Study On The Control Methods Of A EPS With AC Electromotor And The Development Of The Control System For It's Testrig

PrefaceEPS (Electric Power-Assisted Steering) adopts motor to provide assist torque, which is controlled by ECU (Electric Control Unit), according to the velocity of the vehicle and the torque of the steering wheel. Because EPS can save energy, improve vehicle active safety and conduce to environment protection, it is considered as a new high-tech which closely follows the modern vehicle development topic and has been paid close attention as soon as it's appearance. Almost all the famous automobile company abroad have developed their own EPS and have the ability to volume-produce EPS by now. EPS has been also applied to some car as a elective product. In the recent years, the research on EPS is carried out in china,and it springs up like mushrooms. There are Jilin University, Tsinghua University and some other Universities and companies engaging in the research and development of EPS.This paper first study the characteristic of EPS, and then analyse the control method and control strategy, establish the testrig of the Electric Power-Assisted Steering control system, design a CAN-USB connection card and a test-control software. And this paper also design a EPS ECU, carry out the control strategy based on the embedded operating system uC/OS-II. The paper mainly use the test method to study the control strategy and the effect.Main ContentsThe paper contain 5 chapters, and the main contents as follows: In chapter one, the merits and defects of the conventional Hydraulic Power Steering and Electric Hydraulic Power Steering are summarized based on investigating in mass reference paper. Development status, principle, structure, key parts, classification of the EPS are introduced by contrast EPS to HPS and EHPS, and EPS has the merits of saving energy, improving vehicle active safety and conducing to environment protection, and it is one of the future development direction of power steering.In chapter two, the paper studied and analyzed the EPS control content and the control strategy, and analysised and researched three phase ac electrical machinery actuation principle, and has achieved the electrical machinery control target through the regular sample SPWM method.The goal of EPS is through the change of the electrical machinery output moment of force, makes the hand power change according to the steering wheel torque and the vehicle speed changes. When low speed travel or big corner, driver can carry on the operation by the very small extension, and feell streering easier; When high speed travel, driver carry on the operation with slightly heavy hand power to strengthen the road feeling.EPS characteristic and the control strategy is the main content of the EPS ECU. The EPS control strategy is the key of EPS systems control performance. According to the EPS control content difference, the systems control algorithm divides into the Power-Assisted control, the damped control and the return control. The Power-Assisted control assists driver steering, and reduces steering power. The Power-Assisted control characteristic divides into the straight line, the broken line and the curve three kinds, according to the Power-Assisted characteristic; When automobile high speed travel, damped control suitablely increases the resistance, to achieve the high speed driving " steady feel"; Return control makes the assistance automobile steering wheel automatically return after change just or facile returns under the driver operation. At present, the commonly used exchange asynchronous machine velocity modulation control method includes the frequency conversion live pressure law, the vector controls the facture and the direct torque controls the facture. Through comparing several methods the good and bad points with the union reality, this article chooses the middle and small scale electrical machinery control, achieved the simpler frequency conversion live pressure law. In the frequency conversionlive pressure, law essence is counter turns the direct current the rectangular wave alternating current which the frequency may move, controllably provides a frequency to the exchange asynchronous motor, the peak-to-peak value controllable power source.In chapter three, the paper developed the electrically Power-Assisted controller, and built the testrig and the PC monitoring environment. Electrically Power-Assisted controller uses the DSP chip TMS320LF2407A primarily controller chip, and expanded the simulation quantity gathering module, the switch quantity gathering module, the photo electricity code gathering module, the electrical machinery control module as well as SCI, CAN and the USB communication module, electrical machinery control section. Because the MOSFET array includes power electric circuit, the paper has used the independent electric circuit board arrangement. The Power-Assisted electrical machinery is a three phase ac electrical machinery, so the control method the article uses is therule picks method the production SPWM method, and controls the electrical machinery through the adjustment modulating wave frequency and the modulation depth.This article has built the small electrical machinery testrig and the simple EPS testrig. The former uses in the test of electrical machinery characteristic, and the latter electrically operated to Power-Assisted the control strategy preliminary confirmation. The PC monitoring environment including develops CAN-USB connection card and compiles PC monitoring software. The CAN connection card function is to make the interconversion of the CAN data and the USB data, the hardware uses the MC9S12DP256B master controller and USB controller PDIUSBD12, follows the USB1.1 communication agreement. The connection card development includes the hardware design and the firmware procedure, the equipment actuates, connection Dll as well as the test order. Its actual test communication maximum speed is the 350k byte/second. The PC monitoring software development environmentis Microsoft Visual C++ 4.0, completes using MFC, mainly contains the module, the CAN transmission module, the data display module, the control algorithm module, the data storage module, the CAN data puts the module and the multimedia timer.In chapter four, the paper achieved electrically operated under the uC/OS-II overhead construction has the Power-Assisted control strategy, and has carried on the experimental preliminary confirmation. Embeded Real-time Operating System (EROS) is one kind operating system software supporting application system. It is the extremely important constituent of the application system (including hard, software system). The real time system includes soft real-time, issturdy and healthy, and it may seizing and may not the seizing discrimination. Embeded Real-time Operating System can enhance the system reliability, and enhance the development efficiency, and reduce the development cycle. This paper chooses EROS uC/OS-II. uC/OS-II is complete, may transplant, the solidification, the tailor takes the lead the type real-time multi-duties EROS. This paper has first carried on the transplant to the operating system, then has carried out the EPS control strategy under the uC/OS-II frame.The paper through the Power-Assisted characteristics test, the damping characteristics test and the returns characteristics test to carry on the preliminary confirmation to the control strategy. In the characteristics test, under the different vehicle speed, the electrical machinery actual output helps the moment of force to beable to be better according to boosts the characteristic, follows the goal whichthe controller outputs to help the moment of force. The damping characteristics test mainly has carried on the test from the elimination reverse impact angle, establishes the electrical machinery to be at the damping condition, may the better reduction impact. In the returns characteristic test, in the low speed and the highspeed situation, the electrical machinery outputs the different size the moment of force control steering wheel to return to the middle position, the effect is not bad.In chapter five, the contents and conclusions are summed up. Also some advice on the improvement of the later research is given.