Optimized Design for Control Functions of Elevator Teaching and Training Equipment

Given the current limitations of the existing elevator teaching and training equipment, which commonly use limit switches for floor positioning and have simplified control functions, the electrical control deviates significantly from actual elevator systems. As a result, there is a lack of programming training content, which hinders students' ability to meet the requirements for elevator installation, maintenance, and servicing. In order to address this issue, we propose enhancing the existing control system based on a four-story elevator by adding an encoder floor positioning circuit, a weight control circuit, and an emergency rescue device. Furthermore, we will optimize the existing control program to better align with the control requirements of real elevator systems.

1. Expansion of hardware circuit functionalities:
a. Encoder floor positioning circuit:
- Installation method: Place the rotary encoder directly on the output shaft of the traction machine, allowing it to rotate along with the traction machine. This setup enables us to obtain pulse signals proportional to the motor's rotational speed from the encoder's pulse output terminal. These signals serve two purposes: providing feedback speed to the frequency converter and calculating the pulse distance between floors for elevator floor counting.
- Connection between the encoder and control system: For incremental encoders with only two-phase pulse outputs (A and B), they have four wires. Two wires are for pulse output, and they connect to the high-speed counting input of the PLC. One wire is for the COM terminal, and another wire is for the power supply, which connects to the positive and negative terminals of the power supply. Absolute encoders directly output the number of pulses as a digital signal. Their signal output methods include parallel output, serial output, bus output, or conversion into standard signals.

b. Weight control circuit: The weight control circuit consists of a weight sensor and a control device. The weight sensor converts weight signals into electrical signals and transmits them to the control device, which performs calculations and completes the elevator weighing process. The control device can output multiple sets of relay contact signals, such as 0-10mA current signals, 0-10V or -10V~+10V voltage signals, corresponding to the weight changes within the elevator. In the case of overweight, the control device triggers audio and visual alarms to provide accurate data for elevator weighing and operation.

c. Emergency rescue device: The emergency rescue device automatically activates when there is a power interruption (e.g., power outage or phase loss) or when the elevator itself experiences soft faults (non-elevator safety circuit or door lock circuit failures). It slows down the elevator car and brings it to the nearest landing, opens the car and hall doors, and releases trapped passengers. The emergency rescue device is a vital skill that elevator maintenance technicians must master. Therefore, it is necessary to design an emergency rescue device in the elevator teaching and training equipment.

2. Software optimization design:
To meet the control requirements of a four-story elevator, we will optimize the control program while keeping the functionalities of the existing training equipment unchanged.

a. Encoder floor positioning program: This program calculates the elevator's position and speed based on the input pulse count. During field debugging before elevator operation, the pulse counts corresponding to signal points such as speed change, leveling, and braking points are stored in corresponding memory units. During elevator operation, the program uses the rotary encoder for real-time detection and calculates the elevator's floor position, speed change points, and leveling points. This allows for floor counting, speed change signal generation, leveling signal generation, and control of the elevator doors (car and hall) through the frequency converter.

b. Weight control program: The weight control program first reads the load signal from the pressure sensor, performs A/D conversion, and compares it with the rated load capacity stored in memory. When the weight inside the car reaches or exceeds 95% of the rated load capacity, the program outputs a full load signal, indicating that the elevator is loaded and no longer responds to hall call signals. When the weight inside the car reaches or exceeds 102% of the rated load capacity, the program triggers the overload relay, displays the overload signal, and prevents the elevator from closing its doors until the overload condition is resolved, ensuring safe and reliable elevator operation.

c. Emergency rescue program: The emergency rescue program distinguishes between online and offline modes and handles them accordingly. In offline mode, the emergency rescue function is not used. In online mode, when the external power supply is normal, the hardware circuit automatically controls the battery charging and displays the charging status using LED indicators (e.g., fast charge, slow charge, and charge complete). In the event of a power outage, phase loss, or elevator control system failure, the emergency rescue program takes full control of the elevator, activates the inverter circuit, converts the DC voltage from the battery into three-phase AC voltage, and supplies power to the elevator. This allows the elevator to continue operating at a slow speed for 5-30 minutes until it reaches the nearest landing, opens the doors, and ensures the safe evacuation of passengers. Even if the external power supply is restored during the rescue process, the emergency rescue device will continue its operation until the rescue is completed before returning to normal elevator operation. To prevent external interference, the emergency rescue program will not respond to rescue operations if the duration of the power supply failure is less than 3 seconds, or if the control system failure time is less than the device's set time, ensuring priority elevator operation.

In conclusion, by considering the control requirements of a four-story elevator and the features of the existing elevator teaching and training equipment, we propose expanding the hardware to include encoder floor positioning, weight control, and emergency rescue circuits. We will also optimize the control programs by adding encoder floor positioning, weight processing, and emergency handling programs to make the functionality of the elevator teaching and training equipment closely align with the actual control requirements of elevators. This will enable students to better grasp the working principles and maintenance skills of elevators