“The elevator is an indispensable tool in modern people’s lives. The current elevator door machine control system has its inherent defects, which make the elevator unable to operate normally, heavy maintenance workload and even cause personal injury. Therefore, it is of great practical significance to develop an elevator door machine control system with high performance, high reliability, easy maintenance, and moderate cost.
Author: He Weiting
The elevator is an indispensable tool in modern people’s lives. The current elevator door machine control system has its inherent defects, which make the elevator unable to operate normally, heavy maintenance workload and even cause personal injury. Therefore, it is of great practical significance to develop an elevator door machine control system with high performance, high reliability, easy maintenance, and moderate cost.
1 System hardware design
The hardware structure of the system is shown in Figure 1. The input and Display circuit completes the human-computer interaction function and sets the execution process of the elevator door machine; the calculation control circuit is based on the set parameters and external input signals, in accordance with certain control laws, Complete calculation and control logic output; and the drive and protection circuit accepts the control logic of the calculation control circuit, controls the action of the actuator according to this logic, and monitors the status of itself and the actuator at the same time, and protects the circuit action in the event of a failure to protect the components Safety. The following briefly introduces the calculation control circuit and the actuator.
1.1 Calculation control circuit
The calculation control circuit is composed of MSP430F149 as the processing unit of the control circuit, plus various signal adjustment circuits and parameter power-down retention circuits. Mainly include: parameter power-down retention circuit; motor speed feedback and running direction identification circuit; current acquisition feedback circuit; position feedback and switch decoding circuit; level conversion circuit.
Motor speed feedback and running direction identification circuit This circuit uses a photoelectric encoder to measure the speed of the motor, and uses the grating method to identify the running direction of the motor. The way to achieve this is to separate the two photoelectric sensors by 90°. The phase is installed so that they have a 90° phase difference. The phase A, B phase pulse waves are sent to the direction identification circuit after shaping.
The position feedback and switch decoding circuit is shown in Figure 2. The three-phase position of A, B, C is the square wave signal sent by 3 photoelectric sensors with 120° electrical angle difference. After LM324 shaping, it is sent to MSP430F149 for optimal current conduction angle processing, and the processed output 3 The square wave signal with a mutual difference of 120° electrical angle is sent to GAL16V8 for switch decoding. GAL16V8 decodes the decoded control on signal together with PWM modulation signal, fault lockout signal, and motor forward and reverse signals at the same time to realize motor speed, direction control and fault protection functions.
1.2 Executive agency
The elevator door switch actuator is composed of a rare earth permanent magnet brushless DC motor. The motor is a double-redundant winding samarium-cobalt permanent magnet square wave motor (300V, 200W, 600r/min), adopts a concentrated full-pitch winding, and the air gap magnetic field distribution is a square wave. The rotor position sensor is a photoelectric position sensor, which detects the position of the motor rotor relative to the stator winding in real time, and outputs 3 rectangular waves with a width of 180° in electrical angle and a phase difference of 120° in electrical angle. According to the different combinations of the three signals, determine the current rotor position and the armature winding that should be turned on.
2 System software design
The main software of the system includes: system initialization program, human-computer interaction program, data access program, system monitoring program, motor control and driver program, etc.
2.1 System initialization
The system initialization includes the initialization of the MSP430F149 microcontroller and peripheral devices, the definition and initial value assignment of system global variables. After the initialization is completed, the program enters the main loop body, and the motor is controlled and adjusted according to the preset parameters or according to the operator’s input. The initialization process is shown in Figure 3. When setting the timer, timer A is used for timing query in the program loop, timing sampling of A/D, timing acquisition of speed. Timer B is used to generate PWM waves and the set 4 acceleration and deceleration times. By default, the LED displays the speed information of the motor, and only when the operator intervenes, the current, acceleration and deceleration time and other information are displayed. At the end of the initial program, the interrupts of timer A, timer B, each I/O port and watchdog are turned on, and then the speed signal sent from single-chip microcomputer B to single-chip microcomputer A (MSP430F149) is repeatedly inquired in an infinite loop.
2.2 System monitoring procedures
The signals that the program monitors at any time are: external position switch signal, alarm number given by IPM, reset request signal, elevator door jam signal, door opening signal and door closing signal. These signals are all input from the external interrupt port. The position switch signal tells the system the limit position of the elevator door; the IPM alarm signal is automatically sent out when the IPM detects overcurrent or overheating; the elevator door jam signal is sent out after the program encounters an external force when the door is closed; the door is opened and The door closing signal directly determines the running direction of the motor, and the door opening action is also controlled by the elevator door jam signal.
2.3 Motor control and drive
The motor control and driver program mainly completes the processing of the motor operating speed curve and the instant calculation of the optimal current opening angle. When the program adjusts the speed, it compares the actual speed of the motor with the default data, and then adjusts the actual speed. In order to reduce the torque ripple, the rotor position signal needs to be offset by a certain angle. In the system, after calculating the motor current signal, the optimal current opening angle of 3° is used. The rotor position signal of the motor causes the MSP430F149 to be interrupted. In the interrupt processing program, the MSP430F149 first calculates the time required for the 3° angle according to the actual speed signal of the motor sent to the person, and then processes the position signal in advance or lag according to the direction signal of the motor. . After exiting the interruption, Timer-B outputs a new three-phase position signal to the GAL16V8 decoder according to the calculation result, and the GAL16V8 outputs the switch signal to control the working state of the inverter, thereby controlling the running speed of the motor. The program flow chart is shown as in Fig. 4.
Through design and debugging, the system has achieved basic performance indicators. In the system design process, due to the emphasis on generalization and modular design, the software and hardware used can be slightly expanded, used in most brushless DC motor control systems, and become a universal inverter.