Development of an automatic test and evaluation system for closing force of car doors

frozenviolet

Development of an automatic test and evaluation system for closing force of car doors [Copy link]

　Abstract : Using force and displacement sensors and computer technology, an automatic measurement system for closing force and displacement of car doors is developed. The system can simultaneously collect the closing force and displacement of the car door during the closing process. The actual measurement results show that the measurement system has a simple structure, is easy to operate, and the measurement accuracy meets the actual requirements. Keywords : car door; sensor; closing force; displacement; automatic test system摘要CH(结束)←
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　With the development of the automobile industry, the closing force and sealing of car doors have become an important indicator for measuring automobile performance. Although the portable test system for closing force and displacement of car doors [1] is simple, convenient, easy to carry, and not limited by the experimental site, its test accuracy can meet the experimental requirements, but there are still some problems in the experimental process, such as the uncertainty of the position of the reference point of each experiment, the speed of door closing is greatly affected by human factors, and the closing force of the car door is closely related to the closing speed. In order to eliminate these influences, an automatic test system is designed. The system is controlled by a computer, and the stepper motor drives the screw nut to complete the door closing process. At the same time, the computer controls data acquisition and processing. The automatic test system has the following advantages:
　　(1) It overcomes the disadvantage of inconsistent reference points of the manual test system and ensures a unified starting point in the repeated experiment process;
　　(2) The door closing process is controlled by a computer, so that the closing speed can be controlled, eliminating the human factors in the experimental process;
　　(3) During the door closing process, the time interval of the collection point is controlled by the computer to ensure that the closing force value at the fixed point is collected in the repeated experiment process, eliminating the human factors in the data collection process of the manual test system.

1 System Principle　　
　　The closing force-displacement automatic test system for car doors consists of two parts: hardware and software. The hardware mainly includes: drive device, transmission device, force measuring device, displacement measuring device, measurement system base, computer and communication interface, etc. The software mainly includes: computer control program, data acquisition and communication, data processing and analysis, output and storage, etc. The following functions can be realized:
　　(1) Simultaneous measurement of force and displacement can obtain the change curve between closing force and displacement, obtain the maximum force deformation parameter, and communicate with the computer in real time;
　　(2) Computer controls the measurement and data acquisition process.
　　During the test, the stepper motor controls the movement of the system and controls the closing process. The measurement process of force sensor and displacement sensor, as well as the data acquisition and processing process are controlled by software. The closing force and door displacement measured by the force and displacement sensor are converted into electrical signals and transmitted to the data acquisition part. After being amplified and filtered by the secondary instrument, the signal is converted into a digital signal and input into the computer through the COM serial port to realize real-time data acquisition and communication of the computer, and the data is saved as a text file. The computer processes the data according to the real-time transmitted data and saves it in a file. The system principle is shown in Figure 1.

　　

2 System Mechanical Structure
　　The system uses a stepper motor as the driving link, a screw nut mechanism as the transmission mechanism, and a coupling connects the screw and the stepper motor, thereby converting the rotary motion into linear motion, driving the door to move, and realizing the simultaneous measurement of the door closing force and displacement. The force measurement link and the displacement measurement link are installed on the door, and the entire system is fixedly installed on the base outside the door. The mechanical system is shown in Figure 2.

　　

3 Control System 　　
　　The car door closing force-displacement test device is a computer integrated control and measurement system that is completely controlled by a computer program, collects measurement data, and analyzes and processes experimental data. It has the following characteristics:
　　the computer generates step pulses in an interrupt mode, sends pulses through the computer parallel port, controls the operation of the stepper motor, and completes the door closing process. At the same time, the forward and reverse rotation and speed of the stepper motor are set through the parallel interface.
　　The computer controls the measurement process of closing force and displacement and the frequency of data collection. The collected data is communicated with the computer in real time through the serial communication port. At the same time, the data is saved as a text file for data processing.
　　Since the hardware needs to be operated directly in the control program, TURBOC++3.0 software is selected as the compilation tool. The workflow of the entire control program is shown in Figure 3.

4 Test device　　
　　The photo of the car door closing force-displacement automatic test device is shown in Figure 4:

5 Measurement results
　　The developed test device was used to test the four doors on the left and right of a domestic car, and the measurement results achieved the design purpose. At the same starting point, the door was closed at the same speed, and the measured force-displacement curve showed that it had high repeatability.
　　Figure 5 shows the ten measurement curves of the left front door of the car. The first peak is the peak value reached after the door locks contact each other, and the values are shown in Tables 1 and 2; the second extreme value is at a displacement of 24.15 mm, when the door reaches the closed state, that is, the maximum closing force value of the door.

　　It can be seen from the force-displacement curve that the closing process of the car door is affected by many factors, including assembly gap, door lock, sealing strip, etc. At 0-11 mm, it is affected by the assembly of the car door itself and the hinge, but the force is small; with the drive of the stepper motor, at 11-14.5 mm, the car door and the door lock contact and reach the first peak; in the process of compression, that is, from 14.5 to 24.15 mm, the role of the sealing strip becomes more and more important, which plays a decisive role in the final closing force of the car door.

6 Conclusion　　(1) The test device can not only measure the closing force of the door, but also automatically measure the force and compression displacement of the sealing strip during the door closing process; 　　(2) It is computer controlled, the program is easy to use, and the force-displacement deformation curve can be easily obtained. 　　(3) Compared with the portable measurement system, the effective data measured is greatly increased, and the measurement repeatability is good.