Abstract : This paper proposes a computer-controlled magnetic particle brake to obtain controllable dynamic torque. The mechanical and electrical components of the complete device were designed and prototyped. Corresponding communication and interface programs were written, and a 750W, 5N•m level controllable dynamic torque mechanical simulation load system was successfully developed. This achieves the goal of outputting arbitrary controllable dynamic torque through computer-controlled mechanical simulation load. Keywords: Torque; Mechanical simulation load; Magnetic particle brake; MSComm control. [align=center]The Research of Mechanics stimulant load In Controllable dynamic torque Shanghai Second Polytechnic University Xindi Shen Chengying Lu[/align] Abstract : Put forward the tentative plan that use the computer to control the Magnetism Arrester in order to get the Controllable dynamic torque. Design and make the mechanism part and the electric part of the equipment, write the relevant program of communication and interface, achieve the goal that use the computer to control the Mechanics stimulant load in order to export any Controllable dynamic torque. On the foundation study out the improvement, design all the drawings of the new project. The complete set of the equipment use an AC servomechanism system to control the electromotor in Speed ​​Control Mode and Direction Control Mode, the speed of the electromotor will be reduced after the reducer and then through the screw and the inertia system to drag the Magnetism Arrester at last. On the other hand, using the program that be programmed in VB (Visual Basic) to control the Program Control Power which can change the Magnetism Arrester's The speed change of the electromotor is then monitored during testing. The 750W, 5N•m equipment of Mechanics stimulant load in Controllable dynamic torque can be used as teaching experimental equipment to test and research the speed change of the electromotor when the torque changes suddenly. The equipment can also be used to discuss the Mechanical Transmission System, the way to use Controlling Stimulant Load, theoretic analysis, and the demonstration of Controllable Dynamic Torque Mechanics stimulant load. After debugging the old project, bugs and shortcomings were found; suggestions and plans were put forward; and all the drawings of the new project were designed. Key words : torque; Mechanics stimulant load; Magnetism Arrester; MSComm Control Model 1 Introduction Developing a computer-controlled mechanical simulation load system capable of generating time-varying dynamic torque is of considerable practical significance for studying the dynamic characteristics of electromechanical transmission control systems and optimizing system parameters. This paper introduces a mechanical simulated load system that uses a magnetic powder brake to output torque. The output torque is controlled by a computer to obtain the dynamic load torque required for the experiment. Using the developed mechanical simulated load to construct an electromechanical transmission control experimental system, general conclusions about the dynamic processes of typical electromechanical transmission control can be obtained. Different types of loads have different T-n characteristics, especially under dynamic conditions. Different load characteristics place different requirements on the performance and control mode of the motor driving the load and its upstream control system. Using the successfully developed 750W, 5N•m level controllable dynamic torque mechanical simulated load system, experimental studies can be conducted on the dynamic torque loading process of various motors under different loads. 2 Electromechanical Transmission System An electromechanical transmission system is a dynamic whole of electromechanical motion driven by an electric motor and driven by a transmission mechanism to operate production machinery. As shown in Figure 1-1, torque in electromechanical transmission systems is the fundamental load form of transmission shafts in various working machines. It is closely related to factors such as the working capacity, energy consumption, efficiency, service life, and safety performance of power machinery. Torque measurement is of great significance for determining and controlling transmission shaft loads, designing the strength of working parts in the transmission system, and selecting the capacity of the prime mover. II. Methods for Simulating Mechanical Loads Currently, there are two main methods for simulating load torque: 1. Using a magnetic powder brake; 2. Using a DC generator with a resistor box load. The method using a DC generator with a resistor box load is relatively complex, while the magnetic powder brake is more cost-effective and easier to control. With a programmable controller, it can be connected to a computer, and the load value can be easily set by programming in VB. III. Magnetic Powder Brakes A magnetic powder brake is a high-performance automatic control element. It uses magnetic powder as the working medium and excitation current as the control means to achieve the basic characteristics of torque control and the purpose of braking or transmitting torque. Its output torque has a good linear relationship with the excitation current and is independent of the speed or slip, and has the advantages of fast response speed and simple structure. It is widely used in the tension automatic control system of winding devices in printing, packaging, papermaking and paper processing, textile, printing, wire, cable, rubber and leather, metal foil and strip processing and other related industries. 