Introduction Currently, most elevators in China use time-based or incremental encoder-based relative distance control to operate. This traditional speed control method inevitably results in a relatively low crawling speed, which significantly impacts elevator performance. To improve elevator comfort and speed, crawling stops during leveling should be minimized. This paper introduces a speed control method based on the absolute residual distance principle. This method uses a sine curve as the ideal speed curve, eliminating crawling stops during braking and effectively addressing the issues of speed and comfort. Traditional Elevator Speed ​​Control Methods Time-based operation utilizes multi-speed commands to control the frequency converter based on an ideal given curve. The given speed curve consists of speed control points stored in the E2PROM and speed frequency values, acceleration/deceleration times, and S-shaped characteristic times stored in the frequency converter. While time-based operation isn't strictly closed-loop control, it determines the elevator's operating stage based on the elevator's characteristics and then operates in an open-loop manner, referencing the speed curve stored in the E2PROM. Therefore, its running time is an estimate, which leads to low leveling accuracy and poor comfort in this operating mode. Furthermore, elevator commissioning personnel have to do a lot of work to find the appropriate control point location. Relative Distance-Based Operating Mode Based on Rotary Encoders The ideal curve for this mode is designed according to the time principle, but the elevator's speed curve and displacement curve correspond to each other. Since the elevator's stopping position is known, and the car's position can be measured relatively accurately using an incremental encoder, the elevator can be controlled more precisely based on the relative distance principle. Compared to the time-based operating mode, this mode represents a significant improvement, offering higher leveling accuracy and better ride comfort. Figure 1 shows the principle diagram of this speed control mode. This mode indirectly obtains the car's position by calculating the rotational speed using a rotary encoder installed on the motor. Due to the inevitable slippage between the traction sheave groove and the wire rope, the controller is prone to losing the car's current accurate position. Therefore, it must use a shaft magnetic switch to provide the elevator's deceleration point position to continuously correct the elevator car's position. Therefore, the deceleration distance in this method is fixed. Because the real-time position obtained by the rotary encoder has errors, the calculated speed of the elevator at the deceleration point varies, resulting in crawling stops during leveling. If the wire rope slips severely, it can lead to serious elevator accidents. Simultaneously, due to interference, lost pulses from the incremental encoder can also cause the elevator to lose its correct position. On the other hand, as shown in Figure 1, this control method is actually a single closed-loop system. Its absolute position feedback only includes a few points such as deceleration and door position, and the real-time performance and accuracy of the system's speed control need improvement. [align=center] Figure 1 Relative Distance Speed ​​Control Principle Diagram[/align] Elevator Operation Mode Based on Absolute Remaining Distance ADCM Absolute Remaining Distance Speed ​​Control Basic Principle ADCM Absolute Remaining Distance Control Principle is a control method that uses an absolute encoder as the absolute position feedback for the elevator car. Absolute position is the actual position of the car, continuously measured in real time, while absolute remaining distance is the real-time distance from the elevator car to the desired leveling position. This is a relatively ideal elevator speed setting method. It calculates the elevator speed in real time based on the measured absolute remaining distance and sends speed control commands to the frequency converter to control the elevator's operation. Figure 2 shows the absolute remaining distance ADCM control principle, which is a control method that uses an absolute encoder as feedback for the elevator car's absolute position. Absolute position refers to the car's position, which is the actual position measured continuously in real time. Absolute remaining distance is the real-time distance from the elevator car to the desired leveling position. This is a relatively ideal elevator speed setting method. It calculates the elevator speed in real time based on the measured absolute remaining distance and sends speed control commands to the frequency converter to control the elevator's operation. Figure 2 is a schematic diagram of an elevator system based on the absolute remaining distance principle. When the elevator levels, the system calculates the remaining distance based on the elevator's real-time position value, provides a deceleration signal within a sufficiently short distance, and provides a corresponding speed to achieve a smooth transition from the deceleration point