Practice teaching is the core link of training applied talents. Aiming at the shortcomings of traditional practice teaching of PLC, such as poor standard, poor design, and less exercise for students’ practical ability, this paper proposes practical engineering teaching reform based on engineering, and designs related experimental equipment and teaching materials. At the same time, emphasis is laid on standardization and precision in the basic verification experiment, innovation in the comprehensive design, engineering in the whole practical teaching process, and practical ability training. Through engineering teaching, students’engineering ability has been greatly improved, and the teaching effect is good. Programmable Logic Controller (PLC) is a new and universal automatic control device which takes microprocessor as the core and integrates computer technology, electrical control technology, automatic control technology and communication technology. At present, it has become the mainstream control equipment in the field of industrial control and has been applied more and more widely. It plays a more and more important role in all walks of life. With its own characteristics, programmable logic controller has been playing a leading role in the field of industrial automation control. The principle and application of programmable logic controller is a professional course of “electronic information science and technology” and “Electronic Information Engineering” in our college. Because of its strong practicality, how to effectively construct the practical teaching link of the course to meet the needs of transformation and development put forward by the Ministry of education has become a top priority for teaching reform. The experimental equipment is the key factor determining the quality of practical teaching in the course of principle and application of programmable logic controller. Because the experiment of programmable logic controller involves 380V power, thermostatic element AC and DC motor, frequency converter and other equipment, it has certain danger in operation. The current mainstream teaching equipment has the characteristics of high integration, complete cable and single input and output. It is very convenient for students to operate. As a result, students only need to close the switch, plug in the input and output signal cables, and download the program to complete the experiment. Although this method is safe, there is a big gap between the actual system and the students after graduation. Therefore, it is imperative for the students to use the “fool” equipment to train the engineering ability. The experimental content of traditional practical teaching textbooks mainly trains students’basic programming ability. The subjects involved are focused on simple systems such as running lights and traffic lights, lacking engineering application background. Through this kind of experiment, the students only realized the basic programming training, lacked the understanding of all kinds of sensors, transducers, touch screen and frequency converters involved in the practical application system of PLC.
At the same time, they knew little about the process flow and sequence control in the relevant application fields of PLC, and their engineering thinking ability could not be effectively cultivated, and their practical ability could not be improved. After completing this course, students can not independently design a practical PLC control system. Therefore, only by updating the practical teaching materials and adopting open experimental equipment, can we provide the students with the hardware and software environment of engineering practical teaching. The traditional practice teaching mode is that the teacher puts forward the experiment goal and content, drives the students to complete the experiment, and the students submit the experiment report or on-site operation.
The teacher only evaluates the students’report or operation from the point of view of the feasibility of the design. The evaluation system is single and lacks the engineering evaluation system, which can not effectively cultivate the students’ engineering consciousness and innovation ability. In order to restore the real application site of PLC, the project team and equipment suppliers have been closely communicating, and an open advanced electrical experiment cabinet based on PLC has been developed and put into use. The equipment changes the integrated structure and adopts open discrete components. The discrete components such as circuit breaker, contactor, FX series PLC, switching power supply, relay, switch and LED lamp can be configured by the students themselves. After the experiment target is determined, the students complete the preliminary connection of the whole hardware circuit by designing the circuit by themselves and manually making the terminal. Then the discrete components are set up according to the electrical cabinet. The meter specification is fixed on the backplane to form the final hardware system. Through the above practice, students have got good engineering training in electrical circuit design, ladder diagram programming, various terminal production, line diameter selection, protection device use, wiring specification, low-voltage electrical appliances use, electricity safety and other engineering skills.
In order to adapt to engineering teaching and improve the engineering background of experimental contents, the project group has compiled “industrial automation comprehensive application training” teaching material, which is published by Xi’an Electronic and Science University press as a series of planning teaching materials for “project 13th Five-Year”. The selected items focus on the basic knowledge and technology of modern manufacturing, automatic control and robotics in modern industrial production. This skill is developed, involving low-voltage electrical appliances, PLC, touch screen, frequency conversion speed control system, servo control system, Industrial Ethernet and other common equipment. The textbook promotes the training process with project-based training and comprehensive engineering application, so that students can apply the technology they have learned to solve practical engineering problems. It not only helps students quickly grasp the whole engineering process of simple PLC automatic control system from conception, design, implementation to operation, but also improves students’innovative ability and engineering application ability. In order to cultivate students’engineering thinking mode, change the old thinking of “just use it”, and enable students to have the ability to transform concepts into prototype systems, it is necessary to cultivate students’ engineering consciousness, that is, on the basis of feasibility, to establish engineering consciousness of reliability, standardization, quality control, process control, time control and cost control. Feasibility means that the design must be feasible and can be realized by various existing engineering technologies; Reliability means that after the functional design of products is completed, reliability tests such as hardware test, software black box test, vibration test, EMC test must be carried out to ensure the integrity and reliability of the design; Normality means whether the designed system meets the corresponding standards; Quality control means how to control in mass production. Making the quality of each component. Process control refers to whether the production process can meet the design requirements and whether it can be optimized in terms of accuracy and materials; time control refers to the time control of design cycle and production cycle; cost control reflects whether the design can save costs and find the balance between quality and cost in different design schemes. In the evaluation of students’design, the seven engineering elements are used to evaluate comprehensively, from a single evaluation to a composite evaluation.
For the basic validation experiment, students are required to design the sequence function chart SFC first, then the ladder diagram, emphasizing the standardization and accuracy. For the comprehensive design experiment, the factors of reliability, technology, production cycle and cost control are emphasized, so that students receive engineering training at both design level and process quality level. The diversified evaluation system makes the training close to the real needs of enterprises and effectively improves students’engineering literacy. At the same time, in order to ensure the effect of experimental teaching, multi-round teaching in small classes is adopted, each experiment is completed by teachers and experimenters. At the same time, the laboratory is open for 12 hours, and students can train themselves in their spare time.
Practice shows that this kind of engineering practice teaching, which is close to the needs of enterprises and emphasizes the application background, enables students to receive better engineering training and improves their ability to solve practical problems. At the same time, change the relevant enterprises think that students’design is naive, students’ employment ability is significantly improved. Because of the fast updating speed of PLC products, the reform of engineering practice teaching is a long-term work. Teachers should carefully study teaching theory, flexibly use teaching methods, and strengthen the engineering consciousness of teaching in order to truly achieve the purpose of stimulating learning interest, improving classroom teaching effect and cultivating students’engineering practice ability.