Abstract: This paper introduces the use of a PMAC (Programmable Multi-Axis Controller) programmable motion controller as the motion control card to automatically test the performance indicators of a transmission mechanism, such as no-load drive torque, break-in period, rocker arm mechanism clearance, and transmission mechanism torsional clearance. It also describes the hardware design and corresponding software flowchart for real-time motion control of the performance test using PMAC. To address interference in the system, corresponding hardware and software filtering was designed to improve the accuracy of the system test. Experiments show that using speed control combined with position closed-loop control improves the system's positioning accuracy; software filtering combined with the use of a filtering circuit reduces system interference and improves measurement accuracy. Keywords: Programmable motion controller; drive torque; clearance; real-time control; filtering 1. Introduction This transmission mechanism is an important control component in the warhead of a certain type of missile. Its performance directly affects the missile's flight attitude and hit probability. Therefore, testing the various performance indicators of the transmission mechanism during production is a crucial step. The rapid development of modern testing technology has provided many advantages for equipment testing. Leveraging automated testing technology and based on the testing system's requirements for control accuracy and real-time performance, a transmission mechanism performance testing system based on the PMAC multi-axis control card from Delta Tau (USA) was designed, meeting the system's real-time and control accuracy requirements. Rapid testing of indicators such as no-load drive torque, break-in performance, rocker arm mechanism clearance, and transmission mechanism torsional clearance allows for determination of whether the transmission mechanism meets processing and assembly quality requirements. Recording test results facilitates accurate analysis and judgment of product performance, thereby improving product qualification rates. 2. System Composition and Working Principle The system mainly consists of mechanical components (tooling test bench), hardware control circuitry, and system software, which together complete the measurement of performance indicators. The testing system also incorporates multiple safety measures to prevent damage to the tested product and endanger testing personnel. Based on the system's test specifications, the system's working principle block diagram is shown in Figure 1: [align=center] Figure 1 System Working Principle Block Diagram[/align] The industrial control computer sends commands through the interface board to control the drive circuit to complete the action requirements of the test process. Simultaneously, it collects the necessary test signals for the test system in real time. After collection, the industrial control computer performs centralized processing and finally provides the test results of the product performance indicators. 3. Hardware System Design According to the product's test process flow, the position, speed, and torque of the test product must be controlled simultaneously during the test. This requires not only accurate positioning but also the ability to achieve different movement speeds during testing, and monitoring of torque changes to address the test gap requirement. Therefore, a PMAC (Programmable Multi-Axis Controller), servo drivers, and AC servo motors are used to jointly complete the required motion control. In this control system, the servo driver completes the speed loop control loop, the PMAC completes the position loop control loop, and finally, the torque control loop is closed-loop controlled by real-time torque detection via software commands. The entire test project is completed through these three closed-loop control loops. The corresponding speed closed-loop control block diagrams and position closed-loop control block diagrams are shown in Figures 2 and 3. [align=center] Figure 2 Speed ​​Closed-Loop Control Block Diagram Figure 3 Position Closed-Loop Control Block Diagram[/align] The performance of the test system is influenced by the accuracy of the controlled motion. In this test system, the control accuracy is achieved by a servo AC motor, and the quality of its electrical characteristics directly affects the performance of the test system. The motor must act according to the command without delay or error; to ensure this, the motor gain must be adjusted. As shown in block diagrams 4 and 5, the motor gain adjustment in this test system can be accomplished by two control modules. One gain adjustment module is set by the servo controller, and the other by the PMAC. In the servo controller, this is accomplished by adjusting the variable parameters related to the motor gain characteristics. In the PMAC, as shown in the position closed-loop control block diagram, it is necessary to adjust the PID parameters and auxiliary characteristic parameters to complete the setting. Each variable in the PMAC card comes with an initial value at the factory, but these variables need to be changed in different control systems. Adjustments to motor characteristic parameters can be made using relevant software packages, by viewing the system's motor output characteristic curve and adjusting the PMAC's PID parameters. The performance of the test system also depends on the accuracy of the test signal. Whether the test signal meets the performance requirements of the test system is influenced by both the sensor selection and whether the sensor signal is affected by external signal interference. After careful analysis and research of the test system, two types of torque sensors