Currently, our existing products are developed in line with the standard process in this industry - V-pattern development process (refer to Figure 1). Base on the CACSD (computer-aided control system design), modernized V-pattern runs the computer support tool through the whole process of control system development and test. The computer can not only aid the control system for design, scheme designs and offline simulation, but also can be applied to rapid real-time control prototyping, product code generation, and hardware test in the loop. Referring to the "Verification" and "Validation", the "V" herein forms a set of rigorously scheme to develop the system. The pattern primarily is composed of five stages which are mutually supplementary: Functional Requirements Definition, Control Scheme Design, Rapid Control Prototyping (RCP), Code Generation, Hardware Simulation in-the-loop, System Integration Test/Standardization.
In traditional development, millions of words are required in the section for elaboration and many troubles may occur due to the vague description in development. In order to avoid this, the V-pattern process adopts the signal flow diagram (Simulink model) for definition. Meanwhile, control scheme design adopts the previous method no longer in which object model is required to be simplified to the form accessible to manual processing followed by manual design based on experience, it adopts MATLAB/SIMULINK and other computer-aided modeling and analysis software to set up a model in which the object will be as accurate as possible and then makes offline simulation, preventing embarrassment due to the design schemes of simple object failing to meet the actual object requirements.
According to the modern design scheme, after the scheme design is finished, computer-aided design tool will automatically convert block diagrams of control schemes to codes and download them to the hardware development platform instead of waiting for the programming of software engineers and following code hardware integration so as to quickly create the prototype of control systems. Next, computer-aided test management tool software will be used to make all kinds of tests so as to verify the control effects of control schemes on the actual object and optimize online control parameters. By then, it will take just a few minutes to regenerate test prototype in spite of massive modification. In this way, final schemes and effects will be basically confirmed before creating the final control scheme, preventing too many resources from being wasted and too much time from being consumed.
There are defects introduced in traditional manual programming which is also very slow; whereas, modern development method is different with the majority of product codes automatically generated by the computer. For most engineers, the loss of some operation effects of the code is acceptable if the development is accelerated; besides, the computer can encode automatically, which makes it easy to be away from all kinds of human errors.
In addition to the prototype of control product, it is also necessary to conduct a comprehensive test so as to compare and make verification of product compared with actual indicator requirements. Particularly fault test and extreme tests, many tests are conducted under environmental conditions or with too much cost. Computer-aided design tools will play its role again in the modern development (software/hardware) with tests under all kinds of conditions via HILS methods and tools, particularly fault tests and extreme tests. It is what the traditional method fails to achieve.
The product molding controller is required to link with other sub-systems and constitute an intact closed loop for comprehensive and detailed testing as soon as it is completed so as to confirm that the product fulfills all design indicators and requirements definition. The major difficulty in the stage lies in that integration cannot be available if other sub-systems are not ready in parallel development. HILS application can replace those not ready or accessible in the closed-loop system, simulate their characteristics in mathematic model and offer corresponding feedback signals for controller by I/O port. In this way, all sub-systems can conduct integration tests and complete the confirmation and adjustment to the system performance without waiting for each other. Later in the integration test, the control parameters in the finished product controller will be adjusted depending on specific service conditions, namely, standardization.
In line with the principle of this development process, we have successfully and independently developed many electronic control products, including A01, A02, B, C01, E01 and other VCUs; Motor MCUs in the power of 2kw, 3.5kw, 7kw, 10kw, etc. and BMS is being developed. Figure 2 below shows actual conditions of VCU control strategy development and realizes complicated control strategy and dynamic algorithm with the help of MATLAB/SIMULINK, such as full-speed intelligent cruise and automatic hill-start assist; It overcomes traditional problems in which manual code development is time-consuming and error-prone, shortens the period of project development and enhances the development efficiency.
Figure 2 MATLAB/SIMULINK-based Control Strategy Development
Figure 3 Actual Loading Test
Similarly, we benefit a lot in actual standardization thanks to the computer-aided design test tool. Figure 3 below shows the process of a VCU in actual test. In the test, it offers feedback on validity and reasonability of parameter settings throughout the whole process of previous development based on actual conditions, optimizes all control parameters, promotes the functionality of our product as a whole and accumulates experience for other new products' development.
At present, by the aid of the V-pattern development process, we fully independently develop and accomplish the development of VCU and MCU in multiple models and levels, BCM, instruments, insulation monitors and others, with some product samples as follows:
图4 A02 VCU样品