Abstract: This paper introduces the common types of traction motors in elevator systems and their advantages and disadvantages, pointing out that permanent magnet synchronous motors will be the mainstream choice for elevator traction machines. It also discusses several main control methods of traction motors and their characteristics, focusing on fuzzy control and neural network control in intelligent control systems. Through analysis and comparison, it concludes that multi-variety, intelligent and green environmental protection will be the development direction of elevators. Keywords: Elevator; Traction motor; Control mode [b][align=center]Present situation and prospects of motor and control system for Elevator Ni XinChang[/align][/b] Abstract: This paper introduces the commonly used types of tractive motors in elevator systems and their advantages and disadvantages. It points out that permanent magnetism synchronous motors will become the mainstream choice for elevator tractors. Simultaneously, it elaborates on several primary control methods and characteristics of tractive machinery. Emphasis is placed on the fuzzy control and neural network control of intelligent control systems. Through analysis and comparison, it aims to achieve multi-variables, intellectualization, and green environmental protection, which will be the future development direction of elevators. key word: Elevator; tractive motor; Control mode 1. Introduction Elevators are indispensable transportation tools in high-rise buildings. As buildings become larger, higher requirements are placed on the speed regulation accuracy and speed regulation range of elevators. For passengers, elevator performance requires safety, comfort, high speed, low vibration, and high leveling accuracy; for users, it also requires low cost, high efficiency, easy maintenance, and small footprint. Therefore, a high-quality elevator system needs to meet both performance requirements simultaneously, which presents new challenges to motor performance and its control mode. 2. Common Types of Traction Motors The performance of an elevator system largely depends on the performance of its motor. Therefore, selecting an ideal motor structure plays a crucial role in the normal operation of the elevator, making the choice of structure very important. Commonly used motor types in elevators include: AC asynchronous motors, brushed DC motors, and permanent magnet synchronous motors (including brushless DC motors). The advantages and disadvantages of each type of motor are as follows. 2.1 DC Motors Due to their excellent starting performance and smooth and rapid speed adjustment over a wide range, DC motors were once widely used in elevator systems. However, in recent years, the mechanical commutator of brushed DC motors has limited power increases, causing significant difficulties in maintenance and repair. Furthermore, radio interference from commutation sparks can affect the normal operation of the traction drive system. Due to these drawbacks, DC motors have been phased out of mainstream elevator traction systems. 2.2 Induction Motors Compared to other motors, induction motors have advantages such as simple structure, reliable operation, easy manufacturing, low cost, and durability. Using modern vector control methods, induction motors can achieve good speed regulation performance. The disadvantages of induction motors are: firstly, high losses, low efficiency, and high temperature; secondly, they must draw lagging current from the power grid, reducing the power factor of the grid. Therefore, induction motors will gradually be phased out of elevator traction systems. 2.3 Permanent Magnet Synchronous Motors Elevator drive systems have certain requirements for motor acceleration, speed stabilization, braking, and positioning. In the 1970s, with the development and maturation of frequency conversion technology, variable frequency speed control drives of asynchronous motors quickly replaced DC speed control systems in the elevator industry. In recent years, the latest drive technology in the elevator industry is the permanent magnet synchronous motor speed control system. It is small in size, has good control performance, and can achieve direct drive at low speeds, eliminating gear reduction devices; its low noise, leveling accuracy, and comfort are superior to previous drive systems, making it suitable for use in machine-room-less elevators. Permanent magnet synchronous motor traction technology utilizes high-performance permanent magnet synchronous motors, field-oriented vector transformation control technology, fast current tracking frequency converters, and low-friction gearless structures. It represents a leap forward in elevator drive technology and can completely replace existing traction technologies. 3. Control Technology of the Drive System The performance of an elevator system largely depends on the performance of the motor and the control mode employed. Therefore, selecting the ideal motor control mode plays a crucial role in the normal operation of the elevator. 3.1 Vector Control In inverter-powered systems, the analysis of permanent magnet synchronous motors typically employs the Park model in a synchronously rotating d,q coordinate system. In this model, the voltage, current, and magnetic flux of the synchronous motor can be decomposed into mutually decoupled d,q axis components. The control of the output torque of the permanent magnet synchronous motor can be reduced to the control of the quadrature-axis current and the direct-axis current. AC speed control systems using vector control outperform the speed control performance of DC motors. 