1. Load characteristics The allowable slip power of the magnetic powder brake is a constant value under certain heat dissipation conditions. When it is running continuously, the actual slip must be within the allowable slip power. When the speed is high, the torque needs to be reduced. Its characteristics are shown in Figure 3-1. [align=center] Figure 3-1[/align] 2. Features: (1) The excitation current is linearly related to the torque: The torque transmitted by the magnetic powder device is shown in Figure 3-2, which is roughly linearly related to the magnitude of the excitation current. Generally speaking, within 5 to 95% of the rated torque, the excitation current is directly proportional to the torque. (2) Stable slip torque: When the excitation current remains unchanged, the torque will be transmitted stably and is not affected by the slip, as shown in Figure 3-3. The static and rotating torques remain unchanged. Therefore, the magnitude of the torque can be controlled simply by controlling the current. (3) Fast response characteristics: The torque rise time and torque fall time of the magnetic powder brake are extremely short, so it can be used in situations with frequent start-stop and reversal. (4) Low control power: The power amplification factor is high, and a very small excitation current can be used to control a large transmission power, making it easy to achieve automatic control. (5) Smooth operation, no vibration, no impact, and low noise. (6) Overload protection: In the case of torque overload, automatic slip operation plays an overload protection role . IV. Main structure diagram [align=center] Figure 4-1 [/align] Figure 4-1 is the main connection structure diagram, in which the "transmission link" can be any combination of reducer, counterweight plate, screw drive and other systems. V. Introduction to MSComm control in VB (Visual Basic 6.0) The MSComm control in VB can be used to easily develop computer communication programs that use the computer serial port. The MSComm control provides two ways to handle communication: one is the event-driven mode, which is equivalent to the interrupt mode in general program design. When a serial port event or error occurs, the MSComm control generates an OnComm event, which the user program can capture and handle accordingly. Another method is polling, where the user program is designed to periodically or irregularly check whether certain properties of the MSComm control have changed, thus determining the appropriate action. This method can be used when the program has a lot of idle time. This design mainly uses VB to control the WLKC-3B programmable power supply via an RS-232 interface. Communication with RS-232 requires the use of the MSComm control in VB. The key to implementing computer communication using the MSComm control is understanding and correctly setting its numerous properties and methods. CommEvent: This is a very important property. This property is invalid at design time and read-only at runtime. Once a serial port communication event or error occurs, the MSComm control assigns different codes to the CommEvent property based on the event and error, simultaneously generating an OnComm event. The user program can then perform corresponding processing in the OnComm event handler based on the different codes. VI. VB Program The VB program is designed as a button program, and can automatically send data and generate waveforms at regular intervals after the button is pressed, which facilitates the function in actual operation. It can also generate various random torques as shown in Figure 6-1. [align=center] Figure 6-1[/align] Conclusion (1) Having a simulated mechanical load that can output controllable time-varying torque is of great significance for improving the experimental environment of electromechanical transmission system. This means that any loading form under simulated actual working conditions can be obtained under laboratory conditions. The successfully developed "simulated mechanical load device with controllable time-varying torque" provides an effective means for loading dynamic experiments of electromechanical transmission control system, motion control system, and CNC servo system. (2) It is feasible to use a magnetic powder brake as a dynamic torque output device. The output torque of the magnetic powder brake is linearly related to the input current. In the dynamic torque output test, when the time interval between two different torque values ​​is 30ms, the magnetic powder brake works normally. (3) Using a computer to control the mechanical system is one of the key points of this design. The key technology is the interface between the computer and the programmable power supply of the magnetic powder brake. The interface program of the interface program was written using VB programming language, which enables the generation of arbitrary torque curves on the computer as inputs of the magnetic powder brake, thereby realizing the output of arbitrary time-varying torque. References: [1] Zhang Fengsheng, Xu Zhiliang. Research on dynamic torque measurement technology. Modern Metrology and Testing, June 1997. [2] Jia Guixi, Qi Le, Zhang Bingda. Design of controllable load in dynamic simulation of power system. Journal of Power System and Automation, 2005, No. 06. [3] LZ Shuck, JL Fogle and RR Haynes. Dynamic micro-torque Experimental Mechanics Springer Boston February 18, 2006 [4] Dai Gil Lee, Seung Woo Lee Kwang Seop Jeong Static and Dynamic Torque Characteristics of Composite Cocured Single Lap Joint. Journal of Composite Materials, Vol. 31, No. 21, 2188-2201 (1997)