were adopted: one with a small torque range and a frequency signal output, and the other with a large torque range and an analog signal output. The latter sensor also has its own operational amplifier, whose output signal can be measured using two methods: single-ended input and differential input. Considering that the test system uses a servo driver and an AC servo motor control circuit, both of which can generate strong signal interference to the sensor, differential input method was selected to acquire the analog signal, effectively eliminating the influence of interference sources on the sensor. To eliminate the influence of signal interference on the sensor, shielded cables were used to connect the circuit, and the test signal needed to be filtered to restore the signal. There are two filtering methods: circuit filtering and software filtering. Both methods are used in this test system. This circuit filters the frequency signal from the sensor. The principle is to first filter, then use a trigger to shape the waveform, and then filter again. This circuit has a very good filtering effect on this frequency signal. 4. Software System Design The software test system is implemented using Visual C++ on the Windows 2000 platform. In this test system, the PMAC is plugged into the ISA slot of the industrial control computer, and the data acquisition card is plugged into the PCI slot, working in conjunction with the host computer. First, the host computer initializes these boards, setting relevant variables and operating modes. After initialization, the system self-test module is entered. If the self-test is successful, the test interface is entered. After clicking the corresponding test item on the test interface, the host computer transmits control commands to the multi-axis control card through the ISA interface. The multi-axis control card sends the received commands to the driver, which drives the motor to move at a certain speed. Simultaneously, sensor signals are acquired in real time according to different positions. Then, the acquired data signals are transmitted to the host computer through the PCI interface for data processing. The data processing and process control algorithms are the core algorithms of the testing system. Figure 4 shows the software flowchart of this core algorithm. The data processing algorithm involves signal filtering. By analyzing the acquired signals, the Butterworth algorithm is used for filtering, which has a very good effect. [align=center] Figure 4 System Software Flowchart[/align] 5. Analysis of Difficulties and Solutions • Technical Difficulty 1: Avoiding the influence of assembly errors on test results. Solution: Use AC servo motor drive, with controllable position, torque, speed, and acceleration; use torque and force sensors to directly acquire loading force and torque signals, which is simple to operate; adopt an integrated design for loading and displacement measurement, making it easy to eliminate the influence of random factors in result analysis; in addition, a friction torque software compensation method is adopted to eliminate the influence of non-random factors. • Technical Difficulty 2: Test accuracy. Solution: A dual torque sensor is used, utilizing input and output torque signals to accurately determine the backlash-free boundary position. Combined with an AC servo motor drive, position, torque, speed, and acceleration are controllable. An optical encoder measures angular displacement, ensuring accurate and reliable measurements. The torque sensor directly acquires input/output torque signals, improving test precision, accuracy, and reliability. • Technical Challenge 3: Applying constant torque to the rudder shaft. Solution: To solve the problem of applying constant torque to the rudder shaft, electromagnetic loading (with a pneumatic loading solution as a backup) is used in the design. The power source is easily guaranteed, stable, impact-free, and clean. Torque and force sensors directly acquire loading force and torque signals, facilitating data acquisition and processing in the control system. A multi-force/torque closed-loop control system is used, making it easy to eliminate the influence of random factors in the test results and simplifying operation. 6. Analysis and Summary The PMAC multi-axis motion control card manufactured by Delta Tau (USA), combined with Panasonic servo drivers and servo motors, forms the control system. Under the Visual C++ environment, the real-time characteristics of the operating system are utilized to achieve real-time motion control requirements, completing the automatic testing of transmission performance indicators. Two closed-loop controls, position and acceleration, were adopted. Hardware filtering and software algorithm processing were designed. The above methods have been well applied in the development of a transmission mechanism performance test and have achieved good results. Through the design of this system, a deeper understanding of computer control system has been achieved, and it can also be used as a reference for the analysis and design of other control system performance. The innovation of this paper is: two closed-loop controls, position and acceleration, are adopted, which greatly improves the positioning accuracy of the system; hardware filtering and software algorithm processing are designed to reduce the interference of the system. References: [1] Hu Youde, Zeng Lesheng, Ma Dongsheng. Servo System Principles and Design Beijing Institute of Technology Press [2] Tong Baishi, Hua Chengying. Analog Electronic Technology Basics Higher Education Press [3] He Xicai. Sensors and Their Applications Electronic Industry Press [4] PMAC Software Manual Version 1.0 Beijing Yuanmaoxing Control Equipment Technology Co., Ltd.