to the leveling position. While the system feeds back the car position directly obtained from the absolute encoder to the elevator main controller, it also feeds back the elevator speed to the frequency converter so that the system can adjust the given speed based on the elevator's real-time speed, improving the real-time performance of elevator speed control. Through the above measures, the system forms a dual closed-loop control of elevator speed, realizing the control of elevator running speed based on the accurate position of the elevator, eliminating the crawling stop during elevator braking and docking. It effectively solves the crawling stop problem during elevator leveling and docking, and at the same time realizes direct leveling of the elevator, improving leveling accuracy. [align=center] Figure 2 Absolute Remaining Distance Speed ​​Control Principle Diagram[/align] [align=center] Figure 3 Elevator Operation Diagram Based on Remaining Distance Mode[/align] Elevator Direct Leveling Control Process Based on ADCM * Acceleration Section When the elevator starts, the car position pulse generated by the incremental encoder is fed back to the microcomputer. The displacement counter inside the microcomputer accumulates the number of pulses to form the distance S that the elevator has traveled. Two elevator running curves with different rated speeds are stored in the E2PROM inside the microcomputer, namely the curves for multi-level operation and single-level operation. The microprocessor first determines whether the elevator is operating at a single level, selects a speed curve, and then uses the distance S that has been traveled as the address in the E2PROM to look up the corresponding curve value, and then converts it into a frequency value and sends it to the frequency converter. * **Constant Speed ​​Section:** During the constant speed section of the elevator, the microprocessor continuously sends the frequency value corresponding to the constant speed ν to the inverter and constantly monitors the car's position to see if it has reached the deceleration point. * **Deceleration Section:** When the car reaches the deceleration point, the microprocessor uses the number of pulses from the elevator car to the end point as a reference to calculate the distance L from the end point. The microprocessor uses the distance L to be traveled as the address of the running curve in the E2PROM, looks up the corresponding curve value in a table, and then converts it into a frequency value to send to the inverter. * **Leveling End Section:** When L=0, the brake is activated in time to engage, achieving accurate stopping without crawling during the deceleration phase. * **Single-Floor and Multi-Floor Operation Control Modes:** * **Single-Floor Operation Control Mode:** When the control board receives a call signal, it subtracts the received absolute encoder position value from the absolute position value of the next floor to obtain the distance between the elevator car and the target floor. As the elevator runs, the distance between the elevator car and the target floor continuously decreases. Simultaneously, the main controller continuously samples the real-time position of the elevator car through the absolute encoder and calculates the "remaining distance" value required for elevator operation. * Multi-level Elevator Operation Control Mode: When the elevator operates across multiple levels, the "remaining distance" is given in segments. First, the controller gives the "remaining distance" to the next floor. As the elevator runs, the value of the "remaining distance" continuously decreases. If the "remaining distance" decreases to the "deceleration distance" value, and no external call has yet occurred for that floor, then the "remaining distance" is the sum of the "deceleration distance" for that floor and the "floor spacing" for the next floor: the "remaining distance" has a step at this point. However, the decrease in the "remaining distance" is continuous as the elevator runs. As shown in Figure 3 above. Experimental Simulation The experimental equipment includes: elevator main controller – German Infineon C167CS simulator, THPLC-3 elevator model, embedded absolute remaining distance speed control module, one absolute encoder, one rotary encoder, and other equipment. The elevator speed operation curve measured under experimental conditions is shown in Figure 4. As can be seen from Figure 4, the actual curve matches the ideal curve well, improving the elevator's speed control characteristics. [align=center]Figure 4 Comparison of Theoretical and Actual Speed ​​Curves[/align] Conclusion Based on the research and analysis of existing elevator speed control systems, this paper introduces an absolute encoder as a new position feedback device and proposes a novel ADCM elevator speed control system architecture. This architecture adopts a double closed-loop structure, which improves the system's stability and better meets the requirements of comfort and speed. References: 1. Li Yanggeng, He Qiaozhi, He Fengfeng, *Elevator Basic Principles and Installation and Maintenance Complete Book*, Machinery Industry Press