3.2 Direct Torque Control Direct torque control is a new type of high-performance AC variable frequency speed control technology developed after vector control. The basic idea is to control the motor's torque and speed by adjusting the slip frequency, while maintaining a constant stator flux amplitude, and thus adjusting the rotational speed of the stator flux in space. This method analyzes the mathematical model of the AC motor in the stator coordinate system, emphasizing direct control of the motor's torque and omitting complex transformations and calculations such as vector rotation transformations. Therefore, direct torque control greatly reduces the problem of control performance being easily affected by parameter changes in vector control technology, and largely overcomes the shortcomings of vector control. Currently, direct torque control is mainly applied to induction motors, with less research on its application to permanent magnet synchronous motors. This is because the difference in rotor structure makes the direct torque control method for induction motors unsuitable for permanent magnet synchronous motors. In addition, although direct torque control has less dependence on motor parameters (only stator resistance needs to be known), the algorithm is more complex; otherwise, torque ripples will occur, requiring improvements in motor design and control methods. 3.3 Adaptive Control Adaptive control can continuously extract information about the model during system operation, gradually improving the model, and is therefore a powerful means of overcoming the influence of parameter changes. Adaptive control methods include: model reference adaptation, parameter identification self-correction control, and various newly developed nonlinear adaptive controls. The problems with these methods are: firstly, the mathematical models and calculations are cumbersome, complicating the control system; secondly, identification and correction both require a process, which may not be sufficient for systems with rapidly changing parameters, resulting in poor performance. 3.4 Intelligent Control Intelligent control theory represents a new stage in the development of automatic control, possessing several unique advantages compared to traditional classical and modern control methods. Firstly, it breaks through the framework of traditional control theory, which must be based on mathematical models, relying not on or only partially on the mathematical model of the controlled object, but solely on actual effects. Secondly, inheriting the nonlinearity of human thought, intelligent controllers also possess nonlinear characteristics; simultaneously, utilizing the convenience of computer control, the controller structure can be switched according to the current state, using variable structure methods to improve system performance. In complex systems, intelligent control also possesses hierarchical information processing and decision-making functions. Utilizing the nonlinearity, variable structure, and self-optimization functions of intelligent control to overcome the adverse factors of variable parameters and nonlinearity in AC servo systems can improve system robustness. Currently, intelligent control is relatively mature in AC servo system applications, including fuzzy control and neural network control, and most methods add certain intelligent control techniques to model control to eliminate the effects of parameter changes and disturbances. Fuzzy control utilizes fuzzy sets to characterize the fuzziness of concepts used in daily life, enabling controllers to more realistically mimic the control experience and methods of skilled operators and experts. It comprises two parts: fuzzification of precise quantities, fuzzy inference, and fuzzy decision-making. Early fuzzy controllers were intended simply to replace traditional PID controllers. While their robustness was improved, most fuzzy controllers lacked integral action, resulting in steady-state error when the transmission system was subjected to load disturbances. Fuzzy controllers with added integral effects, while equivalent to variable-coefficient PID regulators and capable of zero steady-state error control, still did not achieve satisfactory performance when simply using a simple traditional fuzzy controller in a high-precision motor drive system. Fuzzy control systems only achieve excellent performance when combined with other control methods. Neural networks are information processing systems that simulate the structure and function of the human brain using engineering techniques. Research on neural networks began in the early 1940s, and breakthroughs in neural network theory occurred in the 1980s, making it an important branch of intelligent control. Neural network models are used to simulate the activity of neurons in the human brain, including information processing, handling, and storage. The applications of neural network control in AC drives mainly include the following aspects: 1) Replacing traditional PID control; 2) Due to the sensitivity of actual vector control effects to transmission system parameters, neural networks are used for online identification and tracking of motor parameters, and adaptive adjustment of flux and speed controllers; 3) Vector control of induction motors requires knowledge of the instantaneous amplitude and position of rotor flux, while sensorless vector control also requires knowledge of rotational speed. Neural networks are used to accurately determine rotor flux amplitude, position, and rotational speed; 4) Combining model reference adaptive control, neural network controllers are applied to adaptive speed controllers. Although some progress has been made in the research of intelligent control for AC drive systems, many problems remain to be solved. For example, intelligent controllers are mainly designed based on experience, lacking objective theoretical foresight regarding system performance (such as stability and robustness). Furthermore, designing a system requires acquiring a large amount of data, and the designed system is prone to oscillations. 4. Conclusion In summary, the evaluation of modern elevator performance mainly focuses on safety reliability and ride comfort. In addition, there are corresponding requirements for economy, energy consumption, noise, and electromagnetic interference. Machine room-less and small machine room, gearless, electromagnetic compatibility, remote monitoring and other technologies will be the main research directions of the elevator industry in the future. Multi-variety, intelligent and green environmental protection will be the development direction of elevators. References [1] Zhu Changming. Elevator market and technology development trend [J]. China Elevator, 2005, 1 [2] Dai Yuying. Application prospect of permanent magnet synchronous motor in gearless traction elevator [J]. Motor Technology, 2006, 3. [3] Li Huiyi. Elevator control technology [M]. Beijing: Machinery Industry Press, 2006