensure the safety of system operation, the system also uses an isolation driver card to ensure the isolation of computer signals and external signals through means such as photoelectric isolation, and amplify the output signal of the interface card into the required intensity control signal of the servo drive and clutch.

Motion Control Module

It mainly includes servo system and loading system. The servo system consists of servo motor driver, servo motor and photoelectric encoder. Its main function is to control the reducer under test to operate according to a motion law during the test. In this system, 3 sets of Panasonic (MINAS) servo systems are used to control the X, Y1 and Y2 axes respectively. The system has three control modes: speed control, position control and torque control, which can meet various motion control requirements during the test. Before use, parameter settings are required. The relevant parameter settings are as follows:

No.25=10000, No.26=7200

NO.27=1, NO.29=3

The servo drive is controlled by the computer interface card. When the servo command output of the interface card is +3V, the servo motor speed is 1500 rpm. The computer also controls the sign bit, output prohibition, SV-ON bit and C-MODE bit of the servo drive through the interface card. When the sign is 1, it corresponds to the CCW direction (forward rotation), when the pulse output is 1, prohibition is effective, SV-ON low level is effective, C-MODE low level is speed control mode, and high level is position control mode. During the test, according to different test items, the computer changes these control signals according to the program to make the servo motor work in different modes and states.

The loading system is mainly responsible for providing a virtual load to the shaft end. The loading controller receives the analog signal output by the computer and adjusts the current flowing through the loading device according to this signal, thereby controlling the torque at the shaft end.

Sensor Module

The proximity sensor uses the WYD series DC displacement sensor with a range of 20mm and an output voltage of 0~5V. The sensor is integrated with the electronic circuit, easy to install and use, does not require an external amplifier, and can be directly connected to the computer input and output interface card for analog-to-digital conversion and data processing, and then provide the micro-variables of relative displacement to the computer. The system uses a total of 8 proximity sensors to test and adjust the accuracy.

The torque sensor uses JN338 torque sensor, which can realize non-contact transmission of energy and signals, and the transmission is independent of whether it rotates, the speed, and the direction of rotation. The output signal is a pulse signal.

As a speed and displacement sensor, the output of the incremental photoelectric encoder is provided to the servo system for motion control on the one hand, and to the computer for collection on the other hand. The computer converts and counts the encoder output signal through software. The product of the total count value and the pulse equivalent is the displacement, and the displacement in a short period of time is the instantaneous speed.

Interface software development

The main application program of the system interface software is developed under the Windows operating system using the visual program development tool Visual Basic 6.0. The software operation interface adopts the Windows style, and its block diagram is shown in Figure 2.

Figure 2 System software block diagram

Visual Basic 6.0 is a powerful high-level visual programming language for computers, but it cannot directly access the computer input and output interfaces. To solve this problem, the system uses C++ language to compile a dynamic link library (DLL). All the access functions to the hardware ports are implemented in the link library. When a port needs to be accessed, the corresponding link library function is called to perform dynamic connection. This not only realizes the predetermined functions, but also optimizes the software structure and saves a lot of system resources.

in conclusion

The machine tool testing system designed with this system runs smoothly, has a friendly interface, is easy to operate, has high control accuracy, and the positioning accuracy of the X-axis, Y1-axis, and Y2-axis all reaches 0.024mm, and the repeat positioning accuracy of the X-axis, Y1-axis, and Y2-axis all reaches 0.015mm.